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Analytical procedures for reducing uncertainty in the technological control of eutrophication Summers, Trevor J. 1978

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ANALYTICAL PROCEDURES FOR REDUCING UNCERTAINTY IN THE TECHNOLOGICAL CONTROL OF EUTROPHICATION TREVOR J . SUMMERS B . A . , University of Calgary, 1975 A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTER OF SCIENCE i n . , . \ •.. THE FACULTY OF GRADUATE STUDIES THE SCHOOL OF COMMUNITY AND REGIONAL PLANNING We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA December, 1978 . QTrevor J . Summers, 1978 / I n presenting t h i s t h e s i s i n p a r t i a l f u l f i l m e n t of the requirements f o r an advanced degree at the U n i v e r s i t y of B r i t i s h Columbia, I agree t h a t the L i b r a r y s h a l l make i t f r e e l y a v a i l a b l e f o r reference and study. I f u r t h e r agree t h a t permission f o r extensive copying of t h i s t h e s i s f o r s c h o l a r l y purposes may be granted by the Head of my Department or by h i s r e p r e s e n t a t i v e s . I t i s understood t h a t copying or p u b l i c a t i o n of t h i s t h e s i s f o r f i n a n c i a l g a i n s h a l l not be allowed without my w r i t t e n permission. Department of Graduate Studies The U n i v e r s i t y of B r i t i s h Columbia 1075 Wesbrook Place Vancouver, Canada V6T 1W5 December, 1978 ABSTRACT The management of aquatic resources by technological means generates a significant degree of uncertainty regarding a system's performance and i t s potential impact upon the natural environment. The central concern of this thesis i s to i l l u s t r a t e the kinds of analyses that are required i n order to identify and reduce the uncertainties associated with the technological control of water quality. Provided as background informa-tion i s a general review of the seasonal dynamics of lakes, a statement of the concepts of natural and cultural eutrophication, an outline of the socio-economic costs associated with eutrophication, and a description of prominent remedial technologies. The specif ic situation examined herein i s Deer Lake within the Municipality of Burnaby. The natural and cultural environments of Deer Lake are described i n addition to the lake's morphology and indigenous biota. Specific water quality problems relevant to the intended cultural use of the lake (outdoor recreation) are, i n turn, ident i f ied and discussed These include water temperature, dissolved oxygen, turbidi ty , nutrient concentrations, and lake depth. As part of the analysis, the thesis proceeds to demonstrate the manner i n which water quality problems may be conceptualized from the perspective of intended resource use, and how the art iculat ion of these problems i n the prescribed form fac i l i ta tes the i n i t i a l selection of technologies appropriate to the task. The i l l u s t r a t i v e analyses of three remedial technological options are then conducted with a view to i i i i l l u s t r a t i n g how the d e f i c i e n c i e s of knowledge and the problems of l i m i t e d data may, to some extent, be overcome. This research concludes that the a n a l y t i c a l procedures employed here serves to introduce a greater degree of o b j e c t i v i t y to the process than might otherwise occur. In addition, such a structured approach provides f o r a more complete analysis of the problem with a greater degree of ri g o u r i n the r e s u l t s . F i n a l l y , recommendations f o r fu r t h e r research i n t h i s area are made with a view towards expanding the a p p l i c a -b i l i t y of, and introducing greater rigour i n , t h e format employed. i v TABLE OF CONTENTS CHAPTER Page I. INTRODUCTION 1 Overvi ew 1 Technological Uncertainty i n Aquatic Systems 2 A Statement of Thesis Objectives 3 II. THE CONCEPT OF EUTROPHICATION 5 Overview of the Aquatic Environment 5 Eutrophication as a Natural Process 8 Eutrophication as a Cultural Phenomenon 12 The Consequences of Cultural Eutrophication 14 The Control of Cultural Eutrophication 1? III. DEER LAKE: THE NATURE OF THE PROBLEM 25 The Natural Environment 25 Lake Morphometry and Aquatic Biota 26 The Cultural Environment 28 Problems of Water Quality 29 IV. ANALYSES OF LAKE RESTORATION TECHNOLOGIES 41 The Selection of Alternatives. 41 The Mechanical Removal of Hydrophytes for Nutrient Control 45 An Algicide for Turbidity Control 4 8 A r t i f i c i a l Destratification for Turbidity Control 56 V. CONCLUSION 6 4 LITERATURE CITED 69 APPENDIX 77 A. Deer Lake Stream Data 78 B. Deer Lake Algal Enumeration (cells ml ) Station 1 - September 25, 1976 79 C. Deer Lake Zooplankton Enumeration ^ Station 1 - September 25, 1976 (numbers ml - ) 80 D. Deer Lake Water Temperature Profile Station 1 October 30, 1976 81 V LIST OF TABLES Table Page 3-1. Morphometries Data f o r Deer Lake 27 3-2. Surface Areas at 0.5 m Contour Intervals 27 3-3. Suggested Water Quality Standards f o r Summer Recreational A c t i v i t i e s 29 3-4. Percent Light Transmission with Depth (Deer Lake) 35 _i 3-5. Deer Lake Colour (mg 1 Pt) 35 3-6. Secchi Disc Transparency (Deer Lake) 35 3-7. T o t a l P & T o t a l N Concentrations i n Deer Lake (vg l " 1 ) 37 3- 8. Very Approximate Ranges of Nutrients 37 3~9• Nutrient Loading of Deer Lake 38 3-10. Permissible Loading Levels f o r T o t a l Nitrogen and T o t a l Phosphorus (Biochemically A c t i v e ) ( g m - 2 y r -l) 38 3-11. Deer Lake pH (September, 1976) 39 4- 1. Recreational Levels of Use.and Water Quality Requirements 43 4-2. Chemical Composition of N. advena and N. odorata (as % dry weight) 4 6 4-3. Assumed Chemical Composition of N. advena and N. odorata 4 6 4-4. T o x i c i t y of CuS0v5H20 (% k i l l e d ) 51 4-5• Exemplary Case H i s t o r i e s of A l g a l Control C u s o ^ 53 v i LIST OF TABLES (CONTINUED) Table Page 4-6. Copper S u l f a t e ( C u S 0 4 ' 5 H 2 0 ) T o x i c i t y t o Salmo g a i r d n e r i 55 4-7. Successes and F a i l u r e s of A r t i f i c i a l D e s t r a t i f i c a t i o n i n C o n t r o l l i n g A l g a l Concentrations 58 4-8. A Comparison of P h y s i c a l and Chemical P r o p e r t i e s between Kezar Lake, New Hampshire (before and a f t e r ) and Deer Lake 59 4-9. Kezar Lake A l g a l Enumeration I968-I969, Genus Aphanizomenon ( c e l l s m l ~ l ) 61 v i i LIST OF FIGURES Figure Page 2- 1. Theore t ica l Temperature and Dissolved Oxygen P r o f i l e s i n TemperateeDimictic Lakes 6 3- 1. Deer Lake Water Temperature P r o f i l e s Stations 1 and 2 September 26, 19?6 (From Zoology 404 Laboratory Data) 31 3-2. Deer Lake Dissolved Oxygen P r o f i l e s Stations 1 and 2 September 26, 19?6 (From Zoology 404 Laboratory Data) 33 v i i i ACKNOWLEDGMENT I would l ike to express my appreciation to Professor Irving K. Fox for the suggestions and guidance given me i n writing this thesis. In addition, Dr. Ken Hal l provided constructive cr i t ic ism and a sense of humour during a d i f f i c u l t period of time. I am also indebted to Valerie J . Dann B . S c , for her love, companionship, and typing expertise. Also of great importance was the companionship provided by my dog, Socrates, and the support of my friends, Doctors Gerald P. and El len Belton. Trevor J . Summers 1 CHAPTER I INTRODUCTION " . . . during the 1950 's approximately 75 percent of . . . outdoor recreation was water oriented . . . by the year 2000 the demand for water recreation w i l l t r i p l e . " Clawson, 1959 "Sometime before the year 2000, unless something i s done to avert the situation, we sha l l f ind ourselves l i v ing i n the middle of an Algal Bowl." Valientyne, 197^ Overvi ew A phenomenon well known to psychology i s the personal "aha" experience (Krech et a l . , 19^9) that reflects the spontaneous compre-hension of factual information, an abstract idea, or the solution to a problem. While significant progress has been made to date towards the proper management of Canada's invaluable freshwater resources, the degradation of aquatic systems continues. From the successes enjoyed i t may be speculated that the national consciousness has indeed had an "aha" experience and found the desire to avoid Vallentyne's future scenario. Judging from the less than overwhelming response, however, he and those before him cannot be accused of inc i t ing a r io t towards this cause. The environmental malaise i n Canada, as evidenced by eutrophicated aquatic systems, results from myriad complex factors. A consumer ethic, 2 f e d e r a l and p r o v i n c i a l j u r i s d i c t i o n a l disputes, and the complex i n t e r a c t i o n between the components of Canadian society (government bureaucracy, economic imperatives, and s o c i a l mores) often generates formidable b a r r i e r s t o the attainment of water q u a l i t y and resource management objectives. Whereas the mechanisms of government l e g i s l a t i o n and/or the i n s t i t u t i o n s of p r i v a t e property are often s u f f i c i e n t i n s t r u -ments with which to resolve the a l l o c a t i v e c o n f l i c t s i n land management, they are often inadequate i n the context of water resources. The problem originates from the h i s t o r i c a l treatment of water as a f r e e good, and the ubiquitous nature of t h i s resource (Anderson, 19?4). I r o n i c a l l y , i n urban regions where land use controls through mechanisms such as zoning are most s t r i c t , aquatic resources continue to exhibit r e l a t i v e l y poor water q u a l i t y . In such instances the causal f a c t o r i s often non-point source nutrient inputs. Obviously l e g i s l a t i o n i s i n e f f e c t u a l , and p r i v a t e property often contributes to the nutrient supply of lakes and r i v e r s . In these s i t u a t i o n s , planners and water resource managers are often compelled to resort to technological i n - l a k e procedures i n s p i t e of the uncertainties associated with t h e i r use. Technological Uncertainty i n Aquatic Systems Planning i s the exercise of choice-making under conditions of imperfect knowledge and uncertainty (Davis, I968). Whereas i n i t i a l phases of the planning process are concerned with problems of value ( i . e . c o n f l i c t s between resource users), the employment of technological methods may be s a i d to involve problems of knowledge and uncertainty 3 (Richerson and Johnston, 1975)' While i t i s common f o r the planning process t o design optimal s t r a t e g i e s towards economic e f f i c i e n c y and s o c i a l e g a l i t a r i a n i s m , i t i s not always evident t h a t equal energy i s a l l o c a t e d towards the m i t i g a t i o n of u n c e r t a i n t i e s a s s o c i a t e d w i t h a t e c h n o l o g i c a l programme. At a time when technology i s oft e n r e q u i r e d t o remedy environmental problems, i t would seem imperative t h a t a great d e a l of a t t e n t i o n be given t o the s e l e c t i o n of t e c h n o l o g i c a l methods i n order t o ensure the achievement of planning o b j e c t i v e s . T e c h n o l o g i c a l u n c e r t a i n t y , i n a general context, i s meant t o i n c l u d e those aspects surrounding a p o t e n t i a l t e c h n o l o g i c a l programme about which knowledge i s l a c k i n g . For i n s t a n c e , there i s u n c e r t a i n t y regarding the performance of a given t e c h n o l o g i c a l option i n d i f f e r e n t environmental contexts. A l s o , u n c e r t a i n t i e s e x i s t concerning the number of n o n - i n f e r i o r a l t e r n a t i v e s t r a t e g i e s t o consider (Cohon and Marks, 1974), and the s e l e c t i o n of a t e c h n o l o g i c a l method co n s i s t e n t w i t h the problems of water q u a l i t y and/or management requirements. Furthermore, the presence of s t o c h a s t i c processes w i t h i n the a q u a t i c environment generates u n c e r t a i n t i e s about e c o l o g i c a l response and success towards achie v i n g the d e s i r e d o b j e c t i v e s . A Statement of Thesis Objectives This research intends t o i l l u s t r a t e , through the study of a s p e c i f i c s i t u a t i o n and i n the context of l i m i t e d data, the kinds of analyses of t e c h n o l o g i c a l options t h a t are r e q u i r e d i n order t o i d e n t i f y and m i t i g a t e the u n c e r t a i n t i e s a s s o c i a t e d w i t h t h e i r use i n the c o n t r o l of water 4 q u a l i t y . The problems of water q u a l i t y d escribed h e r e i n are concep-t u a l i z e d from the pe r s p e c t i v e of intended resource use (i<?e. water-based r e c r e a t i o n ) , a step t h a t allows the i d e n t i f i c a t i o n of the most r e l e v a n t problematic parameters. The study then demonstrates how these parameters are c o r r e l a t e d w i t h designated l e v e l s of use ( i . e . s p e c i f i c a c t i v i t i e s ) , and i n t u r n how the water q u a l i t y problems r e q u i r i n g remedial a c t i o n are i d e n t i f i e d . From t h i s , and from the t h e o r e t i c a l knowledge a v a i l a b l e i n the l i t e r a t u r e , an i n i t i a l s e l e c t i o n of a l t e r n a t i v e t e c h n o l o g i c a l options i s then conducted i n a manner than enhances the p r o b a b i l i t y t h a t the remedial methods w i l l f i t the water q u a l i t y problem (Greene, 1973). I t must be s t a t e d t h a t the analyses of the engineering technologies s e l e c t e d f o r t h i s study are not intended t o be d e f i n i t i v e i n the sense th a t a p a r t i c u l a r option i s u l t i m a t e l y recommended. Instead, the analyses are meant t o exemplify the methods by which u n c e r t a i n t i e s p e r t a i n i n g t o the use of these technologies may be exposed and m i t i g a t e d . The a n a l y t i c a l procedures should be capable of generating a s h o r t - l i s t of n o n - i n f e r i o r a l t e r n a t i v e s t r a t e g i e s t h a t would, i n a r e a l i s t i c water q u a l i t y management s c e n a r i o , be subjected t o more d e t a i l e d s c r u t i n y i n the context of e m p i r i c a l data by a l i m n o l o g i s t . From these e f f o r t s an optimal t e c h n o l o g i c a l programme could then be formulated. 5 CHAPTER II THE CONCEPT OF EUTROPHICATION Overview of the Aquatic Environment The genesis of many temperate lakes can tie traced to the g lac ia l and tectonic processes of the past 15,000 years. Through time there evolved within each lake basin the water chemistry and biological communities that ref lect , i n part, the origin of the lake, i t s size and shape (morphology), the contribution of materials and energy from i t s watershed (edaphic factor) , regional climate, and the influence of Man. Consequently, temperate lakes di f fer i n ways that often defy visual recognition but can nevertheless be detected by instruments of limnological research. Basic physical processes associated with the water environment remain, however, common to most lakes of the temperate zone. Occurring as a seasonal phenomenon i n most temperate lakes i s the process of thermal cycling (Figure 2-1). Basically a response to seasonal differentials i n solar heating of the lake surface, thermal cycling consists of alternate periods of mixing (spring and autumn) and s trat i f i cat ion (summer and winter). Whereas to ta l mixing i s induced by wind forces acting upon the water column as i t approaches a uniform temperature, s trat i f i cat ion takes place when resistance forces imparted by f r i c t i o n , water density, or basin morphometry exceed the force of the surface wind. Because the density of water i s temperature-related T E M P E R A T U R E / D I S S O L V E D O X Y G E N D E P T H epilimnion metalimnion -summer str a t i f i c a t i o n autumnal overturn 1 ce cover winter st r a t i f i c a t i o n vernal overturn Figure 2-1. Theoretical Temperature and Dissolved Oxygen Profiles i n Temperate Dimictic Lakes 7 (maximum d e n s i t y at 3'94°C) and heat i s imparted t o lakes through the surface l a y e r , a temperature/density gradient g e n e r a l l y develops at depth where d e n s i t y r e s i s t a n c e i s equal t o the wind energy. A tempera-t u r e d i f f e r e n t i a l of only s e v e r a l degrees i s o f t e n s u f f i c i e n t t o produce a d e n s i t y gradient t h a t w i l l impede c i r c u l a t i o n (Wetzel, 1975). At t h i s point thermal s t r a t i f i c a t i o n of the lak e commences. The p a t t e r n of s t r a t i f i c a t i o n c o n s i s t s of three d i s t i n c t v e r t i c a l zones c a l l e d the e p i l i m n i o n , metaM.mm.on, and hypolimnion. The e p i l i m n i o n i s the uppermost zone of warm, i s o t h e r m a l , and c o n s t a n t l y mixed water. The metalimnion i s a temperature and d e n s i t y t r a n s i t i o n zone that demarcates the e q u i l i b r i u m depth between the mixing f o r c e of the wind and the r e s i s t a n c e f a c t o r s mentioned above. The metalimnion i s o l a t e s from atmospheric i n f l u e n c e s the lowermost r e g i o n of c o l d , i s o t h e r m a l , and r e l a t i v e l y s t a t i c water termed the hypolimnion. Subsequent t o summer s t r a t i f i c a t i o n i s the autumnal overturn (Figure 2 - l b ) . This mixing of the water column occurs as atmospheric c o o l i n g of the lake surface e f f e c t s a net heat l o s s and i n i n c r e a s e i n surface water d e n s i t y . When i t s d e n s i t y exceeds t h a t of the underlying l a y e r s , the surface water mixes by g r a v i t y displacement. Further e r o s i o n of the thermal g r a d i e n t i s accomplished by the mixing induced by sur f a c e winds u n t i l an i s o t h e r m a l p r o f i l e r e s u l t s . The formation of winter i c e e f f e c t i v e l y i s o l a t e s the lak e from wind disturbances thus t e r m i n a t i n g the autumn overturn (Figure 2 - l c ) . The winter thermal p r o f i l e , a l b e i t the apparent reverse of summer, 8 exhibi ts less dense water ( 0 ° C ) o v e r l y i n g water of greater density ( 4 ° C ) . The loss of heat beyond 4 ° C i s prevented by the in su la t ing act ion of the i c e . I t i s for t h i s reason that lakes do not freeze throughout t h e i r depth. The breakup of winter i c e exposes lakes to solar heating and surface winds. Isothermal temperatures are generally achieved quickly af ter breakup whereupon complete mixing of the water column occurs. This vernal mixing extends u n t i l the d i f f e r e n t i a l absorption of heat at the lake surface agai'n produces the period of summer s t r a t i f i c a t i o n . A phenomenon c lose ly re la ted to thermal cycl ing processes i n lakes i s the d i s t r i b u t i o n of dissolved oxygen. The s o l u b i l i t y of oxygen varies nonl inear ly with temperature, although i t also varies d i r e c t l y with the atmospheric p a r t i a l pressure of oxygen. I t i s d i s t r ibu ted throughout the water column during the biannual mixing periods by mechanical wave ac t ion and wind-induced water currents. While the primary source of oxygen i n water i s the atmosphere, plant photosynthesis may account for s ign i f i can t contributions to lake suppl ies . Figure 2-1 also depicts the re la t ionsh ip between oxygen concentration and water temperature, but i n i t s s i m p l i c i t y ignores the other factors of supply and demand. These factors are addressed i n the fol lowing sect ion. Eutrophication as a Natural Process Lake trophy refers to the rate of supply of organic matter from sources ei ther external (allochthonous) or i n t e r n a l (autochthonous) to the lake . Furthermore, i t i s an expression of the aggregate response 9 of the lake to the supply of nutrients that i s manifest i n i t s biology, chemistry, and physical water quality. Conceptually, the natural process of eutrophication refers to a spectrum of states of lake metabolism between the extremes of oligotrophy and eutrophy (Wetzel, 1975). While the concept of eutrophication has undergone an evolution i n meaning since i t s introduction (Hutchinson, 19&9), and the identifying c r i t e r i a have s imilarly changed (Hooper, I969), there i s general agreement regarding the relevant parameters and qualitative, distinctions that have been developed for assessing the trophic status of lakes. Oligotrophic lakes are characterist ical ly nutrient poor, and unproductive. Low rates of productivity and the minimal accumulation of organic matter results i n non-turbid water, a low to ta l biomass, and low biological oxygen demand (B.O.D.) . Because of morphometric character-i s t i c s (deep basins and large surface areas) that yie ld high hypolimnion to .epilimnion rat ios , their capacity to assimilate a given loading of nutrients and decomposing organic matter with l i t t l e or no effect upon water quality i s high. Oxidizing conditions within the hypolimnion, therefore, are common to oligotrophic lakes - a factor that i s in f luent ia l i n eliminating the regeneration of nutrients from the sediments (Mortimer, 1972). In fact , under oxidizing conditions the sediments act as a nutrient sink, especially for phosphorus, by absorbing amounts -1 -1 approaching 2.5 mg 1 day (Fi l los and Biswas, 1976). The functioning of the metalimnion during thermal s trat i f i cat ion further impedes the interzonal transfer of nutrients thereby res tr ic t ing production (Olah, 1975). Overt time, b a s i n i n f i l l i n g by the d e p o s i t i o n of organic d e b r i s and i n o r g a n i c sediments t r a n s p o r t e d t o a l a k e by streams brings about a r e d u c t i o n of the hypolimnion t o .-:epilimnion r a t i o . Under a given c l i m a t i c regime the heat budget of lakes i s consequently i n c r e a s e d . Resultant higher temperatures near the sediments exert a considerable i n f l u e n c e on the r a t e of chemical r e a c t i o n s and exchange processes, the r a t e of organic decomposition, the s o l u b i l i t y of oxygen i n water, and o v e r a l l lake metabolism. Furthermore, a shallow morphometry o f t e n precludes the thermal s t r a t i f i c a t i o n of l a k e s . With the disappearance or p a r t i a l erosibhoof the metalimnion there remains no d e n s i t y b a r r i e r t o the n u t r i e n t replenishment of the trophogenic or euphotic zone (zone of primary production) from sources w i t h i n the t r o p h o l y t i c zone (underlying zone of darkness). With s u f f i c i e n t a v a i l a b l e wind energy, the water column i s e a s i l y mixed, the e p i l i m n i o n i s r e s u p p l i e d w i t h n u t r i e n t s , and f u r t h e r production takes p l a c e . The l o s s of thermal s t r a t i f i c a t i o n through the gradual r e d u c t i o n of lake depth induces fundamental changes i n the dynamics of n u t r i e n t c y c l i n g . I n o l i g o t r o p h i c systems the primary source of n u t r i e n t s i s leachate from w i t h i n the lake's watershed. With s h i f t s i n trophy as measured by the p r o g r e s s i v e accumulation of organic matter, however, d e t r i t u s ( a l l dead p a r t i c u l a t e organic carbon) as a n u t r i e n t source predom-i n a t e s . I n l a k e s , the primary d e t r i t a l sources are l i t t o r a l v e g e t a t i o n and p e l a g i c algae. A f t e r the death of these organisms, n u t r i e n t s r e l e a s e d d u r ing t h e i r decomposition a c c e l e r a t e l a k e metabolism while consuming d i s s o l v e d oxygen. As b i o l o g i c a l oxygen demand exceeds the 11 oxygen supply, oxygen depletion occurs and a reducing environment prevai ls . Under anaerobic conditions phosphorus, for example, can he released at a -1 -1 rate approaching 3 nig 1 day (Fi l los and Biswas, 1976). At this point lakes become s e l f - f e r t i l i z i n g , and capable not only of sustaining produc-t ion , but of generating further shifts i n trophy independently of external perturbations and nutrient inputs, lakes exhibiting these characteristics are considered to be eutrophic. Concomitant with increases i n lake trophy from the i n i t i a l stage of development (oligotrophy) to the stage of maturity (eutrophy) i s the gradual evolution of the aquatic ecosystem i n terms of i t s structure and dynamics (Odum, 1969). Of perhaps greatest importance there occur structural changes involving species composition and increases in-sspecies diversity (Kormondy, 1976). On the functional side there i s a progressive accumulation of organic matter, concomitant with which i s a shift i n community metabolism from an autotrophic (photosynthesis/respiration >1) to a heterotrophic (photosynthesis/respiration< 1) condition. The latter represents the terminal state of eutrophication and the evolution to a t e r r e s t r i a l community. Before t e r r e s t r i a l succession i s achieved, however, the act iv i t ies of Man often bring about a substantially different sequence of events i n lakes. The nature of Man's influence on lakes i s considered next. 12 E u t r o p h i c a t i o n as a C u l t u r a l Phenomenon The a r t i f i c i a l i n t r o d u c t i o n of n u t r i e n t s i n t o freshwater l a k e s , and t h e i r subsequent response i n terms of p r o d u c t i v i t y i n c r e a s e s , the accumulation of biomass, and a general d e t e r i o r a t i o n of water q u a l i t y , i s c a l l e d c u l t u r a l e u t r o p h i c a t i o n . I n contrast t o the i m p e r c e p t i b l y slow process of the n a t u r a l form, c u l t u r a l e u t r o p h i c a t i o n i s a r a p i d phenomenon t h a t o f t e n becomes manifest a f t e r only s e v e r a l years of n u t r i e n t enrichment. Other d i s s i m i l a r i t i e s i n c l u d e the l a c k of accom-panying morphometric change, and the displacement of e v o l u t i o n a r y sequences t h a t would occur under c o n d i t i o n s of n a t u r a l f e r t i l i z a t i o n ( i j a r k i n , 1974). Other aspects of water q u a l i t y such as high t u r b i d i t y , a clinograde d i s s o l v e d oxygen p r o f i l e , reducing c o n d i t i o n s w i t h i n the hypolimnion, and high chemical concentrations may not, however, d i f f e r s u b s t a n t i a l l y from n a t u r a l consequences. I n accordance with the "law of the minimum1,"1 p r o d u c t i v i t y i s l i m i t e d by the f a c t o r of growth i n l e a s t supply r e l a t i v e t o that r e q u i r e d (Brady, 1974). Since phosphorus i s the l e a s t abundant element i n n a t u r a l waters, i t i s of t e n the l i m i t i n g n u t r i e n t . Through the in a d v e r t e n t or i n t e n t i o n a l i n t r o d u c t i o n of phosphorus t o lakes by Man, phosphorus l i m i t a t i o n s are oft e n overcome thereby s t i m u l a t i n g growth u n t i l another n u t r i e n t ( i . e . s i l i c a ) or f a c t o r of growth becomes l i m i t i n g . Phosphorus enters lakes from a v a r i e t y of poin t sources ( i . e . sewers, i n d u s t r i a l o u t f a l l s ) and non-point sources ( i . e . urban and a g r i c u l t u r a l r u n o f f , groundwater seepage). Because of gr e a t e r e f f i c i e n c i e s i n the c o l l e c t i o n and removal of p r e c i p i t a t i o n i n urban areas (Cordery, 1976), 13 nutrient contributions from non-point sources often exceed point source inputs (Cowan et a l . , 1976; Cowan and Lee, 1976). S imilarly , the contr i -bution of B.O.D. from re lat ive ly clean urban environments i s often high (Whipple et a l . , 197*0 and a contributing causal factor of the oxygen depletion of cultural ly eutrophicated lakes. Among the most v i s ib le manifestations of cultural eutrophication are increases i n l i t t o r a l f lora and the algae populations of the pelagic zone. In severely eutrophic lakes, one or more of the Bacillariophyceae (diatoms), Chlorophyta (green), Cyanophyta (blue-green) a lgal groups are often manifested i n the form of dense "blooms" within the pelagic zone. Meanwhile, the l i t t o r a l areas are often comprised of the climax macrophyte families Nymphaeaceae and Pinaceae. In many instances, the above populations and/or communities are p r o l i f i c and dense to the point that l imitations of l ight and/or space play a major part i n controlling further growth. While excessive growth of aquatic f lora i s a v i s ib le sign of eutro-phication, i t i s by no means an adequate indicator of trophic change. Since cultural eutrophication i s such a rapid phenomenon, i t has become necessary to develop indices that pinpoint incremental shifts or manifestations of increasing trophy. To this end such parameters as Secchi disc readings (Shannon and Brezonik, 1972), zooplankton species (Brooks, I969)> and changes i n f i sh species (Larkin and Northcote, I969) have been employed. One of the major problems involved with such indices, however, i s that a l l are responses to past occurrences of nutrient 14 enrichment. Also, morphometric change i s additionally unsuitable since i t does not necessarily accompany the cultural form of eutrophication (Hooper, 1969). One of the more commonly used mechanisms with which to detect trophic change i s the nutrient loading tables of Vollenwieder (I968). With these predictive tables, Vollenwieder attempts to relate the loading of phosphorus and nitrogen to trophic state (Table 2-1). Against mean depth of the lake, Vollenwieder provides permissible and dangerous loading rates on a weight per area per time basis. I f the dangerous loading l imit i s exceeded, the probability of eutrophication occurring i s high. Although this predictive tool may lack preciseness, i t provides a va l id mechanism with which to identify eutrophication i n i t s incipient stages, thereby allowing time for remedial action and the avoidance of the associated costs that the phenomenon of eutrophication entai ls . The Consequences of Cultural Eutrophication The cultural eutrophication of Canada's freshwater lakes i s one of the most pressing of our contemporary water resource problems (Schindler, 1974). Because water, unlike land, i s not easily rendered into private property i t i s a public resource or "commons" and as such i s available to a l l members of society. The public have tradi t ional ly had free access to lakes for recreational pursuits, while municipal governments often use lakes for the disposal of domestic wastes, and industry uses lakes and rivers for inputs to production and receptacles for industr ia l effluents. Like the "commons" described by Hardin (I968), therefore, our freshwater lakes are mistreated because of common ownership with no attendant responsibi l i t ies for proper management. Consequentially, the water quality problems of manyylakes today are acute to the point that short-f a l l s i n freshwater supplies are not caused by ineff iciencies i n the demand for and supply of physical quantities of water, but by the degradation of available water resources. Aside from the ethical implications and immorality of a socio-economic philosophy that permits such degradation, myriad socio-economic costs accrue either direct ly or ind irec t ly . A brief review of these should be indicative of the importance and relevance of the problem. From an economic perspective, some direct costs of cultural eutro-phication include the loss of revenue through decreased recreation demand, the loss of a municipal or provincial tourist attraction, the loss of an i r r i g a t i o n and industr ia l water source, and the costs incurred i n the search for alternative sources of freshwater. In most instances the individual i n society i s assessed the majority of costs either as a consumer through the increased price of goods, or as a taxpayer,by supporting the administrative and regulatory agencies of government charged with the responsibi l i t ies of resource management, protection, and u t i l i z a t i o n . In addition, with a commitment towards lake rehabi l i ta -t ion, the taxpayer i s assessed the cost of maintaining a pollution control agency, and through i t the cost of materials, energy, labour, and the development of appropriate remedial technologies. During the time required for remedial efforts to restore environ-mental quality, there accrue to society the opportunity costs of eutro-phication. Opportunity costs involve the lost opportunities i n investment 16 and development i n other social or economic f ie lds that society would normally have had, but that for the commitment of money, energy, and time to rehabil itate eutrophicated lakes, i s unable to take advantage of. Essential ly, these costs represent a reduction i n the number of planning options that are open to society, and as such fetter i t s economic and social development. The social costs of cultural eutrophication are both tangible and intangible. Tangible costs include the physical loss of the resource, and a lower standard of l iv ing as efforts are diverted from other soc ia l and economic development to cleanup ac t iv i t i e s . Intangible considerations include the psychic costs of resource degradation, decreases i n the quality of l i f e , and the costs born from the relationship between poor water quality and health. Cultural eutrophication i s fait-accompli i n many lakes today and incipient i n many others. Thus, many opportunities for social or economic development are, or w i l l be, lost . Astonishingly the concern and involvement of the public appears to be negatively correlated with the magnitude of the problem (Janisse et a l . , 197*+) • As the mitigation of cultural eutrophication i s increasingly left to the technologist and the array of technological remedies that exist, the importance of under-standing the limitations and purposes of these technologies must not be underplayed. In order to aquaint the reader with the remedial methods at their disposal, a review of several technologies i s presented next. 17 The C o n t r o l of C u l t u r a l E u t r o p h i c a t i o n While the behav i o u r a l and c o g n i t i v e approaches t o resource management (Hebe r l e i n , 1973) are valuable conceptual t o o l s f o r the c o n t r o l of c u l t u r a l e u t r o p h i c a t i o n , the most commonly employed methods are technolog-i c a l i n - l a k e schemes. B a s i c a l l y , the common o b j e c t i v e of the i n - l a k e technologies i s not complete l a k e r e h a b i l i t a t i o n , but an improvement t o a p r e s e l e c t e d standard i n one or more aspects of water q u a l i t y . As the n u t r i e n t l o a d i n g of lakes occurs p r i m a r i l y from non-point sources, complete r e s t o r a t i o n i s p o s s i b l e only i n conjunction w i t h appropriate land use c o n t r o l s (Howells, 1975)- As the i n - l a k e technologies impact only the symptoms of c u l t u r a l e u t r o p h i c a t i o n and not the causal f a c t o r s , t h i s l i m i t e d o b j e c t i v e i s not i n c o n s i s t e n t w i t h the methods employed. The t e c h n o l o g i c a l options developed f o r w a t e r - q u a l i t y management programmes may be dichotomized i n t o those t h a t address the problem of f e r t i l i t y , and those t h a t manage the consequences of o v e r f e r t i l i z a t i o n (Peterson et a l . , 197*0. Representative of the former are d i l u t i o n / f l u s h i n g and n u t r i e n t i n a c t i v a t i o n schemes, w h i l e i n c l u d e d i n the l a t t e r group are dredging, mechanical removal of macrophytes, a e r a t i o n systems, and a l g i c i d e s . As these options are designed t o r e l i e v e s p e c i f i c symptoms of e u t r o p h i c a t i o n , the s e l e c t i o n of methods i n a given s i t u a t i o n can be made only f o l l o w i n g anaassessment of the water q u a l i t y problem and an ev a l u a t i o n of the p o t e n t i a l environmental impact. Due t o energy l i n k a g e s w i t h i n ecosystems the p o s s i b i l i t y of i n d u c i n g adverse p e r t u r b a t i o n s through t e c h n o l o g i c a l i n t e r v e n t i o n must be minimized. 18 This study i n t e n d s , i n Chapter IV, t o provide an i l l u s t r a t i v e a n a l y s i s of three of the above t e c h n o l o g i c a l options. I n order t o f a m i l i a r i z e the reader w i t h the o b j e c t i v e s and modus operandi of these and other commonly employed t e c h n o l o g i e s , and t o provide a b a s i s f o r the s e l e c t i o n of t h r e e a l t e r n a t i v e s , a b r i e f review of each i s presented here. T e c h n o l o g i c a l o p t i o n ; mechanical removal of aq u a t i c macrophytes. The mechanical removal of aquatic macrophytes i s a r e l a t i v e l y s w i f t and simple procedure t h a t m i t i g a t e s , t e m p o r a r i l y , one of the most v i s i b l e symptoms of c u l t u r a l e u t r o p h i c a t i o n . Although the method i s , perhaps, more commonly employed t o c o n t r o l the s p a t i a l development and d e n s i t y of aquatic p l a n t s , under co n d i t i o n s of extensive macrophyte growth i t can be an e f f e c t i v e method of removing n u t r i e n t s from lakes (Livermore and Wunderlich, 19&9. Boyter and W a n i e l i s t a , 1973). I n t h i s c a p a c i t y the q u a n t i t y of n u t r i e n t s removed through h a r v e s t i n g must exceed the n u t r i e n t i n p u t t o the l a k e (Neel et a l . , 1973)- A p r e d i c t i o n of i t s n u t r i e n t removal p o t e n t i a l i s based upon a r e l a t i v e l y simple mathematical c a l c u l a t i o n . I n i t i a l l y , the n u t r i e n t (P and N) composition of the t a r g e t species must be determined. Since t h i s i n f o r m a t i o n i s a v a i l a b l e i n the l i t e r a t u r e f o r a number of aq u a t i c species the data o f t e n need not be generated e m p i r i c a l l y . A simple estimate of the number of t a r g e t p l a n t s per u n i t area, and by e x t r a p o l a t i o n the q u a n t i t y of n u t r i e n t s o r g a n i c a l l y bound i n the t a r g e t species w i t h i n the l a k e i s then p o s s i b l e . A comparison of the r e s u l t with the l a k e n u t r i e n t l o a d i n g i n f o r m a t i o n then provides a q u a n t i t a t i v e answer regarding the f e a s i b i l i t y of t h i s method. 19 In conjunction with the assessment of mathematical f eas ib i l i t y , the advantages and disadvantages of macrophyte removal must also be considered. For instance;,, the removal of large and highly v i s ib le quantities of aquatic f lora may be a pacif ier of public concern (Nicolson and Mace, 1975). Also, i t allows the immediate access to the lake for water-contact sports, and i t i s less ecologically harmful than chemical or other options. Furthermore, wi ldl i fe and wildfowl u t i l i z e the l i t t o r a l macrophytes for food and shelter (Fassett, 1940). Because many macrophyte species require specialized equipment for their removal (Mitchell , 1974), ambient nutrient levels remain unaffected, and success i s often only temporary (National Academy of Sciences, I968). Technological option: di lut ion/f lushing. The objective of di lution/f lushing i s to replace or dilute nutrient-rich water with a nutrient-poor supply i n order to curta i l lake productivity. The employ-ment of this technique for nutrient control i s feasible only i n situations where a source of nutrient-poor water i s available i n sufficient quantity, and where lake volume i s small. The water quality of small, urban lakes recharged by urban drainage, however, would benefit l i t t l e unless appropriate control of the quality of urban runoff accompanies the di lut ion scheme. While di lution/f lushing i s a theoretically acceptable method of mitigating nutrient-rich conditions, other important considerations are identi f ied by Dunst (1974). For instance, i t i s found that algal biomass may be reduced i n direct proportion to the amount of d i lut ion water supplied, that the effectiveness of di lut ion may be reduced by nutrient 20 leachate from the sediments, and because of a lake's morphology and hydrodynamics the hydraulic residence time may he suff ic ient ly long to prevent the real izat ion of optimal "benefits. Technological option; nutrient inact ivat ion. The objective of nutrient inactivation schemes i s to (1) remove essential nutrients ( i . e . phosphorus) from the trophogenic zone thereby l imit ing productivity, (2) change the form of nutrients so as to render them unavailable to the biota, and (3) prevent the recycling of nutrients from lake sediments (Peterson et a l . , 1974). With i r o n , aluminum, and calcium compounds the removal of P i s accomplished through the mechanisms of sorption, precipitation, and physical entrapment (Dunst, 1974). The effectiveness of these mechanisms, however, i s dependent upon such factors as pH of the receiving waters (Boyter and Wanielista, 1973) > "the hydraulic residence time, and nutrient loading rate (Environmental Protection Agency, 1973). Provided that conditions within the receiving waters are favourable, a re lat ive ly swift reduction of nutrient concentrations often occurs along with a decrease i n turbidi ty , and an improvement i n water colour. Poten-t i a l l y adverse consequences include fluctuations i n pH that are dangerous to aquatic organisms, the toxic effects of chemicals upon the aquatic biota, the decreased effectiveness of this technology i n deep lakes, and the short-term benefits i f nutrient loading to the lake i s not decreased. Technological option: dredging. Dredging freshwater lakes i s often undertaken to remove nutrient-rich sediments that have accumulated 21 over time, and t o i n c r e a s e h a b i t a t (Wilbur.?., 1974). A l s o , i t i s oft e n intended t h a t l i t t o r a l development be c o n t r o l l e d by lak e deepening,sand t h a t the subsequent i n c r e a s e i n l a k e volume promotes thermal s t r a t i f i c a -t i o n (Dunst, 1974). While older mechanical dredges of t e n ensured f a i l u r e r a t h e r than success, the reverse i s now oft e n t r u e w i t h new h y d r a u l i c dredge technology (Turner and Fairweather, 1974). The e f f e c t i v e n e s s of dredging a l s o depends upon such f a c t o r s as the depth and area dredged, the occurrence of slumping of p e r i p h e r a l sediments i n t o dredged areas, the n u t r i e n t content of sediments underlying the dredged areas, and the post-dredging morphological c h a r a c t e r i s t i c s t h a t i n f l u e n c e thermal s t r a t i f i c a t i on. I n h i b i t i n g f a c t o r s t o the implementation of dredging i n many s i t u a t i would undoubtedly c o n s i s t of the high economic cost (Dunst, 1974), the problem of t r a n s p o r t a t i o n and d i s p o s a l of dredged m a t e r i a l t o beyond the watershed boundaries, and the u n c e r t a i n t i e s regarding the p o t e n t i a l b e n e f i t s of a l t e r i n g the temperature regime of l a k e s . T e c h n o l o g i c a l option; a l g i c i d e s . A common method of c o n t r o l l i n g nuisance a l g a l populations i n eutrophicated lakes i s the a p p l i c a t i o n of t o x i c chemicals t o the trophogenic zone. I n order t o be e f f e c t i v e , the t a r g e t a l g a l species must be i d e n t i f i e d and mat'ched with the most e f f e c -t i v e chemical and method of a p p l i c a t i o n . A l s o , due t o the p e r i o d i c i t y and succession of a l g a l species during the summer growing season (Wetzel, 1975)» the t i m i n g of lak e treatment i s a c r i t i c a l c o n s i d e r a t i o n . Furthermore, the t o x i c i t y of most a l g i c i d e s i s r e l a t e d t o s p e c i f i c water q u a l i t y parameters ( i . e . pH, a l k a l i n i t y ) , environmental i n f l u e n c e s 22 ( i . e . p r e c i p i - t a t i o n ) , morphological c o n s i d e r a t i o n s ( i . e . h y d r a u l i c residence t i m e s ) , and chemical concentrations a p p l i e d . While a l g i c i d e s are an e f f e c t i v e method of reducing a l g a l d e n s i t i e s , success i s o f t e n only temporary (Dunst, 1974). Because some chemicals merely e x h i b i t a l g i s t a t i c p r o p e r t i e s ( i n h i b i t i n g the organism's growth r a t h e r than k i l l i n g i t ) , the o r i g i n a l problem may be exacerbated by a change i n species composition ( F i t z g e r a l d , 1971). The eventual sedimen-t a t i o n of t o x i c a n t s or l o s s t o the o u t l e t allows the f u r t h e r regeneration of a l g a l populations under favourable environmental c o n d i t i o n s . The t o x i c i t y of many chemicals t o non-target species ( i . e . f i s h , zooplankton, benthic organisms, and w i l d f o w l ) may i n f a c t negate the b e n e f i t s of t h e i r use. Furthermore, a massive d i e - o f f of algae over a short p e r i o d of time may very e a s i l y deplete oxygen reserves of the water column thereby rendering the l a k e , or s e c t i o n s of i t , u n i n h a b i t a b l e t o other aquatic b i ota. T e c h n o l o g i c a l option; d e s t r a t i f i c a t i o n / h y p o l i m n i o n a e r a t i o n . The primary purpose of a e r a t i o n systems i s t o c o r r e c t ' d i s s o l v e d oxygen d e f i c i e n c i e s t h a t normally occur i n the hypolimnion of eutrophic l a k e s . Under s p e c i f i c c o n d i t i o n s these systems provide the a d d i t i o n a l b e n e f i t s .of a l g a l ..control, and the suppression of n u t r i e n t regeneration from the sediments. Indeed, a e r a t i o n techniques are o f t e n employed t o r e s t o r e water q u a l i t y f o r e c o l o g i c a l (Halsey and G a l b r a i t h , 1971), m u n i c i p a l (Symons, 19&9), a n d- r e c r e a t i o n a l purposes (Compressed A i r Magazine, 1973). 23 Basical ly , aeration techniques are dichotomized into destrat i f icat ion systems, and hypolimnion aeration systems (Dunst, 1974). Destratif ication involves either mechanical pumping of oxygen-deficient hypolimnic water to the surface for natural aeration, or a i r diffuser systems that, placed near the lake bottom, oxygenate the surrounding water column (Boyter and Wanielista, 1973)- Because ver t ica l water currents are induced by both aeration techniques, the erosion of thermal s trat i f i ca t ion occurs with lake temperatures approaching pre-aeration surface temperatures. Also, isochemical conditions are generally consequent to aeration mixing. If re-oxygenation i s successful at the sediment/water interface, however, the release of nutrients from the sediments i s greatly inhibi ted . Besides having direct applications i n nutrient control, d e s t r a t i f i -cation methods are also proposed as a means to the control of algae (Symons, I969). The theoretical basis for their use as such i s "the concept of c r i t i c a l mixed depth" (Sverdrup, 1953)' This theory assumes that vert ica l mixing induced during destrat i f icat ion drives a lgal cel ls below the trophogenic zone for a period of time sufficient to cause their death. From th i s , production theoretically f a l l s below respiration, the algal biomass i s decreased, v i s i b i l i t y i s improved, and satisfactory oxygen levels are reestablished. Additional considerations that are required of this remedial technology include the potential impact of temperature changes upon aquatic biota, and the effects of mixing on turbidi ty . Furthermore, i f i n i t i a l assess-ments of the water quality problem result i n the use of inadequate 24 aeration equipment relat ive to the lake size, the desired, benefits w i l l not be real ized. Hypolimnion aeration, on the other hand, involves the aeration of the lake hypolimnion only, with l i t t l e or no disruption of the thermal gradient. Through a system of enclosed piping, hypolimnic water i s elevated to the lake surface, where i t i s aerated and returned to the hypolimnion (Speece, 1970). The methods employed may also include side stream pumping using l iqu id oxygen (Fast, Overholtz and Tubb, 1975)» or submerged hypolimnion aerators (Fast, Dorr and Rosen, 1975)• The advantages of these systems include (1) the retention of the original thermal regime, (2) the suppression of nutrient regeneration from the sediments, and (3) the movement of a smaller water volume since the epilimnion and metalimnion are not involved. Prerequisite to the use of these systems i s , however, sufficient depth and strength of thermal s trat i f i ca t ion i n order to avoid the erosion of thermal s trat i f i ca t ion through inadvertent circulation of the water column (Fast and Lorenzen, 1976). The preceding review of limnological theory and several technological systems i s intended as background for the reader. While much of the theory and review i s simplified and condensed, i t should provide an adequate foundation for the understanding of the implications, problems, and analyses presented i n the following chapters. 25 CHAPTER III DEER LAKE: THE NATURE OF THE PROBLEM The Natural Environment The Deer Lake watershed i s situated near the geographical center of the Municipality of Burnaby, Br i t i sh Columbia. The catchment basin encompasses an area of 825 hectares (ha) within an elevation from 60 meters (m) to I65 m. The basin topography includes re lat ive ly f la t marsh and meadow land to gently sloping h i l l s covered by assorted grasses, shrubs, and trees ( i . e . Alnus rubra). Six small streams flow into Deer Lake, the largest of which discharges 65 l i t e r s per second (Appendix A). Primarily charged by groundwater, these streams occasionally carry high loads of urban runoff during the rainy season. A single outlet stream, to Burnaby Lake, discharged 180 l i t e r s per second on the date sampled. Burnaby's climate i s mesothermal according to the de Candolle c lass i f icat ion, or a "C" climate according to Koppens scale (Colinvaux, 1973)- The proximity of the Pacif ic Ocean typica l ly provides warm, dry summers and cool, wet winters. Meteorological records from the Atmospheric Environment Service indicate that about 161 centimeters of precipitation i s received intthe Municipality annually. The distribution follows a normal curve with the mode i n December. Mean dai ly temperatures are 17-9°C i n July and 2.6 °C i n January. The number of frost-free days per year approximates 326. The annual average hours of sunshine for Burnaby i s 1780, and as expected 26 the distribution i s negatively correlated with precipitat ion. Although wind data do not exist for Burnaby, an extrapolation from the Vancouver and Abbotsord airport data suggests prevailing westerly surface winds of 7 to 15 kilometers per hour. Lake Morphometry and Aquatic Biota Deer Lake i s a small, shallow body of water (Table 3-1)- These data indicate nearly c ircular surface development and s l ight ly rounded basin geometry ( e l l i p t i c a l sinusoid from Wetzel, 1975)• This i s confirmed by the depth-area curves (Table 3-2) that also reveal an areal potential for l i t t o r a l development of about (ca) 10 hectares (maximum depth at which macrophytes w i l l grow i s ca 3 m). The point of maximum depth occurs near the geographic center. Assays of the aquatic biota indigenous to Deer Lake indicate organisms at succeeding trophic levels . The enumeration of major a lgal groups (Appendix B) shows a predominance of diatoms (g. Melosira) at a l l depths. The diatoms g. Gyclotella and g. Navicular, the green algae g. Chlorococcum, and the golden-brown g. Synura are the next abundant forms. The zooplankton data (Appendix C) indicate the order Copepoda to be most abundant with minor representation from the orders Gladocera and Rotifera. The only f i sh species reported to exist i n Deer Lake are rainbow trout (Salmo gairdneri) and stickleback (Gasterosteus aeuleatus). Aquatic macrophytes appear to be limited to water l i l i e s of the Nymphaeaceae family (Nuphar advena and Nymphaea odorata) although the Pinaceae family (Typha spp.) i s represented i n proximity to the in le t Table 3-1• Morphometric Data for Deer Lake Maximum Length (L) 896 m Maximum Width (b) 495 m Mean Width (b) 355-9 m Maximum Depth (zm) 6.25 m Mean Depth (z) 3.71 m Relative Depth (z-^ ) O.98I m Shoreline Length (L s ) 2,330 m Shoreline Development 1.16 _ Volume (V) _ 1,183,062 nr Volume Development (z:zm) 0.593 * From Zoology 404 Laboratory Data (1976) Table 3-2. Surface Areas at 0.5 m Contour Intervals Depth Area (m )^ (ha) Surface 319,036 31.9 2.0 267,354 26.7 2.5 244,357 24.4 3 .0 222,381 22.2 3-5 189,301 18.9 4.0 152,019 15.2 4.5 116,684 11.6 5-0 ;:84?>376 8.4 5.5 47,499 4477 6.0 13,147 1.3 From Zoology 404 Laboratory Data (1976) streams. Regarding wildfowl, at the time of sampling a small mallard duck population (Anas platyrhyncho) was present. 28 The Cultural Environment The Deer lake watershed presently_.accommodates a. variety of socio-economic a c t i v i t i e s . At present, land i s allocated to residential (434 ha), industrial (58 ha), commercial (65 ha), forest/grassland (128 ha), and public institutional (140 ha) development (Zoology 404 laboratory Data). The small scale agriculture and timber harvesting activities previously conducted are apparently absent from the watershed now. Residential gardening i s present although i t i s known to what extent. The future of the Deer Lake watershed, at this time, does not appear to include any major spatial encroachment by the residential, commercial, or industrial development list e d above. Instead, Burnaby intends that Deer Lake become a component park within the concept of the Municipality's linear parks system (Deer Lake Development Concept, 1974). The available land component of the watershed w i l l be designed for appropriately scaled shore-based ac t i v i t i e s , while Deer Lake i s to become the park's focal feature. As such, i t must conceivably accommo-date such activities as swimming/wading, snorkeling, canoeing, small craft sailing, and sport fishing. Whereas appropriate land-based recreational activities are determined by the carrying capacity of the land (iae. physical s o i l properties and spatial requirements), water-based recreation depends upon various aspects of water quality. For the purposes of this study, standards for the above-mentioned activities might well be represented by those li s t e d i n Table 3 _3» 29 Table 3-3. Suggested Water Q u a l i t y Standards f o r Summer R e c r e a t i o n a l A c t i v i t l e s A c t i v i t y Water Temp. (°G) D.O. (mg l " 1 ) Depth (m) V i s i b i l i t y (m) Wading/Swimming/Snorkeling (Surface Water) 20 >5 3 >2 Canoei ng/Sai11ng >0 >5 3 >1 Sport F i s h i n g (Hypolimnion) <18 >6 >6 >2 P r e f e r r e d c o n d i t i o n s f o r rainbow t r o u t from Smith and B e l l a , 1973 The water q u a l i t y problems of Deer Lake t h a t c o n f l i c t w i t h the intended r e c r e a t i o n a l use of the lak e as def i n e d by the a b o v e - l i s t e d standards i s the t o p i c of the f o l l o w i n g s e c t i o n . Problems of Water Q u a l i t y On the b a s i s of data presented i n t h i s study, Deer Lake i s considered m i l d l y t o moderately eutrophic. C e r t a i n l y , i t does not e x h i b i t the extensive l i t t o r a l development and severe a l g a l blooms of advanced eutrophy; nevertheless, i t a l s o f a i l s t o conform w i t h , or remotely approach, the q u a l i t a t i v e standards f o r o l i g o t r o p h i c systems. The water q u a l i t y parameters r e f l e c t i n g i t s t r o p h i c s t a t e are commonly employed i n d i c e s of e u t r o p h i c a t i o n (Hooper, 1969)> "but i n view of the l i m i t e d data no conclusion regarding the r a t e of t r o p h i c change i s p o s s i b l e . A l b e i t , the r a t e at which e u t r o p h i c a t i o n proceeds i s 30 certainly important, i t Is not deemed central to this research. The selected parameters do, however, have fundamental implications from a recreational planning perspective, as they allow an assessment of Deer Lake i n terms of i t s su i tab i l i ty for i t s intended role while identifying the target parameters requiring remedial action. The water quality parameters reviewed here include (1) water temperature, (2) dissolved oxygen, (3) turbidi ty , (4) nutrient concentrations, and (5) lake depth. Water temperature. Measurements of the Deer Lake water column reveal "multiple thermal discontinuities" (Figure 3-1), a phenomenon characteristic of shallow lakes that undergo alternate periods of heating and mixing (Wetzel, 1975). An extrapolation of these data, however, indicates that mid-summer temperatures throughout the water column may, i n fact , be appreciably higher ( i . e . exceeding 20°C). Available winter data (Appendix D) suggest that Deer Lake i s dimictic , but i n keeping with Wetzel's (1975) correlation of lake type to i t s altitude and position (in degrees North latitude), the fact that these data represent different sampling years, and that warm monomictic lakes remain above 5°C (Smith and Bel la , 1973)» such an interpretation i s not conclusive. According to the data (Appendix A) , the influent streams are appreciably colder than Deer Lake. Because inflowing water seeks a stratum of equal temperature/density, the streams discharge into the lake at the sediment/water interface, yet appear to have no observable impact upon temperatures within the lower water column. It i s apparent, also, that the outlet discharges from the Deer Lake epilimnion. Figure 3 _1• Deer Lake Water Temperature P r o f i l e s S t a t i o n s 1 and 2 September 26, 1976 (From Zoology 404 Laboratory Data) NOTE: S t a t i o n 2 data provided f o r a l l parameters i n t h i s t h e s i s i s a c t u a l l y S t a t i o n 6 Zoology 404 data. From a recreational perspective Deer Lake water temperatures are satisfactory for aesthetic appreciation/boating, and water-contact ac t iv i t i e s . The potential for surface and hypolimnion temperatures to exceed the preferred l imi ts , and perhaps the lethal l imit of ca 24°C (Smith and Bel la , 1973) for cold-water f i sh ( i . e . rainbow trout) , however, appears high. It must be concluded therefore that Deer Lake does not constitute a viable sport f i sh environment. Dissolved oxygen. Assays of dissolved oxygen i n Deer Lake disclose a clinograde oxygen prof i le (Figure 3~2) that i s characteristic of eutrophic lakes. Relatively high surface concentrations are caused, no doubt, by frequent mixing and as a by-product of photosynthesis. As i n most eutrophic lakes, the pelagic and l i t t o r a l zones probably undergo-high diurnal fluctuations i n dissolved oxygen i n response to fluctuating rates of photosynthesis. This phenomenon, however, occurs only within the trophogenic zone. In view of the information presented to this point, an anoxic water column below J.O meters i s entirely predictable. The algal data, (Appendix B), for instance, show densities approaching ca 57f000 organisms per l i t e r below this depth that, as evidenced later , i s also below the trophogenic zone. Disregarding other sources of biochemical oxygen demand, the decomposition of algae alone may be sufficient to maintain anoxia especially since the oxygen renewal mechanisms i n Deer Lake appear weak, i rregular ly timed, or non-existent. Concerning recreation, the dissolved oxygen levels i n Deer Lake are marginally 0.0 1.0 2.0 D I S S O L V E D O X Y G EixN (mg l " 1 ) 3.0 4.0 5-0 6.0 7.0 8.0 9-0 10.0 11.0 12.0 Station 1 Station 2 Figure 3-2 Deer Lake Dissolved Oxygen P r o f i l e s Stations 1 and 2 September 26, 1976 (From Zoology 404 Laboratory Data) acceptable for a l l water-contact sports except snorkeling. While anoxic sediments often lead to the generation of foul odours, the act ivi t ies , aesthetic appreciation/boating, are deemed not to be adversely affected. It i s obvious, though, that the Deer Lake environment i s extremely stressful to cold-water species resident i n the lake. Their existence may be described as marginal, and their survival tenuous. Turbidity. The l ight transmission and colour data (Tables 3~k and 3-5) indicate a re lat ive ly rapid attenuation of incident l ight energy. Staining of the water by dissolved organic substances i n conjunction with the high algal populations produces a compensation depth (1% l ight transmission level) of ca 2 meters. Perhaps a more relevant parameter from a recreational point of view i s the Secchi disc measure-ment (Table 3-6), which for Deer Lake indicates a transparency value of ca 1 meter. Such high turbidity renders Deer Lake unsafe for swimming and therefore unsatisfactory for a l l water-contact ac t iv i t i e s . Provided that f loating sol ids, l iquids , and algal blooms are absent, however, use of the lake for viewing/boating i s not impeded. Referring to Deer Lake as f i sh habitat, i t i s well documented i n the l i terature ( i . e . Wetzel, 1975) that growth and behaviorr of cold-water species i s adversely affected by poor l ight penetration that inhibi ts their ab i l i t y to detect and capture prey organisms. Also, the distribution of these organisms (Appendix C) may be sub-optimal with regards to the search behavior of f i sh and i n view of the survival requirements of the Table 3-4. Percent Light Transmission with Depth (Deer Lake) Depth (m) 0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6 1.8 2.0 2.2 Stn 1 100 667 49 34 21 13 8 6 3 2 0 -Stn 2 100 89 61 36 27 19 11 7 5 3 1 -From Zoology 404 Laboratory Data (1976) —1 * Table 3~5- Deer Lake Colour (mg 1 Pt) Depth (m) Station 1 Station 2 0 38 38 3 40 43 5 42 45 From Zoology 404 Laboratory Data (1976) Table 3~6. Secchi Disc Transparency (Deer Lake) Stati on Depth (cm) 1 91 2 100 * From Zoology 404 Laboratory Data (1976) 36 organisms. Furthermore, the underwater l ight f i e l d of the epilimnion, into which the Deer Lake f ish are forced by reason of the oxygen and temperature conditions, possibly undergoes a continuous alteration of spectral properties due to the d i f ferent ia l optical characteristics of the seston. Consequently, Deer Lake turbidity i s adversive to the cold-water f i sh species. Nutrient concentrations. Ambient concentrations of the major nutrients are often indicative of the trophic status of lakes. A comparison of Deer Lake P and N values (Table 3-7) with Northcote's (1976) correlation of nutrient ranges to trophic state (Table 3-8) suggests Deer Lake to be meso- to eutrophic. The nutrient loading of Deer Lake (Table 3_9)> when reviewed i n the context of Vollenwieder's ( I 9 6 8 ) predictive tables (Table , strongly substantiates this conclusion. While the data represent conditions at only one point i n time, i t i s unlikely that the symptoms apparent i n the lake are of a temporary nature given the types of land use, water ac t iv i t i e s , and the high probability of non-point source pollution within the watershed. While many of the causal factors of Deer Lake eutrophication are evident from the previous sections, several minor points merit discussion. For instance, under anaerobic conditions, disturbance of the sediments may effectively double the regeneration rate of nutrients to the over-lying water column (Wetzel, 1975)- The presence of a re lat ive ly high speed motor-boat on Deer Lake i s , no doubt, an inf luent ia l factor i n this regard (Yousef, 197*0. T h e pH of lake water i s s imilarly in f luent ia l i n regulating the so lubi l i ty of the major nutrient, phosphorus, from the 37 Table 3-7. Total P & Total N Concentrations i n Deer Lake (ug 1 ) Depth (m) Station 1 Station 2 Total P Total N Total P Total N 0 72 19 34 230 3 60 23 160 5 70 19 57 160 From Zoology 404 Laboratory Data (1976) Table 3-8• Very Approximate Ranges of Nutrients Nutrients Trophic Status (pg I" 1) Ultra-Oligotrophi c Oligotrophic Mesotrophic Eutrophi c Total P 1 1 - 5 5 - 3 0 30 Total N 100 100 - 200 200 - 500 500 From T . J . Northcote (1976) 38 Table 3-9- Nutrient Loading of Deer Lake Phosphorus 0.92 g m yr -2 Nitrogen 2.8? g m yr *• Values calculated, from Laboratory Data (1976) Zoology 404 Table 3-10. Permissible Loading Levels for Total Nitrogen and. Total Phosphorus (Biochemically Active)(g m~2yr-i) * Mean Depth Permissible Loading Up To Dangerous Loading i n Excess of N P N P 3 m 1.0 0.07 2.0 0.13 From Vollenwieder, 1968 sediments. The so lubi l i ty of P i s at a minimum at lower pH values and increases with higher pH values (Hal l , 1978). The Deer Lake pH (Table 3 _ H ) equals 7.8 at one station, which indicates that the so lubi l i ty of P i n Deer Lake i s enhanced. Other sources of nutrients i n Deer Lake include leachate from decomposing aquatic macrophytes (SolskL, I962) from which nutrients can be u t i l i zed within minutes of entering the water column (Rigler, 1964), and the contributions from terre s t r ia l f lora such as alder (Alnus rubra) which has the capacity to -1 -1 f i x nitrogen i n quantities approaching 225 kilograms ha yr (Wetzel, 1975). The nutrient problem i n Deer Lake i s , then, one of excessively high allochthonous loading from non-point sources i n conjunction with a potentially high rate of internal nutrient cycling. While nutrient levels are of no direct significance for recreational pursuits, the problem i s acute as i t relates to the effects on turbidity and dissolved oxygen levels . Table 3-11. Deer Lake pH (September, 1976) Depth (m) Station 1 Station 2 0 7.2 6.2 3 7.8 6.5 5 7-7 6.7 From Zoology 404 Laboratory Data (1976) Lake Depth. An important consideration i n the problem of eutro-phication i s whether natural occurrences ( i . e . basin morphometry) would not, i n the absence of allochthonous nutrient inputs, lead to a similar trophic state. Thienemann (1925), for instance, asserts that although the edaphic factor i s important, basin morphometry determines the nature of the thermal environment, the epilimnion/hypolimnion ra t io , and therefore the assimilative capacity of lakes. Further, Rawson (1939) states that while the edaphic contribution determines trophic status, morphometry and climate set the rate of nutrient u t i l i z a t i o n . Given the basin morphometry of Deer Lake, i t s depth must be considered a significant contributing factor that leads to i t s eutrophic status. As a greater depth would enhance thermal s tra t i f i ca t ion , increase the assimilative capacity, and have a positive impact upon turbidity and dissolved oxygen (Dunst, 197*0, while increasing cold-water f i sh habitat, 40 i t must be considered a t a r g e t f o r remedial e f f o r t s . This chapter i d e n t i f i e s the major water q u a l i t y problems t h a t are of d i r e c t concern t o the f u t u r e of water-based r e c r e a t i o n i n Deer l a k e . The f o l l o w i n g chapter arranges t h i s i n f o r m a t i o n i n a manner th a t provides a r a t i o n a l b a s i s f o r the i n i t i a l s e l e c t i o n of remedial technologies t h a t are then analyzed i n the Deer Lake context. 41 CHAPTER IV ANALYSES OF LAKE RESTORATION TECHNOLOGIES The Selection of Alternatives The purpose of this research i s to i l l u s t r a t e the kinds of analyses of technological options that are required for an informed assessment of their performance potential and su i tab i l i ty for mitigating specif ic symptoms of eutrophication. The three options selected for study herein are evaluated i n the context of the Deer Lake sampling data and recrea-t ional water quality objectives. The uncertainties pertaining to their implementation i n the aquatic environment are ident i f ied by numerous references to the relevant limnological l i terature and published case histories . In a r e a l i s t i c water resources management scenario such analyses would result i n a "short l i s t " of alternative strategies from which the ultimate remedial programme would be formulated. Due to resource limitations researchers seldom have ample time to generate analyses to the extent suggested here of the myriad technol-ogies available for the purpose. A f i r s t step, therefore, i s to eliminate those alternatives that are either deficient i n some respect or inappropriate i n the context of the water resource under study. In this instance a consideration of the nature of the water quality problems i n Deer Lake, and of the desired recreational water quality objectives provides a perspective from which this elimination i s made. 42 The approach employed here i s one whereby three levels of recrea-t ional use are established for Deer Lake i n order of increasing water quality requirements (Table 4 - 1 ) . The f i r s t level of use (aesthetic appreciation and small-craft boating) would require no restoration of water quality since none of the f ive water quality problems ident i f ied i n Chapter III would impede these leisure ac t iv i t i e s . Deer Lake water temperature, dissolved oxygen, and lake depth parameters are satisfactory for the second level of use (water-contact sports), but turbidity must be reduced. The th ird level of use (sport f ishing) , however, requires that a decrease i n hypolimnic temperatures, turbidity and nutrient levels , with an increase i n dissolved oxygen and possibly lake depth (optional) be effected. Through this method of association the desired level of use and the conflicting water quality parameter i s easily visualized. A review of the limnological l i terature would reveal to the reader various means by which the adversive water quality conditions ident i f ied above may be remedied. For our purposes, however, i t i s assumed here that the l i s t of technological options reviewed i n Chapter II presents the primary water quality control techniques with which the restoration of Deer Lake may be undertaken so that i t may accommodate the second level of use. From this l i s t may be culled those options that, on the basis of a l i terature search and i n the context of the sampling data, are inappropriate. In the context of Deer Lake, for example, four of the options l i s ted can be dismissed from existing information. Hypo-limnion techniques, for instance, are successful only when a strong thermal gradient (stratif icat ion) i s present. Since Deer Lake does Table 4-1. Recreational Levels of Use and Water Quality Requirements Level of Use Water Quality Problem Rationale Small-craft boating and none aesthetic appreciation - temperature and dissolved oxygen are adequate „. - nutrient concentrations are irrelevant since no algal blooms exist at present - lake depth i s adequate for boating Water-contact sports 1. turbidity - v i s i b i l i t y i s reduced by algal populations and dissolved organic compounds - this compromises safety and subtracts from the recreational experi ence 2. nutrient concentrations - P and N levels exceed those neces-sary for shift to eutrophication -potential for algal growth i s high Sport f ishing 1. temperature - a decrease i n hypolimnion tempera-tures i s required -1 2. dissolved oxygen - a minimum of 5 mg 1 of dissolved oxygen must be maintained throughout the water column 3. turbidity - v i s i b i l i t y must be increased i n order that predator prey relationships between f i sh and lower trophic organisms are not impeded. (concluded on next page) Table 4-1. (concluded) Level of Use Water Quality Problem Rationale Sport f i s h i n g 4. nutrient concentrations high nutrients favour abundant a l g a l growth, undesirable species and high b i o t i c t u r b i d i t y 5. lake depth while depth i s adequate, greater depth would, perhaps, favour lower temperatures, and hi higher assimilative capacity f o r the lake 45 not display a dist inct thermal regime this option i s not considered feasible. Secondly, nutrient inactivation methods are not deemed appropriate due to the re lat ive ly high nutrient loading from the influent streams. Furthermore, i t i s not established whether P and N are the factors l imit ing growth. I f not, then their removal from the water column would have l i t t l e effect upon biot ic production. The dilution/f lushing option i s likewise omitted from these analyses due to the mitigating effects of high nutrient loading, re lat ive ly large lake volume to be diluted/flushed, the potentially large supply of nutrients from the sediments to the water column, and the abundance of organic matter that would result i n a regeneration of nutrients upon decomposition. F ina l ly , lake depth i s omitted as i t i s not a direct turbidi ty- or nutrient-controll ing mechanism. The three remaining options for analysis are, therefore, the mechanical removal of vascular hydrophytes, algicides, and a r t i f i c i a l destrat i f icat ion. The Mechanical Removal of Hydrophytes for Nutrient Control The spat ial growth of N. advena and N. odorata i n Deer Lake i s visually estimated to be ca 2 hectares. As these hydrophyte communities do not, at present, impede the use of the lake for recreational purposes, their removal can only be just i f ied as a nutrient control measure with the end objective being a decrease i n turbidi ty . The basis for adopting or rejecting this method, therefore, must derive from a mathematical calculation that defines, quantitatively, the benefits i n terms of nutrients removed relat ive to nutrient loading. Empirical determinations of the chemical composition of N. advena and N. odorata i n Deer Lake are not available. Instead, l i terature values provided by Boyd (1974) (dry weight of N. advena = 0.8 metric -1 tons ha ), and by Riemer and Toth (1970) i n Table 4-2 are considered representative of the species, (while Boyd (1974) cautions against the use of published data because of possible variances i n chemical composi-t ion they provide, nevertheless, a reasonable approximation.) In the interests of s implicity and conservatism, the chemical composition of the morphological parts of each species are rounded to the highest value (Table 4-3), each species i s assumed to occupy an area of 1 hectare, and the dry weight of both species i s deemed ident ica l . I f the f i n a l computations are somewhat less than def init ive , then a more rigorous analysis including i n s i tu nutrient assays would be warranted. Table 4-2. Chemical Composition of N. advena and N. odorata (as % dry weight) Species % P % N N. advena peti oles leaves 0.30 0.41 1.17 3-98 N. odorata petioles leaves 0.28 0.31 1.22 2.72 -* From Riemer and Toth, 1970 Table 4 -3 . Assumed Chemical Composition of N. advena and N. odorata Species % P % N N. advena N. odorata 0.40 0.30 4.00 3.00 47 The data show that a 1 hectare community of N. advena represents f, 1 3.2 kg P ( i . e . 0.8 x 10 g ha~ x 0.004), and 32.0 kg N. The N. odorata community represents 2.4 kg P and 24 kg N. Together, the two species covering an area of 2 ha contain 5-6 kg P and 56 kg N. From Appendix B, the P and N loading of Deer Lake i s 295.098 kg and -2 -1 918.277 kg respectively. This i s equivalent to 0.92 g m yr P and -2 -1 2.87 g m yr N. By subtraction, the complete removal of both communities -2 -1 -2 -1 would reduce the loading to 0.90 g m yr P and 2.70 g m yr N. Such a reduction i s f a r from meaningful as the annual loading remains s i g n i f i -cantly above the dangerous loading levels suggested by Vollenwi eder (1968) (Chapter I I I ) . Given ten harvestings per year the P loading would s t i l l -2 -1 only be reduced to ca 0.77 g m yr . This method i s therefore not recommended. I t should be noted that i f harvesting had proven feasib l e as a nutrient control mechanism, then other important factors must be weighed before employing t h i s remedial technique. The l i t e r a t u r e (Newroth, 1974) shows that occasionally lake restoration attempts f a i l because s i g n i f i c a n t aspects of the aquatic system/and/or the operational requirements of the technolo-gies employed, are not f u l l y understood or taken i n t o account. As part of a r e a l i s t i c hydrophyte management programme, therefore, non-quantitative considerations must be incorporated i n t o the pre-implementation analyses. Involved would be an estimate of the underground biomass to be removed (Wetzel, 1975), a recognition of the dynamics of reproduction, perennation, and succession of species (Sculthorpe, 1971)1 the influence that the target species has upon basin morphology 48 (Bursche, 1971), and trophic status (Wetzel, 1975)> and their importance as habitat and food sources for wi ld l i fe (Fassett, 1940; Sculthorpe, 1971). Final ly , the role of hydrophyte communities as habitat for vectors of diseases (Mitchell , 1974), and their value as inspirat ional objects i n art , architecture, and for aesthetic appreciation (Sculthorpe, 1971) are important points to consider before a harvesting programme i s undertaken. An Algicide for Turbidity Control The pelagic algae of Deer Lake include genera from the diatom (Bacillariophyceae), green (Chlorophyta) and blue-green (Cyanophyta) algal groups. Of these at the time of sampling Melosira spp., Navicula spp., and Cyclotel la spp. of the diatom group were the most abundant with Melosira spp. comprising the major genera (Appendix B). Due to the lack of seasonal data the succession and periodicity of algae i n Deer Lake i s unknown, albeit the phenomenon i s a common occur-rence i n most temperate lakes (Wetzel, 1975). This Information deficiency constitutes a serious uncertainty i n the consideration of algicide use within the lake. The uncertainty involves the d i f ferent ia l toxic i ty of algicides to the three major algal groups. An ident i f icat ion of the periodicity of the target algal organisms constitutes, therefore, important information. Due to their d i f ferent ia l tox ic i ty , the applica-t ion of algicides may create a competitive advantage of one species or genera over another resulting i n the succession of undesirable types. In the interests of mitigating this uncertainty a hypothetical scenario 49 of a lgal succession i n Deer Lake i s developed here from factual informa-t ion and the relevant l i terature . The period of vernal c irculat ion creates a growth environment ( i . e . uniform nutrients and temperature, increasing turbidity) that favours diatom algae i n general, and g. Melosira, g. Asterionella, and g. Stephanodiscus i n particular (Patrick, 1969; Steel, 1971; Wetzel, 1975). As summer progresses, vernal algae generally decline i n favour of g. Gyclotella and g. Tabellaria (Wetzel, 1975) which i n turn are replaced by green and blue-green genera as an increase i n water temperature and a decrease i n available nutrients (especially N and Si) l imits diatom growth (Patrick, I969). Green algae perfer high nutrient levels and moderate temperatures (30°C - 35°C from Cairns and Lanza, 1972); they reproduce quickly and are exceedingly adept at concentrating phosphorus (Provasoli, 1969). Meanwhile, blue-green algae prefer high temperatures (> 35°C from Cairns and Lanza, 1972) and nitrogen deficient conditions where their nitrogen-fixing capability and morphological adaptations provide a competitive advantage (Bush and Welch, 1972). In theory, however, g. Melosira predominate during most of the summer season i f -1 ; s i l i c a i s abundant (> 5 nig 1 ), the temperatures are re lat ive ly low (< 30°C from Cairns and Lanza, 1972) and abiot ic /b iot ic turbidity i s high (Wetzel, 1975). Regardless of the dynamics of summer succession, the autumnal overturn generates an environment ( i . e . increasing nutrients and turbidi ty , 'decreasing temperatures) that again favour the diatoms (Steel, 1971). 50 From the Deer Lake data g. M e l o s i r a i s dominant at a time when the environmental f a c t o r s described above would normally m i t i g a t e against the diatom group. Since the date at which they are the dominant group (September 25, 1967) cannot be c o r r e l a t e d w i t h the date of the autumnal overturn (October 30, 1976 - Appendix D), i t i s not unreasonable t o speculate t h a t g. M e l o s i r a dominates during summer i n response t o a g e n e r a l l y favourable environment ( S i >5 mg 1 , high t u r b i d i t y and moderate temperatures) created by frequent mixing (discussed i n Chapter I I I ) . For the purpose of the f o l l o w i n g a n a l y s i s t h i s study assumes, t h e r e f o r e , t h a t g. M e l o s i r a are the t a r g e t organisms t o be c o n t r o l l e d . By developing the above s c e n a r i o of a l g a l dominance i n Deer Lake, a b a s i s i s e s t a b l i s h e d from which t o s e l e c t an a l g i c i d e f o r the c o n t r o l of t u r b i d i t y . I n t h i s regard, copper s u l f a t e pentahydrate (CuSO^^HgO), h e r e i n a f t e r c a l l e d copper s u l f a t e , i s chosen due t o i t s t o x i c i t y t o the tar g e t s p e c i e s , and because i t i s reported t o be the s a f e s t , most e f f e c t i v e , Inexpensive, and e x t e n s i v e l y used a l g i c i d e ( N a t i o n a l Academy of Sciences, 1968). The t o x i c i t y of copper s u l f a t e t o a l l a q u a t i c b i o t a i s a f u n c t i o n of water chemistry ( i . e . pH, a l k a l i n i t y , d i s s o l v e d organic matter), and the concentration a p p l i e d , w h i l e i t s e f f e c t i v e n e s s decreases with p r e c i p i -t a t i o n and absor p t i o n ( F i t z g e r a l d , 1971)- Furthermore, given a uniform environment, copper s u l f a t e i s shown t o be d i f f e r e n t i a l l y t o x i c t o the three a l g a l groups present i n Deer Lake. The evidence presented (Table 4-4) r e v e a l s t h a t the t o x i c i t y of a given concentration decreases 51 i n the order of diatom, blue-green, and green algae. Other evidence ( F i t z g e r a l d , 1971) suggests, however, th a t at c e r t a i n concentrations ( i . e . between 1 and 2 mg 1 ) copper s u l f a t e e x h i b i t s a l g i s t a t i c r a t h e r than a l g i c i d a l p r o p e r t i e s t o green algae. While the argument may appear academic, the question of d i f f e r e n t i a l t o x i c i t y and the a l g i s t a t i c / a l g i c i d a l p r o p e r t i e s of copper s u l f a t e generates a s i g n i f i c a n t degree of u n c e r t a i n t y regarding the p o s s i b l e e f f e c t s t h a t i t s use w i l l have upon the Deer Lake a l g a l community. The u n c e r t a i n t y i s , of course, whether or not a d i f f e r e n t i a l e l i m i n a t i o n of a l g a l groups w i l l promote the succession of more undesirable species and the exacerbation of current water q u a l i t y problems ( i . e . higher t u r b i d i t y ) . This concern may be examined f u r t h e r by developing a h y p o t h e t i c a l a l g i c i d a l programme. Table 4-4. T o x i c i t y of CuSO^HgO {% k i l l e d ) * Concentration 7 Species 17 Species 6 Species A l l (30) (mg l - ! ] ) : Cyanophyta Chlorophyta B a c i l l a r i o p h y c e a e Species 0.25 - - - -0.50 28 - 33 13 1.0 43 29 50 37 2.0 57 35 100 53 * Gratteau, 1970 Assume t h a t i n a h y p o t h e t i c a l a l g i c i d e treatment s c e n a r i o a 75% diatom m o r t a l i t y i s achieved. With a pre-treatment surface d e n s i t y of -1 -1 16,000 c e l l s ml a post-treatment d e n s i t y of 4,000 c e l l s ml would be r e a l i z e d . Given a p e r s i s t e n c e time f o r copper s u l f a t e i n s o l u t i o n of ca 24 hours (Elms, 1905; M u l l i g a n , I968), the regeneration of diatoms could conceivably commence a f t e r a p e r i o d of 1 day. A l s o given a median 52 generation time of 6 days (Wetzel, 1975). the o r i g i n a l diatom p o p u l a t i o n of 16,000 c e l l s ml would t h e o r e t i c a l l y he re p l a c e d i n approximately 2 weeks. From the above s c e n a r i o , and s u b s t a n t i a t e d by the l i t e r a t u r e ( N a t i o n a l Academy of Sciences, I968), i t i s evident that m u l t i p l e a l g i c i d e treatments would be necessary during the summer season t o suppress nuisance growths of diatom algae (see f o r i n s t a n c e the exemplary case h i s t o r i e s i n Table 4-5). I t may a l s o be concluded from the above tha t a d i s p r o p o r t i o n a l removal of diatoms w i l l occur due t o the d i f f e r e n t i a l t o x i c i t y of copper s u l f a t e . As the diatom uptake of s i l i c a represents by f a r the major cause of e p i l i m n i c s i l i c a d e f i c i e n c i e s (Wetzel, 1975)» "the r e g u l a r mass removal of diatoms would produce an eventual d e p l e t i o n of s i l i c a thereby l i m i t i n g f u r t h e r diatom growth. While s i l i c a was i n s u f f i c i e n t abundance at the time of sampling t o maintain a dominant diatom p o p u l a t i o n , there i s no guarantee t h a t the renewal mechanisms at work i n Deer Lake w i l l overcome frequent l o s s e s r e s u l t i n g from an a l g i c i d e programme. Since normal processes alone are oft e n capable of reducing the a v a i l a b i l i t y of s i l i c a t o l i m i t i n g l e v e l s (Wetzel, 1975)> a copper s u l f a t e treatment programme may very w e l l generate a s h i f t i n competitive advantage t o the green and blue-green a l g a l groups. Such an occurrence t h e o r e t i c a l l y poses more d i f f i c u l t questions of e r a d i c a t i o n , and threatens t o induce more undesirable environmental impacts. Table 4-5. Exemplary Case Histories of Algal Control by CuSO. Morphometry Lake Name and Location Programme Result Surface Area Maximum Depth Glen Lake, New Hampshire 30 ha 16.8 m algal reduction temporary Province Lake, New Hampshire 4.1 km2 5-2 m algae reduced for 2 - 3 weeks Skatutakee Lake, New Hampshire 70 ha 5.2 m algal reduction temporary Tuxedo Lake, New York 1.2 km2 18.3 m algal reduction temporary Dunst, 1974 54 In addition to the primary uncertainties discussed above, prior to implementing a programme there must be a comprehensive study into the f u l l range of potential impacts, especially those concerning non-target organisms. Although copper sulfate has a low mammalian toxic i ty (Mulligan, I 9 6 9 ) , repeated applications combined with extensive mixing of the water column could conceivably create adverse conditions that would impede human use. From the l i terature , i t Is evident that much of the aquatic biota would certainly be imperiled. A brief survey of the l i terature shows copper sulfate to be toxic to f i s h , zooplankton, benthic organisms, and wildfowl. For instance, a concentration of 1.25 mg 1 ^ i s a median lethal dosage for rainbow trout over a period of 24 hours (Table 4-6). A rainbow trout prey, Daphnia pulex (also indigenous to Deer Lake), has shown a median lethal dosage of 0.096 mg 1 over 96 hours (Mcintosh and Kevern, 1974). The same study -1 shows also that 0,3 i g 1 of copper sulfate w i l l depress the cladoceran and rot i fer zooplankton. Other research (Fitzgerald and Faust, 19&3) indicates that copper sulfate destroys benthic organisms through i t s toxic effects and by suffocation after i t precipitates to the sediments. _1 Fina l ly , while the median lethal dosage of ca 2,000 mg 1 of copper sulfate for young mallard.ducks (Anas platyrhyncho)(Pimental, 1971) may appear high, because of the phenomenon of bio-magnification these species may be equally vulnerable to this chemical. The foregoing analysis generates important information regarding the potential effects of a copper sulfate treatment programme i n Deer Lake. While there i s no question concerning the a b i l i t y of this chemical to drast ical ly reduce the dominant algae i n Deer Lake, there appears to be a high degree of r i s k i n terms of inducing a shift i n dominance to more noxious genera. In view of this concern, and with knowledge of i t s potentially destructive effects upon non-target organisms, copper sulfate i s not recommended for use i n Deer Lake. Table 4-6. Copper Sulfate (CuSO^-jSHgO) Toxicity to Salmo gairdneri — Exposure Time Concentration (mg 1 ) 24 hour LC50 1.25 96 hour LC50 0.89 14 day LC50 0.87 Calamasi and Marchetti, 1973 NOTE: LC50 refers to the concentration of toxic substance required to k i l l 50% of the organisms exposed by the time stated. While the major purpose of these analyses i s to identify and probe the uncertainties inherent i n the use of selected technologies, i t also intends to exemplify how, through such analyses,iimportant information concerning possibly superior alternatives can be generated. During the l i terature search for copper sulfate, for instance, the beneficial aspects of potassium permanganate (KMnOg) as a turbidity control remedy were often referred to. Apparently, i t i s more toxic to more algal species at lower concentrations than i s copper sulfate (Fitzgerald, 1966); i t decreases turbidity through oxidation and precipitation (Kemp et a l . , I966); and i t reduces the formation of hydrogen sulfide (Willey et a l . , 1964) while controlling tastes and odours (Smith,- , 56 1961). Prom this evidence, potassium permanganate would def initely warrant a separate analysis i n a r e a l i s t i c management programme. A r t i f i c i a l Destratification for Turbidity Control The employment of destratif ication technology i n Deer Lake for the purpose of algal control (biotic turbidity) raisess several important questions and areas of uncertainty. Since the most obvious product of a r t i f i c i a l aeration methods i s the creation of an isothermal/i so chemical environment, i t i s f i r s t necessary to consider the impact that a r e d i s t r i -bution of nutrients w i l l have on the algal population. Also, working under the premise that success i n algal control i s a function of the c r i t i c a l mixed depth, the depth l imitation of Deer Lake must be evaluated • i n terms of i t s effect upon algal redistribution. F ina l ly , as changes i n the composition of species are closely correlated with environmental changes i n the aquatic environment, an assessment i s required concerning algal succession i n Deer Lake. Considering the redistribution of nutrients, i t i s necessary to refer to the Deer Lake data (Table 3 _ 7) . It i s evident from these data that P and N are currently distributed i n a re lat ive ly homogeneous manner; therefore, i t i s suggested that a r t i f i c i a l mixing w i l l change only margin-a l l y the distribution of nutrients and growth of algae i n Deer Lake. The major stimulant to g. Melosira growth may come, however, from a renewal of s i l i c a within the upper water column. From Wetzel (1975)» i t i s learned that s i l i c a i s typ ica l ly at a minimum i n the epilimnion due to diatom ut i l i za t ion , a factor that often l imits diatom growth. The hypolimnion 57 s i l i c a maximum characteristic of eutrophic lakes i s due to a large degree to sedimentation of the siliceous algae and the mineralization by bacteria of the s i l i c a shel ls . Assuming that s i l i c a i s so distributed i n Deer Lake, following destratif icat ion the s i l i c a prof i le would become isochemical thereby raising the growth cei l ing which i t may very well now provide. An increase i n the s i l i c a supply would enhance the growth and perpetuate the dominance of Melosira spp. The above speculation that diatom algae would increase i n response to the resupply of s i l i c a disregards the .^simultaneously intended effects that the concept of c r i t i c a l mixed depth entai ls . In the interests of determining the impact of mixing on algal numbers and the limitations that depth w i l l impose i n Deer Lake, published case histories of destrat i -f i cation for algal control are reviewed (Table 4 - 7 ) . Upon examination, however, i t i s evident that there i s no discernible correlation between available mixed depth and success i n reducing algal populations. In fact, destrat i f icat ion fa i led to prevent, and indeed apparently generated, algal blooms i n lakes of considerable mixed depth. In anticipation of the charge that such a general review of lakes morphologically dissimilar to Deer Lake i s of marginal value, well-documented Kezar Lake with only a s l ight ly greater mixed depth i s herein referred to for comparative purposes. The va l id i ty of employing control lakes i s , of course, established i n the l i terature (Toetz et a l . , 1972). Kezar Lake i s similar to Deer Lake i n the following respects (Table 4 - 8 ) . F i r s t , both lakes are considered to be cultural ly eutrophic as a result of urban runoff and other non-point nutrient sources. Also, Table 4-7. Successes and Failures of A r t i f i c i a l Destratification i n Controlling Algal Concentrations Lake Name Surface Area (ha) Maximum Depth (m) Result Buchanan Lake, U.S.A. 8.9 13 algal increase of 500 - 600%; water c lar i ty decrease of 50% Zeeuws-Vlaandern, Netherlands 22 11 blue-green algal blooms Pfaffikerser, Switzerland 3.3 km2 35 repeated algal blooms Schleinsee, W.S. 15 11.6 algal blooms Babson Reservoir, U.S.A. 14 9.1 increase i n algal biomass Bedford Reservoir, U.S.A. 0.4 3 increase i n algal biomass Boltz Lake, U.S.A. 40 19 reduction of algal biomass Cox Hollow Lake, U.S.A. 39 8.8 decrease i n severity of algal blooms but blooms not eliminated Falmouth Lake, U.S.A. 91 13 shift i n algal species away from blue-green with periodic decreases Indian Brook Reservoir, U.S .A. 7.3 8.4 60 - 80% reduction i n algal biomass Lake Roberts, U.S.A. 28 9.1 algal blooms Lafayette Reservoir, U.S.A. 53 24 increase i n blue-green algae From Dunst, 19?4 and Environmental Protection Agency, 1973 vn CO Table 4-8. A Comparison of Physical and Chemical Properties between Kezar Lake, New Hampshire (before and after) and Deer Lake Parameter Kezar Lake, Before Destratif i cati on 1968* After Destratif i cati on Deer Lake, I976 Surface area 73-5 ha - 31 ha Max depth/dean depth 9 m/3 m - 6.5 m/3.5 m July temperatures - surface - at sediment 27°C 16°C 21 °C 21°C September temperatures ca 20OC 16.5°C Secchi disc 0.5 m 1.2 m 0.9 m Dissolved oxygen - at sediment 0.1 mg l " 1 5.7 mg r 1 0 pH - at surface - at sediment 9.4 6.3 6.3 6.3 6.2 6.7 New Hampshire Water Supply and Pollution Control Commission, 1970 From Zoology 404 Laboratory Data (1976) 6o both lakes are destined for recreational purposes but exhibit undesirably-high turbidity due to algal growth. Next, many of the water quality parameters measured indicate a similar range of values for the two systems. While Kezar Lake i s s l ight ly larger and deeper, this i n i t s e l f should be instructive as the results should be better than those expected i n Deer Lake. A review of the Kezar Lake turbidity and algal enumeration data (Table 4-9) shows a definite increase i n a lgal standing crop following the onset of a r t i f i c i a l destratif icat ion i n 1968, i n conjunction with a redistribution of ce l l s . Following th is , the study reports an increase i n Secchi value from 0 .5 m to 1.2 m. By the end of summer, algal density was substantially lower than the mid-summer l eve l . These results , however, raise several concerns since any reasons for the reduction are unclear. For instance, i t i s generally accepted (Environmental Protection Agency, 1973) that destrat i f icat ion i s adversive to blue-green algae as i t neutralizes their morphological advantage for survival and competition while favouring the green algal group. The par t ia l succession by green algae i s referred to i n the Kezar Lake study. Since a green-algae enumeration i s not provided, however, the extent to which algal succession occurred i n Kezar Lake i s unknown. It i s also uncertain whether the factor causing a blue-green reduction i s destratif icat ion or whether the temperature drop to 21°C i s involved. Since destrat i f icat ion affects only the hypolimnion temperature (Symons, I969) to a great degree, the observed temperature reduction may be seasonally induced i n which Table 4 - 9 . Kezar Lake A l g a l Enumeration I968 - I969, Genus Aphanizomenon ( ce l l s ml ) 1968 Dates 0 . 5 1.5 Depth (m) 2.5 3-5 4 . 5 5 .5 May 23 -July 15 27,200 1 ,041,100 31,800 441,100 22,000 4,900 4 ,200 58,000 25,100 9,800 D e s t r a t i f i ca t i on Commenced 5,000 6,000 July 26 August 21 331,800 10,000 348,200 6,400 351,700 314,000 326,300 10,500 7,300 6.400 Des t ra t i f i ca t ion Terminated 320,600 8,200 September 28 10,600 10,900 11,300 11,200 2,800 1,400 1969 May 18 42 190 134 126 25 Des t ra t i f i ca t ion Commenced 61 June 10 June 30 July 19 August 27 September 10 15,500 309,700 18,600 24,600 1,600 15,700 229,900 23,500 17,600 1,600 19,300 17,900 12,900 248,200 289,500 166,700 18,900 19,500 19,000 21,200 28,100 26,600 1,100 1,200 2,000 Des t ra t i f i ca t ion Terminated 10,100 74,500 16,400 24,500 1,400 New Hampshire Water Supply and P o l l u t i o n Control Commission, 1970 62 case the "blue-green population would have declined naturally. Also, due to the seasonally inducedcchanges that typical ly occur i n the aquatic environment, effects thought to result from the termination of destrat i f i cation may merely "be coincidental with expected seasonal populati on dynami cs. The 1969 Kezar Lake data shows destratif icat ion beginning at an earl ier date with maximum summer blue-green populations at one-third of the I 9 6 8 l eve l . As the other algal groups are not enumerated the to ta l algal populations with depth are not known. Even so, surface blue-green -1 algae s t i l l numbered over 300,000 cel ls ml . Consequently, the researchers were prompted to declare that while an improvement i n turbidity was realized, the result was of marginal value as the algal standing crop remained high. Furthermore, destratif icat ion enhanced the reproduction of midge f l i e s which, i n turn, detracted from the recreational value of the lake. The implications of the Kezar Lake study for Deer Lake are several. With a more shallow morphology the Deer Lake trophogenic/tropholytic zone rat io i s smaller than the Kezar Lake ra t io . Consequently, algae w i l l be driven below the trophogenic zone for a proportionately shorter period of time thereby increasing the l ikel ihood of their survival . Also, due to mixing the epilimnion s i l i c a deficiency may very l ike ly be overcome, thereby rais ing the growth cei l ing of the diatom algal group. I f , i n addition, Deer Lake water temperatures are lowered beyond the current suspected summer range, the diatoms would be i n an environment most favourable to the ir growth, reproduction and continued dominance 63 (Lund, 1971; Steel, 1971)• Even disregarding an increase i n standing crop, the mixing of an algal population distributed as i t was on the date of sampling would bring an increase i n surface algal densities. Consequently, i t may be reasonably speculated that surface algal popula-tions would increase substantially. In conjunction with resuspended sediments from the induced water vortices, mixing would l i k e l y exacerbate an already undesirably turbidity condition. It must be remembered that Kezar Lake maintained a surface a lgal density i n excess of 300,000 ce l ls _1 ml with destrat i f icat ion - a population nearly twenty times the current surface layer density i n Deer Lake. In view of the evidence and the above discussion i t would appear that a r t i f i c i a l destratif icat ion would not be a feasible method of controlling Deer Lake turbidi ty . In conclusion, i t should be mentioned that a r t i f i c i a l l y destratifying Deer Lake would, with sufficient equipment, reoxygenate the hypolimnion thereby sealing the sediments to nutrient migration. Given that stream loading of P and N i s excessive, however, sealing the sediments may prove to be of dubious value. Oxygenating the hypolimnion would, however, recreate a viable habitat for the f i sh that remain i n Deer Lake (Gebhart and Summerfelt, 1976), and promote the redistribution of their prey organisms. In the event that th ird level recreational act iv i t ies are considered desired i n Deer Lake, a r t i f i c i a l oxygenation methods would provide the primary tools with which to achieve this objective. 64 CHAPTER V CONCLUSION This research i l lu s t ra te s , through the study of Deer Lake and i n the context of Limited data, the kinds of analyses of technological options that are required i n order to identify and ;;reduce-;- the uncertainties associated with their use i n the control of water quality. The analyses provided are not meant to be def init ive i n the sense that a l l possible technologies are considered and an ultimate remedial programme formulated. Instead, the analyses are i l l u s t r a t i v e , intending only to demonstrate how important information about the aquatic ecosystem and the potential technological impacts upon i t can be generated. From a l i s t of a l l possible options, the non-inferior strategies would, through the analyt ical proce-dures employed here, then be ferreted out from which the f i n a l remedial technology would be selected. As part of the background theory presented i n Chapter I I , a p a r t i a l l i s t of seven technologies for the control of water quality are reviewed. Following an examination of Deer Lake data, however, i t i s apparent to the writer that four technologies are inappropriate i n the Deer Lake context because particular conditions within the lake environment and/or requirements of the Deer Lake Development plan are incompatable with the design objectives of each of the four methods. Thus, they are eliminated from further consideration. 65 The f i r s t technological strategy investigated i s the mechanical removal of aquatic hydrophytes for nutrient control. From a mathematical computation, however, i t i s found that the hydrophyte population of Deer Lake i s insuf f ic ient ly large for there to be a significant impact upon nutrient concentrations. A simple comparison of the organically bound nutrients within the hydrophyte communities with the nutrient loading confirms the relat ive ineff iciency and poor performance potential of this method. For Deer Lake this strategy i s , therefore, rejected. The algicide, copper sulfate, i s examined next for i t s potential usage as a b iot ic turbidity control mechanism. From the Deer Lake data, the analysis proceeds to develop a scenario of algal succession i n Deer Lake while formulating a prediction concerning the impacts of this chemical upon the target species and the long-term implications of i t s use. The scenario suggests that while short-term benefits may i n fact be real ized, the magnitude of probable adverse effects over the long term w i l l negate any successes gained from this technology. The potential impacts upon various non-target organisms that this chemical would impose are also reviewed from the theoretical l i terature . The conclusion reached i s that this strategy does not provide the means of achieving the stated water quality objectives i n Deer Lake. The third technology subjected to analysis i s destrat i f icat ion, also for b iot ic turbidity control. In an i n i t i a l attempt to gain insight into the optimal physical environment for ..this technique, several research lakes are reviewed. Unfortunately, no apparent correlation exists between 66 lake morphology and success i n c o n t r o l l i n g a l g a l populations. Following t h i s , a comparative study i n v o l v i n g Deer Lake and Kezar Lake i s conducted. Since both lakes exhibit s i m i l a r water chemistry, morphology, and are of s i m i l a r socio-economic importance, the research programme of Kezar Lake serves to be i n s t r u c t i v e . f o r p r e d i c t i n g r e s u l t s i n Deer Lake. The an a l y s i s , indeed, suggests that the r e l a t i v e l y minor successes enjoyed i n Kezar Lake may not, i n f a c t , be r e a l i z e d i n Deer Lake due to s p e c i f i c differences i d e n t i f i e d between the two environments. On the basis of t h i s comparison, therefore, the writer concludes that d e s t r a t i f i c a t i o n would not be an appropriate technology f o r Deer Lake. The im p l i c a t i o n s of t h i s research extend to Deer Lake s p e c i f i c a l l y , and s i m i l a r l y to other s i t u a t i o n s wherein the s o c i a l and/or economic importance of a lake requires technological maintenance of water q u a l i t y . Concerning Deer Lake, the analyses provided are a u t h o r i t a t i v e to the extent that they i d e n t i f y several important p o t e n t i a l weaknesses of the technologies discussed. Also, from the t h e o r e t i c a l l i t e r a t u r e and Deer Lake data the scenarios generated concerning ecosystem performance reduce to a large degree the uncertainties regarding p o t e n t i a l impacts and the probable success of each method. The consequence of employing the a n a l y t i c a l procedures described i s that none of the three technologies discussed can be recommended as a panacea f o r the water q u a l i t y problems perceived i n Deer Lake. Equally important to the writer, however, i s the a b i l i t y of t h i s type of a n a l y t i c a l procedure to overcome i n i t i a l prejudices regarding the most appropriate technology to employ. For instance, s t r a t e g i e s , that exhibit t h e o r e t i c a l l y promising r e s u l t s i n i t i a l l y may 67 o f t e n , upon subsequent examination, r e v e a l a high p r o p e n s i t y t o f a i l i n a given environment or perhaps t o exacerbate a water q u a l i t y problem. As a means of a v o i d i n g the myriad costs of t r i a l - a n d - e r r o r resource management programmes, and i n order t o e l i m i n a t e unnecessary or perhaps dangerous i n t e r v e n t i o n s i n the n a t u r a l environment without f u l l y a p p r e c i -a t i n g the consequences, the analyses contained h e r e i n must be considered at l e a s t p a r t i a l l y s u c c e s s f u l . The i m p l i c a t i o n s of t h i s r esearch f o r other aquatic resource manage-ment s i t u a t i o n s i n v o l v i n g t e c h n o l o g i c a l i n t e r v e n t i o n are inherent i n the ideas f o r f u r t h e r research i n t h i s academic area. While the recommenda-t i o n s t h a t f o l l o w stem from a c o n v i c t i o n t h a t t h i s form of a n a l y t i c a l process has v a l i d i t y as a resource management t o o l , the inherent weaknesses must be r e c t i f i e d so as t o make the analyses more adaptable, r e l e v a n t , comprehensive, and r i g o r o u s . With t h i s i n mind, i t i s recommended t h a t : (1) a f u l l l i s t of a l l p o s s i b l e technologies be i n i t i a l l y d r a f t e d w i t h f u l l reasoning provided f o r those methods el i m i n a t e d because of i n c o m p a t a b i l i t y w i t h t h e o r e t i c a l requirements or the resource environment, (2) the conceptual framework provided by Table 4-1 (which c o r r e l a t e s the r e c r e a t i o n a l l e v e l s of use and water q u a l i t y r e q u i r e -ments) be modified t o i n c o r p o r a t e the best remedial technologies w i t h b a s i c economic cost i n f o r m a t i o n . This would enhance the u t i l i t y of the format as a decision-making aid?... (3) a d d i t i o n a l data requirements be i d e n t i f i e d during the analysis procedure, with some mechanism "being devised that allows f o r secondary data c o l l e c t i o n and i t s l a t e r i n t r o d u c t i o n i n t o the a n a l y s i s , (4) the simple one-technology analyses introduced here he developed to incorporate a multi-system approach to water q u a l i t y problems. LITERATURE CITED 70 LITERATURE CITED Anderson, G . B . , 1974. "Water-Quality Management," i n The Allocative  Conflicts i n Water-Resource Management, Agassiz Center for Water Studies, The University of Manitoba, Winnipeg. Boyd, C . E . , 1974. "Uti l ization of Aquatic Plants," i n Aquatic Vegetation  and i t s Use and Control, edited by D.S. Mitche l l . Unesco, Paris . Boyter, C . J . , and M.P. Wanielista, 1973- "Review of Lake Restoration Procedures," i n Water Resources Bul le t in , 9(3) June. Brady, N . 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National Academy of Sciences, Washington, D.C. National Academy of Sciences, I 9 6 8 . Weed Control, 2 . Publication 1567. Washington, D.C. Neel, J . K . , S.A. Peterson, and W.L. Smith, 1973* Weed Harvest and Lake Nutrient Dynamics, EPA-660/3-73-001 , Environmental Protection Agency, Washington, D.C. New Hampshire Water Supply and Pollution Control Commission, 1970. Algal Control by Mixing, Staff Report on Kezar Lake, December. Newroth, P .R. , 1974. Aspects of Aquatic Weed Control by Mechanical  Harvester, Water Investigations Branch, Department of Lands, Forests, and Water Resources, Vic tor ia , B .C. Nicolson, J . A . , and A . C . Mace, 1975- "Water Quality Perceptions by Users: Can It Supplement Objective Water Quality Measures?" i n Water  Resources Bul le t in , 11(6) December. Northcote, T . G . , 1976. Zoology 404 Laboratory Data. Odum, E . P . , 1969. "The Strategy of Ecosystem Development," i n Science, 164(4) . Olah, N . 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Saunders Company, Philadelphia. Whipple, W., J.V. Hunter, and S.L. Yu, 1974. "Unrecorded P o l l u t i o n from Urban Runoff," i n the Journal of the Water P o l l u t i o n Control  Federation, 46(5) May. Wilbur, R.L., 1974. "Experimental Dredging to Convert Lake Bottom from Abiotic Muck to Productive Sand," i n Water Resources B u l l e t i n , 10(2) A p r i l . Willey, B.F., H. Jennings, and F. MurosfcL, 1964. "Removal of Hydrogen Sulfide with Potassium Permanganate," Journal of American Water  Works Association, 5 6 ( 4 ) . Yousef, Y1A., 1974. "Assessing the Effects on Water Quality by Boating A c t i v i t i e s , " i n Environmental Technological Service, EPA-670/2-74-072, Environmental Protection Agency, Washington, D.C. 77 APPENDICES Appendix A. Deer Lake Stream Data Date Stream Discharge ( l s e c - 1 ) Temperature (°c) Tota l P (m 1 - 1 ) Nit ra te N (ug I ' 1 ) September 2 5 , 1976 In le t 1 18 . 5 1 1 . 0 6 . 5 390 In le t 2 2 2 . 8 14 .0 - 230 In le t 3 6 . 0 11.0 62 430 In le t 4 24. ? 1 0 . 0 72 82 In le t 5 9 .2 1 1 . 0 40 600 September 2 6 , 1976 In le t 5A 6.7 - 48 480 In le t 5B 1 - 35 18 In le t 6 ca 66 - 80 50 Outlet 184 2 0 . 0 65 12 From Zoology 404 Laboratory Data Appendix B. Deer Lake A l g a l Enumeration ( c e l l s ml ) S t a t i o n 1 - September 2 5 , 1976 Depth (m) A l g a l Group 0 1 2 4 5 - 5 B a c i l l a r i ophyceae g. Ast e r i o n e l l a - 27 - - 53 g. G y c l o t e l l a 532 680 444 1,800 3,197 g. M e l o s i r a 1 6 , 0 0 0 30,400 2 9 , 7 0 0 5 7 , 0 0 0 2 5 , 9 3 0 g. Navi c u l a 177 240 355 2 , 7 5 0 231 g. St ephanodi s cus 142 - 355 - -g. Synedra - - - - 53 g. T a b e l l a r i a 118 - 266 - 355 other genera 143 201 1,377 175 409 Chrysophyceae g. Synura - 27 89 - 1 0 , 4 7 8 other genera - 27 156 - -Ghlorophyta g• Ghlorococcum - 27 - 2 , 5 4 3 355 other genera 143 142 177 345 -Cyanophysa a l l genera 142 900 89 - -T o t a l Algae 1 7 , 6 2 8 33,851 34,844 66,441 42 , 5 3 5 From Zoology 404 Laboratory Data Appendix C. Deer Lake Zooplankton Enumeration Station 1 -nSeptember 25, 1976 (numbers m l - l ) Order Depth (m) 0 - 1 2 - 3 4 - 5 Cladocera 28.8 88.4 3-6 Copepoda 522.9 299-7 94.5 Rotifera 19.8 90.0 40.5 Total Zooplankton 571-5 487-1 138.6 From Zoology 404 Laboratory Data Appendix D. Deer Lake Water Temperature P r o f i l e S t a t i o n 1 October 30, 1976 (From Zoology 404 Laboratory Data) T E M P E R A T U R E (°C) 6.0 7.0 8.0 9..0 10.0 11.0 12.0 1.0,-D E P (m) 3-0 H T 

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