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Attached algae as indicators of water quality in phosphorus enriched Kootenay Lake, British Columbia Ennis, Gordon Leonard 1977

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ATTACHED ALGAE AS INDICATORS OF WATER QUALITY IN PHOSPHORUS ENRICHED KOOTENAY LAKE, BRITISH COLUMBIA B.Sc.(Hon.), University of B r i t i s h Columbia, 1972 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE THE FACULTY OF GRADUATE STUDIES Department of Zoology We accept t h i s thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA j Gordon Leonard Ennis, 1977 by GORDON LEONARD ENNIS i n A p r i l , 1977 In presenting th is thes is in p a r t i a l fu l f i lment of the requirements for an advanced degree at the Un ivers i ty of B r i t i s h Columbia, I agree that the L ibrary sha l l make it f r ee ly ava i l ab le for reference and study. I fur ther agree that permission for extensive copying of th is thes is for scho la r ly purposes may be granted by the Head of my Department or by h is representa t ives . It is understood that copying or pub l ica t ion of th is thes is for f inanc ia l gain sha l l not be allowed without my wr i t ten permission. Department of JzLcPO I'orfJ The Univers i ty of B r i t i s h Columbia 2075 Wesbrook Place Vancouver, Canada V6T 1WS Date 2 € Afrit /f 7*7 ABSTRACT Kootenay Lake receives high phosphorus loads to i t s south end and low phosphorus loads to i t s north end. These loading differences, combined with the lake's 105 km long f j o r d morphology, should r e s u l t i n a regional trophic gradient i n the lake. I studied attached algae to assess how w e l l they supplemented nutrient data i n providing a more accurate measure of regional water q u a l i t y d i f f e r e n c e s . A l g a l abundance, phosphorus storage, production, species composition and d i s t r i b u t i o n were measured at up to 30 locations i n the rocky l i t t o r a l zone of Kootenay Lake. In addition, p h y s i c a l parameters were measured and water samples were analyzed for major nutrients, anions and cations. Loadings of t o t a l d i s s o l v e d s o l i d s , calcium, and sodium are also highest to the south end of the lake, and concentration gradients of these b i o l o g i c a l l y conservative elements conform to the expected pattern. On the other hand, dissolved and p a r t i c u l a t e inshore phosphate readings, although high, d i d not e x h i b i t regional v a r i a t i o n s . Attached algae remove large amounts of phosphorus for growth, a l t e r i n g phosphorus concentrations i n the lake. Also, attached algae store surplus phosphorus within t h e i r c e l l s , more phosphorus being stored i n the regions of highest phoshate loadings (over 1.0 yg P mg - 1 dry weight algae) than elsewhere. South arm algae had the highest c h l o r o p h y l l a_ l e v e l s , organic weights and production rates. Their r e s u l t s were t y p i c a l of eutrophic waters. In contrast, north arm algae were less abundant, had lower growth rates, and were t y p i c a l of mesotrophic and o l i g o t r o p h i a waters. Eutrophic i n d i c a t o r species, such as the green alga Cladophora aegagvopiZa and the diatom Fragilavia oonstruens, were abundant i n the south h a l f of the lake and generally absent or less common at other l o c a t i o n s . Diatom c l u s t e r analyses divided the lake into regions, stations i n areas of low phosphate loadings forming groups d i s t i n c t from stations located near high phosphorus inputs. One must conclude that aqueous phosphorus concentrations, a l t e r e d by attached algae, are inadequate i n d i c a t o r s of Kootenay Lake's trophic gradient. Attached algae do e x h i b i t regional v a r i a t i o n s consistent with the lake's expected trophic gradient and are therefore good in d i c a t o r s of water q u a l i t y i n phosphorus enriched Kootenay Lake. i i i TABLE OF CONTENTS Page ABSTRACT . . . . i TABLE OF CONTENTS i i i LIST OF TABLES V LIST OF FIGURES v i LIST OF PLATES x i ACKNOWLEDGEMENTS x i i INTRODUCTION 1 DESCRIPTION OF THE STUDY AREA 3 FIELD AND LABORATORY PROCEDURES 8 Sampling Program 8 Physical Measurements 9 Chemical Measurements . 9 A l g a l C o l l e c t i o n s 10 1. Natural Substrates 10 2. A r t i f i c i a l Substrates 11 A l g a l A n a l y t i c a l Procedures 12 1. Biomass 13 2. Diatom Enumeration 13 3. Community Composition 15 A l g a l Nutrient Analyses 15 S t a t i s t i c a l R e l i a b i l i t y of the A l g a l Data 16 1. F i e l d C o l l e c t i o n s 16 2. A l g a l Enumeration 16 A l g a l Transfer Experiment 17 LAKE PHYSICS 20 Water Input 20 Water Level 23 Solar Radiation 23 Subsurface Illumination 25 Secchi Disk Transparency 28 Water Temperature 33 Currents 34 i v LAKE CHEMISTRY 37 Nutrient Loading 37 Phosphorus 40 Nitrogen 45 Total Dissolved S o l i d s 47 A l k a l i n i t y and pH 50 S i l i c a 50 Calcium 52 Sodium 52 ATTACHED ALGAE 55 Abundance 55 1. Chlorophyll a. 55 2. Organic Weight 55 Phosphorus Storage 62 Production 65 Community Composition 69 1. Natural Substrates 69 2. A r t i f i c i a l Substrates 71 Species Composition 74 1. Green Algae 74 2. Blue-green Algae 79 Attached Diatoms 79 1. Diatom Abundance 79 i . Natural Substrates 79 i i . A r t i f i c i a l Substrates 80 2. Diatom D i v e r s i t y 89 i . Natural Substrates 89 i i . A r t i f i c i a l Substrates 92 3. Diatom Cluster Analyses 95 i . Natural Substrates 95 i i . A r t i f i c i a l Substrates 97 4. Diatom Species D i s t r i b u t i o n s 99 i . Natural Substrates 100 i i . A r t i f i c i a l Substrates 107 Transfer Experiments 112 DISCUSSION 117 CONCLUSION 137 LITERATURE CITED 139 V LIST OP TABLES Table Page I Mean dissolved orthophosphate (as P) content of inshore Kootenay Lake water at the 0.1, 1.0, 3.0, and 5.0m depths 46 II A l i s t of the attached a l g a l species, except diatoms, occurring i n the l i t t o r a l zone of Kootenay Lake 77 III A l i s t of the attached diatom species, t h e i r c e l l volumes and numeric and volumetric occurrence on natural and/or a r t i f i c i a l - substrates i n the l i t t o r a l zone of Kootenay Lake. For occurrence; open c i r c l e s (o) denote a species always made up le s s than 10% of a sample's abundance, s o l i d c i r c l e s (•) denote that a species made up greater than 10% of at l e a s t one sample's abundance. I f a species has no record for occurrence that species was never encountered during quantitative diatom analyses but does occur i n the attached f l o r a . . . . 82 v i LIST OF FIGURES Figure Page 1 Kootenay Lake showing the sampling stations on the north, south, and west arms 4 2 P i c t o r i a l representation showing how the tr a n s f e r experiments were conducted for s t a t i o n Nl 19 3 Average monthly discharges, from 1928-1973 and during 1973, of the Kootenay River at P o r t h i l l , 42 km upriver from i t s inflow to the south end of Kootenay Lake 21 4 1973 average monthly discharges of the Duncan River, 9 km upriver from i t s inflow to the north end of Kootenay Lake; and average monthly discharges of the Kaslo River during 1973, 5 km upriver from i t s inflow to Kootney Lake j u s t south of s t a t i o n N4 22 5 Water l e v e l s (m) during 1973 i n the north (station N7), south (station SI), and west (station W7) arms of Kootenay Lake 24 6 Relationship between sunshine at Castlegar a i r p o r t and energy input to Kootenay Lake, 1964-1966 26 7 Relationship between Secchi depth and the depth at which one percent of the surface l i g h t remains i n Kootenay Lake, 1972-1974 27 8 A comparison of measured versus calculated subsurface i l l u m i n a t i o n f o r s t a t i o n S5, 4 J u l y 1974 29 9 Regional v a r i a t i o n s i n Secchi disk transparency of inshore Kootenay Lake water, 1973 31 10 Seasonal changes of inshore Secchi disk transparency i n the north arm (station Nl) and south arm (station S2) of Kootenay Lake, 1973 32 v i i Figure Page 11 Temperature (°C) f l u c t u a t i o n s of 1.0 m deep inshore water at representative stations i n the north arm (Nl), south arm (S2), and west arm (W7) of Kootenay Lake, 1973 35 12 Approximate annual loading l e v e l s f o r phosphorus (reactive orthophosphate expressed as P) and nitrogen ( t o t a l n i t r a t e expressed as N) r e l a t e d to unit surface area of the two major basins of Kootenay Lake, 1949-1970's 39 13 Regional v a r i a t i o n s i n dissolved orthophosphate (as P) content of 1.0 m deep inshore Kootenay Lake water, 1973 4.1 14 Regional v a r i a t i o n s i n t o t a l dissolved phosphate (as P) content of 1.0 m deep inshore Kootenay Lake water, 1973 42 15 Regional v a r i a t i o n s i n t o t a l insoluble phosphate (as P) content of 1.0 m deep inshore Kootenay Lake water, 1973 43 16 Regional v a r i a t i o n s i n disso l v e d n i t r a t e nitrogen content of 1.0 m deep midlake Kootenay Lake water, 1973 48 17 Regional v a r i a t i o n s i n t o t a l dissolved s o l i d content of 1.0 m deep inshore Kootenay Lake water, 1973 49 18 Regional v a r i a t i o n s i n t o t a l a l k a l i n i t y of 1.0 m deep inshore Kootenay Lake water, 1973 51 19 Regional v a r i a t i o n s i n pH of 1.0 m deep inshore Kootenay Lake water, 1973 51 20 Regional v a r i a t i o n s i n s i l i c a (Si02) content of 1.0 m deep inshore Kootenay Lake water, 1973 53 21 Regional v a r i a t i o n s i n calcium content of 1.0 m deep inshore Kootenay Lake water, 1973 53 22 Regional v a r i a t i o n s i n sodium content of 1.0 m deep inshore Kootenay Lake water, 1973 53 v i i i Figure Page 23 Regional v a r i a t i o n s i n yearly average c h l o r o p h y l l a concentration at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973 56 24 Regional v a r i a t i o n s i n average summer chlorophyll a_ concentration at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973 57 25 Regional v a r i a t i o n s i n yearly average organic weight l e v e l s at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973 59 26 Relationship between organic weights and ch l o r o p h y l l a. for 510 attached a l g a l samples at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973 60 27 Regional v a r i a t i o n s i n average summer organic weight l e v e l s at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973 61 28 V e r t i c a l v a r i a t i o n s i n the amount of chlor o p h y l l a and organic weight at a north arm (N5) and a south arm (S5) s t a t i o n i n Kootenay Lake; 1, 2 Sept. 1973 . . 63 29 Seasonal v a r i a t i o n s i n the organic weight content of attached algae at 0.1 m i n a north (Nl), a south (S2), and a west (W7) arm s t a t i o n i n Kootenay Lake, 1973 64 30 Regional v a r i a t i o n s i n the amount of b o i l i n g water extractable phosphorus from algae attached to natural rock substrates i n Kootenay Lake, Autumn 1973 66 31 Regional v a r i a t i o n s i n average d a i l y production (measured as mg organic cm - 2) of attached algae at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973 67 32 Regional v a r i a t i o n s i n average percentage abundance (by volume) of diatoms, green algae, and blue-green algae attached to natural rock substrates at 0.1, 1.0, 3.0, and 5.0m i n Kootenay Lake, 1973 70 33 Seasonal succession i n the percentage abundance (by volume) of diatoms, green algae and blue-green algae expressed as a proportion of the organic weight (mg cm - 2) at selected depths i n the south arm and north arm of Kootenay Lake, 1973 . . 72 ix Figure Page 34 Regional v a r i a t i o n s i n average percentage abundance (by volume) of diatoms, green algae, and blue-green algae attached to a r t i f i c i a l substrates at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973 73 35 Average percentage composition (by volume) of diatoms, green algae, and blue-green algae on natural rock substrates compared to that on a r t i f i c i a l substrates at 3.0 m i n Kootenay Lake, 1973 75 36 Regional v a r i a t i o n s i n the average abundance of Cladophora aegagvopila attached to natural rock substrates at 3.0 and 5.0 m i n Kootenay Lake, 1973 . . 78 37 Regional v a r i a t i o n s i n average diatom c e l l numbers (xlO 5) attached to natural rock substrates at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973 81.. 38 Regional v a r i a t i o n s i n average diatom c e l l volumes (mm3) attached to natural rock substrates at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973 85 39 Regional v a r i a t i o n s i n average diatom c e l l numbers (xlO 5) attached to a r t i f i c i a l substrates, a f t e r two weeks'growth, at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973. 87 40 Regional v a r i a t i o n s i n average diatom c e l l volumes (mm3) attached to a r t i f i c i a l substrates, a f t e r two weeks'growth, at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973 88 41 Regional v a r i a t i o n s i n the average number of diatom species attached to natural rock substrates at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973 90 42 Regional v a r i a t i o n s i n average diatom d i v e r s i t y (Shannon-Wiener function, H') on natural rock substrates at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973 91 43 Regional v a r i a t i o n s i n the average number of diatom species attached to a r t i f i c i a l substrates at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973 . . 93 X Figure Page 44 Regional v a r i a t i o n s i n average diatom d i v e r s i t y (Shannon-Wiener function, H') on a r t i f i c i a l substrates at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973 94 45 Station c l u s t e r s based upon average diatom abundances on natural rock substrates at 0.1, 1.0, 3.0, 5.0 and 10.0 m i n Kootenay Lake, 1973 . . . . 96 46 Station c l u s t e r s based upon average diatom abundances on a r t i f i c i a l substrates at 1.0 m i n Kootenay Lake, 1973 98 47 Average percent numeric composition of common diatom species (> 5 percent of the t o t a l number) attached to natural rock substrates at 0.1, 1.0, » 3.0, and 5.0 m i n Kootenay Lake, 1973 102 48 Average percent volumetric composition of common diatom species (> 5 percent of the t o t a l volume) attached to natural rock substrates at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973 104 49 Average percent numeric composition of common diatom species (> 5 percent of the t o t a l number) attached to a r t i f i c i a l substrates at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973 109 50 Average percent volumetric composition of common diatom species (£ 5 percent of the t o t a l volume) attached to a r t i f i c i a l substrates at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973 I l l 51 Growth response of the diatom Fragitavia construens a f t e r the r e c i p r o c a l t r a n s f e r experiments at 1.0 m i n Kootenay Lake; 21 May-17 June 1973 113 52 Growth response of the diatom Fragilaria vaucheriae a f t e r the r e c i p r o c a l t r a n s f e r experiments at 1.0m i n Kootenay Lake; 21 May-17 June, 1973 114 x i LIST OF PLATES Plate P a 9 e 1 LANDSAT s a t e l l i t e imagery (colour bands 4, 5, 7) of Kootenay Lake, 3 August 1974, showing the influence of the Kootenay River i n l e t on t u r b i d i t y patterns i n the south arm of the lake . . . . 7 x i i ACKNOWLE DGEMENTS F i n a n c i a l support f o r t h i s study was provided by a National Research Council Grant (NRC 67-3454) to Dr. T.G. Northcote and a B r i t i s h Columbia F i s h and W i l d l i f e Grant. Cominco Ltd. provided a grant to cover the cost of chemical analyses i n t h e i r assay laboratory. The B.C. Fish and W i l d l i f e Branch, at Nelson, generously provided boats, laboratory space, and l i v i n g accommodation f o r f i e l d operations on Kootenay Lake. In addition, a National Research Council Postgraduate Scholarship, a B r i t i s h Columbia Salmon Derby Research Bursary, and teaching assistantships i n the Department of Zoology are g r a t e f u l l y acknowledged. I am indebted to Dr. J.G. Stockner for h e l p f u l advice, e s p e c i a l l y during the planning of t h i s study. Mr. E r i c Parkinson's e f f o r t s i n the f i e l d and laboratory contributed greatly to the success of t h i s p r o j e c t . Among the many other people who helped with f i e l d and laboratory work, I would e s p e c i a l l y l i k e to thank Mr. C o l i n MacKinnon. Drs. J.R. Stein and J.G. Stockner provided expert assistance with a l g a l i d e n t i f i c a t i o n s . Mr. S. Borden of the Biology Data Centre and Mr. Pie r r e B e l i e f l e u r p a t i e n t l y advised me on various aspects of computer programming. The B r i t i s h Columbia P o l l u t i o n Control Branch kind l y supplied me with data from t h e i r Kootenay Lake operations. My wife, Marian, provided moral support, and her e d i t o r i a l assistance during the w r i t i n g of t h i s thesis was invaluable. I greatly appreciate the expertise of Mr. Itsuo Yesaki and Mrs. Peggy Henderson i n d r a f t i n g f i g u r e s , and Mrs. Isabel Sanson's c a r e f u l typing. x i i i By guiding my thesis work and many of my other projects, my supervisor Dr. T.G. Northcote contributed greatly to my s c i e n t i f i c development. I t i s a pleasure to thank him for h i s patience, advice, constructive c r i t i c i s m and f i n a n c i a l support. His e d i t o r i a l assistance with the thesis d r a f t was most appreciated. 1 INTRODUCTION The need f o r e f f e c t i v e water q u a l i t y measurements has grown with increasing p o l l u t i o n . Although necessary, water chemistry data alone are inadequate. Seasonal or even hourly changes i n chemical concentrations combined with the usual p r a c t i c e of spot sampling of r e l a t i v e l y few chemical parameters can r e s u l t i n f a l s e conclusions about water q u a l i t y (Ransom & Dorris, 1972). B i o l o g i c a l organisms are constantly exposed to the t o t a l chemical environment and i n this sense are continuous water q u a l i t y monitors. B i o l o g i c a l data supplement chemical data, r e s u l t i n g i n better water q u a l i t y measurements (Patrick, 1949; Cairns, Dickson, and Lanza, 1973). Unfor-tunately, comprehensive b i o l o g i c a l i n v e s t i g a t i o n s of several trophic l e v e l s are too time-consuming and costly to be p r a c t i c a l i n most water monitoring programs. This study examined a sin g l e b i o l o g i c a l community, the attached algae, and t h e i r r e l a t i o n s h i p to water q u a l i t y . My aim was to assess how well the attached a l g a l data supplemented t r a d i t i o n a l chemical data to provide a more accurate measure of water q u a l i t y . I t i s s u r p r i s i n g that attached algae have been so l i t t l e studied (Wetzel, 1975) . Unlike most aquatic organisms attached algae are present i n both lakes and r i v e r s and, as primary producers, they occupy an important p o s i t i o n - i n the c u l t u r a l eutrophication prob lem. While basic p h y s i c a l and chemical data were also measured, I extensively examined attached a l g a l n u t r i e n t storage, production, abundance and species composition i n Kootenay Lake, B r i t i s h Columbia. Kootenay Lake 2 appeared to be a p a r t i c u l a r l y s u i t a b l e study area. P o l l u t i o n from one element, phosphorus, and i t s e f f e c t on several processes within the lake has already been documented by several researchers (reviewed i n Northcote, 1973a). Furthermore, the lake's s p e c i a l morphology r e s u l t s i n regions of low, high and intermediate nutrient l e v e l s (Northcote, 1973a) which should allow an easy assessment of the value of attached a l g a l investigations to water q u a l i t y studies. 3 DESCRIPTION OF THE STUDY AREA Kootenay Lake i s a f j o r d lake f i l l i n g a north-south trough i n the Se l k i r k Mountains of southeastern B r i t i s h Columbia (Fig. 1). The Kootenay River flows i n t o the south end of the lake. The other major t r i b u t a r y , the Duncan River, enters at the opposite end of the lake, 105 km to the north. The lake drains v i a the 35 km long, r i v e r - l i k e west arm, which arises midway up the lake. Although surrounded by mountains, only seven percent of the main lake's l i t t o r a l zone i s sheer rock. The remainder has a moderate slope (generally -.lessthfehan' 45'-fdegreesXesahd^nsuppertstaann abundant attached a l g a l f l o r a which grows on boulder-sized pieces of s c h i s t or granodiorite. Near the lake's extremities, sediments s t a r t a t 2-3 m depths, but elsewhere rocks usually predominate to at l e a s t 10 m. The west arm shoreline has a much gentler slope than that of the main lake. Substrate i n the west arm i s usually composed of sand, pebbles, or cobble-sized rocks which, because of frequent.:shifting, seldom allow a lu x u r i a n t a l g a l f l o r a to develop. Infrequent granodiorite boulder outcrops support larger quantities of attached algae. Although there i s l i t t l e domestic or i n d u s t r i a l development along i t s shores, Kootenay Lake i s showing signs of c u l t u r a l eutrophication (Northcote, 1973a). High phosphate additions reach the south end of the lake v i a the Kootenay River i n l e t . Zyblut (1970), Northcote (1972a,b; 1973a,b) and Parker (1972) have documented that, since 1953, a Cominco Ltd. f e r t i l i z e r p l a n t operating 400 km upstream has s i g n i f i c a n t l y contributed to the high 4 F i g . 1. Kootenay Lake showing the sampling stations on the north, south, and west arms. Main l i t t o r a l sampling locations are indicated with s o l i d c i r c l e s , minor sampling locations with open c i r c l e s , and those locations sampled only once are indicated by dots. 5 Kootenay River phosphate loads. The impact of the Kootenay River on the south h a l f of Kootenay Lake i s dramatically i l l u s t r a t e d i n Plate 1. The Duncan River, on the other hand, adds comparatively l i t t l e phosphorus. Since the west arm arises midway between the two r i v e r s , three major lake regions (north 'arm', south 'arm' and west 'arm') with three contrasting nutrient l e v e l s (low, high and intermediate) are p o t e n t i a l l y formed. \ Plate 1. LANDSAT s a t e l l i t e imagery (colour bands 4, 5, 7) of Kootenay Lake, 3 August 1974, showing the influence of the Kootenay River i n l e t on t u r b i d i t y patterns i n the south arm of Kootenay Lake. O r i g i n a l p r i n t i d e n t i f i c a t i o n : Cycle 42, Day 1, Track 47, Frame 25, 3/8/74 - a v a i l a b l e from Integrated S a t e l l i t e Information Services, Prince Albert, Saskatchewan. 7 8 FIELD AND LABORATORY PROCEDURES Sampling Program F i e l d work on Kootenay Lake took place once i n March, weekly from May u n t i l mid-September, and monthly during October, November and December, 1973. In addition, samples were c o l l e c t e d during September 1972 to f a m i l i a r i z e myself with the research area and relevant f i e l d and laboratory methods. During July 1974 I measured some physical parameters on the lake. For personal safety, while sampling the turbulent main lake, r e g u l a r l y sampled research stations were located near highway access, which was generally only a v a i l a b l e on one side of the lake or the other. The lake's large s i z e generally necessitated sampling the lake over a three-day period. As f a r as p r a c t i c a b l e , north arm stations (N1-N12) were sampled on the f i r s t day, south arm s t a t i o n s ( S l - S l l ) on the second day and west arm stations (W1-W7) on the t h i r d day. The only exception was s t a t i o n N12 which, because of highway access,was sampled with the south arm s t a t i o n s . Two stations on each major arm of the lake were selected for intensive study. Those stations (Nl, N5, S2, S5, W2 and W7—black c i r c l e s i n F i g . 1) were sampled weekly from May u n t i l mid-September and once during each of the other months of study. Remaining main lake stations on the highway side of the lake were sampled twice a month from May u n t i l mid-September as were a l l of the remaining west arm stations (open c i r c l e s i n F i g . 1). Once during the study, stations N8 to N i l and S7 to S l l (black dots i n F i g . 1), across from regular north and south arm s t a t i o n s , were sampled to determine i f conditions were s i m i l a r on opposite shores of the lake. 9 Attached a l g a l samples were c o l l e c t e d a t main research stations from 0.1, 1.0, 3.0, and where possible 5.0 m depths. Occasionally, samples were c o l l e c t e d from 10.0 m below the water surface. Those depths were chosen to represent the lake's splash zone as well as regions of high, moderate and low l i g h t i n t e n s i t i e s . Algae were c o l l e c t e d from the other stations at only the 1.0 m depth except once a month during the intensive sampling period when they were c o l l e c t e d at a l l four depths. Physical and chemical measurements were also performed during the a l g a l sampling periods. Temperature p r o f i l e s from the surface to f i v e meter depths, and Secchi disk readings were taken at a l l s t a t i o n s . Main s t a t i o n chemical samples were c o l l e c t e d weekly from the 1.0 m depth and once a month from a l l sampling depths. Water chemistry c o l l e c t i o n s from the 1.0 m depth were made once a month at the minor s t a t i o n s . Physical Measurements At each s t a t i o n , water temperature was measured with a YSI Model 54 oxygen meter. Water transparency was measured with a standard Secchi disk, and once during the study subsurface i l l u m i n a t i o n was measured using a Montedoro-Whitney illuminance meter (Model LMT-8B). Daily b r i g h t sunshine readings (Atmospheric Environment, 1974) taken at the Castlegar a i r p o r t (36 km from Nelson) were used to obtain energy input i n kc a l m - 2 to the surface waters of Kootenay Lake. Chemical Measurements For the purpose of chemical analyses, o n e - l i t e r polyethylene b o t t l e s were f i l l e d with lake water l y i n g d i r e c t l y above the a l g a l substrates. Water 1 0 samples were frozen and usually analyzed w i t h i n two months f o r pH, t o t a l d issolved s o l i d s , a l k a l i n i t y , sodium, calcium, phosphate (ortho, t o t a l and p o l y ) , n i t r a t e nitrogen and s i l i c o n dioxide, by Cominco Ltd. at T r a i l , B r i t i s h Columbia. A l l analyses were performed as outlined i n Standard Methods (American Public Health Association, 1971), or else by modified versions of those methods. A l g a l C o l l e c t i o n s 1. Natural Substrates Rocks approximately 20 cm i n diameter were c o l l e c t e d by d i v i n g , and sampled q u a n t i t a t i v e l y f o r attached a l g a l growth. The s c h i s t or granodiorite rocks were very s i m i l a r i n chemical composition (Dr. L.H. Green, pers. comm.) and I f e e l that differences i n a l g a l populations cannot be a t t r i b u t e d to d i f f e r e n t rock types. I tested t h i s assumption once by incubating the two d i f f e r e n t rock types at the same l o c a t i o n ; both rocks supported almost i d e n t i c a l a l g a l species and biomasses. Furthermore, Fox, Odlaug, and Olson (1969), working i n western Lake Superior, have also concluded that d i f f e r e n t rock types do not a f f e c t attached a l g a l growth i n any way. A nylon brush sampler made from a modified 50 cc syringe (Stockner & Armstrong, 1971) was used to remove the algae from the rocks. Two samples with a combined area of 13.2 cm2 were taken from each rock, so that within rock variance was taken into account. Between rock variance was also consi-dered, algae being frequently sampled from two and even three rocks at each l o c a t i o n and depth. 11 2. A r t i f i c i a l Substrates A r t i f i c i a l substrates with an area of 225 cm2 were used to measure the production of attached algae i n the l i t t o r a l zone of Kootenay Lake. The r e t r i e v a l of a r t i f i c i a l substrates at selected time periods has long been used to measure a l g a l production, and the l i t e r a t u r e i s extensively reviewed by Cooke (1956), Sladecek & Sladeckova. (1964), Sladeckova (1962), and Wetzel (1975) . There are several possible sources of error i n that technique, which I attempted to eliminate. To reduce the substrate's s e l e c t i v i t y to organisms, I used p l e x i g l a s substrates. Peters (MS 1959), according to King & B a l l (1966) and Backhaus (MS 1965) c i t e d i n Wetzel (1965), found p l e x i g l a s and polyethylene substrates to be non-selective. Glass substrates used by many researchers, besides being e a s i l y broken, are s e l e c t i v e towards diatoms, as the s i l i c a i n the glass i s a major diatom c e l l wall constituent. Hohn and Hellerman (1963) even found that the diatoms on glass substrates were not representative of diatoms growing on adjacent natural substrates. Godward (1937) noticed that green algae seldom colonized glass s l i d e s and Tippett (1970) found that succession on glass s l i d e s d i f f e r s from that of natural substrates, but Brown and Austin (1971) noted that algae other than diatoms seldom colonized t h i s substrate. L i t e r a t u r e reports are c o n f l i c t i n g as to where the a r t i f i c i a l substrates should be placed. Many researchers suspend the substrates from l i n e s at mid-lake, but I f a i l to see how t h e i r data could be representative of conditions i n the l i t t o r a l zone. I placed substrates, mounted on 10 kg concrete blocks, on the rocky l i t t o r a l bottom i n h o r i z o n t a l p o s i t i o n . This p o s i t i o n best represented how natural rock surfaces were aligned ( a l l stations 12 had a slope of . l e s s than 30 degrees) . Castenholz (1961) noted that v e r t i c a l plates supported 6-12 times less material than h o r i z o n t a l plates and that the h o r i z o n t a l plate data very c l o s e l y duplicated natural attached a l g a l conditions. The immersion time of the substrates i s also an important f a c t o r which could be a major source of e r r o r . I f incubation periods of l e s s than one week are used, s e t t l i n g apparently exaggerates the production rate (Castenholz, 1960) . During incubation periods greater than one month, a l g a l competition can s e r i o u s l y a f f e c t production rates (Patrick, Hohn, and Wallace, 1954). I therefore incubated and r e t r i e v e d my p l e x i g l a s substrates every two weeks, a time period recommended i n the above studies by Castenholz and Patrick e_t a l . To reduce c o l l e c t i o n disturbances the substrates were r e t r i e v e d by d i v i n g rather than by p u l l i n g up l i n e s or other mechanical methods. As soon as the plates were r e t r i e v e d , the algae were transferred to a sample j a r by use of a razor blade and wash b o t t l e . The a l g a l c e l l s were then immediately preserved with Lugol's s o l u t i o n . Preliminary observations of unpreserved material i n d i c a t e d that the c e l l s were not harmed by t h i s c o l l e c t i o n method. Observations also confirmed Patrick et a l . ' s (1954) contention that dead organisms are only r a r e l y observed, since the diatoms are washed o f f the substrates as they.die. A l g a l A n a l y t i c a l Procedures In the laboratory, each attached a l g a l sample was subdivided f o r biomass determinations, diatom c e l l counts, and enumeration of the r e l a t i v e 13 importance of each a l g a l phyla. 1. Biomass Biomass determinations were performed on every sample by measuring the organic weight of the algae. The organic weight, sometimes r e f e r r e d to as ash-free dry weight or loss on i g n i t i o n , i s the difference between a dry weight (at 60°C) and an ash weight (at 500°C). This procedure e f f e c t i v e l y weighs only c e l l contents, not s i l i c i f i e d materials such as diatom c e l l walls or small rock c r y s t a l s . Chlorophyll a. biomass determinations were performed monthly from May u n t i l September, using methods out l i n e d i n Stockner and Armstrong (1971), and calculated with the SCOR/UNESCO formula given i n S t r i c k l a n d and Parsons (1968). 2. Diatom Enumeration Diatom i d e n t i f i c a t i o n and c e l l counts were made on subsamples which were incinerated or cleaned i n n i t r i c a c i d XPatrick and Reimer, 1966) and then mounted on microscope s l i d e s with Hyrax media. I t was impossible to t e l l i f the prepared diatom f r u s t u l e s represented l i v i n g c e l l s , but preliminary observations of unpreserved material in d i c a t e d that most c e l l s present i n the samples were a l i v e . To enumerate the diatom f r u s t u l e s on the s l i d e , 36 s t r a t i f i e d random f i e l d s (Ennis, MS 1972) were counted with a phase contrast microscope at 800 times magnification. This method resu l t e d i n a mean of 245 fr u s t u l e s being enumerated per s l i d e . This number i s we l l below the 8000 specimens that Patrick and her co-workers (Patrick et a l . , 1954) enumerated f o r t h e i r time-14 consuming 'detailed readings' but i s probably adequate. According to Williams (1964) , counts of 300 i n d i v i d u a l s accurately represent the propor-t i o n a l abundance of the major species. Furthermore, d i v e r s i t y i n d i c e s such as the Shannon-Wiener function can be r e l i a b l y c a l c u lated with numbers i n t h i s range. Patrick (1968) notes that her d e t a i l e d analysis of community structure i s highly correlated with the easier-to-measure Shannon-Wiener function. Diatom species can d i f f e r greatly i n s i z e , and therefore diatom species volumes, as w e l l as numbers, are compared i n the following sections. Only measurements of Kootenay Lake's diatom species were used to calculate c e l l volumes, since the l i t e r a t u r e reports indicate that the same diatom species o f t e n d i f f e r i n s i z e between lakes. For each species, dimensions of ten separate c e l l s were microscopically measured and used to determine average c e l l measurements f or each species. Scaled p l a s t i c i n e models were then constructed, and by comparing water displacements to standards i t was possible to e s t a b l i s h the species volume. Assuming the models were p e r f e c t l y made, the p r e c i s i o n of the technique was found to be 7 pm3. Results are therefore presented to the nearest 10 ym3. The models were not perfect representations of the diatom c e l l s , but I think that even my crudest models would give better r e s u l t s than volumes determined by applying geometric formulae, because diatoms are not p e r f e c t geometrical s o l i d s but have indentations, p r o j e c t i o n s / e t c . The l a t t e r can at l e a s t be approximated by p l a s t i c i n e models, but not by geometric formulae. The works of Patrick and Reimer (1966), Cleve-Euler (1951-1955), Hustedt (1930, 1931-1959) , Huber-Pestalozzi (1942) , Sreenivasa and Duthie 15 (1973) and Weber (1966) were consulted f o r i d e n t i f i c a t i o n of the diatoms. Bourrelly's (1968) taxonomic scheme was followed to place the diatoms i n t o orders and where applicable (diatom genera A-M) I followed the species c l a s s i -f i c a t i o n o utlined by Van Landingham (1967-1971) except that Cynibella oaespitosa was recognized as a d i s t i n c t species. For genera not covered by Van Landingham ( s t a r t i n g a f t e r the genus Melosira) I followed, i n order of preference, the species taxonomy of Patrick and Reimer (1966), Cleve-Euler (1951-1955), Hustedt (1930) and Huber-Pestalozzi (1942). 3. Community Composition I measured the r e l a t i v e abundance of each a l g a l phyla i n the samples with an inverted microscope using methods d e t a i l e d i n Northcote, Ennis, and Anderson (1975). In the inverted microscope sample, Cyanophyta and Chlorophyta species were q u a l i t a t i v e l y measured f o r r e l a t i v e abundance and i d e n t i f i e d using Prescott (1962)and Hoek (1963) . A l g a l Nutrient Analyses I tested November and December a l g a l samples to see i f they stored surplus phosphorus. Stewart and Alexander (1971) demonstrated that, for blue-green algae at l e a s t , excess phosphorus i s stored i n vegetative c e l l s as polyphosphate bodies. These bodies serve as a store of phosphorus for the algae when exogenous phosphorus i s l i m i t i n g . F i t z g e r a l d and Nelson (1966) developed a p r a c t i c a l method which I used to extract the surplus stored phosphorus. The r e s u l t s , besides determining whether or not phosphorus i s 16 l i m i t i n g to growth, can be used to see i f one region has more ava i l a b l e phosphorus than another region, even i f excess phosphorus i s present i n both systems. The technique involves washing the algae several times i n phosphate free water to remove any aqueous phosphorus. The surplus phosphorus i s then extracted from the algae i n a b o i l i n g water bath, and analysed by the stannous chloride reduction procedure outlined i n Standard Methods (American Public Health Association, 1971) . S t a t i s t i c a l R e l i a b i l i t y of the A l g a l Data 1. F i e l d C o l l e c t i o n s By combining two a l g a l subsamples from a si n g l e rock, variance of species counts was proven to be s i g n i f i c a n t l y reduced (Ennis, 1975) . Hence two subsamples per rock were always taken. In Kootenay Lake attached a l g a l growth i s very uniform, and v a r i a b i l i t y between rocks i s much less than i n most lakes and r i v e r s . Once during the study, at s t a t i o n Nl (3 September 1973, 1.0 m depth) ten d i f f e r e n t rocks were sampled to s t a t i s t i c a l l y examine between rock a l g a l v a r i a b i l i t y . A l g a l species counts, biomasses, and diatom d i v e r s i t y between rocks was more variable than on a s i n g l e rock, but not s t a t i s t i c a l l y so (Ennis, 1975) . Frequent c o l l e c t i o n of algae from r e p l i c a t e rocks p a r t i a l l y compensated f o r the inherent between rock v a r i a b i l i t y . 2. A l g a l Enumeration I had s t a t i s t i c a l l y analysed a l g a l enumeration methods using Fraser River attached algae (detailed data i n Northcote et a l . , 1975). Since the Kootenay Lake specimens were prepared by i d e n t i c a l methods, I assume that 17 my previous conclusions s t i l l apply as follows. The diatom subsampling procedure was random and diatoms were always evenly dispersed on the microscope s l i d e s . Also, subsamples always r e l i a b l y depicted the diatom species i n terms of percentage composition, d i v e r s i t y (Shannon-Wiener function), numbers of species present and transformed c e l l numbers. Untransformed t o t a l counts were not random, although the most extreme deviation between subsamples (23 percent) was w e l l within the acceptable l i m i t s suggested by Lund, K i p l i n g and LeCren (1958). Ten subsamples of Fraser River algae taken to t e s t the r e l i a b i l i t y of a l g a l phyla composition data, indicated that 20 percent of the time the abundance of green algae would be overestimated. The large error presumably occurs because the green a l g a l filaments tend to become entangled and cannot be completely separated by vigorous shaking. Large green a l g a l filaments are not as common i n Kootenay Lake as i n the Fraser River, and the p o s s i b i l i t y of e r r o r i n the present study i s probably considerably less than 20 percent. A l g a l Transfer Experiments To determine how algae growing i n one region of Kootenay Lake respond to chemical and p h y s i c a l conditions i n other parts of the lake, r e c i p r o c a l t r a n s f e r experiments were conducted. Although such a technique seems p a r t i c u l a r l y suited to t e s t i n g the e f f e c t s of varying p h y s i c a l and chemical factors on community structure, Parker, Samsel and Prescott (1973) appear to be the only researchers to have previously used such a technique i n the study of attached algae. Eight p l e x i g l a s s plates were immersed simultaneously at the 1.0 m 18 depth of stations Nl, S2 and W7. At each s t a t i o n , a f t e r two weeks' growth, a plate was scraped and the algae preserved f o r laboratory a n a l y s i s . One pla t e was l e f t at the o r i g i n a l s t a t i o n and the remaining s i x plates were transferred, one to each of the other f i v e main s t a t i o n s , plus s t a t i o n SI near the i n l e t of the Kootenay River. As a con t r o l , uncolonized plates were incubated at a l l seven s t a t i o n s . A f t e r another two weeks' growth, a l l the plates were removed f o r laboratory a n a l y s i s . A p i c t o r i a l representation of the experimental procedure i s presented i n Figure 2. 19 C l e a n s u b s t r a t e s T r a n s f e r f r o m C l e a n s u b s t r a t e s ( p l a t e s ) - i m m e r s e d Nl to o t h e r ( c o n t r o l s ) at S t a t i o n N l S t a t i o n s i m m e r s e d Old- j S u b s t r a t e r e m o v e d A l l s u b s t r a t e s for l a b o r a t o r y r e m o v e d for a n a l y s i s of i n i t i a l l a b o r a t o r y a n a l y s i s a b u n d a n c e I T I M E ( W E E K S ) K E Y I New plat l y i m m e r s e d e P l a t e a f t e r 2 w e e k s g r o w t h P l a t e a f te r 4 w e e k s g r o w t h F i g . 2. P i c t o r i a l representation showing how the transfer experiments were conducted f or s t a t i o n N l . Similar transfers were simul-taneously conducted for stations S2 and W7. See text f o r explanation. 20 LAKE PHYSICS Water Input Over h a l f of the surface water (57.9 percent) entering Kootenay Lake i s supplied by the Kootenay River (calculated from Northcote, 1972b). H i s t o r i c a l data (since 1928) show that most of t h i s water used to enter during 'spring' freshet,which l a s t e d from A p r i l to July but peaked to over 14 m3 s e c - 1 i n May and June (Water Survey of Canada, 1974a; F i g . 3). Since 1972 the Libby dam has regulated the Kootenay River discharge, and during the study year (1973) there were two small but d i s t i n c t discharge peaks of about 4 m3 s e c - 1 (Fig. 3). The o v e r a l l e f f e c t of the dam appears to be a more even yearly water discharge into Kootenay Lake. I t seems l i k e l y that the d r a s t i c reduction i n normal spring freshet could s i g n i f i c a n t l y a f f e c t nutrient and t u r b i d i t y inputs to the lake at the beginning of the a l g a l growing period. The Duncan River, the other major i n l e t , supplies 18.5 percent of Kootenay Lake's surface inflow. This i n l e t has been regulated since 1967, and i n 1973 i t had a very unusual discharge pattern (Fig. 4A). (For purposes of i l l u s t r a t i o n the Duncan and Kaslo River discharge data are p l o t t e d on a more expanded scale than are the Kootenay River data.) There was a winter discharge peak (Dec. 1972-Feb. 1973) of almost 3 m3 s e c - 1 , an A p r i l minimum of less than 0.5 m3 s e c - 1 and a 'spring' freshet of about 3 m3 s e c - 1 . A f t e r the 'spring' freshet (July-September) the discharge s t e a d i l y decreased. There are no h i s t o r i c a l data p r i o r to the Duncan Dam operation to compare with 1973's data, but the winter discharge peak i s i n e x p l i c a b l e as f a r as natural water cycles are concerned, and must be r e l a t e d to water regulation. The 21 14 12 H o o •a c o o 0) a a E o Z3 10 6 H m O CC < X o 4 (/) Q 2H ^ 4 6 Year M e a n ( 1 9 2 8 - 1 9 7 3 ) , 1 9 7 3 M a x i m u m D i s c h a r g e (18 M a y ) 1973 -1973 M i n i m u m D i s c h a r g e ( 9 J a n ) 1 1 1 1 1 1 1 1 1 1 1 J F M A M J J A S O N D F i g . 3. Average monthly discharges of the Kootenay River at P o r t h i l l , 42 km upriver from i t s inflow to the south end of Kootenay Lake. S o l i d l i n e s represent 1973 flows, broken l i n e s represent 46 year average flows (1928-1973) . Maximum and minimum 1973 discharges are marked. Data from Water Survey of Canada. 22 D u n c a n River D i s c h a r g e 1973 M a x i m u m D i s c h a r g e (14 A u g u s t ) o o T3 C o o 0) CO 5 2" Q. -1973 M i n i m u m D i s c h a r g e (16 M a r c h ) J ' F ' M 1 A 1 M~ J ' J ' A ' S ' O ' N ' D u O CC < X o w .6-.3-B K a s l o R iver D i s c h a r g e 0973 M i n i m u m D i s c h a r g e (11 F e d ) M973 M a x i m u m D i s c h a r g e (23 J u n e ) J ' F ' M ' A ' M ' J ' J ' A ' S ' O ' N ' D h-2 Hi UJ o CC < X o 0) F i g . 4,. A-1973 average monthly discharges of the Duncan River, 9 km upriver from i t s inflow to the north end of Kootenay Lake. B-1973 average monthly discharges of the Kaslo River 5 km upriver from i t s inflow to Kootenay Lake, just south of s t a t i o n N4. Maximum and minimum discharges are also marked. Data from Water Survey of Canada. 23 discharge curve f o r the r e s t of the year appeared to be normal. Water inflow from several small t r i b u t a r i e s around the lake's margin accounts for 23.6 percent of Kootenay Lake's surface input. Kaslo River, which has a greater discharge than most of the l o c a l t r i b u t a r i e s , has been chosen to represent lake margin inputs since i t i s the only small t r i b u t a r y whose flow i s monitored year round. Kaslo River's discharge, l i k e that of the other small t r i b u t a r i e s , i s not regulated by dams. I t has a more natural discharge cycle, with almost a l l the water entering during spring freshet (May-July; F i g . 4B). Water Level Water l e v e l f l u c t u a t i o n was s i m i l a r throughout Kootenay Lake, with a 1.95 m difference between the maximum and minimum water l e v e l s (Water Survey of Canada, 1974b; F i g . 5). Water l e v e l s are lowest during A p r i l when discharges into the lake are at a minimum. The lake l e v e l increases r a p i d l y i n May (1.3 m i n a week) corresponding to a large increase i n water input with spring freshet. Not a l l water l e v e l changes can be a t t r i b u t e d to r i v e r inputs though; dams on the lake's o u t l e t have affected water l e v e l s since 1938 (Northcote, 1972b). Whatever the cause of water f l u c t u a t i o n , the e f f e c t s on attached a l g a l populations are the same. Whole populations can be e l i m i -nated through exposure, and photosynthesis i s greatly a f f e c t e d by a l t e r e d water, and hence l i g h t , l e v e l s . Solar Radiation The amount of energy entering Kootenay Lake from s o l a r r a d i a t i o n F i g . 5. Water l e v e l s (m) during 1973 i n the north (station N7), south (station SI), and west (station W7) arms of Kootenay Lake. Data from Water Survey of Canada. 25 was not measured d i r e c t l y . However, 388 d i r e c t energy measurements from the mid 1960's (D.B. F i l l i a n , unpublished) were compared to sunshine data c o l l e c t e d simultaneously at nearby Castlegar a i r p o r t (Atmospheric Environment data) and a s i g n i f i c a n t regression r e s u l t e d (Fig. 6). Transformation of the data produced the best r e l a t i o n s h i p , described by the following formula: square root gm c a l per cm2 = 13.01 + (0.9211 x d a i l y b r i g h t sunshine {hrs}). Therefore, 1973 sunshine data (Atmospheric Environment, 1974) were used with the regression equation to estimate energy input to the lake. These data are not formally presented but were used i n multiple regression analyses to account for differences i n attached a l g a l populations. Subsurface Illumination The i l l u m i n a t i o n at depths where a l g a l populations were c o l l e c t e d , and the compensation depths (below which primary producers cannot survive) were seldom measured d i r e c t l y . Secchi disk readings, used to measure Kootenay Lake's transparency, do not provide s u f f i c i e n t information on these f a c t o r s . During July 1974 I measured the compensation depth, defined as the depth at which there i s only one percent of the surface l i g h t , d i r e c t l y with an underwater l i g h t meter. By using t h i s and s i m i l a r data c o l l e c t e d during 1972-1974 by the B.C. P o l l u t i o n Control Branch (unpublished), I was able to e s t a b l i s h a r e l a t i o n s h i p between Secchi disk transparency and the compensation depth (F i g . 7A). A log^g transformation of the Secchi data r e s u l t e d i n a highly s i g n i f i c a n t regression (Fig. 7B) which i s described by the following equation: 1% surface l i g h t = 1.318 + (19.63 x l o g 1 0 Secchi depth) 26 g c a l per s q c m vs S u n l i g h t = 169 .8 + 3 3 . 5 X DAILY B R I G H T S U N L I G H T ( h o u r s ) 5 o UJ CC < o CC LU CL < o o o CC UJ CC < O to 28 H 24 20 -i 16 S q u a r e R o o t g c a l per s q c m v s S u n l i g h t y = 13.01 + 0.9211 X N = 3 8 8 12 8 -* * 4 4* DAILY B R I G H T S U N L I G H T ( h o u r s ) F i g . 6. Relationship between sunshine at Castlegar a i r p o r t and energy input to Kootenay Lake, 1964-1966. A—untransformed data. B—square root transformed to reduce variance. Sunshine data from Atmospheric Environment, energy input data c o l l e c t e d by Mr. D. B. F i l l i a n . . 27 1 P e r c e n t S u r f a c e L igh t v s S e c c h i D e p t h ~ 24H Q. LU O I-X o < u. _ _ LU a 20-I6-12 H 8H x x x X X X * X * x X X X X xxxx 1 XX XX X * X X $ x x * X X XXX XX X XXX X ^ x v * x X * X X X X X X X X 5 1 1 1 1 r - 1 [ -2 4 6 8 10 12 14 S E C C H I D E P T H (m) 1 P e r c e n t S u r f a c e L igh t vs L o g S e c c h i D e p t h S E C C H I r 3 D E P T H 1 4 (m) 1 — 1 — I -8 9 10 F i g . 7. Relationship between Secchi depth and the depth at which only one percent of the surface l i g h t remains i n Kootenay Lake, 1972-1974. A — l i n e a r scale. B — l o g a r i t h m i c scale. Some data from B.C. P o l l u t i o n Control Branch. 28 As a general r u l e , when using the formula, the compensation depth was about three times the Secchi depth. L i g h t i n t e n s i t y drops l o g a r i t h m i c a l l y with depth and i s described by the following c l a s s i c a l equation: XE = V where 1^ i s the irradiance just beneath the water surface (100%), k i s an e x t i n c t i o n c o e f f i c i e n t and 2 i s any depth below the water surface. Since I and the 1% i l l u m i n a t i o n (I ) depth (Z) are known, I can solve f o r the e x t i n c t i o n c o e f f i c i e n t k (which i s merely the slope of the logarithmic curve between the surface and compensation depth see F i g . 8B). Once the extinc-t i o n c o e f f i c i e n t i s known, I can estimate the amount of l i g h t (I ) at any desired depth (2). This procedure i s s i m i l a r to the reasoning of Poole and Atkins (1929) and Idso and G i l b e r t (1974), except that k, the e x t i n c t i o n c o e f f i c i e n t , i s c a l c u l a t e d from empirical Kootenay Lake data and not from general assumptions. The r e l a t i o n s h i p between a d i r e c t l i g h t e x t i n c t i o n p l o t , a logarithmic p l o t of the data, Poole and Atkins' estimate, and my estimate i s i l l u s t r a t e d g r a p h i c a l l y i n Figure 8. By multi p l y i n g the surface energy (solar r a d i a t i o n determined above) by the amount of subsurface i l l u m i n a t i o n , I was able to obtain the energy av a i l a b l e f o r photosynthesis at any given depth. In l a t e r sections I r e l a t e t h i s a v a i l a b l e energy to the attached a l g a l populations. Secchi Disk Transparency Inshore water transparency, measured with a Secchi disk, was lowest at the main lake's extremities where t u r b i d water from the major 29 F i g . 8,. A comparison of measured versus c a l c u l a t e d subsurface i l l u m i n a t l f o r s t a t i o n S5, 4 J u l y 1974. A—measured data p l o t t e d l i n e a r i l y B--measured data p l o t t e d l o g a r i t h m i c a l l y . C — P o o l e and Atkins (1928) estimate based upon the Secchi depth. D—Ennis estimate based upon the Secchi depth (see text for d e t a i l s ) . k i s the e x t i n c t i o n c o e f f i c i e n t (slope of the.curve), 8B i s the actual e x t i n c t i o n c o e f f i c i e n t , 8C and 8D are calculated c o e f f i c i e n t s . 30 i n l e t s enters the system. Transparency was greatest near the confluence of the lake's three arms where most of the suspended sediments had s e t t l e d out. The north end of the lake was consistently c l e a r e r than the south end, with mean summer Secchi depths generally greater than 5 m i n the north and generally l e s s than 5 m i n the south. The influence of the Kootenay River's sediment input on the transparency of the lake's e n t i r e south arm i s i l l u s -t rated i n Plate 1. The west arm, which receives i t s water from the c l e a r e s t part of the main lake, showed high transparency at i t s o r i g i n . Transparency decreased towards the o u t l e t as several small streams increased the west arm's suspended sediment load. Seasonal changes i n transparency were great and l a r g e l y a r e s u l t of changes i n r i v e r runoff. During early spring, before freshet (Fig. 3, 4), lake transparency was greatest, sometimes over 11 m (Fig. 9a, 10). Near the s t a r t of freshet, the lowest Secchi depth readings were generally recorded, being less than 2 m near the major i n l e t s (Fig. 10). During t h i s period r i v e r s were at t h e i r most t u r b i d state, as a r e s u l t of the erosion from the f i r s t snow melt. A f t e r the i n i t i a l freshet, the lake gradually cleared (Fig. 10) and mean summer Secchi depths were often between 5-6 m (Fig. 9b). Increased l i g h t penetration could no doubt enhance a l g a l photosynthesis and i n f a c t , during l a t e J u l y - e a r l y August, a planktonic blue-green alga (Andbaena) became so abundant i n the south arm as to decrease the transparency there (Fig. 10b; compare.with the north arm, F i g . 10a). A f t e r the a l g a l bloom, transparency again became s i m i l a r throughout the en t i r e lake (Fig. 10). During winter 1973 the transparency increased, and was consistently high at a l l stations with a lake mean of 7.22 m (B.C. P o l l u t i o n Control Branch data, unpublished). 31 MAIN L A K E S T A T I O N S , N ' N 8 N 2 N 3 N , 9 N I 0 N , 4 N 5 N 1 , , N 6 N , 2 N 7 S , , S 6 S 5 S 1 0 S 4 S 9 S 3 S 8 S 2 S | S 7 1 | 1 — 1 1 — 1 — i — i — i — i — I — i 1—-J 1—i—I i I i • ! i i' i X I-a, LU Q X o o LU 3H 4H 5H 6 H 7 H 8H ioH iH A • Nor th <- •> S o u t h i W E S T A R M S T A T I O N S W | W 2 W 3 W 4 W 5 W 6 W 7 _l 1 I I L_ -> W e s t _ _ *• I I I A Nl L_ N8 N , 2 N,3 N , 9 N 1 0 N , 4 N s N ) 1 N , 6 N ! 2 N 7 s " S,6 S , 5 S l O S , 4 S,9 S , 3 S 8 S , 2 S i ^ 7 yy, W 2 V y 3 V y 4 v y - W 6 V y -E 2-f 3H a. LU CJ _ 4-X o o LU w 5H 6H B N o r t h 4 - + -> S o u t h - • W e s t O O O F i g . 9. Regional v a r i a t i o n s i n Secchi disk transparency of inshore Kootenay Lake Water, 1973. A — s p r i n g readings; s o l i d t r i a n g l e s represent average values during freshet, open t r i a n g l e s represent single measurements made before freshet. B—summer readings; s o l i d c i r c l e s represent seasonal average, open c i r c l e s represent single samples i n early J u l y . 32 M A M J J A S F i g . 10. Seasonal changes of inshore Secchi disk transparency i n the north arm (station Nl) and south arm (station S2) of Kootenay Lake, 1973. 33 Both the s p a t i a l and seasonal trends i n Kootenay Lake's transparency are s i m i l a r to e a r l i e r data reported by Zyblut (MS 1967) and Northcote (1973a). Kootenay Lake i s more transparent than most other lake types ( i . e . , Wisconsin lakes, Hutchinson, 1957) during winter and early spring, but i s c h a r a c t e r i s t i c a l l y quite t u r b i d during early summer. Summer transparency was greatest i n 1949 before i n d u s t r i a l a c t i v i t y i n the lake's drainage basin (Zyblut, MS 1967; Northcote, 1973a). In the 1960's summer transparency decreased from e a r l i e r values, e s p e c i a l l y i n the south end of the lake. Northcote (1973a) believes that even though nutrients were more p l e n t i f u l there, planktonic photosynthesis was suppressed because of greater t u r b i d i t y . L i g h t often l i m i t s other phytoplankton assemblages and Pieczyfiska and Straskraba (1969) found l i g h t to also be a dominant l i m i t i n g f a c t o r f o r attached a l g a l growth. The recent regulation of the Kootenay River by the Libby dam which acts as a p a r t i a l sediment trap, and the subsequent reduction i n the t u r b i d spring freshet (Fig. 3), probably account f o r greater summer water c l a r i t y now than i n the 1960's. This c l e a r e r water and the subsequent planktonic blue-green a l g a l (Andbaena) bloom during 1973 add support to Northcote's theory that primary production at the south end of the lake was l i g h t l i m i t e d . Water Temperature Kootenay Lake i s a f i r s t c l a s s , temperate, monomictic lake, s t r a t i f i e d from June to October and isothermal f o r the remainder of the year (Zyblut, 1970). Strong wind ac t i o n and the consequent mixing of water prevents 34 the lake from fre e z i n g during the winter. The lake's thermal p r o f i l e has been described i n d e t a i l elsewhere (Zyblut, MS 1967) and I therefore only measured temperatures i n the upper epilimnion (0-5 m) where a l g a l c o l l e c t i o n s were made. Temperature differences i n the upper waters were s l i g h t , with usually only a 1-2°C differ e n c e between the surface and f i v e meters. Conse-quently,, only data from the 1 m depth i s presented (Fig. 11). Occasionally, during calm sunny periods i n the summer, as much as a 7°C differ e n c e d i d occur ( i . e . , 3 Aug. 1973, Station SI; surface - 27.1°C, 5 m - 19.8°C) but such s t r a t i f i c a t i o n d i d not p e r s i s t during windy weather when the epilimnion again began mixing. The upper part of the r i v e r - l i k e west arm was almost always isothermal, as was observed i n previous years by Zyblut (MS, 1967). Temperatures were lowest i n the north end of Kootenay Lake, highest i n the south end, and intermediate i n the west arm (see F i g . 11 for represent-ati v e data). These regional temperature differences were also present i n e a r l i e r years (Zyblut, MS 1967). Differences i n temperature between lake regions were usually le s s than 5°C however, and a l l regions showed the same yearly trends (Fig. 11) . Spring temperatures gradually rose from, near 4°C to. approximately 20°C i n mid-August, and then gradually decreased to December temperatures of just above 4°C (Fig. 11). Currents Attached a l g a l populations are greatly a f f e c t e d by current-carried nutrients, t u r b i d i t y and even sloughed o f f algae. A b r i e f report by MacKay (1951) on temperature i n f e r r e d current patterns i n 1950-1951, documented the ov e r r i d i n g influence of the lake's l a r g e s t i n l e t s , the Duncan and Kootenay 35 F i g . 11. Temperature ( C) f l u c t u a t i o n s of 1.0 m deep inshore water at representative stations i n the north arm (Nl), south arm (S2), and west arm (W7) of Kootenay Lake, 1973. 36 Rivers, on lake currents. Unfortunately, major d e t a i l s of the actual currents are not given i n that report. Subsequent r i v e r r e g u l a t i o n by the Duncan and Libby dams may, at any rate, have changed recent currents from those measured by MacKay. In d i r e c t data, such as the t u r b i d i t y patterns i n Plate 1, do however indicate that the major i n l e t s are s t i l l an important fa c t o r i n determining current patterns. In contrast to the main lake the r i v e r - l i k e west arm of Kootenay Lake had noticeable currents flowing towards the lake o u t l e t . This i s not s u r p r i s i n g since Northcote (1973a) c a l c u l a t e d the west arm's yearly mean renewal time to be 5.5 days, with a renewal time of only 1.6 days during June. At s t a t i o n Wl near the s t a r t of the arm I measured current speeds of 10 m per minute (29 August 1973). In the wider portions of the west arm currents decreased, but i n narrower sections the lake again resumed i t s l o t i c tendencies. 37 LAKE CHEMISTRY Nutrient Loading Few wastes discharge d i r e c t l y i n t o the main basin of Kootenay Lake. Considering the basin's large s i z e , r e l a t i v e l y high turnover rate (1.5 years; Northcote, 1973b), and few inhabitants (only 800 i n the l a r g e s t town; Ennis, 1975), sewage inputs are i n s i g n i f i c a n t . There are few in d u s t r i e s on the lake, and very l i t t l e a g r i c u l t u r e on i t s mountainous shores (Northcote, 1972a). A currently non-operative mine and smelter at Riondel could have, i n the past, added small quantities of sulphates and other materials (Northcote, 1973a). In contrast to l o c a l waste e f f l u e n t s , n u t r i e n t inputs from r i v e r s are important. Kootenay Lake's drainage basin i s immense, covering an area of over 45,000 km2, more than a hundred times the lake's surface area. Even before European col o n i z a t i o n , nutrient loads from the drainage basin entering the lake v i a the main tr i b u t a r y (the Kootenay River) must have been high. Northcote (1973 a, 1973b) calculates that p r i o r to the i n d u s t r i a l i z a t i o n of the Kootenay basin, phosphorus loading to the lake was approaching Vollenweider's (1971) danger l e v e l f o r producing a l g a l blooms, whereas nitrogen loads were not close to c r i t i c a l concentrations. In 1953, Cominco Ltd. began operating a f e r t i l i z e r plant 400 km up the Kootenay River i n l e t (Zyblut, 1970). Phosphate, l o s t i n the extraction process, entered t r i b u t a r i e s to the Kootenay River and i n peak years increased phosphate loadings to the lake by over 8,000 metric tons (Northcote, 1972a,b; 1973a). This 'extra' phosphorus caused loads to Kootenay Lake to exceed 38 Vollenweider's (1971) c r i t i c a l l e v e l (Fig. 12). Loads also exceed c r i t i c a l l e v e l s determined from more r e f i n e d models which account f o r lake f l u s h i n g rates i n addition to mean depths (symbol Ko, F i g . 2 i n Vollenweider and D i l l o n , 1974). Northcote (1973a) describes some b i o l o g i c a l e f f e c t s of the eutrophication with respect to the n u t r i e n t loadings. In recent years 'extra' phosphate loadings have decreased to 1455 metric tons per year, but t o t a l inputs to the lake are s t i l l above c r i t i c a l l e v e l s . N itrate loadings to the lake have not been greatly increased by i n d u s t r i a l i z a t i o n . Loadings have been r e l a t i v e l y constant throughout the years and well below l e v e l s which lead to excessive a l g a l growths (Northcote, 1973a,b; F i g . 12). The west arm of Kootenay Lake, with an average water retention time of only 5.5 days, i s e s s e n t i a l l y d i f f e r e n t from Kootenay's main basin and loadings must be treated d i f f e r e n t l y . The region has more inhabitants, and l o c a l sewage inputs could be more important than i n the main lake. Nelson, j u s t above the lake's o u t l e t , has several small i n d u s t r i e s including a sawmill and r a i l y a r d s , and i n d u s t r i a l waste dumpings into the lake could have deleterious e f f e c t s on organisms near the c i t y . These l o c a l nutrient inputs combined with inputs from the main lake r e s u l t i n high annual phosphorus loadings to the west arm (> 14 g,m 2 ) , e s p e c i a l l y when expressed per u n i t area (since the west arm i s much smaller i n area than the main l a k e ) . Although the short retention time i n the west arm may ameliorate the con-sequences of high n u t r i e n t loadings (Northcote, 1972b), annual inputs do exceed the dangerous value of 6 g -m-2 determined from models which include t h i s retention f a c t o r (Vollenweider and D i l l o n , 1974). 39 P L o a d i n g W e s t A r m N L o a d i n g W e s t A m a> 3CM 20 H 10 o ' i 11 i I I 1 1 1 1 1 "i 'i M i i r I'I 'i o o \00-\ 50 H o I I I I I 1 I I I I I I I I o o •O K o> (S E o z a < o 6 n 5H 4 H 2H i H P L o a d i n g Ma in L a k e Dangerous Loading Level / 11 i 11 i i i i i*i i'i r r i I I I o o o u-> o K O* Ov 5l 3 2 -1 -N L o a d i n g Ma in L a k e Dangerous Loading Leve l I I I I I I I I I I I T I | I I I | | o o o u-> O K 0> Ov F i g . 12. Approximate annual loading l e v e l s for phosphorus (reactive ortho-phosphate expressed as P) and nitrogen ( t o t a l n i t r a t e expressed as N) r e l a t e d to unit surface area of the two major basins of Kootenay Lake, 1949-1970's. Stippled portion of bars represent co n t r i b u t i o n from Kootenay River, shaded portion from Duncan River (excluding Lardeau River f o r N), s o l i d p ortion from l a t e r a l lake margin. Redrawn from Northcote (1972b). 40 Phosphorus Not s u r p r i s i n g l y , considering the increased phosphorus loadings to Kootenay Lake, that nutrient has shown an increase since the 1950's. Ortho-phosphate, the phosphorus compound d i r e c t l y assimilable by algae (McCarty, 1970), has shown over a 50 f o l d increase (Northcote, 1973a). Concentrations were approximately 0 .OOimgjl'-1: i n 1949/1950, but i n the l a t e 1960's dissolved orthophosphate values tended to f a l l i n the 0.05mgjl'-1 range. These l e v e l s exceeded the c r i t i c a l concentration of 0.01 mgjP l " - ' 1 at which a l g a l problems can develop (Vollenweider, 1971; D i l l o n and R i g l e r , 1975). Davis (MS 1973) claims there has been a great reduction i n Kootenay Lake's phosphorus concentrations since 1969 and that the lake i s o l i g o t r o p h i c ; my data and B.C. P o l l u t i o n Control Branch data do not support h i s contention. Water samples from the 1.0 m depth analyzed as a part of t h i s study, generally had concentrations of 0 .02-0 .03 mg^i -- of dissolved orthophosphorus, but samples c o l l e c t e d during spring freshet were usually over 0.05 mg. T - 1 with some samples having con-centrations as high as 0.18 mg l - 1 (Fig. 13). (Chemistry data f o r a l l parameters examined and a l l samples c o l l e c t e d are stored on computer tape, av a i l a b l e from the I n s t i t u t e of Animal Resource Ecology, B i o l o g i c a l Data Centre at the University of B r i t i s h Columbia.) As mentioned previously, most of the phosphorus load to Kootenay Lake enters v i a the Kootenay River at the south end of the lake. The highest dissolved phosphate value (0.18 mg l - 1 ) was recorded i n the south end of the lake. S u r p r i s i n g l y though, l e v e l s of dissolved, t o t a l dissolved and t o t a l i nsoluble phosphate were not consistently higher at the south end of the lake ( F i g . 13, 14, 15). Data presented i n Figures 13-22 usually represents seasonal means which could obscure the gradient, yet even f o r sin g l e samples 41 14H .12-^  .10 H co E UJ i -< x a. in O x 0. H CC o a UJ > -I O w w 08-.06 H .04-.02 H A u t u m n I I S u m m e r S p r i n g 1 o o o N o r t h •< ( • S o u t h O O Nl N 8 N 2 N ' 3 N ^ N ^ 5 Ni l ^ N U ^ s ' l l S'6 S 5 s i o S 4 S " 9 S 3 S ' 8 S2 S'' s'7 M A I N L A K E S T A T I O N S -> W e s t Wiw'2w3w;4w5w'6W7 W E S T A R M S T A T I O N S F i g . 13. Regional v a r i a t i o n s i n dissolved orthophosphate (as P) content of 1.0m deep inshore Kootenay Lake water, 1973. S o l i d symbols represent seasonal averages, open symbols represent single measurements. 42 < o> -10 E .09 H LU I-< o I a a LU > .07 H S 0 6 • co Q _i .05 H <t t-o .04 H .03 H .02 H .01 • o o 0.17 I T 0.14 " ^ ^ A u t u m n / S u m m e r / S p r i n g O O N o r t h -> S o u t h 0.15 A > I 0.31. 0.22 < < West N l " 0 N 2 , , J N 9 , , , u N 4 , " N l l , , 0 N 1 2 , , , S l l 0 0 S 5 0 , u S 4 o y S 3 0 0 S 2 ° l S 7 M A I N L A K E S T A T I O N S W l W 2 W 3 ^ 4 W 5 W 6 W 7 W E S T A R M S T A T I O N S F i g . 14. Regional v a r i a t i o n s i n t o t a l dissolved phosphate (as P) content of 1.0 m deep inshore Kootenay Lake water, 1973. S o l i d symbols represent seasonal averages, open symbols represent single mea-surements. 43 . 0 . 1 9 E -10H < x a w O x Q. 03 _> o < 1-o .09 H .08H .07 H .06 H .05-.04-03H .02 H .01 / S p r i n g 4 4 4 O o $ o A u t u m n ill S u m m e r I o o o N o r t h 4 1 • S o u t h Nl ^ ^ N S N - N i o ^ ^ N l l ^ N W ^ s ' l l ^ S S ^ 0 ^ ^ ^ S ' 8 S 2 S ' ' SV M A I N L A K E S T A T I O N S -> W e s t ~ i i i r ~ W l W 2 W 3 W 4 W 5 W 6 W 7 W E S T A R M S T A T I O N S F i g . 15. Regional v a r i a t i o n s i n t o t a l insoluble phosphate (as P) content of 1.0 m deep inshore Kootenay Lake water, 1973. S o l i d symbols represent seasonal averages, open symbols represent single mea-surements. 44 (as i n d i c a t e d by the open c i r c l e s and open t r i a n g l e s i n the figures) there i s no apparent phosphate gradient. Lack of phosphate gradient could a t t e s t to i t s b i o l o g i c a l u t i l i z a t i o n rather than w i t h i n lake homogeneity of phosphorus. I f the phosphate was u t i l i z e d only by planktonic algae, t o t a l phosphate readings, which include an analysis of c e l l u l a r phosphorus, might show the expected w i t h i n lake pattern. In Kootenay Lake's inshore waters, t o t a l phosphate does not show a gradient probably because of phosphorus u t i l i z a t i o n and storage by attached algae, which are not present i n chemical water samples (see s e c t i o n on attached a l g a l phosphorus storage). Dissolved orthophosphate nut r i e n t l e v e l s are highest i n the spring and lowest during the summer (Fig. 13). Nutrient l e v e l s are exceptionally high i n early May at the s t a r t of freshet (open t r i a n g l e s i n the figures) and decrease i n l a t e r spring. Samples c o l l e c t e d i n early July (open c i r c l e s ) were the lowest i n phosphorus with most concentrations being 0.02 mg l - 1 or l e s s . The summer decrease i n phosphorus i s apparently common i n a l l lakes. I t i s often a t t r i b u t e d to b i o l o g i c a l u t i l i z a t i o n . Loadings (calculated by multipl y i n g r i v e r concentrations by discharge) of phosphorus and other chemical ions are also less during the summer, since less water enters the lake then than during spring freshet. Because of the summer decrease i n phosphorus, Vollenweider (1971), D i l l o n and R i g l e r (1974), Edmondson (1972) and others use lat e winter or spring maximum phosphorus values i n determining a lake's trophic state and p r e d i c t i n g the.planktonic a l g a l biomass f o r the next summer. The occurrence of a blue-green a l g a l bloom during summer 1973 on Kootenay Lake was not unexpected, considering i t s high (> 0.05 mg l - 1 ) spring orthophosphate concentrations. 45 Phosphate concentrations i n the west arm of the lake show the same seasonal trends as i n the main lake. Levels are comparable to the main lake and increase towards the lake o u t l e t , although the trend i s not consistent. Loading data i n t h i s region of the lake has shown very high l e v e l s (Northcote, 1972b, 1973a), which cannot be a t t r i b u t e d to the phosphate f e r t i l i z e r p l a n t operations alone. Dissolved orthophosphate varies with depth (Table I ) . Water from 0.1 m depth had the lowest concentrations (0.02-0.025 mg l - 1 averages). Des-p i t e the vast differences i n loadings to the north and south arms of the lake, a phosphorus gradient d i d not occur w i t h i n the lake. Water from the 3.0 m depth had the highest amounts (0.02-0.07 mg. I - 1 averages) of orthophosphate. While there was not a d e f i n i t e phosphate gradient at the 3.0 m depth, the south arm of the lake d i d have the highest l e v e l s . T o t a l dissolved phosphorus and t o t a l insoluble phosphorus showed trends that were s i m i l a r to those f o r dissolved orthophosphate (Fig. 13, 14, 15). There were no nutrient gradients within the lake, and spring values were higher than summer values. Levels of t o t a l dissolved phosphorus are generally 0.03-0.04 mg 1 1 , only 25% higher than dissolved orthophosphate l e v e l s . Total i n s o l u b l e phosphorus had a concentration of around 0.03 mg 1 1 and was not as variable as the other phosphate species. Nitrogen The main inorganic nitrogen forms found i n water are dissolved nitrogen gas, ammonia, n i t r a t e and n i t r i t e s a l t s (McCarty, 1970). In well oxygenated lakes such as Kootenay, n i t r a t e - nitrogen i s dominant and the 46 Table I. Mean dissolved orthophosphate (as P) content of inshore Kootenay Lake water at the 0.1, 1.0, 3.0, and 5.0 m depths. Depth S t a t i o n Nl .N5 S5 S2 W2 W7 0.1m .025 .023 .023 .020 .023 .023 1.0 m .027 .030 .030 .028 .027 .027 3.0 m .020 .028 .073 .035 .020 .038 5.0 m - .025 .037 .020 .020 .030 47 only form l i k e l y to be u t i l i z e d by autotrophs (Keeney, 1972; Lee, 1970; McCarty, 1970). Nitrate - nitrogen concentrations i n Kootenay Lake's 1.0 m mid-lake water ranged from 0.02-0.09 mg l - 1 with no apparent w i t h i n lake gradient (B.C. P o l l u t i o n Control Branch, unpublished data; F i g . 16). Inshore n i t r a t e values obtained during t h i s study are not presented, as laboratory problems in v a l i d a t e d the r e s u l t s . However, there i s probably l i t t l e difference between inshore and mid-lake n i t r a t e readings. Inshore n i t r a t e samples c o l l e c t e d during 1971 (Water Quality Branch, 1974) had l e v e l s of about 0.05 mg l - 1 which are comparable to mid-lake concentrations. Nitrate concentrations have shown l i t t l e change from 1949 to the present, which i s not s u r p r i s i n g since n i t r a t e loadings to the lake have shown l i t t l e change (Northcote, 1973a). Total Dissolved Solids Total dissolved s o l i d s (TDS) content of Kootenay Lake 1.0minshore water usually ranges from 50-80 mg l - 1 , with some values near spring freshet being over 100 mg l - 1 (Fig. 17). These data tend to be lower than concentra-tions of 80-100 mg l - 1 reported by Northcote (1973a). Kootenay Lake's TDS l e v e l s are t y p i c a l of B r i t i s h Columbia waters, l e v e l s of 100 mg l - 1 being close to the average obtained from a study of 100 B.C. lakes (Northcote and Larkin, 1956) . Regionally, there are more t o t a l dissolved s o l i d s i n the south end of the lake, concentrations decreasing northward except f o r a s l i g h t increase at s t a t i o n Nl near the Duncan River i n l e t . West arm TDS concentrations are s i m i l a r to south arm concentrations. 48 .08 H cn E .06-S p r i n g z UJ o o cc < CC t-1 .04 H / A u t u m n .02-^ S u m m e r North<4- -> S o u t h — i 1 m i N4 N5 S l l S5 57 35 34 33 M A I N L A K E S T A T I O N S S2 S i 32 31 < P C B S t a t i o n N o s . ) F i g . 16. Regional v a r i a t i o n s i n dissolved n i t r a t e nitrogen content of 1.0 m deep midlake Kootenay Lake water, 1973. S o l i d symbols represent seasonal averages, open t r i a n g l e represents a sin g l e measurement i n June. Drawn from data supplied by the B.C. P o l l u t i o n Control Branch. 49 130-120-110-100 9 0 -8 0 -70 60-50-j 40 S p r i n g . g -° • o * I S u m m e r \ . -N o r t h •« -A u t u m n •> S o u t h A -> W e s t Nl ^ N ^ N V " ' 0 ^ ^ 1 1 ^ 1 2 N ' 7 S U S ' 6 S > ' 0 S 4 S ' 9 S 3 S ' 8 S2 & sV W, W 2 W 3 W 4 W 5 W 6 W 7 Regional v a r i a t i o n s i n t o t a l dissolved s o l i d content of 1.0 m deep inshore Kootenay Lake water, 1973. S o l i d symbols represent seasonal averages, open symbols represent single measurements. 50 A l k a l i n i t y and pH Carbon i s p l e n t i f u l i n Kootenay,Lake with t o t a l carbon ( a l l i n the form of CO2 and HCO3-) concentrations of between 45-65 mg l - 1 (Fig. 18). Highest a l k a l i n i t y concentrations (often > 60 mg l - 1 ) occur i n Kootenay Lake during spring freshet; lowest concentrations (often < 50 mg l - 1 ) occur during the summer (Fig. 18). A l k a l i n i t y , according to mean summer values, i s highest i n the south end of the lake (generally > 50 mg l - 1 ) and decreases northwards (generally < 50 mg l " 1 ) (Fig. 18). Transport of carbon ions by the Kootenay River into the south end of the lake probably creates the gradient. A l k a l i n i t y l e v e l s i n the Kootenay River just before i t enters Kootenay Lake are higher than the lake l e v e l s (Northcote, 1973a). Carbon compounds are i n t r i c a t e l y connected i n pH rela t e d e q u i l i b r i a . Decreases i n COg caused by a l g a l u t i l i z a t i o n r e s u l t i n HCO3 s h i f t s to C0 2 and subsequent decreases i n hydrogen ions r e s u l t i n pH increases. The gradual reduction i n Kootenay Lake's a l k a l i n i t y over the years (Northcote, 1973a) and the corresponding increase i n pH are probably caused by denser a l g a l popula-t i o n s . pH values of between 7.5 and 8.0 that I recorded (Fig. 19) are lower than 1960 l e v e l s , and are more c h a r a c t e r i s t i c of early 1950 conditions. This trend perhaps indicates that a l g a l populations, i n response to s l i g h t l y lower phosphate concentrations, are no longer increasing. S i l i c a Concentrations of s i l i c a i n 1.0 m Kootenay Lake water range from 1.0 to 7.0 mg 1 - 1 (Fig. 20) and are comparable to a 1961 value of 2.0 mg 1 1 (Engineering D i v i s i o n Health Branch, MS 1965) . During t h i s study, l e v e l s were highest i n the spring freshet period and lowest i n the summer, a f t e r loadings decreased and a f t e r diatom c e l l s u t i l i z e d much of the s i l i c a (Fig. 20). 51 F I G U R E 18 O (J ra O 70 H « 65-E Z < < o 6 0 H 55 H 50H 45 H 40 I N o r t h • « -O O - • S o u t h Nl N 8 N 2 N 3 N 9 N 1 0 N 4 N 5 N „ N 6 N 2 N 7 S l l S 6 S 5 S , 0 S 4 S 9 S 3 S 8 S2 S l S 7 M A I N L A K E S T A T I O N S A •> W e s t W l W 2 W 3 W 4 W 5 W 6 W 7 W E S T A R M S T A T I O N S F i g . 18. Regional v a r i a t i o n s i n t o t a l a l k a l i n i t y of 1.0 m deep inshore Kootenay Lake water, 1973. S o l i d symbols represent seasonal averages, open symbols represent si n g l e measurements. F I G U R E 19 8.5 H 8.0-o. 7.5 H 7.0 A 6.5 , S u i n m e r ^ A u t u m n S p r i n g ! I I I N o r t h 4 1 • S o u t h •> W e s t Nl N ' 8 N2 N ' 3 N9 N ' 1 0 N4 " 5 N ' „ ^ N> s ' n So s ' 5 S l O s ' 4 S9 s ' 3 S8 s ' 2 Sl g"7 MAIN L A K E STATIONS Wl W 2 W 3 W 4 W 5 W o W 7 W E S T A R M S T A T I O N S F i g . 19. Regional v a r i a t i o n s i n pH of 1.0 m deep inshore Kootenay Lake water, 1973. S o l i d symbols represent seasonal averages, open symbols represent single measurements. 52 Concentrations d i d not drop below 1.0 mg 1 , which i s well above the c r i t i c a l l e v e l of 0.1 mg Si02 l - 1 which Schelske and Stoermer (1971) claim to be s i l i c a ' s l i m i t i n g concentration. A study of the lake's sediments indicates that large amounts of quartz ( s i l i c a ) p a r t i c l e s are washed in t o the lake from the Kootenay River i n l e t , which would compensate f o r diatom depletions (Ennis, Northcote, and Stockner; unpublished). S i l i c a concentrations are s l i g h t l y higher i n the south arm of the lake (> 2.5 to 7.0 mg l - 1 ) than i n the north and west arms (1.0 to 5.4 mg l - 1 ) (Fig. 20). Calcium Calcium concentrations i n Kootenay Lake are above 16 mg l - 1 , and are u n l i k e l y to a f f e c t a l g a l growth since calcium i s needed i n only trace amounts. Spring and average summer concentrations i n the lake show a pronounced gradient with higher l e v e l s at the south end of the lake (Fig. 21). The cation can be reduced with photosynthesis though, through chemical p r e c i -p i t a t i o n . A reduction i n HCO3 a l k a l i n i t y by a l g a l incorporation causes an increase i n pH which decreases the s o l u b i l i t y of Ca and there i s CaC03 p r e c i p i t a t i o n (Ruttner, 1963) . This could explain the July calcium minimum and reverse north-south gradient, since higher phosphate inputs to the south end of the lake allow greater a l g a l populations to e x i s t there, and more p r e c i p i t a t i o n of calcium to occur. Shortly a f t e r the July calcium minimum a planktonic blue-green (Anabaena) a l g a l bloom became noticeable at the south end of the lake. Sodium Sodium i s the most abundant member of the a l k a l i - m e t a l group £ LU Q >< O Q Z o o • 8H 6 4-2-0 53 FIGURE 20 t I llo I | o l I l o S » o . o J o t l o l i l t . . , North 4 - -*• South ->• West Nl ^8 N ' 2 N3 M ' oN10 , N'5 „'„ N6 J„tt: N9' 7 o'„ S6 0 ' c SlO N4" JN11 " " N 1 2 " ' S l l o u S5 MAIN LAKE STATIONS S4 S 9 S 3 S 8 S 2 S ' S7 |Wl W 2W 3 W 4 W 5 W 6 W 7 WEST ARM STATIONS F i g . 20. Regional v a r i a t i o n i n s i l i c a (Si0 2) content of 1.0 m deep inshore Kootenay Lake water, 1973. S o l i d symbols represent seasonal averages, open symbols represent single measurements. 24H L 22 14-FIGURE 21 o E 4 i t w 20-_ _ 18-1 1 0 i o o i o _i < o 16-< » < • > II 1! i . • t « North 4 -O O O O -> South -> West N l N8 N'3 ' N'lO ' N 5 M ' rJ6. N2 " J N 9 JN4 " - ' N i l , , , UN12 N 7S11 S 6 S 5 MAIN LAKE STATIONS Regional v a r i a t i o n s i n calcium content of 1.0 m deep inshore Kootenay Lake water, 1973. S o l i d symbols represent seasonal averages, open symbols represent single measurements. . S 1 0 S 4 S 9 S 3 S 8 S ' 2 S ' , g'7 F i g . 21. WEST ARM STATIONS 2.0-\ _ 1.5-i 0.5 FIGURE 22 Spring & \ Autumn A Summer North 4-Nl N 8 N 2 N 3 N 9 N 1 0 South 1-N4 N 5 Nil N ' 6 N ,2 N > Si, S ' 6 S5 S ' 1 0 S 4 S'9 s V ^ S ^ ^ s T MAIN LAKE STATIONS 1*1..»• -> West WI W 2 W 3 W 4 W 5 W 6 W 7 WEST ARM STATIONS F i g . 22. Regional v a r i a t i o n s i n sodium content of 1.0m deep inshore Kootenay Lake water, 1973. S o l i d symbols represent seasonal averages, open symbols represent single measurements. 54 (Hem, 1970), but i s needed i n only small amounts f o r a l g a l growth. Con-centrations i n Kootenay Lake are generally under 2.0 mg l - 1 . There i s a d i s t i n c t gradient i n the lake with highest values (2.3 mg l - 1 ) at the south end, and lowest values (1.0 mg l - 1 ) at the north end (Fig. 22). 55 ATTACHED ALGAE Abundance 1. Chlorophyll a_ Highest chlorophyll a values recorded i n t h i s study (readings up to 63 yg cm ~ 2) occurred at the 0.1 m depth, during periods of stable water lev e l s ( F ig. 5) i n early May. ( B i o l o g i c a l data f o r a l l samples c o l l e c t e d are stored on computer tape, av a i l a b l e from the I n s t i t u t e of Animal Resource Ecology, B i o l o g i c a l Data Centre at the University of B r i t i s h Columbia.) However, water l e v e l s usually fluctuated throughout the summer and chlorophyll a. content near the lake surface was l e s s , on the average, than at other depths. (Fig. 23, 24) . Chlorophyll a. content was also low at the 1.0 m depth (Fig. 23) with values near 3 yg cm ~ 2 i n the south arm and lower values elsewhere. Data from the 3.0 m depth (Fig. 23) also indicate that attached a l g a l populations are densest i n the south arm, with average chlorophyll a_ readings of about 8 yg cm ~ 2 of rock surface. At t h i s depth, chlorophyll gradually decreases to about 3 yg cm ~ 2 at the uppervend of the north arm and to about 2 yg cm at s t a t i o n W7 at the lower end of the west arm. St a t i o n S6 located i n Crawford Bay, i s o l a t e d from the main lake, has an unusually high chloro-p h y l l content of about 17 yg cm 2 . Amounts and d i s t r i b u t i o n of chlorophyll at the 5.0 m depth (Fig. 23) are s i m i l a r to patterns recorded at the 3.0 m depth. Both the 3.0 and 5.0 m depths also had t h e i r highest chlorophyll a. content during summer (Fig. 24) , i n contrast to the spring maximums at the 0.1 and 1.0 m depths. 2. Organic Weight Organic weight estimates of community biomass d i f f e r e d somewhat from 56 CM I E o N I 4 73;»i * * n i , 6 4 » 3 * i < ij*<7 * . » i > N,8 , 3 ,10 4 5 „ 6,2 7g„6 510 4 9 , S , ?|V< North. —| .South Ni« 7 4 > . »i'i " l i 'Sn 4 i » i * i" 4 i '• i 7 North. 1 .South .West F i g . 23. Regional v a r i a t i o n s i n yearly average chlo r o p h y l l a. concentrations at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973. S o l i d c i r c l e s represent yearly averages, open c i r c l e s represent single measurements i n early J u l y . 57 CM r cn 5.0 m 1 - o ' so-• I ld— _ o 1 • 1 • 12— • • 8 — o — • • o o - l o *o > • 1 ' O 0 • Nl B 2 9 1 0 4 ^ 11 'li 'Sll* i R A 4 ' i 8 i i 7 North'" 1 »South -•West F i g . 24. Regional v a r i a t i o n s i n average summer chlor o p h y l l a_ concentration at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973. S o l i d c i r c l e s represent summer averages, open c i r c l e s represent single measurements i n early J u l y . 58 chlorophyll a. estimates (Fig. 25) . Whereas ch l o r o p h y l l a_ content increased towards the south end of the lake, organic weights were s i m i l a r (some-depths had s l i g h t l y more organics i n the south arm) throughout the main lake. This difference i s s u r p r i s i n g , as a regression of organic weight versus chloro-p h y l l a. showed the two estimates of biomass to be highly c o r r e l a t e d (Fig. 26) . But at low biomasses the r e l a t i o n s h i p between organic weight and chlorophyll a. e x h i b i t s much sc a t t e r (Fig. 26), which may p a r t i a l l y explain the d i f f e r e n t trends i n the two parameters. Moreover, the sampling schedule probably accounts for most of the d i f f e r e n c e s . Three of the f i v e chlorophyll sampling periods were during summer, when phosphorus l e v e l s were low and therefore l i k e l y to l i m i t the a l g a l populations. The higher chlorophyll abundances i n the south arm (where phosphorus loading i s highest) are therefore not unexpected. Organic weights were sampled up to twenty times during the study, on several occasions during high phosphorus conditions when that nutr i e n t was less l i k e l y to l i m i t a l g a l abundance. An organic weight gradient (using yearly averages) would therefore be l e s s l i k e l y than a chlorophyll gradient. However, during early July when phosphorus concentrations were low, organic weights were consistently greater ( p a r a l l e l i n g chlorophyll a_ results) i n the south arm of the lake than i n the north arm (Fig. 27). Yearly mean data (Fig. 27) d i d show both the 1.0 and 5.0 m depths to have s l i g h t l y more organic weight determined biomass i n the south arm of Kootenay Lake than i n the north arm. There was no obvious yearly regional v a r i a t i o n at the 0.1 and 3.0 m depths. The v e r t i c a l d i s t r i b u t i o n of biomass determined by organic weight was s i m i l a r to the chlorophyll a pattern, with the shallower 0.1 and 1.0 m 59 Nl» 2 3 9 1 0 4 5 n «,2 'Sll4 5 1 0 ' ' 3 8 j ' ?l Norths 1 .South CM I E o O) E ,Wl ], 3 ^ 5^7 -•West Nl 8 2 3 9 1 0 4 5 11 6 12 'Sir* 5 1 0 4 ' i 8 j ' 7|W|; 3 4 ' t ' North. 1 .South .West I O LU 3 Z < o DC o Nl8 i 3 J ' 6 . . * ,', ',3 'Snr5 '°4 ' j "1 p5"^ North. 1 .South .West Nl8 1 3 9 1 0 4 5 „ 4 ,2 7Sll6 5 1 0 4 ' 3.8 2 North. 1 .South F i g . 25. Regional v a r i a t i o n s i n yearly average organic weight l e v e l s at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973. S o l i d c i r c l e s represent yearly averages, open symbols represent single measurements. 60 25 20-15-0.1 m data N = 151 y = 0.4 785 + 0.3693 x o o o *y 10--l 1 1 r 0 1 m data N = 144 y = 0 4652+ 0.3781 x O ©O .' ~10 20 30~ 40 50 60 70 "0 o o " o o I— 10 —i— 20 30 15-o rx o i o n 5H 3 m data N = 124 y = 0.6428+ 0.2969x ° o ° / y ° y y y OS o o O o —r-10 20 T— 0 5 m data N = 89 y = 0 6860 + 0.2140x o o o 30 40 0 CHLOROPHYLL a f^ igcm" ' ) 10 - 1 — 20 30 F i g . 26. Relationship between organic weights and chlo r o p h y l l a. for 510 attached a l g a l samples at 0.1, 1.0, 3.0, and 5.0 m in~~Kootenay Lake, 1973. 61 I £ o CO E North. ( .South .West 1.0 m • o ° 00* o. I-V Nl 8 2 3 9 10 4 S II 6 12 7Sll6 5 10 4 * 3 8 2 1 7fV' 2 3 4 5 « 7 North. 1 .South .West X a UJ 5 o z < o cc o Nl8 2 3 9 1 0 < 5 II « I2 7 S » 6 S 1 0 4 » 3 8 2 frV'i : North. 1 .South .West N>I 3 . KI t 3 „ 4 | 2 7 S „ » s » , I , i ; North-" 1 .South West F i g . 27. Regional v a r i a t i o n s i n average summer organic weight l e v e l s at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973. S o l i d c i r c l e s represent summer averages, open c i r c l e s represent si n g l e measurements i n early J u l y . 62 depths having less biomass (generally < 2 mg cm - z ) than the 3.0 and 5.0 m depths (generally > 2 mg cm ~ 2; F i g . 25). Data from a single sampling period i n e arly September (Fig. 28) c l e a r l y shows the v e r t i c a l d i s t r i b u t i o n of both chlorophyll a_ and organic weight determined biomass. In both the north and south arm st a t i o n s , biomass increases to the 5.0 m depth and then decreases. On a r e l a t i v e basis (note d i f f e r e n t scales i n F i g . 28), organic weight indic a t e d greater biomass than chlorophyll at the shallower depths, but the reverse was true at the deeper depths. More chlo r o p h y l l i s probably needed at the lower depths to u t i l i z e the reduced l i g h t energy. Regressions u t i l i z i n g data from 510 samples that were analyzed for both organic weight and chl o r o p h y l l a also showed that below the 1.0 m depth the amount of chlorophyll a_ increased r e l a t i v e to the organic weight (Fig. 26). The seasonal v a r i a t i o n of organic weights p a r a l l e l e d the chlorophyll a_ pattern. An early May biomass peak at 0.1 m produced the highest organic weight values i n the study, with one sample having 26.5 mg organic cm ~ 2 . Biomass at 0.1 m were very low during the r e s t of the year (Fig. 29), with a s l i g h t increase i n August when fl u c t u a t i o n s i n water l e v e l were s l i g h t . Spring readings were also generally higher than summer readings at the 1.0 m depth (Fig. 27). As observed with the chlo r o p h y l l data, the deeper 3.0 and 5.0 m depths had higher values i n summer than i n spring. Winter values were close to the yearly means, except at the 1.0 m depth where organic weights were very high, e s p e c i a l l y i n the north arm of Kootenay Lake. Phosphorus Storage Water extractable (surplus) phosphorus storage i n algae ranged from about 0.15-2.50 yg P mg - 1 dry weight (Fig. 30, A). Lowest amounts 63 C H L O R O P H Y L L a ( j jg c m " ' ) X r-a LU a 5 _ l : N O R T H A R M N 5 2 S e p t 1 9 7 3 10 0-1 -L9.Q m mm w w l i W*V W W w w J w K v w w ) w w J w w 5 w*w WW* w*w w*w w K v w*w w K v w*w w*w w*w w l w w*w w*w w*w w K v v K w w l w w l w w *w w*w :wW: wW:« V W W w % w w * w w K v w * w w J w w * w w ; w w l w w * w w * w w * w w * w 15 _ L _ O r g a n i c W e i g h t C h l o r o p h y l l a 10 A-O R G A N I C W E I G H T ( m g c m " 2 ) F i g . 28. V e r t i c a l v a r i a t i o n s i n the amount of c h l o r o p h y l l a and organic weight at a north arm (N5) and a south arm (S5) s t a t i o n i n Kootenay Lake; 1, 2 Sept. 1973. 64 F i g . 29'. Seasonal v a r i a t i o n s i n the organic weight content of attached algae at 0.1 m' i n a north (Nl), a south (S2), and a west (W7) arm s t a t i o n i n Kootenay Lake, 1973. 65 of stored phosphorus, with some values below 1.0 yg mg - 1 , occurred only i n samples from north arm stations and i n the westernmost s t a t i o n . Higher l e v e l s , i n d i c a t i n g more eutrophic conditions (Lin, 1971), occurred i n the south arm of the lake where readings were always above 1.0 yg mg _ 1 dry weight algae. The surplus phosphorus gradient i s not unexpected since phosphate loadings to the south- end of the lake are high while north end loadings are low (Fig. 12). Paradoxically, the water phosphate data (Fig. 13-15) do not show south arm stations to be higher i n phosphate, perhaps because i t i s ra p i d l y picked up and stored by attached a l g a l populations. In addition to ambient phosphorus l e v e l s , a l g a l abundances could influence the surplus phosphorus r e s u l t s . Low biomass i n one region, for instance, could increase the surplus phosphorus l e v e l s per u n i t algae since there would be less algae to u t i l i z e the phosphorus. Consideration of the amount of surplus phosphorus per unit area of rock surface (Fig. 30, B) indicates that a l g a l abundances have not greatly a f f e c t e d the surplus phosphorus gradient, except that the 0.1 m depth of s t a t i o n S5 has a lowered concentration. Surplus phosphorus ranges from about 5-30 yg cm ~ 2 rock surface with highest values i n the south arm and lower values i n the north and west arms of Kootenay Lake. Production Attached a l g a l production was measured every two weeks from early May u n t i l mid-September. Daily growth rates near the lake surface (0.1 m depth) ranged from about 0.001 to 0.05 mg organic cm ~ 2 , with highest values i n the south arm of the lake (Fig. 31), production decreasing both northwards and westwards. Contrary to the biomass r e s u l t s , highest production occurred A 66 2 H E 0) 1 m < i -o < CC 1-X LU N o r t h B 3.0 mg 20 H Mean 4-10 H P A I 0.1 m A 1.0mo N l N5 S 5 S2 W2 W 7 N o r t h S o u t h " W e s t F i g . 30. A—Regional v a r i a t i o n s i n the amount of b o i l i n g water extractable phosphorus per mg dry weight algae at 0.1, 1.0, and 3.0 m i n Kootenay Lake, Nov.-Dec. 1973 . B—Regional v a r i a t i o n s i n the amount of b o i l i n g water extractable phosphorus per cm2 rock surface at 0.1, 1.0, and 3.0 m i n Kootenay Lake, Dec. 1973. 67 0.1 m « .04 CM £ u .2 .02 j c ra cr co 1 1 0 C z g H O Q O CC o. s p r i n g A N3 S5 • S2 N o r t h - * 1 ^ S o u t h W2 W7 — » » W e s t .02 H 3.om No Ciedophora growth r i N o r t h -S5 S2 , W2 - S o u t h - W e s t N o r t h . • S o u t h | w , W 2 „ 3 w V 5 w V * - W e s t .01 i 0 5.0 m No Cladophoro growth i f S2 W2 N o r t h - - S o u t h - W e s t F i g . 31. Regional v a r i a t i o n s i n average d a i l y production (measured as mg organic cm"2) of attached algae at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973. Horizontal bars represent yearly averages, s o l i d symbols represent seasonal averages and open symbols represent si n g l e measurements. 68 i n the summer rather than i n the spring. This i s probably an a r t i f a c t of the sampling schedule, as the spring biomass peak occurred p r i o r to measure-ments of growth rates. S t a t i o n Wl, a t the mouth of the west arm, was unique i n having a spring growth peak one week l a t e r than at the other s t a t i o n s . Production at the 1.0 m depth there, from 8-23 May, 1973, was the highest recorded i n t h i s study (average d a i l y growth rate of 0.32 mg organic cm ~ 2) . At the 1.0 m depth, annual d a i l y growth rates were generally about 0.02 mg organic cm ~ 2 i n the productive south arm of the lake, decreasing to about 0.005 mg organic cm - 2 a t the north and west extremities. Except f o r the 1.0 m depth at stations Wl and W6, growth rates were greater i n the summer than i n the spring at the 1.0, 3.0 and 5.0 m depths. Regional v a r i a t i o n s i n growth rates at the 3.0 and 5.0 m depths were minimal, with s l i g h t l y greater production i n the north arm than i n the south arm. Average d a i l y production values at the 3.0 and 5.0 m depths were approximately 0.01 and 0.005 mg organic cm ~ 2 r e s p e c t i v e l y . Rates of growth were much lower than at the 0.1 and 1.0 m depths, which i s s u r p r i s i n g since biomasses were greater at the deeper depths. Reduced energy input may have resul t e d i n slower growth at these depths. In the south arm production i s undoubtedly underestimated, since the large green alga Cladophora aegagropila (L.) Rabh., a major component of the south arm a l g a l community at the deep depths, d i d not grow on the p l e x i g l a s production substrates (see more de t a i l e d discussion below). I f Cladophora could have grown on the a r t i f i c i a l substrate, i t seems l i k e l y that there would also have been a marked production gradient at the 3.0 and 5.0 m depths with highest values i n the south arm of Kootenay Lake. 69 Community Composition Diatoms (Chrysophyta-Bacillariophyceae) consistently dominated the attached a l g a l f l o r a of Kootenay Lake (Fig. 32). Green (Chlorophyta) and blue-green algae (Cyanophyta) were also present i n most samples. In addition, three other a l g a l groups (Pyrrhophyta, Cryptophyta, and Chrysophyta-Chrysophyceae) were occasionally present, but never contributed greatly to the a l g a l biomass. 1'. Natural Substrates At the lake surface (0.1 m depth) the attached a l g a l f l o r a was composed mainly of diatoms (roughly 75-85 percent by volume) and green algae (10-20 percent)(Fig. 32). Blue-green algae made up about 5 percent of the a l g a l biomass i n the main p a r t of the lake, increasing to approximately 20 percent i n the populated west arm. Regional v a r i a t i o n i n the percent com-p o s i t i o n of the a l g a l community was great but, except f o r the increase i n blue-green algae along the west arm, there were no c l e a r trends evident. A s i m i l a r s i t u a t i o n p r e v a i l e d at the 1.0 m depth except that diatoms were s l i g h t l y (about 5 percent) more abundant and green algae less abundant than a t the lake surface (Fig. 32). At the 3.0 and 5.0 m depths, the a l g a l community exhibited d e f i n i t e regional trends i n the percentage abundancies of diatoms, green algae and blue-green algae (Fig. 32). At the south end of the lake about 80 percent of the attached algae consisted of diatoms. Diatom abundance s t e a d i l y increased to over 90 percent at the north end of the lake. Green algae had an opposite gradient, forming less than 5 percent of the biomass at the north 70 •South .West North. '• h - .South .West F i g . 32. Regional v a r i a t i o n s i n average percentage abundance (by volume) of diatoms, green algae and blue-green algae attached to natural rock substrates at 0.1, 1.0, 3.0 and 5.0 m i n Kootenay Lake, 1973 .71 end and about 20 percent of the biomass at the south end of Kootenay Lake. Cladophora aegagropila (L.) Rabh., which thrives i n areas of high phosphorus content (Hoek, 1963), grew mainly i n the south arm of Kootenay Lake and was pri m a r i l y responsible f o r the increased green a l g a l abundance (and decreased diatom percentage abundance) there. Blue-green a l g a l trends were s i m i l a r to those observed at the other depths, the main lake community co n s i s t i n g of about 5 percent blue-green algae, increasing to 10-20 percent along the west arm of the lake. In the upper meter of Kootenay Lake there was a marked seasonal succession of the a l g a l groups. While yearly averages ( F i g . 32) showed the o v e r a l l importance of the diatoms, there were periods i n the year when green algae p r e v a i l e d (Fig. 33). In early May at the 0.1 m depth, the spring growth peak consisted almost e n t i r e l y of green algae (Ulothrix spp.), with diatoms predominating at other times. In contrast, at the 1.0 m depth there was a l a t e summer-early f a l l growth peak of green algae (primarily Spirogyra sp.), diatoms being of major importance during spring and other sampling dates. Large changes i n abundance of the a l g a l groups did not occur at 3.0 and 5.0 m depths i n the lake. There are in d i c a t i o n s though, that i n the south arm green algae (primarily Cladophora aegagropila) were s l i g h t l y more common i n ear l y f a l l than a t other times. In the north arm of the lake, which had low phosphate loadings, C. aegagropila d i d not grow and green algae were never common (bottom graph of F i g . 33) . 2. A r t i f i c i a l Substrates The attached a l g a l composition on a r t i f i c i a l (production) substrates di d not accurately r e f l e c t the composition on natural rock substrates (Fig. 34) . 72 E o CO 9 E I g UJ g 2 < O CC o UJ X r -S t a t i o n S 2 8 H 6 H 2 H 0.1 m D e p t h M A M J J A S O N D cc O Q. o CC Q. < UJ o •2 < Q 2 CO 3.0 m D e p t h B l u e - g r e e n s G r e e n s < 4 H Sta t ion Nl 3.0 m D e p t h r ~ ~ 1 " i 1 i M A M J J A S O N F i g . 33'. Seasonal succession i n the percentage abundance (by volume) of diatoms, green algae and blue-green algae expressed as a proportion of the organic weight (mg cm - 2) at selected depths i n the south arm and north arm of Kootenay Lake, 1973. 73 34. Regional v a r i a t i o n s i n average percentage abundance (by volume) of diatoms, green algae, and blue-green algae attached to a r t i f i c i a l substrates at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973. 74 Major features, to be sure, were s i m i l a r , with diatoms being the most abundant group, green algae le s s abundant and blue-green algae l e a s t abundant. But the l e v e l s of abundance and trends i n regional v a r i a t i o n usually d i f f e r e d from those observed for natural populations of attached algae. Diatoms, with some exceptions, formed about 90 percent (by volume) of the attached a l g a l biomass at a l l depths (Fig. 34). S t a t i o n Wl had fewer diatoms than the other s t a t i o n s , but otherwise l i t t l e regional v a r i a t i o n occurred. Green algae likewise exhibited few regional trends, with an average abundance of about 10 percent except at s t a t i o n Wl where they were more abundant. At the deeper depth Cladophora d i d not grow on the a r t i f i c i a l substrates, so there was no increase i n green algae southwards, as observed on natural substrates (Fig. 35). Green algae, other than Cladophora, were more abundant on p l e x i g l a s than oimthe rock substrates. As a r e s u l t , the south arm showed s i m i l a r proportions of green algae ( t o t a l a l g a l abundance) on both kinds of substrate, while the north arm (where Cladophora did not grow naturally) showed la r g e r proportions of green algae on the p l e x i g l a s substrates. Blue-green algae, forming less than two percent of the community biomass, were even less common on p l e x i g l a s s than on rocks . There was no increase i n blue-green abundance along the length of the west arm, contrary to the pattern observed on natural rock substrates a t a l l depths. Species Composition 1. Green Algae Owing to the general lack of green algae throughout the year (Fig. 33) and the d i f f i c u l t y i n accurately enumerating the filamentous species, c e l l 75 Alga l C o m p o s i t i o n on Natura l S u b s t r a t e s 100-. 10 • LU O z < a z ZD to < o CC I-LU 5 _/ O > z LU o CC LU a 1 A l g a l C o m p o s i t i o n on Art i f ic ia l S u b s t r a t e s 100 • 10 - D i a t o m s i ' B l u e - g r e e n s s - G r e e n s Nl N5 N o r t h - * — S5 S 2 • • - S o u t h W2 W7 -•-West F i g . 35. Average percentage composition (by volume) of diatoms, green algae, and blue-green algae on natural rock substrates compared to that on a r t i f i c i a l substrates at 3.0 m i n Kootenay Lake, 1973. Note logarithmic scale. 76 counts were not performed and parameters such as d i v e r s i t y therefore could not be ca l c u l a t e d . However, while i d e n t i f y i n g the green a l g a l species and estimating the percentage abundance of the a l g a l groups, I was able to appraise the importance of each green a l g a l species at the various sampling locations and sampling times. In a l l , twenty-four species of green algae were i d e n t i f i e d from Kootenay Lake's attached a l g a l assemblages (Table I I ) . Many of the features of green algae, as a whole, were discussed i n the previous s e c t i o n . Most of the green a l g a l species exhibited l i t t l e regional v a r i a t i o n . Ulothrix aeqvalis Ktitz., and U. tenuissima which formed the spring growth peak and Spirogyra spp. predominant i n the f a l l belonged to t h i s category, being common at a l l locations i n the lake. Oedogoniim spp. and Elak.atoth.Ti-x sp. which were moderately abundant were also widespread. Most other green a l g a l species occurred i n small numbers but appeared to be present i n a l l regions of Kootenay Lake. Cladophora aegagropila, Bulboahaete sp. and Rhizoclonium sp., unlike the other green a l g a l species, were associated with p a r t i c u l a r regions of the lake. Cladophora aegagropila, a shade-loving species f l o u r i s h i n g i n eutrophic water (Hoek, 1963), was common i n the south arm of the lake and at some west arm s t a t i o n s , but was seldom encountered i n the north arm (Fig. 36). In the south arm C. aegagropila had an upper growth l i m i t at the 2.5 m depth, peaked at 3-5 m then gradually disappeared and was not present at the 10.0 m depth. As previously mentioned, C. aegagropila never grew on a r t i f i c i a l substrates, being r e s t r i c t e d to the natural rock h a b i t a t . In contrast, Bulboahaete sp. was only enumerated i n the a r t i f i c i a l substrate samples, 77 Table II. A l i s t of the attached a l g a l species, except diatoms, occurring i n the l i t t o r a l zone of Kootenay Lake. Chlorophyta: Cyanophyta: Ankistrodesmus falcatus (Corda) Ralfs *Bulbochaete sp. Coelastrum microporum Naegali Chlamydomonas sp. Cosmarium sp. Cladophora aegagropila (L.) Rabh. Dictyosphaerium sp. Elakatothrix sp. Gloeocystis ampla (Kutz.) Lagerheim Gongrosira sp. Oedogonium spp. Ooaystis sp. Pediastrum duplex Meyen Rhizoclonium sp. Scenedesmus. sp. Spirogyra sp. Spondylosium sp. Ulothrix aequalis Kutz. Ulothrix tenuissima Kutz. Vlothvix sonata (Weber & Mohrp Kutz. U n i d e n t i f i e d Desmidiaceae Un i d e n t i f i e d spp. Un i d e n t i f i e d Volvocales sp. Zygnema sp. Anabaena flos-aquae (Lyngb.) De Breb. Anabaena oircinalis Rabh. Anaoystis sp. Aphanoaapsa sp. Calothrix sp. Chvoococcus sp. Coelosphaevium sp. Gomphosphaeria sp. Lyngbya novdgaavdii wille Lyngbya spp. Mevismopedia sp. Microcystis sp. Nostoc sp. Oscillatoria spp. Phormidium sp. Rivularia sp. Sacconema rupestre B o r z i Spirulina sp. Tolypothrix distorta Kutz. U n i d e n t i f i e d c o l o n i a l form Peridiniopsis penardii (Lemm.) Bourr. Pyrrhophyta: Cryptophyta: Cryptomonas borealis (Skuja) Chrysophyta-Chrysophyceae: Mallomonas sp. ^Occurred on p l e x i g l a s s substrates only. 78 a. O cc C3 < o UJ < < CC O X C L O Q < O LL o UJ O z < Q Z ZD co < 3.0 M e t e r D e p t h abundant o c c a s i o n a l rare never L Nl N8 N2 N3 N9 N10N4 N5 Ni l N6 N12 N 7 S l l S 6 S 5 SlO S 4 S 9 S 3 S 8 S2 N o r t h - * 1 f » S o u t h 5 .0 M e t e r D e p t h abundant -^occas ional N8 N2 N3 N9 N10N4 N5 N i l N6 N12 N7 S l l S 6 S 5 S10S4 S 9 S 3 S 8 S 2 N o r t h - * ; 1 >»-South Wl W2 W3 >*-West W2 W 7 W7 - • - W e s t Fig. 36. Regional variations in the average abundance of Cladophora aegagropila attached to natural rock substrates at 3.0 and 5.0 m in Kootenay Lake, 1973. Absence of vertical bars at a station indicates the alga was never encountered. 79 although there must have been small amounts present on the natural substrates. This species was also r e s t r i c t e d to the south and west arms of the lake, as was Rhizoclonium sp. 2. Blue-green Algae Because of t h e i r small populations, the twenty species of blue-green algae i d e n t i f i e d i n t h i s study (Table II) were not enumerated i n d i v i -d u a l l y . The abundance of the e n t i r e group i s discussed i n the previous s e c t i o n . Lyngbya novdgaavdii W i l l e and Oseillatoria spp. were the most frequent and widespread species. Calothrix sp., TPhovmidiiwi sp., Saooonema rupestve B o r z i , and Tolypothrix distorta Ktitz. were often present i n the west arm, and less frequently encountered elsewhere. Others were found occasionally, although some, such as Nostoc sp., formed a large proportion of the attached a l g a l biomass when they d i d occur. Attached Diatoms Diatoms formed the major po r t i o n of the attached a l g a l community and were therefore examined i n d e t a i l . The diatom species were i d e n t i f i e d ( i n many cases to the subspecies level) as w e l l as enumerated f o r c e l l counts and c e l l volumes. The following sections present r e s u l t s i n terms of diatom c e l l numbers, c e l l volumes, numbers of species, d i v e r s i t y , s t a t i o n c l u s t e r s based upon diatom d i s t r i b u t i o n s , and species d i s t r i b u t i o n s . 1. Diatom Abundance i . Natural Substrates Yearly and seasonal mean diatom numbers ranged from about 80 1 x 10:? to 9 x 105 ce l ls cm." 2 of rock surf ace (Fig. 37) . Cells increased with depth, ranging from approximately 1 x 106 diatoms per cm2 near the lake surface, to counts generally greater than 3 x 106 cel ls cm ~ 2 at the 5.0 m depth. At a l l depths, spring numbers tended to be highest and summer counts lowest. Station N5 at the 3.0 and 5.0 meter depths had an immense number of diatoms during spring, 8.5 x 106 cel ls cm ~ 2 , much more than observed else-where. Consistent regional trends i n c e l l numbers were not detectable at any depth, the seasonal variation at specif ic locations being far greater than most differences between stations. Total c e l l volumes for each station were calculated by multiplying c e l l count by average volume for each species (Table III) and summing the results for a l l species i n the sample. -. Yearly•* and seasonal average diatom c e l l volumes (not including gelatinous sheaths and stalks) ranged from about 0.5 mm3 to 4 mm3 per cm2 of rock surface (Fig. 38). Cel l volumes were not consistently greater at the deeper depths (as numbers were), indicating that the diatoms near the lake surface were larger. Seasonal variation i n c e l l volumes, as observed with c e l l counts, was generally greater than regional variat ion. The 5.0 m depth was an exception, greater diatom volumes occurring in' the less turbid north arm.(Fig. 9) than at other locations. i i . A r t i f i c i a l Substrates C e l l counts and volumes from a r t i f i c i a l substrates cannot be direct ly compared to abundance on rocks. Both plexiglas.. grown c e l l numbers and volumes (accumulated i n two weeks) are considerably less than those accumulated on rocks over an unknown but undoubtedly longer period of time. 81 0.1 m l.O m c/5 cc LU m 5 z LU o 5 o < o 3.0 m 5.0 m 80 -60 -40 H 20-S p r i n g Mean Summer Autumn Nl N5 S5 S2 North-* 1 : —»South W2 W7 "-West F i g . 37. Regional v a r i a t i o n s i n average diatom c e l l numbers (xlO-3) attached to natural rock substrates at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973. Horizontal bars represent yearly averages, s o l i d symbols represent seasonal averages and open symbols represent sin g l e measurements. 82 Table III'. A l i s t of the attached diatom species, t h e i r c e l l volumes and numeric and volumetric occurrence on natural and/or a r t i f i c i a l substrates i n the l i t t o r a l zone of Kootenay Lake. For occurrence; open c i r c l e s (o) denote a species always made up less than 10% of a sample's abundance, s o l i d c i r c l e s (•) denote that a species made up greater than 10% of at least one sample's abundance. . I f a species has no record f o r occurrence that species was never encountered during quantitative diatom analyses but does occur i n the attached f l o r a .  C e l l Volume Occurrence Natural Substrates A r t i f i c i a l Substrates Ba c i l l a r i o p h y c e a e Species Coscinodiscales: 1 Cyalotella atomue Hust. 2 Cyclotella comta (Ehr.) KUtz. 3 Cyalotella glomerata Bachm. 4 Cyalotella kuetzingiana Thwaites . 5 Cyclotella meneghiniana KUtz. 6 Cyalotella ocellata Pant. 7 Cyclotella pseudoetelligera Hust. 8 Cyclotella sp. 9 Cyclotella stelligera C l . s Grun. 10 Cyclotella striata (KUtz.) Grun. 11 Cyclotella vorticosa A. Berg. 12 Coecinodiecus lacustris Grun. 13 Meloeira arenaria Moore 14 Meloeira binderana KUtz 15 Meloeira granulata (Ehr.) Ralfs 16 Meloeira ielandica O. MU11. 17 Meloeira varians Ag. 18 Stephanodiacus astraea (Ehr.) Grun. 19 Stephanodiecue astraea var. minutula (KUtz.) Grun. 20 Stephanodiecus dubiue (Fricke) Hust. 21 Stephanodiecue hantzschii Grun. Phizosoleniales: 22 Rhizoeolenia erienaia H.L. Sm. F r a g i l a r i a l e s : 23 Aeterionella formosa Hass. 24 Diatoma anaeps (Ehr.) Kirchn. 25 Diatoma hiemale (Lyngb.) Heib. 26 Diatoma tenue Ag. 27 Diatoma vulgare Bory 28 Fragilaria capucina Desm. 29. Fragilaria comtricta Ehr. 30 Fragilaria conetruens (Ehr.) Grun. 31 Fragilaria conetruens var. binodie (Ehr.) Grun. ' 32 Fragilaria construens var. venter (Ehr.) Grun. 33 Fragilaria crotonensis K i t t o n 34 Fragilaria heiden O s t r . 35 Fragilaria leptostauron (Ehr.) Hust. 36 Fragilaria pinnata Ehr. 37 Fragilaria vaucheriae (KUtz.) Peters. 38 Hannaea arcus (Ehr.) Patr. 39 Opephora martyi HSrib. 40 Synedra acne KUtz. 41 Synedra Cf. amphicephala var. auetriaca (Grun.) Hust. 42 Synedra arcuata (Ostr.) A. C l . 43 Synedra delicatissima w. sm. 44 Synedra famelica KUtz. 45 Synedra faeciculata (Ag.) KUtz. 46 Synedra mazamaensis Sov. 47 Synedra rumpene KUtz. 48 Synedra sp. 49 Synedra ulna (Nitz.) Ehr. 50 Tabellaria feneetrata (Lyngb.) Kutz. 51 Tabellaria flocculoea (Roth) KUtz. 52 Unidentified Araphe Eunotiales: 53 Eunotia pectinalia (KUtz.) Rabh. <um3) Numeric Volumetric- Numeric Volume 20 0 o o o 400 o 9 o o 20 • o • o 100 o o o o 160 o o 180 o o o o ' 50 o o o o 110 o o 50 o o' 50 o o o o 120 o o 410 o o o o 41560 o • -200 • o o o 1780 o o o o 530 o o o o 5260 o • o • 1240 • • • • 110 • • • 90 o o o o 110 o o o o 180 o o o o 270 • • • • 280 o o o o 520 o o o o 250 • • • • 2290 • • o o 760 • • • • 200 o o 150 • • • • 180 • • • • 80 • • • • 530 • • • • 140 o o o o 880 o • o o 170 • o 380 • • • • 1260 o o o o 270 • • o o 1040 • • • • 370 o o 1680 o o 670 o o o o 150 o o 900 o o 210 • o o o 1050 • • o 630 o o o o 6640 • • o • 1330 o • o o 430 o o 300 o o 1340 o o o o 83 Table III (Continued) Bac i l l a r i o p h y c e a e Species Occurrence C e l l Volume Natural Substrates (pro3) Numeric Volumetric A r t i f i c i a l Substrates Numeric Volumetric Achnanthales: 54 Achnanthee Cf. bergiana A. C l . 190 55 Achnanthea Cf. biaaolettiana (KUtz.) Grun. 400 56 Achnanthee aalaar (Cl.) C l . 190 57 Achnanthea clevei Grun. 220 58 Achnanthea clevei var. roatrata Hust. 220 59 Achnanthea divergens A. C l . 80 60 Achnanthea exigua Grun. 61 Achnanthea flexella (KUtz.) Brun 62 Achnanthea Cf. inflata (Kutz.) Grun. 63 Achnanthee lanceolata (Bre"b.) Grun. 64 Achnanthea lewieiana Patr. 65 Achnanthea linearis (w. Sra.) Grun. 66 Achnanthea minutissima KUtz. 67 Achnanthea peragalli Brun & H£rib. 68 Achnanthea pinnata Hust. 69 Achnanthea spp. . 70 Achnanthea spp. 71 Cocconeia diaculus (Schum.) C l . 72 Cocconeis pediculus Ehr. 73 Cocconeia pellucida Hantz. 74 Cocconeis plaaentula Ehr. 75 Cocconeia sp. 76 Ehoicoephenia curvata (KUtz.) Grun. Naviculales: 77 Amphipleura pellucida (Kutz.) KUtz. 78 Amphora coffaeformis (Ag.) KUtz. 79 Amphora ovalis Kutz. 80 Amphora ovalia var. pediculua (KUtz.) Van Heurck 81 Amphora sp. 82 Caloneia bacillum (Grun.) C l . 83 Caloneia hyalina Hust. 84 Caloneia Cf. patagonica (Cl.) C l . .85 Caloneia ailicula v a r . limoea (KUtz.) Van Lan. 86 Caloneia sp. 87 Cymbella affinia KUtz. 88 Cymbella aepera (Ehr.) C l . 89 Cymbella caeepitosa (Kutz.) Brun 90 Cymbella cietula Hempr. 91 Cymbella heteropleura Ehr. 92 Cymbella prostrata (Berk.) C l . 93 Cymbella reinhardtii Grun. 94 Cymbella sp. "A" 95 Cymbella sp. 96 Cymbella tumidula Grun. 97 Cymbella turgida Greg. 98 Cymbella ventriaosa KUtz. 99 Diploneia decipiens A. C l . 100 Frustulia rhomboides (Ehr.) De T. 101 Gomphonema acuminatum Ehr. 102 Gomphonema constrictum Ehr. 103 Gomphonema geminatum (Lyngb.) Ag. 104 Gomphonema gracile Ehr. 105 Gomphonema herculeanum Ehr. 106 Gomphonema montanum var. eubclavatum Grun. 107 Gomphonema olivaceum (Lyngb.) KUtz. 108 Gomphonema olivaceum var. genuinum f. minutula (May.) May. 109 Gomphonema parvulum (Kutz.) Kutz. 110 Gyroeigma eoiotense ( S u l l i v . s wormley) C l . 130 o o o o 90 o o o o 500 o o i90 o o o o 50 o o • o 180 o o o o 60 • • • • 240 o o o o 140 o o 200 o o o o 200 o o 140 o o o o 880 o o o o 2500 0 o 610 o • o o 860 o o o o 760 • - • • • 2600 o o o o 500 o o 320 o o o o 70 • o • o 640 o o 450 • o o o 2200 o o 2160 o o 1200 o o 1500 o o o o 1300 o • o o 16480 o • o o 630 • • • 6850 o • o • 10620 7210 o • o • 320 o o 99060 o • • • 3000 o o o o 1330 890 o o o o 100 • • • o 920 o o o o 3840 o o o o 1630 o o 2080 o o Large 980 o o 13000 • • • • 1390 • • • 470 • • o o 210 o • o o 560 • • • . • 4600 o • 84 Table I I I (Continued) B a c i l l a r i o p h y c e a e Species Occurrence C e l l Volume Natural Substrates (ym3) Numeric Volumetric A r t i f i c i a l Substrates Numeric Volumetric Naviculales (cont * d) 111 Navicula aaaomoda Hust. 60 • 112 Navicula amphibola C l . 2020 o 113 Naviaula angliaa R a l f s 140 114 Naviaula aurora Sov. 4200 115 Naviaula cincta (Ehr.) Ralfs 310 • 116 Navicula cocconeiformis Greg. 720 o 117 Naviaula aryptooephala KUtz. 660 o 118 Navicula decussis O s t r . 480 o 119 Navicula elginensis (Greg.) Ralfs 620 o 120 Navicula Cf. festiva Krasske 360 o 121 Navicula gottlandica Grun. 1090 o 122 Naviaula graciloides May. . 320 • 123 Navicula minuscula Grun. 80 o 124 Navicula odiosa Wallace 220 o 125 Naviaula pseudoscutif'ormis Hust. 420 o 126 Navicula pupula KUtz. 600 127 Navicula radiosa KUtz. 1320 o 128 Navicula reinhardtii (Grun.) Grun. 940 o 129 Navicula ealinarum var. intermedia (Grun.) C l . 810 130 Navicula echonfeldii Hust. 420 o 131 Navicula ecutelloides w. Sm. 290 o 132 Navicula spp. 140 o 133 Navicula spp. 140 o 134 Navicula spp. 140 o 135 Navicula tripunctata (0. MU11.) Bory 1600 o 136 Pinnularia biceps Greg. 3960 137 Pinnularia sp. 3900 o 138 Stauroneis anceps Ehr. 600 o 139 Stauroneis sp. 600 140 Unidentified Raphe 400 o S u r i r e l l i n e e s : 141 Cymatopleura eolea (BreTo) W. Sm. 142 Denticula elegans KUtz. 143 Epithemia sorex KUtz. 144 Epithemia turgida (Ehr.) KUtz. 145 Epithemia zebra (Ehr.) KUtz. 146 Hantzschia amphioxys (Ehr.) Grun. 147 Nitzschia acicularis w. Sm. 148 Nitzsahia actinastroides (Lemm.) V. 149 Nitzschia affinis Grun. 150 Nitzschia angustata (w. Sm.) Grun. 151 Nitzschia dissipata (KUtz.) Grun. 152 Nitzschia fonticola Grun. 153 Nitzschia frustulum (KUtz.) Grun. 154 Nitzschia hantz8ahia?uz Rabh. 155 Nitzschia heufleuriana Grun. 156 Nitzschia linearis w. Sm. 157 Nitzschia regula Hust. 158 Nitzschia sigmoidea (Ehr.) W. Sm. 159 Nitzsahia sinuata (W. Sm.) Grun. 160 Nitzschia sp. "X" 161 Nitzschia sp. 162 Rhopalodia gibba (Ehr.) O. MU11. 163 Rhopalodia gibberula (Ehr.) 0. MU11. 164 Surirella helvetica Brun Unknown: 165 Unidentified 3360 400 o o 820 • • • • 16100 • • • • 1880 o o 1310 300 620 0 • • • 900 o o 1260 o o o o 560 • • • 110 o o 150 • • • • 680 • • • • 960 1650 o • 1710 o o 3840 o • o o 200 o o o o 540 o o 790 o o 8920 o • • • 600 o o 12600 o • o • 200 o 0 85 0.1 m .0 m N5 Ss Si I W! W7 North. 1 .South 'West Nl Ns SJ SJ North-" 1 —• South W3 W7 3.0 m •Spring I Autumn -Mean ] Summer [ -i Nl NS SS SJ I W2 W7 North-" —.South .West 5.0 m Regional v a r i a t i o n s i n average diatom c e l l volumes (mm3) attached to natural rock substrates at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973. Horizontal bars represent yearly averages, s o l i d symbol represent seasonal averages and open t r i a n g l e s represent single samples. 86 Diatom c e l l numbers (Fig. 39) p a r a l l e l e d organic weight (production) r e s u l t s (Fig. 31) . At the shallow depths, diatoms increased from about 2 x 10 5 c e l l s per cm2 i n the north arm to over 3.5 x 10 5 c e l l s cm - 2 i n the south arm. At the 3.0 m depth diatom numbers were over 3.5 x 10^ cm _ 2 i n the north arm, but decreased i n the south arm. The 5.0 m depth had lowest numbers of diatoms with values near 1.5 x 10 cm everywhere, values i n the north arm being only s l i g h t l y higher than south and west arm values. Trends i n the v e r t i c a l pattern of diatom numbers on a r t i f i c i a l substrates d i f f e r e d from those observed on natural substrates. Though more diatoms are produced at the shallow depths, natural assemblages contain fewer diatoms there than at the deeper depths. Likewise, despite the slower diatom growth rates at the deeper depths, p a r t i c u l a r l y i n the'south arm, populations increase to high l e v e l s . The slower growth rates at the deeper depths are probably r e l a t e d to less l i g h t energy. Greater diatom numbers i n the north arm, where more l i g h t reached the deeper depths (Fig. 9), support t h i s contention. C e l l volumes on the a r t i f i c i a l substrates (Fig. 40) exhibited s i m i l a r trends i n v e r t i c a l and regional v a r i a t i o n to those observed f o r c e l l numbers on the a r t i f i c i a l substrates. Diatom volumes generally decreased with depth. At the shallow depths, volumes were highest i n the south arm (over 0.2 mm3 cm ~ 2) and lowest i n the north arm (under 0.2 mm3cm ~ 2 ) . At the 3.0 m depth, north arm stations had over 0.1 mm3 cm. - 2 while south arm stations had less than 0.1 mm3 cm. - 2. There were no apparent trends at the 5.0 m depth, with values ranging from approximately 0.02 to 0.11 mm3 cm."2 of rock surface. 8 7 0.1 m N l 5 N o r t h-t-en rr LU CO 2 D Z S5 2 H • S o u t h W2 7 — • W e s t O i -< 4 O 3 .0m N l 5 S 5 2 |W2 7 N o r t h - * 1 • S o u t h • W e s t 1.0 m 3H Nl 2 3 4 5 6 ' ? 7 S 6 5 4 3 2 , W l 2 3 4 56 7 N o r t h - * - , — • S o u t h 1 — • W e s t 5.0 m Nl 5 N o r t h - * -S 5 2 |W2 7 — • S o u t h — • W e s t F i g . 39. Regional v a r i a t i o n s i n average diatom c e l l numbers (xlO 5) attached to a r t i f i c i a l substrates, a f t e r two weeks' growth, at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973. 88 .9 .7 .5 0.1 m uj Nl 5 North-3 _l O > S5 2 |W2 7 —*-South *-West UJ O 5 o I -< Q 3.0 m Nl 5 N o r t h - * -I I S5 2 |W2 7 - • - S o u t h • -West .5 1 1.0 m Ui Nl 23 45 6 1 2 7 S ° 5 4 3 2 , W l 2 3 4 5 6 7 North-* H— • - S o u t h — * - W e s t .1 i 5.0 m Nl 5 North-*-S5 -South |W2 7 » -West F i g . 40. Regional v a r i a t i o n s i n average diatom c e l l volumes (mm3) attached to a r t i f i c i a l substrates, a f t e r two weeks' growth, at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973. 89 2. Diatom D i v e r s i t y i . Natural Substrates The average number of diatom species i d e n t i f i e d per sample ranged from about 10 to 30 species (Fig. 41). The number of species was l e a s t near the lake surface (about 10-15 species) and greatest at the 3.0 and 5.0 m depths. Regional v a r i a t i o n s i n the numbers of species were not apparent. The number of d i f f e r e n t . s p e c i e s encountered, at each s t a t i o n , during the e n t i r e study ranged from about 40 to 70 species (Fig. 41). Again, species numbers were l e a s t near the surface and greatest at the 3.0 and 5.0 m depths, with no apparent regional v a r i a t i o n . Results are not e a s i l y com-parable to other studies since the number of species i d e n t i f i e d i s r e l a t e d to the e f f o r t spent i n enumerating i n d i v i d u a l samples. A measure of diatom species d i v e r s i t y which depends on both the number of taxa and abundance of i n d i v i d u a l s within each taxa was also c a l -culated. This index, c a l l e d the Shannon-Wiener function, produces r e s u l t s that are e a s i l y compared with other studies. The sampling e f f o r t has l e s s influence on the r e s u l t s because increases i n the number of rare species are o f f s e t by the greater abundance of i n d i v i d u a l s i n the common species. The n Shannon-Wiener function H 1, (H' = -E- , Pi l o g 2 P i , where n = number of i = l species and p = proportion of the t o t a l sample belonging to the i^-h species) ranges from values below 1 for low d i v e r s i t y (often polluted) waters (Weber, 1973) to values as high as 3 or 4 i n unpolluted waters. In Kootenay Lake, average Shannon-Wiener d i v e r s i t i e s of the attached a l g a l community range from 2.5 to 3.5 (Fig. 42). D i v e r s i t y i n the north arm of the lake i s greater than i n the south arm, except at the lake 90 w LU o LU CL 2 O < O LU CO 5 Z N I 3 ¥5 ~T North - * — I — • - S o u t h 60 40 H 20 0 3.0 m |W2 7 • West 30 ^ 20 10 3.0 m Autumn Spring +Mean Summer Nl 5 S 5 2 N o r t h - * — | • -South 60-40-20 0 1.0 m Total Species 30H 20 10 l.o m Average Species M M Nl 5 S 5 2 N o r t h - * ( • - S o u t h W2 7~ -West Nl 5 S 5 2 N o r t h - * — | • - S o u t h F i g . 41. Regional v a r i a t i o n s i n the average number of diatom species attached to natural substrates at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake 197 3. V e r t i c a l bars represent the t o t a l number of species i d e n t i f i e d during the e n t i r e study. Horizontal bars represent yearly averages, s o l i d symbols represent seasonal averages and open t r i a n g l e s represent si n g l e samples. 91 0.1 m o o o North. 1 .South N i N s S s S2 1.0 rn >-H-V) or LU > 3.0 m < Q Autumn O' Pooled .Spring "Mean Summer 1 ~] North* S s S2 I W2 W7 5.0 m F i g . 42. Regional v a r i a t i o n s i n average diatom d i v e r s i t y (Shannon-Wiener function, H') on natural rock substrates at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973. Large open c i r c l e s represent d i v e r s i t i e s c a l c u l a t e d a f t e r pooling a l l the species counts for the e n t i r e sampling period. Horizontal bars represent yearly averages, s o l i d symbols represent seasonal averages and open t r i a n g l e s represent sin g l e samples. 92 surface where trends are not apparent. Shannon-Wiener d i v e r s i t y i n d i c i e s were also c a l c u l a t e d f o r each s t a t i o n , a f t e r pooling a l l the species counts from the i n d i v i d u a l samples c o l l e c t e d throughout the year. These pooled d i v e r s i t i e s would correct f o r any e r r a t i c i n d i v i d u a l samples which could a f f e c t the yearly mean d i v e r s i t i e s presented above. Furthermore, unlike yearly mean d i v e r s i t i e s , yearly pooled d i v e r s i t i e s would be lower i n p o l l u t e d regions where a few p o l l u t i o n t o l e r a n t species p e r s i s t throughout the year. In Kootenay Lake yearly pooled diver-s i t y values (3.5 to 4.5) are higher than average values (Fig. 42), i n d i c a t i n g that the lake i s not badly p o l l u t e d . North arm d i v e r s i t i e s are again higher than south arm d i v e r s i t i e s , except at the lake surface where there i s no apparent pattern. i i . A r t i f i c i a l Substrates The average number of diatom species i d e n t i f i e d on the a r t i f i c i a l substrates ranged from about 10 to 20 species (Fig. 43). The number of taxa on the a r t i f i c i a l substrates was generally lower than observed for natural assemblages, probably because of the shorter (two-week) immersion period. As observed with natural substrates, consistent regional v a r i a t i o n s i n the number of taxa were not apparent. The number of d i f f e r e n t species encountered during the en t i r e study generally ranged from about 40 to 50 species with no apparent regional trends (Fig. 43) . Shannon-Wiener d i v e r s i t y values were s i m i l a r (2.5 to 3.5) to those observed f o r natural assemblages ( F i g . 44). Trends i n d i v e r s i t y were less obvious, with d i v e r s i t i e s from the 5.0 m depth alone showing consistent north-ward increases. Pooled d i v e r s i t i e s were usually between 3.0 and 4.5 with 93 0.1 m 1.0 m w LU O LU a N5 North*— S2 •South W7 •West < a or LU co 5 Z 3.0 m N5 North*— Ss S2 H 'South W2 W7 'West 5.0 m  Total Species Average Spec ies Ni Ns North"— S5 S2 H 'South W2 W7 •West F i g . 43. Regional v a r i a t i o n s i n the average number of diatom species attached to a r t i f i c i a l substrates at 0.1, 1.0, 3.0, and 5.0m i n Kootenay Lake, 1973. S o l i d v e r t i c a l bars represent the t o t a l number of species i d e n t i f i e d during the ent i r e study. Hatched v e r t i c a l bars represent yearly averages. 94 0.1 m o Pooled Average _ Nl 5 55 J X N o r t h * — — H •South WJ 7 •West 1.0 m p o o o ° o o o . o , oo Nl 73 45 6 a 7 So 5 4 3 31 North- 1 •South ,Wl 2 3 4 5 6 7 •West 00 CC UJ > 3.o m O f-< a 5.0 m i F i g . 44. Regional v a r i a t i o n s i n average diatom d i v e r s i t y (Shannon-Wiener function, H 1) on a r t i f i c i a l substrates at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973. Large open c i r c l e s represent d i v e r s i t i e s c a l c u l a t e d a f t e r pooling a l l the species counts for the entire sampling period. S o l i d v e r t i c a l bars represent yearly averages. 95 generally high values i n the north end of the lake (Fig. 44). 3. Diatom Cluster Analyses A sum of squares amalgamation c l u s t e r analysis (U.B.C. Computing Center, MS 1973) was performed to group together s i m i l a r Kootenay Lake s t a t i o n s . This multivariate technique q u a n t i t a t i v e l y uses a l l the diatom data to form clusters of s i m i l a r s t a t i o n s . Three c l u s t e r analyses for each substrate type were computed, using numerical counts, numerical percentage abundance and volumetric percentage abundances of the 59 species that formed 10 percent or more of the diatom abundance at any one time (closed c i r c l e s , Table 3) . i . Natural Substrates When diatom counts from the 0.1, 1.0, 3.0 and 5.0 m depths of the s i x major stations were clustered, three groups of stations with high within-group diatom s i m i l a r i t i e s became evident (Fig. 45, top). One group consisted almost e n t i r e l y of samples from 0.1 and 1.0 m where l i g h t l e v e l s , turbulence and r i s k s of exposure are great. The 3.0 and 5.0 m depths of a l l stations were included i n the other two major groups. In a l l groups there was a s l i g h t tendency for stations from the same major region of the lake to be clustered together, i n d i c a t i n g that highest s i m i l a r i t i e s of diatom d i s t r i -butions usually occur within one lake region. Clusters based upon numerical percentage abundances produced four major groups of s t a t i o n s . ( F i g . 45, middle). With some exceptions, the shallow depths again clustered separately from the deeper depths. Interest-96 NUMERICAL CLUSTER PERCENT NUMERICAL CLUSTER 10 3 5 I 3 3 3 t .1 5 3 1 5 1 1 I I ,1 1 3 1 .1 ,1 J PERCENT VOLUMETRIC CLUSTER i l 10 5 3 3 5 3 5 3 3 1 3 1 3 1 1 . 1 1 3 3 F i g . 45. Station c l u s t e r s based upon average diatom abundances on natural rock substrates at 0.1, 1.0, 3.0, 5.0, and 10.0 m i n Kootenay Lake, 1973. Top c l u s t e r based upon absolute numbers, middle c l u s t e r based upon percent numerical occurrence, bottom c l u s t e r based upon percent volumetric occurrence. 97 in g l y , shallow stations from the more protected west arm of the lake were more s i m i l a r to the deeper stations than to the shallow stations i n the main lake. Within the c l u s t e r s , stations from s i m i l a r regions of the lake were strongly clumped, diatom d i s t r i b u t i o n s w i t h i n one lake region being very s i m i l a r . Clusters using volumetric percentage data gave s i m i l a r r e s u l t s to the other two c l u s t e r analyses. Again shallow stations clumped together (Fig. 45, bottom) although there were more exceptions than i n the other t e s t s . Within the major c l u s t e r groups, highest s i m i l a r i t i e s once more occurred between stations from the same lake region. i i . A r t i f i c i a l Substrates Data from the 1.0 m depth of the 21 stations were clustered. Since only data from a si n g l e depth was clustered, between depth comparisons could not be made, as i n the l a s t section, but the great number of stations allow for a more rigorous assessment of regional d i f f e r e n c e s . When diatom numbers were clustered (Fig. 46, top) three major groups of stations occurred. One group consisted of north arm stations as well as s t a t i o n Wl bordering on the north arm of the lake. Another group contained mainly south arm and some west arm s t a t i o n s . The l a s t group contained two west arm stations and s t a t i o n N12 located near the confluence of the three arms. Almost without exception, stations located nearest one another were t i g h t l y clustered i n d i c a t i n g that they had very s i m i l a r diatom f l o r a s . Clusters based upon numerical percentage abundance also formed three main s t a t i o n groups (Fig. 46, middle) roughly corresponding to the 98 N U M E R I C A L C L U S T E R J A P E R C E N T N U M E R I C A L C L U S T E R P E R C E N T V O L U M E T R I C C L U S T E R F i g . 46. Station c l u s t e r s based upon average diatom abundances on a r t i f i c i a l substrates at 1.0m i n Kootenay Lake, 1973. Top c l u s t e r based upon absolute, numbers, middle c l u s t e r based upon percent numerical occurrence, bottom c l u s t e r based upon percent volumetric occurrence. 99 three major lake regions. As before, the highest s i m i l a r i t i e s occurred amongst c l o s e l y located s t a t i o n s . Clusters using volumetric percentage data also produced three major groups, with r e s u l t s s i m i l a r to the other two c l u s t e r analyses (Fig. 46, bottom). One group consisted almost e n t i r e l y of north arm stations while the other two groups were less r e g i o n a l l y d i s t i n c t . Nevertheless, nearby stations were t i g h t l y clustered, i n d i c a t i n g close s i m i l a r i t i e s i n t h e i r diatom f l o r a . 4. Diatom Species D i s t r i b u t i o n s In the attached f l o r a of Kootenay Lake there were over 165 diatom species recorded (Table III),.of which only 59 made up more than 10 percent of any si n g l e sample's numeric and/or volumetric abundance (closed c i r c l e s , Table III). ( I t i s impossible to t e l l the actual number of species encountered, since categories such as 'unident i f i e d raphe'.may have had d i f f e r e n t taxa recorded i n the i n d i v i d u a l samples.) When yearly averages were calculated, there were only 34 taxa that made up 5 percent or more of the abundance at the 0.1, 1.0, 3.0 or 5.0 m depths of reg u l a r l y sampled stations (Fig. 47-50). Most diatom species belonged to the following orders: Coscinodiscales, F r a g i l a r i a l e s , Achnanthales, Naviculales or S u r i r e l l i n e e s . The Rhizosoleniales and Eutoniales were also represented i n the attached f l o r a (Table III). Although there were 21 diatom species belonging to the Coscinodiscales, the group (except f o r Stephanodisous astvaea and v a r i t i e s ) seldom contributed greatly to the attached diatom biomasses. The order Coscinodiscales i s generally considered planktonic, and those species observed 100 may represent i n d i v i d u a l s that have s e t t l e d out of the plankton, or else species i n the process of increasing t h e i r numbers p r i o r to entering the planktonic community (Round, 1971). There were 30 species of F r a g i l a r i a l e s i d e n t i f i e d , many of which formed a large proportion of the diatoms' numeric or volumetric abundance. Achnanthales species, although attached forms, seldom contributed s i g n i f i c a n t l y to the f l o r a except for the species Achnanthes minutissima Kiitz. More than 64 species of Naviculales were i d e n t i f i e d , and, although i n d i v i d u a l species were seldom numerically important, large Cymbelta or Gomphonema species were often volumetrically important. Of the more than 25 species of Naviaula i d e n t i f i e d , only Navieula aooomoda Hust. occurred more than 5 percent of the time i n yearly average data, although several Navieula species were common i n i n d i v i d u a l samples (Table III). Most of the 24 S u r i r e l l i n e e s species were large forms, and often volumetrically abundant. Species such as Epithemia sorex Kutz. and some of the Nitzsahia species were also numerically important. In the following sections abundancies of a l l the Nitzsahia species are combined, because of the s i m i l a r water q u a l i t y tolerances of a l l species i n the genus (Hancock, 1973) and the d i f f i c u l t y and uncertainty involved i n i d e n t i f y i n g the i n d i v i d u a l Nitzsahia species. i . Natural Substrates Most of the 24 diatom species that were considered numerically and/or vol u m e t r i c a l l y important (on natural substrates over the course of the year) occurred at a l l s t a t i o n s , but i n varying amounts. However, only a few species were common (accounted for 5 percent or more of the averaged samples) at a l l s t a t i o n s . Aehnanthes minutissima exhibited such a trend i n the numerical F i g . 47. Average percent numeric composition of common diatom species (> 5 percent of the t o t a l number) attached to natural rock substrates at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973. The species are: Af, Asterionella formosa; Am, Achnanthes minutissima; Aop, Amphora ovalis v. pediculus; Cc, Cymbella oaespitosa; Cv, Cymbella ventrioosa; Es, Epithemia sorexj Fc, Fragilaria construens complex; Fca, Fragilaria aapuoina; Fcr, Fragilaria erotonensis; Fv, Fragilaria vaueheriae; Gp, Gomphonema parvulum; Nit, Nitzsohia species complex; 0th, a l l other species; Sam. Stephanodisous astraea v. minutula. 102 100-50-oth Ce Fv Fca Am Nil 0.1 m depth Fcr Am Am Nit Fc oth I oth ' El Gp Cc Fv F» At Fc» Sam Am Am Nit Nit Fc Fc N l N5 S5 S2 W2 100-1 I so-il 3 oth Cv Cc Fv Fcr Fca Am Nit Fc 1.0 m depth E» Fv Am Nit oth oth Es Es Fv Fcr Fcr Fca Am Nit Am Fc Nit I FC N l NS SS S2 W2 100-z o V) o a £ o o z iu u 50-oth Cc Aop Fv Fca Am Nit Fc 3.0 m depth oth El Fv Am Nit Am Nit Am Nit Fv  Fcr Am Nit N l NS S5 S2 W2 100-50-oth Aop Fv Am Nit Fc 5.0' m depth Fv Am Nit Oth Am Am Nit Fv Fcr Am Nit N l N5 North«»-S5 S2 - • S o u t h W 2 W 7 ->West MAIN L A K E STATIONS WEST ARM STATIONS F i g . 48. Average percent volumetric composition of common diatom species (•> 5 percent of the t o t a l volume) attached to natural rock substrates at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973. The species are: Af, Asterionella formosa; Cc, Cymbella caespitosa; C c i , Cymbella aistula; Cs, Cymbella sp. "A"; Cp, Cymbella prostrata; Cya, Cymbella aspera; Dv, Diatoma vulgare; Es, Epithemia sorex; Et, Epithemia turgidaj Fc, Fragilaria construens complex; Fca, Fragilaria aapuaina; Fcr, Fragilaria arotonensis; Fv, Fragilaria vauoheriae; Gh, Gomphonema hereuleanum; Gp, Gomphonema parvulum;. Mv, Melosira variansj Nit, Nitzsahia species complex; 0th, a l l other species; Rg, Rhopalodia gibba; Sa, Stephanodisous astraea; Su, Synedra ulna. 104 WO-y 50-0.1 m d e p t h C i G p S a Nit Et E s " C s ~  C p  F v Sa N i t N5 S5 S2 W2 W 7 I O O - I c o a 50-o t h 1.0 m o t h o t h d e p t h Es E t E t C p C c E l E l C y a S i C l C l Fcr C c F c a S u Fv Fv Nit Nit S a Fc Fc N i t F c r F c a U « " Fv  F c r Fc Oth m Et E s C s F c r S a N i t N5 S5 S 2 W7 100-O P 35 O a S o u Z LU O cc iu a. 50H o t h Es C s C P C c F v F c a Sa Nit Fc 3.0 m d e p t h E l Fca Rg E s F c r Sa N i t I O O - i 50-Nl o t h C p S u F v S a N i t Fc 5.0 m depth N5 Fv S a N i t S2 VV2 *3-E s  C s  Fv  F c r S a M v N i t Fc W7 Nl N5 North-*-S 5 S2 ->South W2 W7 - • W e s t MAIN ARM STATIONS WEST ARM STATIONS 105 analysis (Fig. 47), although t h i s small species was not volumetrically abundant (Fig. 48) . The Nitzsahia species complex was also widespread, both i n terms of c e l l numbers and c e l l volumes. Epithemia sorex contributed greatly to the diatom volume at a l l s t a t i o n s . Cymbella sp. "A", a r e l a t i v e l y large species was volumetrically important near the lake surface at a l l l o c a t i o n s . There were d e f i n i t e d i s t r i b u t i o n a l patterns r e l a t e d to the depth at which the diatoms were c o l l e c t e d . As mentioned previously, species near the main lake surface were larger (and had gelatinous sheaths or s t a l k s ) . In the protected west arm of the lake, however, the surface f l o r a more clo s e l y resembled the diatoms at deeper depths (Fig. 47, 48). Gomphonema hereuleanum Ehr. and Cymbella sp. "A" are representative diatoms from the splash zone of the main lake. Some species were r e s t r i c t e d to, or more common i n , s p e c i f i c regions of Kootenay Lake. Epithemia turgida (Ehr.) Kutz.., important i n terms of c e l l volume, was generally more common i n the south end of the lake ( Fig. 48). Fragilaria aonstruens and v a r i t i e s c l e a r l y increased i n abundance southwards and westwards i n the lake ( Fig. 47, 48). The F. aonstruens complex also increased i n abundance with depth; at the 5.0 m depth i n the south arm of the lake i t accounted f o r 75 percent of the diatom numbers and about 50 percent of the diatom volume. No other species consistently dominated the diatom f l o r a as d i d F. aonstruens, and few species exhibited such d i s t i n c t d i s t r i b u t i o n a l gradients. Fragilaria vauoheriae (Kiitz.) Peters., Cymbella aaespitosa (KUtz.) Brun, Cymbella prostrata (Berk.) C l . and Synedra ulna (Nitz.) Ehr. tended to 106 be more abundant i n the north arm of Kootenay Lake (Fig. 47, 48). Asterionella fovmosa Hass., Fragilaria orotonensis Kitton, Melosira vdrians Ag. and Stephanodisaus astraea (Ehr.) Grun. were most common i n the west arm (Fig. 47, 48). I t i s i n t e r e s t i n g to note that t h i s e n t i r e species group i s generally considered planktonic. Their greater abundance i n the r i v e r - l a k e west arm may be a r e s u l t of planktonic species s e t t l i n g out of water which originates from the more l e n t i c parts of the lake. Most of the species enumerated were only occasionally common or else had d i s j o i n t e d d i s t r i b u t i o n s , apparently unrelated to lake l o c a t i o n . In the numerical a n a l y s i s , Stephanodisous astraea v. minutula (KUtz.) Grun., Fragilaria capueina Desm., F. orotonensis, Amphora ovalis v. pedioulus (KUtz.) Van Heurck, Cymbella ventricosa Kutz., Gomphonema parvulum (KUtz.) KUtz., and Epithemia sorex KUtz., a l l i l l u s t r a t e t h i s d i s t r i b u t i o n a l pattern. In the volumetric a n a l y s i s , Diatoma vulgare Bory, F. capueina, Cymbella aspera (Ehr.) C l . , G. parvulum and Rhopalodia gibba (Ehr.) O. Mull, were occasionally common and had spotty d i s t r i b u t i o n s . In addition to a consideration of i n d i v i d u a l species d i s t r i b u t i o n s , a comparison of the average number of common species i n various regions of the lake i s u s e f u l . A large number of common species at a s t a t i o n would represent diverse conditions, while fewer species at a s t a t i o n would represent less diverse conditions (where fewer species form a major proportion of the y community biomass). In Kootenay Lake, the north arm supports more common species than does the south arm. Numerically, there are an average of 5.9 common species at the north arm stations while the south arm has only 4.6 common species per s t a t i o n . Volumetrically, there are an average of 6.9 107 common species i n the north arm and only 5.0 common species i n the south arm. i i . A r t i f i c i a l Substrates Diatom d i s t r i b u t i o n a l patterns on a r t i f i c i a l substrates (Fig. 49, 50) were s i m i l a r to patterns observed on the natural substrates. A l l but one of the 24 species that were common (over the year) on natural substrates were also common the a r t i f i c i a l substrates. Although there were more common species on the a r t i f i c i a l substrates (32 versus 24) the ad d i t i o n a l species were only occasionally abundant and had spotty or single common occurrences. As observed f o r natural populations, few species on a r t i f i c i a l substrates were widespread or abundant i n a l l the arms of Kootenay Lake. Also, species which had d i s t i n c t patterns of occurrence on the natural substrates exhibited the same d i s t r i b u t i o n (with only a few exceptions) on the a r t i f i c i a l substrates. Furthermore, most species on a r t i f i c i a l substrates were only occasionally common or else had d i s j o i n t e d occurrences that could not be re l a t e d to major lake regions. Although diatom species trends were s i m i l a r on the two types of substrate, actual l e v e l s of abundance were seldom i d e n t i c a l . Most common species, p a r t i c u l a r l y Achnanthes minutissima and the Fragilaria construens complex, were not as abundant on the a r t i f i c i a l substrates. The more even d i s t r i b u t i o n of species numbers could perhaps be r e l a t e d to the short two-week exposure period which should reduce the amount of diatom competition on the a r t i f i c i a l substrates. Not s u r p r i s i n g l y , there are, on a yearly average, more common diatoms per sample on the a r t i f i c i a l substrates than on the F i g . 49. Average percent numeric composition of common diatom species {>. 5 percent of the t o t a l number) attached to a r t i f i c i a l substrates at 0.1, 1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973. The species are: AF, Asterione^la formosa; Am, Aohnanth.es minutissima; Aop, Amphora ovalis v. pediculus; Cc, Cymbella caespitosa; C c i , Cymbella cistula; Cv, Cymbella ventrioosaj Cyg, Cyclotella glomerata; Dt, Diatoma tenue; Es, Epithemia sorex; Fc, Fragilaria eonstruens complex; Fca, Fragilaria capucina; Fcr, Fragilaria arotonensis; Fv, Fragilaria vaucheriae; Gh, Gomphonema herculeanum; Gms, Gomphonema montanum v. subolavatum; Na, Navioula acoomoda; Nit, Nitzschia species complex; Oth, a l l other species; Sa, Stephanodiscus astraea; Sam, Stephanodisous astraea v. minutula; Sh, Stephanodiscus hantzsohii; Sm, Synedra mazamaensis; Ss, Synedra aous. 109 tOO-i Sam Nl 0.1 m depth Cc Ss NS SS S2 W2 Sam "Sa-cyo. W7 KX)-i Am sir 1.0 m depth Fc Fcr Fc Nl N2 N3 N4 N5 N6 N12 N7 S6 S5 S4 S3 S2 SI ' w i W2 W3 W4 W5 W6 W7 — W O - i S O H 3.0 m depth oth Es Fcr Al TUT Es At  Sam Am Nit Al Sam N l NS SS S2 W2 W7 WO-i Aop 5.0 m depth 3E Am Sh Sam Al Sam Sa £jra_ N l N S North-O-SS S2 - • S o u t h W2 W7 - • W e s t j MAIN LAKE STATIONS WEST ARM STATIONS F i g . 50. Average percent volumetric composition of common diatom species (> 5 percent of the t o t a l volume) attached to a r t i f i c i a l substrates at 0.1,1.0, 3.0, and 5.0 m i n Kootenay Lake, 1973. The species are: AF, Asterionella formosa; Ap, Amphipleura pellucida; Cas, Caloneis sp.; Cc, Cymbella caespitosa; Cs, Cymbella sp. "A"; Cp, Cymbella prostrata; Cya, Cymbella aspera; Es, Epithemia sorex; Et, Epithemia turgida; Fc, Fragilaria aonstruens complex; Fca, Fragilaria capuoina; Fcr, Fragilaria arotonensis; Fv, Fragilaria vauoheriae; Gh, Gomphonema herauleanum; Gms, Gomphonema montanum v. subalavatum; Mv, Melosira varians; Nit, Nitzsahia species comple: 0th, a l l other species; Rg, Rhopalodia gibba; Sa, Stephanodisous astraea; Sam, Stephanodisous astraea v. minutula; Ss, Synedra aaus; Su, Synedra ulna; Suh, Surirella helvetica. I l l wo-, J O -c. . 0.1 m depth Gh oth TT Gh Fc Es Fca A l NS SS S2 W2 W7 1.0 m depth tOO-i Cc Su F» ISanJ R9 p a Es S3. SL" « Nl N2 N3 N4 N5 N6 N12 N7 S6 S5 S4 S3 S2 SI ' w i W2 W3 W4 W5 W6 W7 I O O - i s o so-o z LU O CC Cp 3.0 m depth Sa E t F c r Es F c r Nl NS S5 S2 W2 W7 WO-i S O H Gms Fee Al Sa Nit 5.0 m depth Et Fcr  AI Sam Sa Es Gh Fcr Sa TJTT Fc JE»-oth Fcr Sa HL" Fc Nl NS North-O-SS S2 - • S o u t h MAIN LAKE STATIONS W2 W7 - • W e s t WEST ARM STATIONS 112 natural substrates (and, as mentioned previously, more i n d i v i d u a l common spec i e s — 3 2 versus 24). However, trends i n lakewide d i s t r i b u t i o n s of common species on the two types of substrates were s i m i l a r , with more common species i n the north arm than i n the south arm of Kootenay Lake. Numerically, there were 7.5 common species i n the north arm and only 5.5 common species i n the south arm, on a r t i f i c i a l substrates. S i m i l a r l y , i n the volumetric analysis there were 6.7 common species i n the north arm and 5.7 common species i n the south arm. Transfer Experiments Reciprocal t r a n s f e r experiment r e s u l t s are summarized for the diatoms Fragilaria aonstruens plus v a r i e t i e s (Fig. 51) and for F. vaucheriae (Fig. 52). These two morphologically s i m i l a r species were chosen as diatom d i s t r i b u t i o n data i n d i c a t e d that they represent opposite extremes i n t h e i r type of d i s t r i b u t i o n . Fragilaria aonstruens i s more common i n the eutrophic southern and westerm extremities of the lake, while F. vaucheriae i s common i n the more o l i g o t r o p h i c north arm. The r e c i p r o c a l transfers i n v o l v i n g these two species were designed to provide a d d i t i o n a l data on the r e l a t i v e importance of water chemistry i n determining t h e i r d i s t r i b u t i o n a l patterns. At the time the a l g a l substrates were transferred from the o r i g i n a l s i t e s (see methods f o r a complete d e s c r i p t i o n of the procedure), the abun-dances of the diatom species were supposedly the same at a l l s t a t i o n s . This i n i t i a l abundance i s represented by the dashed h o r i z o n t a l l i n e s i n figures 51 and 52. Since l i t t l e a d d i t i o n a l production should occur on these plates which were already colonized for two weeks (Patrick et. al_., 1954), any 113 co LU CC < > LU o z < Q Z D CO < < o cc LU 5 3 Z LU o cc 5CM 40H 30H 20-104 Init ial G r o w t h at S t a t i o n N l © In i t ia l a b u n d a n c e © © - A b u n d a n c e a f t e r t r a n s f e r C o n t r o l a b u n d a n c e 1 © 1 N l N5 S5 S i W2 W7 4 0 H Ini t ial G r o w t h at S t a t i o n S 2 © 30H 20H 10H © © 60 H 50H 40H 30-20H 10H 0 L-1H N l N5 Ini t ial G r o w t h at S t a t i o n W7 S5 S 2 S i W 2 W 7 N l N5 S5 S i W2 W7 F i g . 51. Growth response of the diatom Fragilaria aonstruens a f t e r the r e c i p r o c a l t r a n s f e r experiments at 1.0 m i n Kootenay Lake; 21 May-17 June, 1973. Dashed hor i z o n t a l l i n e s indicate i n i t i a l abundances, open rectangles are control abundances, s o l i d rectangles are t r a n s f e r abundances, p o s i t i v e symbols represent successful com-p e t i t i o n , negative symbols represent unsuccessful competition. Missing values are the r e s u l t of l o s t a r t i f i c i a l substrates. 114 In i t i a l G r o w t h at S t a t i o n N l F i g . 52. Growth response of the diatom Fvagitaria vaucheviae a f t e r the r e c i p r o c a l t r a n s f e r experiments at 1.0 m i n Kootenay Lake; 21 May-17 June, 1973. Dashed hor i z o n t a l l i n e s indicate i n i t i a l abundances, open rectangles are control abundances, s o l i d rectangles are tr a n s f e r abundances, p o s i t i v e symbols represent successful com-p e t i t i o n , negative symbols represent unsuccessful competition. Missing values are the r e s u l t of l o s t a r t i f i c i a l substrates. 115 increases or decreases i n a species' r e l a t i v e abundance should p r i m a r i l y be a r e s u l t of competition as influenced by factors such as water chemistry. Nevertheless, uncolonized control substrates (open rectangles, F i g . 51 and 52) were immersed at the time of the tr a n s f e r to measure diatom production and s e t t l i n g r ates. Since r e s u l t s are plo t t e d i n terms of percentage abundance rather than actual numbers, l o c a l s e t t l i n g rates could only a l t e r a species abundance when control percentage abundances are greater than transfer percentage abundances ( s o l i d rectangles. F i g . 51 and 52). Fragilaria aonstruens, whether i n i t i a l l y grown i n the north, south or west arm showed negative competitive responses or else very minor p o s i t i v e responses when transferred to the north arm of the lake (Fig. 51). (Missing values are the r e s u l t of l o s t a r t i f i c i a l substrates.) When transferred to the south arm, F. aonstruens markedly increased i t s percentage numerical abundance, except f o r one s l i g h t l y negative response. Results f o r populations transferred to the west arm are comparable to south arm responses. Evidently t h i s species, which i s most abundant i n the eutrophic areas of the lake, i s generally competitively successful i n those areas when compared to the other species. When tra n s f e r r e d to the more ol i g o t r o p h i c regions, F. aonstruens loses i t s competitive advantage and i t s percentage numerical abundance decreases s l i g h t l y . Fragilaria Vauoheriae, most abundant i n the north arm of the lake, greatly increased i t s percentage abundance when transferred to the north arm of the lake (Fig. 52). Responses i n the south arm are l e s s c l e a r , for i t . twice increased i n abundance and once decreased. Results also i n d i c a t e d only s l i g h t p o s i t i v e or negative responses when F. vauoheriae was grown i n the lake's west arm. ( I n i t i a l growth of F. vauoheriae i n the west arm was 116 below detection l i m i t s so that tran s f e r r e s u l t s are only presented f o r populations i n i t i a l l y grown i n the north or south arms of the lake.) 117 DISCUSSION Since 1953, when a Cominco Ltd. f e r t i l i z e r plant began operations, increased phosphate loadings to Kootenay Lake have aff e c t e d the lake's limnology. Chemical data from t h i s and other studies (Davis, MS 1973; Northcote 1972b, 1973a) have confirmed that phosphorus concentrations within the lake have increased i n response to the increased loadings. P r i o r to the f e r t i l i z e r plant development, dissolved orthophosphate concentrations i n 1949/1950 were about 0.001 mg 1 - 1 (Northcote, 1973a), placing Kootenay Lake i n the o l i g o t r o p h i c category. In response to p o l l u t i o n loads of as much as 8000 metric tons of phosphorus per year, dissolved orthophosphate concen-tr a t i o n s within the lake are now usually over 0.05 mg 1 - 1 during spring freshet. The phosphate concentrations are sometimes as high as 0.18 mg 1 - 1 and, as values over 0.01 mg 1 - 1 often cause a l g a l problems (Vollenweider, 1971; D i l l o n and Rigler, 1975), the lake can now be described as eutrophic. Since most of the natural background phosphorus and v i r t u a l l y a l l the i n d u s t r i a l p o l l u t i o n phosphorus enters the southern extremity of the lake (Northcote, 1973a - F i g . 5) v i a the Kootenay River i n l e t , a phosphate gradient would be expe:cted within Kootenay Lake. T h e o r e t i c a l l y , the south arm should have high l e v e l s ; the north arm, fed by the nutrient poor Duncan River, should have low l e v e l s ; and the west arm ou t l e t , which receives water from the south and north basins, should have intermediate phosphorus l e v e l s . Loadings of most other materials are also highest at the south end of the lake and the d i s t r i b u t i o n s of conservative'elements such as t o t a l dissolved s o l i d s , calcium and sodium do conform to the expected gradient (Fig. 17, 118 21, 22). S u r p r i s i n g l y , however, there appears to be l i t t l e measurable v a r i a t i o n i n the lake's phosphorus content (Fig. 13, 15). But phosphorus i s rap i d l y u t i l i z e d by algae and t h i s b i o l o g i c a l u t i l i z a t i o n often creates differences between expected and observed phosphorus concentrations. To minimize the e f f e c t s of phosphorus uptake by algae, Vollenweider (1971), Edmondson (1972), D i l l o n and Rigle r (1974, 1975) and others use l a t e winter or spring maximum phosphorus values i n determining a lake's trophic state and i n p r e d i c t i n g the planktonic a l g a l biomass during the next summer. But i n Kootenay Lake, even early spring phosphorus values (Fig. 13) showed l i t t l e regional v a r i a t i o n , compared to the expected phosphorus gradient based upon the vast differences i n loadings to the north and south extremities of the lake (Fig. 12). The r e l a t i o n s h i p between early spring phosphate l e v e l s and planktonic a l g a l biomass, while accounting f o r phosphate uptake by planktonic algae, do assume that early spring a l g a l populations are low and of minimal importance. In Kootenay Lake, attached a l g a l populations d i d not decrease dramatically during winter ( Fig. 29). I t is' therefore not s u r p r i s i n g that, even during early spring, inshore phosphorus readings i n Kootenay Lake do not e x h i b i t the expected regional v a r i a t i o n s . Phosphorus incorporation by Kootenay Lake's attached algae was determined i n d i r e c t l y , by multip l y i n g d a i l y growth rates by the amount of phosphorus normally occurring i n a l g a l c e l l s . At s t a t i o n Wl, f o r instance, maximum growth rates reached 0.32 mg organic cm ~ 2 day _ 1 or 1.423 mg dry weight cm " 2 day - 1 (using an e m p i r i c a l l y derived conversion f or Kootenay Lake attached algae of 1 mg organic: 4.45 mg dry weight). Assuming an average a l g a l phosphorus content of 11 yg mg 1 (Healey, 1973), phosphorus 119 incorporation during the day would be near 15.65 yg P cm or up to 46.96 yg P cm . f o r c e l l s r i c h i n phosphorus (phosphorus content can reach 33 yg mg 1 algae; Healey, 1973), . Phosphate incorporations t h i s high i n growing algae (not considering luxury uptake by algae already present) would reduce the phosphorus content of the water near the attached algae, and could conceivably mask any phosphorus gradient within Kootenay Lake. The amount of surplus stored phosphorus i n the a l g a l c e l l s was measured, and r e s u l t a n t data in d i c a t e that attached a l g a l phosphorus u t i l i z a t i o n and storage are high (Fig. 30, top). Furthermore, the regional v a r i a t i o n i n the a l g a l phosphorus storage corresponds w e l l with the lake's expected phosphorus gradient, south arm phosphorus storage being greater than north arm storage. The amounts of phosphorus storage i n the south arm were always i n d i c a t i v e of eutrophic conditions (F i t z g e r a l d , 1969). But a maximum l e v e l of about 2.5 yg mg - 1 dry weight algae at s t a t i o n S5 was not excessively high. L i n (1971) reported values as high as 8.4 yg from Ctadophora populations, and F i t z g e r a l d (1969) noted that during a planktonic blue-green a l g a l bloom i n eutrophic Lake Mendota phosphorus storage reached l e v e l s of 4.2 yg mg - 1 dry weight algae. Data from the north and west arms of Kootenay Lake are often, but not always, t y p i c a l of phosphorus l i m i t e d a l g a l popula-t i o n s . Some readings from s t a t i o n N5, for instance, were as high as 1.5 yg, while several other readings i n the north arm were below 1 yg, i n d i c a t i v e of phosphorus l i m i t e d populations ( F i t z g e r a l d , 1969) . The amount of surplus stored phosphorus per u n i t area of rock surface (rather than per dry weight of algae) also shows that there i s more phosphorus storage i n the south arm of the lake (Fig. 30, bottom). Differences 120 i n a l g a l abundance per u n i t area d i d not s i g n i f i c a n t l y a f f e c t the surplus phosphorus storage r e s u l t s , and the argument that less algae i n one lake region enables more phosphorus to be stored per u n i t weight of algae i s not v a l i d . A l g a l populations are influenced by many physical factors which must be accounted f o r , as these variables can p o t e n t i a l l y complicate or negate the attached a l g a l responses to nutrient conditions alone. Physical factors such as turbulence, lake l e v e l f l u c t u a t i o n s , temperature and l i g h t energy were measured, when p r a c t i c a b l e , and a stepwise multiple regression analysis was performed using these variables and chemical data, to assess the r e l a t i v e importance of each f a c t o r . Unfortunately, the variables alone, or i n combination, seldom accounted f o r much of the v a r i a b i l i t y i n a l g a l abundance, production or species composition. Furthermore, factors which were most important i n explaining some aspect-of a l g a l v a r i a b i l i t y , say abundance, were seldom as important i n explaining other aspects of the a l g a l v a r i a b i l i t y , such as the amount of green algae present. Probable short-comings which could explain the i n a b i l i t y of the multiple regression analyses to account f o r differences i n a l g a l populations include: the masking of chemical conditions by b i o l o g i c a l u t i l i z a t i o n and luxury consumption, the d i f f i c u l t y i n quantifying p h y s i c a l factors such as lake l e v e l f l u c t u a t i o n s , lack of data on lake turbulence and grazing rates, and the d i f f i c u l t y i n assessing the short term h i s t o r y of several parameters on the a l g a l community. However, the sampling program, whereby a l g a l c o l l e c t i o n s were made at several depths, does allow a q u a l i t a t i v e measure of the r e l a t i v e importance of various p h y s i c a l variables compared to chemical variables i n regulating Kootenay Lake's attached algae. Near the lake surface, f o r instance, 121 regional differences i n l i g h t penetration would be of minimal importance, whereas the amount of lake turbulence (1.0 m waves -.frequently occurred) and degree of water l e v e l f l u c t u a t i o n s (up to 1.3 m per week, F i g . 5) could possibly override any a l g a l responses to nutrient v a r i a t i o n s . S i m i l a r l y , at the deeper depths differences i n l i g h t penetration could complicate the a l g a l response to chemical d i f f e r e n c e s , but other p h y s i c a l factors such as lake turbulence would have l i t t l e e f f e c t . Chlorophyll a_ content near the lake surface (Fig. 23) was generally low, but conditions were extremely v a r i a b l e . During stable water l e v e l periods, the highest chlorophyll l e v e l s of the study occurred at the 0.1 m depth. This extreme v a r i a b i l i t y , combined with a lack of regional v a r i a t i o n , indicates that p h y s i c a l factors such as lake turbulence and water l e v e l f l u c t u a t i o n s are more important than chemical conditions i n regulating a l g a l populations near the lake surface. The general increase i n ch l o r o p h y l l content with depth i s i n d i c a t i v e of a more p h y s i c a l l y benign.environment. Despite the lower l i g h t penetration i n the south arm of the lake (Fig. 9) chlor o p h y l l i s highest there, i n d i c a t i n g the major importance of regional phosphorus v a r i a t i o n s and the minor e f f e c t of phys i c a l factors i n regulating the a l g a l abundance. Chlorophyll a content averaging 7 yg cm i n Kootenay Lake's south arm i s i n d i c a t i v e of eutrophic conditions, while north arm readings are lower and i n d i c a t i v e of more o l i g o t r o p h i c conditions (Fig. 23, 24). Kootenay Lake and lakes from the Okanagan Valley of B r i t i s h Columbia both drain i n t o the Columbia River, and both lake systems show s i m i l a r attached a l g a l responses to eutrophication. Chlorophyll content i n Kootenay Lake's south arm i s comparable to l e v e l s found i n Wood Lake, Skaha Lake and 122 Osoyoos Lake which also s u f f e r from over-enrichment (Stockner, Pomeroy, Carney, and Findlay; MS 1972). Kootenay Lake's north arm has chlorophyll l e v e l s that resemble those from Kalamalka Lake—the most o l i g o t r o p h i c of the Okanagan chain (Stockner et a l . , MS 1972). These north arm values are also s i m i l a r to l e v e l s found at Stony Point Bay i n o l i g o t r o p h i c Lake Superior (Stokes, Olson, and Odlaug; 1970), where mean chlor o p h y l l a_ content ranged from 1.49 - 7.35 yg cm ~ 2 . However, north arm values are c e r t a i n l y much higher than i n u l t r a o l i g o t r o p h i c systems such as Carnation Creek on Vancouver Island, where chlorophyll a_ values i n non-estuary regions average only 0.19 yg cm ~ 2 (Stockner and Shortreed, 1975) . V e r t i c a l v a r i a t i o n s i n organic weight p a r a l l e l e d chlorophyll a patterns. However, regional v a r i a t i o n s i n the amount of organics only occurred during summer months (Fig. 27)' when phosphorus concentrations were lowest. At that time, south arm organic weights were higher than north arm organic . -weights. Summer organic weights i n the south arm of the lake (Fig. 27) were s i m i l a r to maximum values of 2 - 3 mg organic cm ~ 2 reported from the more eutrophic lakes i n the Okanagan Val l e y (Stockner e_t a l . , MS 1972) . Biomasses were also equal to or greater than attached a l g a l weight i n other eutrophic systems such as the Ohio River near C i n c i n n a t i where weights were l e s s than 1 mg cm - 1 (Weber and Raschke, 1970) , Sedlice Reservoir i n Czechoslovakia where weight ranged from 0 - 4.91 mg cm ~" 2(Sladecek and Sladeckova, 1964) and the productive Ohanapecosh Hot Springs i n Washington State where accumulations only reached 0.764 mg cm ~ 2(Stockner, 1968) . But, south arm values were not excessively high, and were c e r t a i n l y less than values of 7.3 mg cm ~ 2 reported from eutrophic Lake Ti b e r i a s i n I s r a e l (Dor, 1970). 123 Summer organic weights from the north arm of the lake (Fig. 27) 9 — 7 were usually under 2 mg cm. at the deeper depths, and under 1 mg cm . at the shallow depths. Although these weights were s i m i l a r to some i n s u r p r i s i n g l y low biomass eutrophic waters, they were more t y p i c a l of o l i g o t r o p h i c systems. Kalamalka Lake i n the Okanagan, f or instance, had weights of about 1.0 mg cm ~ 2 (Stockner et a l . , MS 1972), Lake Superior's periphyton averaged between 0.91 - 1.7 mg organic cm ~ 2 (Fox et a l . , 1969) and a maximum reading i n u n f e r t i l i z e d Lake 240 of the Experimental Lakes Area i n northwestern Ontario was only 1.25 mg organic cm ~ 2 (Stockner and Armstrong, 1971). But, values were much greater than i n u l t r a o l i g o t r o p h i c Carnation Creek on Vancouver Island, where average crops only reached 0.086 mg cm - 2 i n non-estuary regions (Stockner and Shortreed, 1975). Furthermore, organic weights i n the north arm during non-summer periods, when phosphorus readings were higher, resembled south arm weights and were t y p i c a l of weights i n many eutrophic waters. Estimates of net primary production rates i n t h i s study are, at best, crude approximations of true production rates within Kootenay Lake, and r e s u l t s must be inte r p r e t e d with care. The absence of Cladophora aegagropila, an important component of the natural attached a l g a l assemblage at the deeper depths i n the lake's south arm, combined with the greater abundance of most other green a l g a l species on the a r t i f i c i a l production substrates, surely r e s u l t s i n some errors i n estimation of production rates. At the beginning of the incubation period, the bare a r t i f i c i a l substrates present an exce l l e n t habitat for attached a l g a l growth i n the normally crowded and space-limited l i t t o r a l zone. These p o t e n t i a l production rates 124 no doubt exceed actual production rates on the space-limited natural surfaces, a problem inherent, i n the method used but not encountered i n studies using C11* and oxygen light-dark p r o d u c t i v i t y methods. Comparisons with production rates determined by these other methods are also d i f f i c u l t because the a r t i f i c i a l method i s subject to natural regulating factors such as grazing, peeling and sloughing-off while C 1 4 and oxygen light-dark techniques l a r g e l y avoid these complications. Kootenay Lake's attached a l g a l production rates at the 0.1 and 1.0 m depths r e f l e c t e d the regional differences i n phosphorus loadings, with highest production rates occurring at the lake's south end.and decreasing northwards and westwards (Fig. 31). Regional v a r i a t i o n s d i d not occur at the deeper depths but, as mentioned, Cladophora aegagropila d i d not grow on the a r t i f i -c i a l production substrates as i t d i d on natural rock surfaces i n the lake's south end. If C. aegrogropila had grown on the a r t i f i c i a l substrates, production rates at the deep depths would c e r t a i n l y have been greatest i n the south arm as observed at the shallow depths. Inte r e s t i n g l y , production rates exhibited opposite depthwise trends to a l g a l biomass, with highest production rates at the shallow depths and lowest rates at the 3.0 and 5.0 m depths (even i n the lake's north arm where C. aegagropila never occurred and could not bias the comparisons). This high a l g a l production rate at the shallow depths (Fig. 31) contrasted with the low biomasses a c t u a l l y occurring there (Fig. 23, 25) suggests that factors other than water q u a l i t y influence surface a l g a l populations. Furthermore, since surface a l g a l biomasses were approximately the same throughout the lake despite the higher production c a p a b i l i t i e s i n the more eutrophic regions, i t appears that those other factors (probably changing lake l e v e l s and 125 turbulence) are most important and completely mask most a l g a l responses to water chemistry at shallow depths. Conversely, the lower production rates at 3.0 and 5.0 m (probably because of l i g h t l i m i t a t i o n s — e s p e c i a l l y i n the lake's south arm) contrasted with the greater biomasses occurring there suggests that these depths are generally benign. These a l g a l populations (with slower growths and higher biomasses than at the shallow depths) are probably older and more l i k e l y to be af f e c t e d by differences i n water chemistry. The occurrence of greater biomasses i n the more nutrient r i c h south arm, despite the lower l i g h t l e v e l s there, a t t e s t s to the importance of water chemistry i n i n f l u e n c i n g those populations. Daily production rates at the 0.1 and 1.0 m depths of about 0.02 -0.03 mg organic cm ~ 2 i n the south arm (Fig. 31) are s i m i l a r to values reported from other eutrophic waters. {'Data from other studies have often been transformed to express production i n terms of units used i n t h i s study. Mg of carbon produced were m u l t i p l i e d by 0.43 (average percent carbon i n dry weight a l g a l c e l l s — H e a l e y , 1973) and then divided by 4.4 (average dry weight/ organic weight r a t i o i n Kootenay Lake's attached algae). Production i n terms of dry weight was likewise divided by 4.4 to express i t i n terms of organic weight.} Daily production i n eutrophic Lake Tiberias i n I s r a e l , f o r instance, ranges from .0027 - .0436 mg organic cm ~ 2 (Dor, 1970) . Daily production rates expressed i n terms of my organic cm - 2 i n other eutrophic waters follow: Sedlice Reservoir i n Czechoslovakia has a mean net production rate of 0.0174 (Sladecek and Sladeckova, 1964), Danish Lake Fures0has a rate of 0.0426 (Hunding, 1971), Borax Lake a rate of 0.038 (Wetzel, 1963), thermal stream Ohanapecosh i n Washington State a rate of 0.0005 - 0.05 (Stockner, 1968), and 126 Red Cedar River i n Michigan a rate of 0.0281 (King and B a l l , 1966). Produc-t i o n rates i n a l l lakes from the Okanagan Valley (Stockner et a l . , MS 1972) were above 0.01 mg organic cm ~ 2 , and s i m i l a r to rates i n the south arm of Kootenay Lake. Although production rates i n even the o l i g o t r o p h i c Okanagan Lakes were high, most other o l i g o t r o p h i c systems had amazingly low rates. Compared to those systems, production rates of about .0.008 mg organic cm ~ 2 i n the surface waters of Kootenay Lake's north arm and at the deeper depths (0.005 - 0.01 mg organic cm ~ 2) throughout the lake could best be described as t y p i c a l of mesotrophic systems. Rates i n Lake Superior, for instance, ranged from 6.0 to 9.0 x 10 ~ 6 mg organic cm ~ 2 (Fox et. al_., 1969) . Carnation and Ritherdon Creeks on Vancouver Island had rates of 0.004-0.006 mg organic cm ~ 2 (Stockner and Shortreed, 1975) while Jacobs (Marion) Lake near Haney, B.C. had an attached a l g a l production rate of 0.0057 mg organic cm ~ 2 (Hargrave, 1969). The attached a l g a l assemblage i n Kootenay Lake i s s i m i l a r i n some respects to attached assemblages i n other north temperate lakes, with diatoms, greens and blue-greens being the only important a l g a l groups. However, diatoms are more abundant i n t h i s lake than i n other North American lakes (Evans and Stockner, 1972; Fox et_ al_., 1969; Stockner and Armstrong, 1971) . The great abundance of diatoms i n Kootenay Lake does not preclude the p o s s i b i l i t y that t h i s lake could be eutrophic, since n u t r i e n t r i c h waters can be dominated by c e r t a i n diatom species as well as by green or blue-green algae. Furthermore, i n Kootenay Lake green algae sometimes dominate f o r short periods, e s p e c i a l l y during the spring and f a l l (Fig. 33) when d i s t i n c t 127 bands of green algae occur near the lake . surface. Despite the general diatom dominance, there were some d i s t i n c t gradients and v a r i a t i o n s i n the abundance of the major a l g a l classes within Kootenay Lake. Blue-green algae generally increased along the length of the west arm (Fig. 32). Several blue-green species, such as Calothrix sp., Vhormidium sp., Saoaonema rupestre and Tolypothrix distorta, were also l o c a l i z e d i n that region of the lake. I t i s well known that t h i s a l g a l group often increases with sewage p o l l u t i o n where n i t r a t e s , phosphates and concentrations of organics are increased. The high n i t r a t e and phoshpate loadings (Northcote, 1972b) i n the heavily populated west arm do indicate the probable existence of sewage p o l l u t i o n and thus explain increases i n blue-green algae there. In contrast, the main lake has only high inorganic ( f e r t i l i z e r plant) phosphate loadings, and smaller populations of blue-green algae occur there. At the deeper depths, the increase i n green algae at the south end of the lake i s a t t r i b u t a b l e to the occurrence of Cladophora aegagropila (Fig. 35 top, 36). This alga i s a shade-loving species which seems to occur only i n eutrophic waters such as the Seine River at Paris (Hoek, 1963) . I t s absence i n the north arm can be a t t r i b u t e d to lack of nutrients but not to subsurface i l l u m i n a t i o n , as C. aegagropila was absent at even the 10.0 and 14.0 m depth where l i g h t l e v e l s are even les s than those at the 3.0 and 5.0 m depths i n the south arm. Other Cladophora species also appear to be i n d i c a -t i v e of waters r i c h i n nutrients, p a r t i c u l a r l y phosphorus. P i t c a i r n and Hawkes (1973) found that i n a number of English r i v e r s the standing crop of Cladophora was correlated with phosphorus concentrations. Adams and Stone 128 (1973) found that Cladophora photosynthesis was c o r r e l a t e d with phosphorus i n Lake Michigan. Also i n Lake Michigan, L i n (1971) noted that Cladophora glomerata biomasses increased near phosphorus sources and that the amount of excess stored phosphorus i n the alga also increased. Cladophora was also reported from a number of other eutrophic lakes and r i v e r s including Lake Ontario ( B e l l i s and McLarty, 1967), the lower Fraser River (Northcote et a l . , 1975) and several lakes i n the Okanagan Valley (Stockner et a l . , MS 1972). In Kootenay Lake, Cladophora populations were also highest during the warmest months, as Verduin (1972) observed i n the Laurentian Great Lakes. During peak growing periods, Whitton (1970) found that C. glomerata could double i t s fresh weight i n 21-26 hours. Such data confirm that Cladophora i s simply unable to grow.on a r t i f i c i a l substrates, not that the two week exposure period was too short a time to grow the species, as Hynes (1960) suggests can be the case for some species, e s p e c i a l l y encrusting forms. I t i s also i n t e r e s t i n g to note that Kootenay Lake's Cladophora was extensively covered with epiphytes, a condition which i s rare for nitrogen l i m i t e d populations (Whitton, 1971) . Apparently, there i s enough background nitrogen loading to the lake to support the large a l g a l biomasses responding to the increased phosphorus loads. The increase i n diatom numbers with depth (Fig. 37) corresponds to the organic weight and c h l o r o p h y l l a_ pattern. Also, the higher diatom production rate (Fig. 39) nearer the lake surface agrees well with other biomass r e s u l t s . Both types of data support the contention that attached algae at 3.0 and 5.0 m are more influenced by the water q u a l i t y than are f a s t growing but more exposed and therefore less abundant surface populations. 129 The length of exposure probably influences the numbers of diatoms and other types of algae produced on a r t i f i c i a l glass or p l e x i g l a s substrates. In Kootenay Lake diatom numbers are higher on natural substrates than on a r t i f i c i a l substrates. Obviously, diatom numbers obtained from a r t i f i c i a l glass or p l e x i g l a s substrates immersed for varying amounts of time cannot be e a s i l y compared unless exposure periods are s i m i l a r . In p a r t i c u l a r , Butcher's (1949) trophic c l a s s i f i c a t i o n of r i v e r s , based upon diatom numbers attached to glass s l i d e s (in h i s case f o r 20-30 day periods; Butcher, 1940) must be considered i n v a l i d because of the e f f e c t of the exposure period. Butcher states that o l i g o t r o p h i c r i v e r s support diatom numbers ranging from 0.1 x 10 6 - 0.5 x 10 6 c e l l s cm ~ 2 and natural eutrophic r i v e r s have populations of 0.5 x 10 6 - 1.0 x 10 6 c e l l s cm ~ 2 . These supposedly high diatom numbers obtained from the a r t i f i c i a l substrates, are i n f a c t much less than diatom numbers obtained from natural substrates i n both o l i g o t r o p h i c and eutrophic lakes and r i v e r s (Fox et a l . , 1969; Northcote et a l . , 1975; Tai and Hodgkiss, 1975). Numerical diatom density i n Kootenay Lake (ranging from 0.5 x 10 6 - 3.5 x 10 e c e l l s cm ~ 2) agrees well with many recent i n v e s t i g a t i o n s where natural assemblages were studied. Results are s i m i l a r to values ranging from .497 x 10 6 - 1.47 x 10 6 c e l l s cm ~ 2 reported from o l i g o t r o p h i c Lake Superior (Fox et_ al_., 1969) and much less than 1.98 x 10 7 c e l l s cm 2 found by Tai and Hodgkiss (1975) i n eutrophic Plover Cove Reservoir i n Hong Kong. However, there do not appear to be d e f i n i t e increases i n diatom numbers with eutrophication. Temporary ponds on B a f f i n Island, for instance, support populations of up to 1.6 x 10 8 c e l l s cm ~ 2 (Moore, 1974) . Douglas (1958) studying a nutrient-poor English stream reported numbers of over 1 x 10 6 Achnanthes species alone. 130 Diatom c e l l volume measurements more accurately describe diatom density. Small species, f o r instance, would not greatly increase a sample's diatom volume but would increase c e l l numbers. In Kootenay Lake average c e l l volumes are highest near the lake surface (Fig. 38, 40). These large diatoms, often possessing j e l l y s t a l k s , are b e t t e r able to remain attached and main-t a i n an aqueous environment when subjected to wave ac t i o n or exposed by a l t e r e d lake l e v e l s (Patrick, 1948). Absolute c e l l volumes of between 0.5-4 mm3 cm - 2,.of rock surface i n Kootenay Lake are less than most diatom volumes i n B a f f i n Island ponds (Moore, 1974) where standing crops reached 218.99 mm3 cm 2 . Volumes di d compare well with volumes ranging from 0.3-10 mm3 cm 2 navigation buoys immersed for 145 days i n Lake Winnepeg (Evans and Stockner, 1972). Obviously much more data i s needed before diatom volumes can accurately be r e l a t e d to trophic conditions. A l g a l d i v e r s i t y has often been used as a measure of water q u a l i t y . Stresses caused by t o x i c wastes r e s u l t i n reductions i n the numbers of species as well as i n other d i v e r s i t y measures (Cairns and Lanza, 1972) . Hohn (1961) noted that the introduction of highly t o x i c pollutants resulted i n the reduction i n diatom d i v e r s i t y , the degree of reduction being dependent upon the s e v e r i t y of the p o l l u t a n t . Besch, Ricard, and Cantin (1972) confirmed that reductions i n the numbers of diatom species occurred i n the Northwest Miramichi River i n New Brunswick as a r e s u l t of mining (primarily z i n c and copper) p o l l u t i o n . Williams and Mount (1965) observed reductions i n a l g a l d i v e r s i t y with additions of zinc, and Cairns et_ a l . (1973) also observed lowered d i v e r s i t i e s i n p o l l u t e d systems. The e f f e c t s of eutrophication on a l g a l d i v e r s i t y are more complex, 131 except i n the zone of i n i t i a l influence of sewage discharges etc., where deoxygenation reduces d i v e r s i t y . Williams (1964, 1972), for instance, i n a study of United States r i v e r s concludes that eutrophic stations were generally les s diverse than "clean" s t a t i o n s . In a paleolimnological study of Lake Washington, Stockner and Benson (1967) found that d i v e r s i t y decreased with eutrophication. However, i n a study of Lake Ontario's sediments, Duthie and Sreenivasa (1972) observed that diatom d i v e r s i t y did not decrease with eutrophication. Apparently, enrichment of waters does not always stress aquatic systems to the point where d i v e r s i t y i s decreased. Krebs (1972) even states that high p r o d u c t i v i t y i s sometimes considered necessary for high d i v e r s i t i e s . Archibald (1972) argues that though severely p o l l u t e d waters have low d i v e r s i t i e s , clean waters can have d i v e r s i t i e s ranging from high to low as a r e s u l t _ o f enrivonmental factors other than p o l l u t i o n which a f f e c t the structure of a community. A great deal of care i s obviously needed i n the i n t e r p r e t a t i o n of t h i s parameter. Shannon-Wiener d i v e r s i t i e s of about 2.5 - 3.5 within Kootenay Lake (Fig. 42) were c e r t a i n l y well above values of 1.0 which Weber (1973) considers i n d i c a t i v e of p o l l u t e d waters. Values i n the north arm of the lake were generally higher than i n the south arm. Though t h i s pattern agrees well with previous measures of the a l g a l community i n d i c a t i n g the "cleaner" nature of the north arm, the d i v e r s i t y v a r i a t i o n s may be c o i n c i d e n t a l , as even south arm values were high. Indeed, there were no regional differences i n the t o t a l numbers of species (Fig. 43), although there were more common species (making up 5 percent or more of the t o t a l diatom abundance) i n the north arm of the lake. 132 Cluster a n a l y s i s , using diatom data from a l l stations and depths, grouped together e c o l o g i c a l l y r e l a t e d areas of Kootenay Lake. These s t a t i o n grouping were remarkably s i m i l a r to q u a l i t a t i v e separations previously made using biomass, production and other types of attached algae data. North arm and south arm s t a t i o n s , which received v a s t l y d i f f e r e n t phosphate loadings, separated into two d i s t i n c t groups (Fig. 45, 46). V e r t i c a l comparisons supported the d i s t i n c t i v e n e s s of the upper splash zone a l g a l community compared to a l g a l populations at the 3.0 and 5.0 m depths. Diatom species (and other types of algae) have long been used as i n d i c a t o r s of s p e c i f i c water types. Although the p h y s i o l o g i c a l requirements of many species are not known, a large number of quantitative d i s t r i b u t i o n a l studies do r e l a t e diatom species to various amounts of nutrients and p o l l u t a n t s . Problems with the use of i n d i c a t o r species occur, as some researchers have 'overanalyzed' t h e i r data, designating q u a n t i t a t i v e l y unimportant species as i n d i c a t o r organisms. The frequent occurrence of abnormal c e l l s i n some species (Cholnoky-Pfannkuche, 1971) can cause m i s i d e n t i f i c a t i o n s and also confuse the l i t e r a t u r e . In t h i s study, only diatoms that were dominant i n yearly average data (rather than i n single samples) were used to form conclusions about water q u a l i t y . This procedure should s e l e c t the most r e l i a b l e information on species d i s t r i b u t i o n s and, by the bulk of c e l l s involved, i s l i k e l y to minimize problems associated with i n c o r r e c t i d e n t i f i c a t i o n s . Even with t h i s procedure, 34 species were dominant at a minimum of one s t a t i o n i n yearly average samples. Analysis of these 34 species d i s t r i b u t i o n s has the p o t e n t i a l to produce many conclusions about the water q u a l i t y and the supportive evidence 133 of a l l the i n d i c a t o r s further minimizes problems r e l a t e d to possible mis-i d e n t i f i c a t i o n s . Perhaps my greatest safeguard against making i n c o r r e c t species i n d i c a t o r assessments was Kootenay Lake's phosphate gradient, which acts as a b u i l t - i n c o n t r o l . Other than t h i s phosphate gradient, attached algae i n the north and south arms of the lake are exposed to very s i m i l a r conditions, which are not l i k e l y to influence the between s t a t i o n a l g a l v a r i a t i o n s . However, i n i n t e r p r e t i n g the a l g a l d i s t r i b u t i o n s , more care i s needed when comparing main lake algae to west arm algae, the west arm^ having a more l o t i c environment as well as domestic sewage inputs. Reciprocal t r a n s f e r experiments strengthen conclusions made about the nutrient preferences of the diatom species. Decreases or increases i n species abundancies a f t e r the transfers can be q u a n t i f i e d and r e l a t e d to the p a r t i c u l a r species' environ-mental preferences, based upon Kootenay Lake d i s t r i b u t i o n a l data and l i t e r a t u r e reports. Kootenay Lake's diatom f l o r a i s dominated by a l k a l i p h i l i c species commonly e x h i b i t i n g eurytopic or eutrophic nutrient preferences. Nevertheless there are several d i s t i n c t diatom d i s t r i b u t i o n a l patterns i n d i c a t i v e of s p e c i f i c regional or depthwise conditions within the lake (Fig. 47-50) . A l g a l assemblages i n the splash zone of the main section of Kootenay Lake, for instance, were dominated by species able to withstand exposure and turbulence. Diatoms at the lake surface, characterized by Cymbetta sp. A and Gomphonema herculeanum, were larger than those found at other depths. This large size and the presence of gelatinous secretions are the main adaptations enabling them to withstand the p h y s i c a l stresses. 134 The lack of regional v a r i a t i o n s i n the main lake for these two species further indicates that they are p r i m a r i l y adapted to p h y s i c a l stresses rather than to nutrient l e v e l s . The Cymbella species i s , as yet, u n i d e n t i f i e d and comparisons with other systems cannot be made. Gomphonema herculeanum, however, not only grows i n the eutrophic south arm of Kootenay Lake but i s also dominant i n u l t r a o l i g o t r o p h i c but turbulent Lake Tahoe (Goldman, 1974) further confirming the species 1 adaptations to p h y s i c a l stresses and i t s wide nutrient tolerances. Diatom patterns i n d i c a t e that the splash zone of Kootenay Lake's west arm i s s i g n i f i c a n t l y d i f f e r e n t from that of the main lake. Species to l e r a n t of p h y s i c a l stresses are v i r t u a l l y absent from the west arm of the lake. Instead, the diatom assemblage more closely, resembles those found at deeper west arm l o c a t i o n s . These data conform, to other evidence that the west arm i s smaller, more protected and l e s s subject to wind and wave acti o n . Furthermore, diatoms from the west arm shoreline are t y p i c a l planktonic species rather than attached forms. These species, characterized by Astevionella formosa, Fragilaria crotonensis, Melosira varians and Stephanodisous astraea, probably originated from the pelagic regions of the main lake and began s e t t l i n g to the bottom once the water entered the r i v e r -l i k e west arm. These "west arm" species t y p i c a l l y dominate eutrophic waters (Brown and Austin, 1973; Gasse, 1974b.; Golowin, 1968; Haworth, 1972; Palmer, 1969; Patrick, 1948; Patrick and Reimer, 1966; Stockner, 1972; Stockner and Benson, 1967; Whitton, 1974), although some of these species are also considered eurytopic (Duthie and Sreenivasa, 1972; Stoermer, Taylor, and Callender, 1971; Turoboyski, 1973), and Fragilaria orotonensis can even be 135 dominant i n some ol i g o t r o p h i c lakes (Goldman, 1974; Patrick and Reimer, 1966). However, the possible transport of these species from the main lake prevents the west arm from being described as eutrophic. The ubiquitous occurrence of a few species underlies some basic lakewide s i m i l a r i t i e s , despite varying phosphate l e v e l s and phys i c a l stresses. Aohnanthes minutissima, for instance, i s equally common i n a l l three major lake regions, perhaps responding to s i m i l a r a l k a l i n i t i e s and s i m i l a r l e v e l s of several other chemical constituents and ph y s i c a l parameters such as tem-perature and energy inputs. Achnanthes minutissima appears to be an i n d i c a t o r of temperate waters i n general (Besch et_ al_. , 1972; Brown and Austin, 1973; Castenholz, I960; Douglass, 1958; Ennis, 1975; Foged, 1954; Godward, 1937; Schoeman, 1972; Stockner and Armstrong, 1971), only disappearing where toxic or anoxic conditions p r e v a i l (Besch et a l . , 1972; Schoeman, 1972). I t s widespread d i s t r i b u t i o n within Kootenay Lake perhaps a t t e s t i f i e s to a generally healthy, non-toxic (even i f eutrophic) environment. The Nitzschia species complex, making up about 5 percent of the diatom population at a l l s t a t i o n s , can be r e l a t e d to r e l a t i v e l y low and evenly dispersed nitrogen l e v e l s within the lake. The Nitzschia abundancies i n Kootenay Lake are c e r t a i n l y w ell below dominance l e v e l s of at l e a s t 50 percent associated with high nitrogen l e v e l s from sewage p l a n t o u t f a l l s (Schoeman, 1972). Species e x h i b i t i n g d i s t r i b u t i o n a l gradients i n the north and south arms have the most p o t e n t i a l as in d i c a t o r s of phosphorus-produced eutrophi-cation. Fragilaria vaucheriae best represents the group of species which grow optimally i n the north arm, barely t o l e r a t i n g the south arm of the lake and i t s high inputs of phosphorus. This species i s reported as being 136 eurytopic to mesotrophic i n d i s t r i b u t i o n (Foged, 1954; Stoermer et a l . , 1971). Reciprocal tran s f e r experiments confirm that F. vauoheriae achieved i t s highest dominance l e v e l s i n the north arm rather than i n the phosphate r i c h south arm. The increased abundance of Fragilaria aonstruens (and v a r i e t i e s ) i n regions of high phosphate loadings, at a l l depths, suggests the species' value as an i n d i c a t o r organism. Indeed, the species has generally been associated with eutrophication i n other lakes (Gasse, 1974a,b; Hunding, 1971; Richardson and Richardson, 1972; Stockner and Benson, 1967), although there are some reports from o l i g o t r o p h i c and mesotrophic lakes also (Patrick and Reimer, 1966; Schoeman, 1972). The t r a n s f e r experiments produced the most conclusive evidence of the value of F. aonstruens as an i n d i c a t o r of high phosphorus l e v e l s . Whether i n i t i a l l y grown i n the north, south or west arms i t usually showed negative competitive responses (occasionally very minor p o s i t i v e responses) when tra n s f e r r e d to the more o l i g o t r o p h i c north arm (Fig. 51) . A l t e r n a t i v e l y , the increase i n F. aonstruens dominance when trans-f e r r e d to the south arm region of high phosphate loadings (Fig. 51) further re i n f o r c e s the species' value as an i n d i c a t o r of phosphorus enrichment. 137 CONCLUSION The trophic c l a s s i f i c a t i o n of major regions within Kootenay Lake, based upon inshore phosphorus concentrations, would r e s u l t i n f a l s e impressions about the lake's water q u a l i t y . Consistent regional v a r i a t i o n s i n concentrations of dissolved orthophosphorus, t o t a l dissolved phosphorus or t o t a l i n s o l u b l e phosphorus were not apparent, despite large differences i n loadings to the north and south arms of Kootenay Lake. Calculations based upon phosphate supplies necessary to sustain the attached a l g a l growth rates show that attached algae remove large amounts of phosphorus from the water. This f a c t could p a r t l y account f o r the i n s u f f i c i e n c y of chemical data alone to detect regional v a r i a t i o n s i n the lake's trophic conditions. Furthermore, extractions of surplus stored phosphorus from the attached algae reveal that algae near areas of highest phosphate loadings contain much more stored phosphorus than do algae i n other regions of the lake. In contrast to the phosphorus r e s u l t s , Kootenay Lake's attached algae e x h i b i t regional v a r i a t i o n s . Resultant conclusions about water q u a l i t y v a r i a t i o n s within the lake do conform to expected patterns, considering the differences i n phosphate loadings to major regions of the lake. The south arm, a region of the high phosphate loading, has the highest amount of excess phosphorus storage, a l g a l abundance and production, r e s u l t s being comparable to those obtained i n several eutrophic waters. In contrast, the north arm algae store l e s s phosphorus, are less abundant, have lower growth rates, and are more t y p i c a l of mesotrophic and o l i g o t r o p h i c waters. Many of the green a l g a l and diatom species i d e n t i f i e d i n the south arm are considered to be 138 eutrophic i n d i c a t o r s . Moreover, these species are generally absent or less common i n other areas of Kootenay Lake. Diatom d i v e r s i t i e s were high throughout the lake, perhaps r e f l e c t i n g a healthy, even i f enriched environment. 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