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Effects of changes in temperature, salinity and undefined properties of sea water on the respiration… Gilfillan, Edward Smith 1970

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THE EFFECTS OF CHANGES IN TEMPERATURE, SALINITY AND UNDEFINED PROPERTIES OF SEA WATER ON THE RESPIRATION OF EUPHAUSIA PACIFICA HANSEN (CRUSTACEA) IN RELATION TO THE SPECIES' ECOLOGY. by Edward Smith G i l f i l l a n J A THESIS SUBMITTED1 IN PARTIAL FULFILMENT* )OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY in the Department of ZOOLOGY and INSTITUTE OF OCEANOGRAPHY We accept this thesis as conforming to the required standard THE UNIVERSITY OF BRITISH COLUMBIA July, 1970 In presenting this thesis in partial fulfilment of the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make it freely available for reference and study. I further agree that permission for extensive copying of this thesis for scholarly purposes may be granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allowed without my written permission. Department of The University of British Columbia Vancouver 8, Canada i Chairman: Dr. B. McK. Bary ABSTRACT Temperature, sa l i n i t y , and other, undefined properties of sea water have been suggested as factors acting to limit the distribution of planktonic organisms through the stresses they impose. The aim of this study was to examine experimentally the effects of changes in these properties on the respiration of Euphausia pacifica Hansen. Both immediate and long term effects of changes in these properties were examined. Assessments of the immediate effects of changes in temperature and salinity on the animals' respiratory rate demonstrated that a sharp reduction in respiratory rate could be used as an indication of stress. The results of these same experiments showed that as the values of temperature and salinity approached the limits of tolerance, the effects of stresses from them interact. The long term effects of changes in temperature and salinity were investigated by determining the limits of these factors that were tolerable to specimens from areas in which the characteristic temperatures and sa l i n i t i e s of the water were different. Specimens from the water having the greatest range of values of temperature and salinity (coastal) possessed the greatest tolerance to changes i n temperature and salinity ; specimens from water having the least range of temperature and salin i t y (oceanic)'had the least tolerance. The tolerances to changes in temperature and salinity observed in these experiments indicated that the distribution of E_. pacifica in British Columbia coastal waters was not likely to be i i influenced by changes in temperature and salinity except near the surface, where the salinity may become low and the temperature high or very low. Experiments taking advantage of the interaction between the effetts of temperature and salinity were used to establish that other properties of sea water, while undefined, could impose stress on adult E_. pacifica. At the same time a method of assessing the effects of changes in undefined properties between sea waters through a comparison of respiratory rates obtained under standard conditions was developed. The results of experiments in which changes i n undefined properties of sea waters collected at two depths in each of two locations were examined indicate that these properties appear to be a function of the origin of the particular water. They also indicate that differences between waters i n these properties did not affect the distribution of jE. pacifica within either of the two areas investigated,nnamely the Strait of Georgia and Indian Arm. The results did indicate, however, that populations of E. pacifica were present i n each of these areas i n which inverse reactions to the same set of undefined properties existed. Presumably these result from persistent differences in undefined properties between the waters resident i n each of the two areas. i i i TABLE OF CONTENTS Page I. GENERAL INTRODUCTION 1 II. GENERAL MATERIALS AND METHODS 8 Field Procedures 8 Laboratory Procedures 11 Respiration Measurements 11 III. OCEANOGRAPHIC CONDITIONS IN THE SAMPLING AREAS . . . 15 Northeastern Pacific Ocean . . . . . . . 20 Juan de Fuca Strait 22 Saanich Inlet 22 The Strait of Goergia 24 Indian Arm 28 IV. THE EFFECTS OF STRESS FROM CHANGES IN TEMPERATURE AND SALINITY ON SPECIMENS FROM OCEANIC, OCEANIC-COASTAL AND COASTAL WATERS 32 Introduction 32 Materials and Methods 34 Results 35 Discussion . . . . . 41 V. THE EFFECTS OF SEVERAL NATURAL SEA WATERS ON TOLERANCE TO VARIATIONS IN TEMPERATURE AND SALINITY 49 Introduction . . . 49 Materials and Methods 51 i v TABLE OF CONTENTS (continued) Page St a t i s t i c a l Analysis 54 Results 55 Dis cussion 62 VI. ANNUAL CHANGES IN THE REACTIONS OF TWO COASTAL POPULATIONS OF EUPHAUSIA PACIFICA TO NATURAL SEA WATERS 69 Introduction . . . . . . . . . . . 69 Materials and Methods 72 Results • 75 Discussion 80 VII. GENERAL DISCUSSION 9 7 VIII. SUMMARY AND CONCLUSIONS 105 IX. REFERENCES 109 X. APPENDIX 1 115 V LIST OF TABLES Table Subject Page Depths at which observations of water properties were made and plankton samples were collected in the Strait of Georgia (Station G.S.-l) and in Indian Arm (Station I.A.-9) 2. Results of analysis of variance: Reactions of Euphausia pacifica from Saanich Inlet to changes in temperature and sali n i t y , data from February 1969 and June 1969 combined . . 38 3. Results of analysis of variance: Reactions of Euphausia pacifica from Juan de Fuca Strait to changes in temperature and sali n i t y , data from November 1968 and July 1969 combined 39 4. Results of analysis of variance: Reaction of Euphausia pacifica from the Pacific Ocean to changes i n temperature and sa l i n i t y , data from February 1969 and June 1969 combined 40 5. The depth of collection and the salinity of sea water samples from Indian Arm and the Strait of Georgia used in the experiments carried out i n May, July and August, 1969 53 6. Results of analysis of variance: Reaction of Euphausia pacifica from the Strait of Georgia to changes in temperature, salinity and 'other' water properties, data from the experiment performed i n May 1969 58 7. Results of-analysis of variance: Reactions of Euphausia pacifica from the Strait of Georgia to changes in temperature, salinity and 'other' water properties, data from the experiment performed i n July 1969 . . . , | 60 8. Results of analysis of variances Reactions of Euphausia pacifica from the Strait of Georgia to changes in temperature, salinity and 'other' water properties, data from the experiment performed i n August 1969 63 9. Temperatures, s a l i n i t i e s , and depths from which the two waters used i n experiments were collected from Indian Arm 73 v i LIST OF TABLES (continued) Table Subject Page 10. Temperatures, s a l i n i t i e s , and depths from which the two waters used i n experiments were col l e c t e d i n the S t r a i t of Georgia 74 11. Results of analysis of variance; Analysis of a l l data obtained over 13 months using Euphausia  p a c i f i c a from both Indian Arm and the S t r a i t of Georgia in four sea waters . . . . 81 12. Results of analysis of variance: Reactions of Euphausia p a c i f i c a from Indian Arm to Indian Arm upper and lower water over 13 months 82 13. Results of analysis of variance: Reactions of Euphausia p a c i f i c a from the S t r a i t of Georgia to S t r a i t of Georgia upper and lower water during 'low salinity,' conditions i n 1968 ( A p r i l , May) and i n 1969 (May, June) 83 14. Results of analysis of variance; Reactions of Euphausia p a c i f i c a from the S t r a i t of Georgia to S t r a i t of Georgia upper and lower waters during 'high s a l i n i t y ' conditions, winter 1968-1969 (November, December, January, February) 84 15. Results of analysis of variance: Reactions of Euphausia p a c i f i c a from Indian Arm to S t r a i t of Georgia upper, S t r a i t of Georgia lower, and Indian Arm composite waters during August, September, and October 1968 compared with those during July, August, and September 1969. 85 16. Results of analysis of variance; Reactions of Euphausia p a c i f i c a from Indian Arm to S t r a i t of Georgia upper, S t r a i t of Georgia lower, and Indian Arm composite waters during February, March, A p r i l and May 1969 86 17. Results of analysis of variance: Reactions of Euphausia p a c i f i c a from Indian Arm to S t r a i t of Georgia upper, S t r a i t of Georgia lower, and Indian Arm composite waters during June, July, August and September 1969 87 18. Results of analysis of variance: Reactions of Euphausia p a c i f i c a from Indian Arm to S t r a i t of Georgia upper, S t r a i t of Georgia lower, and Indian Arm composite water during the period of February, March, A p r i l and May 1969 compared with t h e i r reactions to the same waters during the period June, July, August and September 1969 88 v i i LIST OF TABLES (continued) Table Subject Page 19. . Abundance of adult and juvenile Euphausia i pacifica as numbers/m3 at Indian Arm Station 9: data from plankton samples collected using the Clarke-Bumpus Plankton samplers 89 v i i i LIST OF FIGURES Figure Subject Page 1. A t y p i c a l oxygraph record showing, A, a region of thermal e q u i l i b r a t i o n between the electrode and the fresh medium; B, a region of l i n e a r decrease. The slope of the region of l i n e a r decrease (H/time) was used to c a l c u l a t e the animals' r e s p i r a t i o n rates 14 2. O v e r a l l temperature-salinity diagram, showing the i n t e r r e l a t i o n s of the waters present i n the areas from which euphausiids were c o l l e c t e d . 16 3. Chart of B r i t i s h Columbia coastal waters showing positions of stations from which euphausiids were c o l l e c t e d 18 4. Temperature and s a l i n i t y values observed at s t a t i o n Pac.-l i n February and June 1969, plo t t e d as temperature-salinity diagrams. . . 21 5. Temperature and s a l i n i t y values observed at s t a t i o n J.F.-9 i n November 1968 and July 1969, p l o t t e d as temperature-salinity diagrams. . . 23 6.. Temperature and s a l i n i t y values observed at s t a t i o n SAA-4 i n February and June 1969, plo t t e d as temperature-salinity diagrams. . . 25 7. Temperature p l o t t e d against depth at s t a t i o n G.S.-l from August 1968 to September 1969 . . 27 8. S a l i n i t y p l o t t e d against depth at s t a t i o n G.S.-l from August 1968 to September 1969 27 9. Temperature p l o t t e d against depth at s t a t i o n I.A.-9 from-August 1968 to September 1969 . . 29 10. S a l i n i t y p l o t t e d against depth at s t a t i o n I.A.-9 from August 1968 to September 1969 29 l l ( a - c ) . R e s p i r a t i o n - s a l i n i t y curves f o r Euphausia p a c i f i c a under various combinations of temperature and s a l i n i t y , a. Specimens from Saanich I n l e t , data c o l l e c t e d i n February and June 1969. b. Specimens from Juan de Fuca S t r a i t , data c o l l e c t e d i n November 1968 and July 1969. c. Specimens from the P a c i f i c Ocean, data c o l l e c t e d i n February and June 1969 36 ix LIST OF FIGURES (continued) Figure Subject Page 12(a-c). Respiration-salinity curves for Euphausia  pacifica from the Strait of Georgia while in media made from 4 sea-waters collected at differing depths and locations, a. Data from the experiment performed i n May 1969. b. Data from the experiment performed in July 1969. c. Data from the experiment performed in August 1969 57 13a. Respiration of Euphausia pacifica from the Strait of Georgia in Strait of Georgia upper and lower and i n Indian Arm Composite from April 1968 to September 1969 (Indian Arm Composite from August 1968 to September 1969 only) 75A 13b. Respiration of Euphausia pacifica from Indian Arm in Strait of Georgia upper and lower and in Indian Arm Composite from March 1968 to September 1969 75A X ACKNOWLEDGMENTS I am indebted to a l l the members of my research advisory committee for their guidance and encouragement. I would like to extend my most sincere thanks to my research advisor, Dr. B. McK. Bary, for his patience, advice, encouragement and criticism. I would also like to thank Dr. C.S. Holling, Dr. P.A. Larkin, Dr. A.G. Lewis and Dr. G.L. Pickard, a l l of whom read and cr i t i c i s e d the manuscript, for their helpful suggestions and criticisms. I would like to offer special thanks to Dr. A.G. Lewis and Dr. J. Sibert for the many f r u i t f u l discussions i n which they participated. The officers and men of CNAV Laymore, CNAV Endeavour and CSS Vector deserve sincere thanks for their cheerful and generous assistance in the gathering of the data. To my wife, Katherine, whose encouragement during the research and the preparation of the thesis made these tasks much easier, I offer my most sincere thanks. THE EFFECTS OF CHANGES IN TEMPERATURE, SALINITY AND UNDEFINED PROPERTIES OF SEA WATER ON THE RESPIRATION OF EUPHAUSIA PACIFICA HANSEN (CRUSTACEA) IN RELATION TO THE SPECIES' ECOLOGY. I. GENERAL INTRODUCTION. One important question in the ecology of marine zoo-planktonic organisms is "What limits the distribution of these organisms?". Answers to this question are usually given in terms of a 'limiting' factor or factors. These generally are presumed to impose stress on the animals in question and thus limit their distribution. Brett (1958, p. 74) has defined stress as : "... a state produced by an environmental factor which extends the adaptive response of an animal beyond the normal range, or which disturbs the normal functioning to such an extent that, in either case, the chances of survival are significantly reduced". He divides (p. 75) stresses into two general categories. The f i r s t , discriminate stress, is defined as "... one which applies at any one time to individuals, singly within a population and not to a group or stock as a whole". Examples are predation, parasitic infestation, and injury. Brett's second category, indiscriminate stress, is "... one which applies to every member (of a population) and is not discrete i n i t s action. Stresses like high temperature, low oxygen, or toxic effluents spare no individual entering or inhabiting an environment with such characteristics." -2-Factors which have been suggested as limiting the distribution of zooplanktonic organisms, namely the various properties of sea water, are invariably sources of indiscriminate stress. Much of the information currently available in relation to this subject stems from the large body of literature concerned with the identification and distribution of so-called 'indicator species'. Indicator species are those whose occurrence in an area indicates the presence there of water of a particulars origin, i n i t i a l l y from a specific geographic locality (see Fraser, 1937, 1939, 1952; Russell, 1935, 1939). No physico-chemical characterization of the waters indicated by the species' presence was attempted in the studies cited above. The underlying hypothesis was that these species were limited in their distribution to the water whose presence they indicated because they were unable to li v e in any other. Pickford (1946, 1952) demonstrated that a species of bathypelagic squid was confined to certain water masses by plotting the temperature (T) and salinity (S) values for the depths at which the specimens were captured. Using the same technique Haffner (1952) also demonstrated that certain species of bathypelagic fish were associated with water masses. This general method was developed and extended by Bary (1959, 19J63aJb!>,cJdJ 1964) who worked with surface waters and zooplanktonic animals. Bary's technique uses the temperature-salinity-plankton (T-S-P) diagram as a means of identifying indicator species by relating their occurrences to the 'water bodies' which exist in the sampling area. Studies b'y.9 Eager and McGowan (1963) , and Sherman 1 -3-(1963, 1964) and Cross and Small (1967) have demonstrated further the close association between the occurrence of certain species of zooplanktonic organisms and the water bodies present in the area. The identity of the property or properties of a given water body that might-limit a species' distribution remains a source of speculation. Because temperature and salinity are commonly used to characterize water bodies, i t has been suggested that these properties, either singly or in combination, might be the operative agents. Certainly, in some instances, there is no question that they are (see Kinne, 1964, for a review of the relevant literature). Bary (1963 d; 1964), however, discusses the distribution of zooplanktonic organisms from the Northeastern Atlantic in relation to identifiable water bodies and shows that i t does not depend on the temperature and salinity values by means of which the water bodies were characterized. In view of this finding Bary (1963 d, p. 64) proposed that certain undetermined 'unique properties' charact-e r i s t i c of each water body, combined with the differing tolerances of various species, could be responsible for the species-water body ^relationship. In searching for an improved culture medium for echinoderm larvae, Wilson (1951) compared experimentally the sui t a b i l i t y of water from the English Channel and the Celtic Sea, two areas frequently characterized by different sets of indicator species. The results showed that the Celtic Sea water was a superior culture medium, a situation attributed to 'biological differences' between the waters by Wilson. Further -4-experiments (Wilson and Armstrong, 1952, 1954, 1958, 1961) ind i c a t e d that these ' b i o l o g i c a l differences' were p e r s i s t e n t , but f a i l e d to enable the active p r i n c i p l e causing the differences to be i d e n t i f i e d . An extention i n i n t e r p r e t a t i o n of res u l t s obtained by Wilson and Armstrong from experiments i n which eggs were allowed to develop i n mixtures of two waters suggested, however, that the d i f f e r e n t e f f e c t s produced by the two waters resu l t e d from the lack of some 'good' or required property i n the 'bad' water, rather than from the presence of some toxic q u a l i t y . Lewis (1967) and Lewis and Ramnarine (1969) report that the s u r v i v a l of eggs and naupliar stages of a calanoid cppepod i n sea water c o l l e c t e d from depths where they were l i v i n g was increased by the addition of trace amounts of cobalt and zinc, as w e l l as a chelating agent (EDTA). Their r e s u l t s i n d i c a t e that cobalt and zinc at times may be present i n the i 1 raw sea water i n less than optimal concentrations. The e f f e c t of changes i n the concentration of cobalt and zinc on s u r v i v a l of l a r v a l copepods suggests that va r i a t i o n s i n concen-t r a t i o n of trace elements may be among the factors which a f f e c t the d i s t r i b u t i o n of planktonic organisms. Regan (1968) c a r r i e d out a serie s of experiments on a l o c a l species of euphausiid, Euphausia p a c i f i c a Hansen, i n which he demonstrated that both the behaviour and s u r v i v a l of these animals could be strongly affected by the source of the sea water used as an experimental medium. Further, he found that specimens of _E. p a c i f i c a captured i n three l o c a l i t i e s , -5-reacted differently to sea waters from several sources. Regan explains these results in terms of 'unique properties' of the waters used as experimental media, rather than in terms of reactions to temperature and sali n i t y , or to a T x S interaction. These last causes were ruled out.in the course of his experiments. The above brief review of some of the relevant literature indicates that the temperature and salinity of their environment may affect the distribution of zooplanktonic organisms when extreme values of temperature and salinity are approached. At the same time, however, many species of zooplanktonic animals are capable of reacting to differences in some 'essential quality' or 'property' between natural sea waters, of differing origins but with comparable temperatures and s a l i n i t i e s . It is also indicated that some species may have different requirements and/or tolerances for these qualitative differences between sea waters. And lastly, there i s evidence that a l l members of a species may not have similar requirements or tolerances. Bary (1963 d) summarized the situation with respect to 'unique properties' by saying that there are two aspects of the ecology of zooplanktonic organisms: one is oceanographic -the properties (not only the 'unique properties', but also temperature and salinity) of different waters; the other is biological - the species' differing'reactions to changes in properties between sea waters of differing histories. This second aspect of the ecology of zooplanktonic organisms appears to be fully as important as the f i r s t ; i t has, however, rarely been investigated experimentally (Kinne, 1964). It could -6-be expected therefore that the results of a series of experiments directed toward understanding the way a local species of zooplankton, Euphausiarfeacifica Hansen, reacts to different properties of sea water, would provide an insight into the ecology of planktonic organisms. To this end, three lines of research were pursued. The aim of the f i r s t was to investigate the effects of changes in temperature and sa l i n i t y , of known sources of stress which can be measured and manipulated experimentally, on specimens of E_. pacifica. In order to pursue this object i t was necessary to develop a means of assaying for effects of sublethal stress which in turn was used to determine the point at which specimens, collected from oceanic, mixed oceanic-coastal and coastal waters, became affected by stress from elevated temperatures and reduced s a l i n i t i e s . It should be possible from a, comparison of the reactions of specimens resident i n each of the three waters to infer whether and to what extent adaptation to changes in environmental conditions had occurred. . i The second aim of the experiments was to useuthe knowledge gained about E_. pacifica's reactions to stress imposed by changes i n temperature and sa l i n i t y , to investigate the effects of water properties other than temperature and salinity on the animal's metabolism. • An integral part of the experiments was to develop a method of evaluating the relative amounts of stress exerted on specimens by differences in 'other' properties between sea waters. -7-The third aim has been to relate changes in the distribution of non-measurable properties ('other'properties ' ) from month to month at two locations, to changes in the oceanographic processes. An analysis of the results of this third part of the program indicates what relationship exists between the distribution of the 'other' properties' and the distribution of E_. pacifica and whether adaptation to the unique combination of 'other'properties' of a given water body can occur. Each of these objectives was approached by measuring the respiratory rate of individual specimens of _E. pacifica in sea water under a variety of conditions. In general, the results of the investigations indicate that both temperature and sal i n i t y , as well as 'other' properties of sea water can place adult E_. pacifica under stress. They further indicate that adaptation to environments which differ both with respect to their temperature-salinity characteristics and their 'other' properties has occurred i n B.C. coastal waters. -8-I I . GENERAL MATERIALS AND METHODS. Euphausia p a c i f i c a i s widely d i s t r i b u t e d i n both offshore and inshore areas (Brinton, 1962; Ponomareva, 1963; Bary, 1966; Regan, 1968; Mauchline and Fisher, 1969);jon this basis i t appears to be a highly tolerant species. Even so, i t has been demonstrated that specimens react behaviourally (Regan, 1968) to differences i n properties between water bodies; specimens also are large, generally abundant, and tolerant toward laboratory handling. For these reasons E_. paci f i c a i s a good experimental animal with which to study the r e l a t i o n between the species and the water i n which i t l i v e s . F i e l d Procedures. Each s t a t i o n from which experimental animals were c o l l e c t e d was occupied, whenever f e a s i b l e , by day and by night. There were two aims: f i r s t l y , to obtain data withhwhichoto r e l a t e the experimental r e s u l t s to the daytime d i s t r i b u t i o n of _E. p a c i f i c a and secondly, to collectcexperimental animals at night when they were close to the surface and less l i k e l y to be damaged i n the shortened tows made then. During daylight, observations of temperature and s a l i n i t y were made at selected depths at each s t a t i o n (Table 1). Horizontal plankton tows also were made using Clarke-Bumpus plankton samplers (Clarke and Bumpus, 1950) spaced at 25 m i n t e r v a l s (Table 1), i n order to a s c e r t a i n the daytime d i s t r i b u t i o n of euphausiids. -9-TABLE 1 Depths at which observations of water properties were made and plankton samples were collected i n the Strait of Georgia (Station G.S.-l) and in Indian Arm (Station I.A.-9). Stn. G.S. - 1 Stn. I.A. - 9 (depth = 400m) (depth = 220m) water prop. plankton samp. water prop. plankton samp, 0 25 0 25 10 50 10 50 20 75 20 75 30 100 30 100 50 125 50 125 75 150 75 150 100 175 100 175 150 200 125 200 250 150 250 300 175 300 350 200 350 375 375 -tO-Sea water f o r use i n experiments was a l s o obtained during d a y l i g h t ; thus, experimental r e s u l t s , the daytime d i s t r i b u t i o n of 13. p a c i f i c a and the d i s t r i b u t i o n of water p r o p e r t i e s could be r e l a t e d . The water was c o l l e c t e d from various depths, depending on the l o c a t i o n and the d i s t r i b u t i o n of E_. p a c i f i c a , using a 1 6 - l i t r e Van Dorn Sampler. I t was f i l t e r e d through nylon mesh having a mesh aperture of 160 micra i n t o 2 0 - l i t r e polyethylene carboys and pla c e d i n the ship^s r e f r i g e r a t o r u n t i l used. Specimens of E_. p a c i f i c a were caught i n v e r t i c a l or oblique net hauls using a c o n i c a l sampler, 1-m diameter at the mouth. The bucket of t h i s sampler was a PVC tube, closed at one end, and approximately 9 x 45 cm i n i n t e r n a l dimensions. I t aided i n c o l l e c t i n g specimens i n good c o n d i t i o n by p r o v i d i n g a r e l a t i v e l y non-turbulent refuge during towing. At the su r f a c e the c o l l e c t i o n was immediately poured i n t o s e v e r a l l i t r e s of sea water c h i l l e d to a temperature approaching that of the water i n which they were l i v i n g . The animals r e q u i r e d f o r experimental purposes were then t r a n s f e r r e d i n t o 4 - l i t r e vacuum f l a s k s (isotherms). A l l t r a n s f e r s were made using s t a i n l e s s s t e e l spoons; the animals were always immersed i n water. In s e l e c t i n g experimental animals both l a r g e and s m a l l euphausiids were avoided w i t h the i n t e n t i o n of o b t a i n i n g animals approximating a s i n g l e s i z e c l a s s . U s u a l l y twenty specimens were placed i n each isotherm, :L.e. about 5 / l i t r e . The m o r t a l i t y r a t e was low, p r i m a r i l y because i t was u s u a l l y easy to detect and discard an i n d i v i d u a l damaged during capture. The c u t i c l e of i n j u r e d specimens appeared 'frosty' at the point of i n j u r y i n sharp contrast to i t s normal, glassy appearance. The specimens were held at 5-10 °C i n the ship's r e f r i g e r a t o r u n t i l required. In most instances acclimation to experimental treatments was s t a r t e d within 12 hours of capture. Laboratory Procedures. The medium for many experiments was f u l l - s t r e n g t h sea water; for others, media were made up by d i l u t i n g the f u l l -strength sea water with d i s t i l l e d water (from a Barnstead s t i l l ) . Each medium was placed i n a 1 - l i t r e wide mouthed polyethylene b o t t l e and cooled or warmed to near the f i n a l temperature required for the subsequent experiment. The experimental animals were then placed i n the b o t t l e s and the whole immersed i n a 1 0 0 - l i t r e water bath, which was thermo-s t a t i c a l l y maintained at the experimental temperature, for an acclimation period of 12 hours. Usually seven animals were placed i n each b o t t l e so as to allow for mortality during acclimation (rare) and losses during handling. Any animal which was suspected of having been damaged during handling was discarded. Respiration Measurements. Respiration measurements were made i n a water-jacketed chamber made of glass. The i n t e r n a l volume of the chamber was 4.9 ml; i t was divided i n t o two compartments by a wire-mesh p a r t i t i o n made of s t a i n l e s s s t e e l . The stopper of the chamber was vented through a c a p i l l a r y bore so as to equalize pressure when i t was pushed home. -12-When determining respiratory rates, experimental animals were placed on one side of the mesh partition, and a magnetic s t i r r i n g bar and a polarigraphic oxygen electrode"*" on the other. This arrangement allowed continuous circulation of the medium without any damage to the animal. The chamber and electrode were maintained at the experimental temperature by circulating water from the water bath through the water jacket. The current produced by the electrode is proportional to the oxygen content'of the water in the chamber; i t was 2 continuously recorded on a GME Oxygraph, model KM. The recordings provide a plot of oxygen concentration in the chamber versus time, for each animal. The electrode was calibrated in air-saturated water against Winkler determinations of oxygen content. Frequent checks showed that i t , and the recorder, were stable. One electrode was used for a l l respiration measurements; i t s calibration did not appear to be affected by changing the teflon membrane (.001") indicating that the membranes were uniform in thickness. One batch of membranes was used through-out this study which may have contributed to the s t a b i l i t y of the electrode. The medium in which the respiration rate for each animal was determined was fresh medium similar to that in which they had been acclimated for 12 hours. Between the recordings 1. 2. Yellow Springs Instrument Company, Yellow Springs, Ohio. Gilson Medical Electronics, Middleton, Wisconsin. of rates, when the same medium was being used, the chamber was flushed with several volumes of fresh medium to remove any traces of metabolites. Between series in different media the chamber was flushed f i r s t with d i s t i l l e d water, and then with several volumes of the new medium. Recordings of change in oxygen content of the water in the chamber, as a result of. the respiration of specimens, were carried out for a period of between 15 and 30 minutes. After a sufficiently long record had been obtained, the specimen was removed from the chamber, using clean stainless-steel forceps, and examined under a dissecting microscope to ensure that i t was JE. pacifica. It was then fixed for a few minutes in f u l l -strength formalin, blotted dry, and placed i n a sealed v i a l with a code number. Specimens were later freeze-dried to a constant weight. Respiration rates were calculated by convertingcihe slope of the line on the oxygraph record (Fig. 1) to microlitres of oxygen consumed in an hour and then dividing that value by the freeze-dried weight of the experimental animal. In converting the slope of the oxygraph record to the volume of oxygen respired, account was taken of the effect of changes in temperature on the amount of current produced per unit oxygen content of the chamber. The f i n a l value of the respiration rate for each of the experimental subjects is expressed as microlitres of oxygen consumed per milligram dry weight of euphausiid per hour. These values are reported for each of the experimental subjects in Appendix 1. 15 minutes Figure 1. A t y p i c a l oxygraph. record showing, A, a region of thermal e q u i l i b r a t i o n between the fresh medium and the electrode; B, a region of l i n e a r decrease. The slope of the region of l i n e a r decrease (H / time) was used to calculate the animals' r e s p i r a t i o n rate. I I I . OCEANOGRAPHIC CONDITIONS IN THE SAMPLING AREAS. The object of this study was to investigate the reactions of .E. p a c i f i c a from s e v e r a l areas, ranging from oceanic to coastal waters, to changes i n both measurable (temperature and s a l i n i t y ) and non-measurable ('other') properties of sea water. At the same time i t was desired to r e l a t e changes i n reactions of specimens to water properties to changes i n the d i s t r i b u t i o n of water properties. Therefore i t became important not only to understand the general r e l a t i o n to one another of the waters i n each of the sampling areas, but also to examine t h e i r p a r t i c u l a r d i s t r i b u t i o n during the sampling period. The oceanic JE. p a c i f i c a , which may be considered the source of specimens l i v i n g i n BSC. coastal waters, are associated during the day (Brinton, 1962) with water whose temperature and s a l i n i t y values f a l l w ithin the bounds s p e c i f i e d by Dodimead et a l . (1963) for the deep Central Subarctic Domain. S l i g h t l y warmer water of comparable s a l i n i t y , modified by i n s o l a t i o n and runoff, gives r i s e to those B.C. coastal waters considered i n this study (Herlinveaux and T u l l y , 1961). Figure 2 shows envelopes enclosing maximum and minimum temperature-salinity combinations that can bei'.expected i n each of the areas studied. These envelopes, which have been compiled from data extending over a period of years i n c l u d i n g the:-: period during which this study was c a r r i e d out, are roughly fan-shaped. The greatest bulk of the water i n any one area, designated -16-F l g u r e 2. ( f a c i n g ) O v e r a l l t e m p e r a t u r e - s a l i n i t y d i a g r a m , showing the i n t e r r e l a t i o n s o f t h e w a t e r s p r e s e n t i n the a r e a s from w h i c h e u p h a u s i i d s were c o l l e c t e d . 25 10 _1 15 i 20 25 _ l u 30 | _ 35 40 r 25 Pacific 1-7 Juan de Fuca Strait 5-9 Strait of Georgia 2 0 -cr ID I— < 1 5 -1 0 -5 -/ WZm Saanich Inlet 1-4 ~\ Strait of Georgia 1-3 \ \ Indian Arm - 9 - Saanich Inlet open ocean surface water - 2 0 Indian Arm - 1 5 - 10 Juan de Fuca Strait open ocean deep zone water - 5 - i 1 1 r -40 - i 1 r - " T ~ 10 15 - i 1 1 r -20 — r ~ 25 30 SALINITY %. 35 -1.7-'deep water' i n this study, i s represented by the shaded areas near the apex ( r e l a t i v e l y high s a l i n i t i e s ) of each of the 'fans'. In general the wide variations i n temperature and s a l i n i t y are confined to the near-surface layers. Figure 2 indicates that the deep inshore waters considered i n this study apparently r e s u l t from the progressive d i l u t i o n of water from the deep Central Subarctic Domain (oceanic water). The values of temperature and s a l i n i t y shown for open ocean surface water i n F i g . 2 suggest that i t might also contribute to the deep inshore waters. On the other hand, Dodimead et: al (1963) considers that transport across the boundary (halocline) between the oceanic upper and lower zones i n u n i d i r e c t i o n a l l y upward. As w e l l Lane (1962) considers that the oceanic h a l o c l i n e i s continuous across the continental s h e l f i n the region of the mouth of Juan de Fuca S t r a i t . As a r e s u l t i t appears u n l i k e l y that there i s communication between the open ocean surface water (upper zone) and the water entering Juan de Fuca S t r a i t . The ranges of temperature seen i n the inshore waters r e s u l t from seasonal heating and cooling; those of s a l i n i t y from seasonal v a r i a t i o n s i n fresh-water runoff. On the whole, there i s continuity of temperature and s a l i n i t y values demonstrated between the offshore (oceanic) and inshore (coastal) waters. There are also i n d i c a t i o n s of discr e t e 'water bodies' (Bary, 1963a) coincident with the sev e r a l areas. I t i s to these and the E_. p a c i f i c a i n h a b i t i n g them that t h i s study i s directed. Juan de Fuca S t r a i t and the S t r a i t of Georgia (Fig. 2, F i g . 3) together form'an estuarine system which has been described by Herlinveaux and T u l l y (1961). B a s i c a l l y this system -19-consists of a deep inflowing layer of oceanic water overlain by a layer of less dense outflowing water. These two waters are mixed together and with water from the upper zone of the Strait of Georgia, which includes runoff, in t i d a l passes through the San Juan and Gulf Islands. Part of the mixed water flows seaward to contribute to the upper layer in Juan de Fuca Strait; part flows into the Strait of Georgia where i t occupies the lower zone (Waldichuck, 1957). Part of the mixed water also flows into Saanich Inlet (Herlinveaux, 1962). The close relationship between the deep water In Saanich Inlet and in the Strait of Georgia is shown in Fig. 2. The surface layers of Saanich Inlet show l i t t l e dilution (Fig. 2) because the inlet receives a small amount of runoff (Herlinveaux, 1962) in sharp contrast to the upper zone of the Strait of Georgia. These upper waters receive a large influx of stored runoff (chiefly from snow melt water) during the heating season. Most of the runoff affecting the southern straits is from the Fraser River (Waldichuck, 1957). In Fig. 2 i t s effect is seen as a 'tongue' of warm dilute water. The origin of the water in Indian Arm from water in the upper zone of the Strait of Georgia is strongly suggested by Fig. 2 (Gilmartin, 1962). Because of the shallow (26 m) s i l l depth, only water from the upper zone of the Strait of Georgia could enter Indian Arm. This origin is supported also by the fact that none of the intrusions observed between 1956 and the present (Gilmartin, 1962; Regan, 1968) has contained water having a salinity greater than 27.52 o/oo. The influence -20-of both stored and d i r e c t runoff and of seasonal heating and cooling on the upper zone of Indian Arm i s apparent i n F i g . 2 ' i n the range of temperature and s a l i n i t y . In order to r e l a t e the experimental results obtained with animals from the f i v e areas to oceanographic conditions, the physico-chemical (temperature-salinity) properties of the water column were sampled at the same time as the experimental material (water and animals) was obtained. The r e s u l t s of these surveys w i l l be discussed separately for each of the areas. Northeastern P a c i f i c Ocean (Station Pac-1, 54°15'N, 136°00'W). The p r i n c i p a l oceanographic structures at this s t a t i o n , west of the Queen Charlotte ,Islands are an upper zone (seasonally modified) about 100 m i n depth separated by a h a l o c l i n e from a lower (non-seasonal) zone. Dodimead et a l (1963) have divided both the upper and lower zones i n t o a number of 'domains' which are bodies of water with consistent properties, structure and hehaviour. The 'domains' of the upper zone are probably equivalent to Bary's (1963a) water bodies; i n the lower zone they are subdivisions of the P a c i f i c Subarctic Water Mass. Both the p o s i t i o n of s t a t i o n Pac-1 and the temperature and s a l i n i t y values observed there i n February 1969 and June 1969, (shown i n F i g . 4 and T-S diagram^ Helland-Hansen, 1916), are consistent with the water at Pac-1 belonging to the deep Central Subarctic Domain wit h i n the Subarctic Water Mass (Dodimead ^ t a l . , 1963). These T-S diagrams (Fig. 4) demonstrate the c h a r a c t e r i s t i c oceanographic features of the area; the p r i n c i p a l difference between February and June i s the e f f e c t of surface heating i n June. -21-Figure 4. (facing) Temperature and salinity values observed at station Pac.-l in February and June 1969, plotted as temperature-salinity diagrams. -18-Figure 3. (facing) Chart of B r i t i s h Columbia coastal waters showing positions of stations from which euphausiids were c o l l e c t e d . SALINITY % -22-Juan de Fuca Strait (Station J..F.-9, Fig. 3) Station J.F.-9 located just outside the mouth of Juan de Fuca Strait (Fig. 3) in the Juan de Fuca Canyon. In this area during the summer months, the predominantly northwesterly winds produce a net offshore transport (divergence) in the upper layers which results in upwelling of deeper waters (Tully, 1942). In winter the prevailing winds are from the southeast. These produce a net onshore transport (convergence) (Lane, 1962, 1963). The T-S diagrams(Fig. 5) for the data collected at J.F.-9 in November 1968 and July 1969, i l l u s t r a t e the salient structure of the Juan de Fuca Strait system. There is a shallow mixed layer of outflowing water (A), a mid-depth halocline (B), and an inflowing deep layer of oceanic water (C) . A major change between November 1968 and July 1969 is the greater depth range occupied by the lower zone ('C, Fig. 5) in July (100 m to the bottom of 290 m) over that in November (250 m to the bottom). This deep water has temperature-salinity characteristics similar to water from the upper part of the deep Central Subarctic Domain (Dodimead et_ _al, 1963) and presumably enters the Strait. Saanich Inlet (Station SAA.-4, Fig. 3). Saanich Inlet is a fjord situated on the southeastern coast of Vancouver Island. It consists of a basin 24 km long, having a maximum depth of 234 m behind a s i l l 73 m in depth at the mouth. Because of the small amount of runoff entering the fjord at the head, the estuarine circulation is weak (Herlinveaux, -23-Figure 5. (facing) Temperature and salinity values observed at station J.F.-9 i n November 1968 and July 1969, plotted as temperature-salinity diagrams. 1 -24-1962) and at depths greater than the s i l l depth the water tends to become stagnant and i t s oxygen content to be reduced to low levels. Periodically intrusions of outside water enter the inlet. These occur when the density of the water above s i l l depth outside the inlet exceeds the density of the water below s i l l depth inside the i n l e t , thus encouraging a flow into the deeper waters; at such times the oxygen content of these deeper waters is increased. Physico-chemical data collected during the present study are shown in Fig. 6. Effects of runoff and insolation are plainly evident in the data for June 1969 in the reduced salini t y and high temperature of the upper waters. Comparison of the T-S curves below 90 m indicates no large change in T-S relations such as would have ensued on an intrusion; inspection of the distribution of dissolved oxygen (not shown) in the inlet substantiates this. The Strait of Georgia (Station G.S.-l, Fig. _3) • Waldichuck (1957) states that the flushing of the deep water in the Strait of Georgia depends on events occurring at the s i l l s , or ti d a l passes; the characteristics of the mixed water formed there depend, in part, on the amount of oceanic water present i n the inner portion of the Strait of Juan de Fuca and in part on the amount of sea-water modified by runoff present in the upper zone of the Strait of Georgia. If the seasonal upwelling off the mouth of Juan de Fuca Strait leads to an increased amount of oceanic water entering the Strait in summer, -25-Figure 6. (facing) Temperature and s a l i n i t y values observed at s t a t i o n SAA-4 i n February and June 1969, p l o t t e d as temperature-salinity diagrams. J-7 1 L I I I I 1 1 1 1 1— 2 7 . 0 2 8 . 0 2 9 . 0 3 0 . 0 3 1 . 0 S A L I N I T Y % 0 -26-a greater amount of oceanic water could pass into the inner Strait of Juan de Fuca and thence after mixing into the deep zone of the Strait of Georgia. Thus, a combination of seasonal upwelling and the seasonal cycle observed in runoff (Waldichuck, 1957) could give rise to the seasonal cycles in the temperature and salinity of Strait of Georgia deep water observed in the course of this study (Figs. 7, 8). The deep water of the Strait of Georgia is flushed when i t is displaced by water of a greater density (Waldichuck, 1957). Waldichuck suggests also that between flushings fresh water is mixed downward as a result of turbulence produced by the relatively strong bottom currents observed by Pickard (1956). Changes ensuing on this process would be much slower than by displacement. The data presented in Figs 7 and 8 shows in the upper zone a large seasonal variation i n temperature and a lesser one in salinity. In the lower zone the seasonal cycle is evident as a sharp increase in salinity (Fig. 8) from September 1968 to November 1968, followed by a slower decline in salinity u n t i l August 1969 when another increase occurs. A similar pattern is visible in the temperature distribution (Fig. 7). Thus, in the data from the Strait of Georgia displacement of the resident bottom waters appears to be indicated by the sharp increase in the temperature and salinity of the deep water in late summer. The slower turbulent mixing could lead to the slow erosion of the temperature and salinity maxima observed beginning in November-December 1968 and continuing unt i l July-August 1969. -27-Figure 7. (facing) Temperature plotted against depth at station G.S.-l from August 1968 to September 1969. Figure 8. (facing) Salinity plotted against depth at station G.S.-l from August 1968 to September 1969. -28-Therefore, i t is perhaps useful to think of there being two seasons in the deep zone of the Strait of Georgia. The 'low salinity' season occurs during August 1968 and from April to July 1969. During these periods the deep water of the Strait of Georgia is diluted by Fraser River runoff (of the previous year) being mixed downward. In the process the salinity maximum observed i n early winter is eroded. 'Low salinity' conditions - obtain when the salinity of the deep water in the Strait of Georgia is less than 31 o/oo and the temperature less than 9 °C. The second or 'high salinity' season (October 1968 -March 1969) is the period when the influence on the deep waters is primarily from upwelled oceanic water mixed with Strait of Georgia upper water. This would be the period following the displacement of the resident deep water in late summer. 'High salinity' conditions obtain when the deep water in the Strait of Georgia has a salinity greater than 31 o/oo and a temperature greater than 9 °C. Indian Arm (Station I.A.-9 , Fig. _3) . Indian Arm is more or less typical of B.C. fjords although i t is narrower and shorter than the average and has a shallower (26 m) s i l l depth (Gilmartin, 1962). The major portion of the inlet is a basin with a mean depth of about 200 m. The station, I.A.-9, was located approximately in the centre of the deep basin (Fig. 3). Gilmartin (1962) has described the oceanography of Indian Arm. There is a two-layered estuarine system in which st a b i l i t y is maintained primarily by the salinity structure. Indian Arm receives a large amount of runoff; therefore the -29-Figure 9. (facing) Temperature plotted against depth at station I.A.-9 from August 1968 to September 1969. Figure 10. (facing) Salinity plotted against depth at station I.A.-9 from August 1968 to September 1969. -30-temperature and s a l i n i t y values i n the upper zone (0-75 m) vary widely throughout the year (Figs 9 and 10) although i s o l i n e s depicting the d e t a i l s of these changes are not shown i n the figures. The temperature' and s a l i n i t y values c h a r a c t e r i s t i c of the deep zone (100-200 m) show a slow increase i n temperature' and a slow decrease i n s a l i n i t y as fresh water and heat slowly mix down-ward (Gilmartin, 1962). These two trends are v i s i b l e i n Figs. 9 and 10 as a gradual deepening of isohalines and isotherms from August to December 1968 and from March to September 1969. P e r i o d i c a l l y these patterns of the d i s t r i b u t i o n of temperature and s a l i n i t y are disturbed by i n t r u s i o n s . Between intru s i o n s the waters of the deep zone are r e l a t i v e l y s t a b l e except for the above-mentioned trends toward warming and d i l u t i o n . An i n t r u s i o n took place during the period January-February 1969. Other, s i m i l a r intrusions occurred i n 1956-57, 1959, and 1960 (Gilmartin, 1962; Regan, 1968). Intrusions i n t o Indian Arm always have occurred i n early spring when there i s low s t a b i l i t y of the water column broughtftabout by winter cooling and low runoff (Gilmartin, 1962). I f the a i r temperature i s less than 0 °C f o r any length of time streams are frozen and thereby runoff i s greatly reduced and the water column may become almost isopycnal. At such times v e r t i c a l mixing i s f a c i l i t a t e d and a r e l a t i v e l y rapid decrease i n the o v e r a l l density of the water resident i n the i n l e t may ensue. I f , because of v e r t i c a l mixing, the density of the deep water i n the i n l e t f a l l s below that of water present at s i l l depth outside the i n l e t an i n t r u s i o n may occur. -31-Sub-freezing air temperatures were common during large parts of December 1968 and January 1969. During the same period strong (up to 60 kt) down-inlet winds occurred. Vertical mixing appears to have taken place, with the result, that in January 1969 the water column was practically isothermal and isohaline (Figs 9 and 10) and therefore nearly isopycnal. In February-March 1969 an intrusion of water from outside the inlet took place, displacing the resident water. The intruding water had a salinity of approximately 27.2 o/oo and a temperature of 6.6 °C. The ultimate source of the intruding water is from the upper layers of the Strait of Georgia. As a result of a lack of oceanographic data from outside the in l e t , i t is impossible to suggest a more specific origin. -32-IV. THE EFFECTS OF STRESS FROM CHANGES IN TEMPERATURE AND SALINITY ON SPECIMENS FROM OCEANIC, OCEANIC-COASTAL, AND COASTAL WATERS. Introduction Euphausia pacifica is distributed widely in waters which vary considerably in their temperatures and sal i n i t i e s (Regan, 1968; Mauchline and Fisher, 1969). This distribution, taken in conjunction with the results of behavioural and survival experiments carried out by Regan (1968), suggests that _E. pacifica is tolerant of large changes in the temperature and salinity of its environment. The same wide distribution pattern could, however, arise from the existence of a number of morphologically similar populations of E_. pacifica which differed in their tolerance to changes in temperature and salinity. These different populations could be considered as physiological races of E_. pacifica, such as are frequently found in other species distributed over a wide range of environmental conditions (Prosser, 1955; Vernberg, 1962). This wide distribution of E_. pacifica, the possibility of physiological races, as well as i t s tolerance toward laboratory handling (see above) afford an opportunity to examine interactions between the organism and its environment. Data are available on the reactions of several species of euphausiid to temperature changes (McWhinnie and Marciniak, 1964, Teal and Carey, 1967). Also available are similar data for populations of E_. pacifica from Saanich Inlet (Paranjape, -33-1967) and from the Pacific Ocean off Newport, Oregon (Small and Hebard, 1967). However, no data are available on the effects of sali n i t y changes on the metabolism of any euphausiid, other than Regan's (1968) data on survival. Nor are theare data on the effect of simultaneous variation in temperature and salinity on either euphausiids or other zooplanktonic organisms, but i they have been presented for adults and larvae of several i species of benthic animals (Kinne, 1964, Brenko and Calabrese, 1969, Manzi, 19 70). The object of this part of the research program was to investigate the effects of stress from sources that could be measured and manipulated, temperature and s a l i n i t y , on three groups of specimens from three different areas in which the temperatures and s a l i n i t i e s differed. In addition to observing the effect of stress from these sources, i t was desirable to determine whether there were any differences among the three groups in the point at which stress from either, or both, sources became apparent. To this end, respiratory rates of individuals from each of the three locations were determined under a standard set of pairs of values for temperature and salinity. These experiments provided information relating changes i n the animals' respiration rates to the changes in stress resulting from variations in temperature and sal i n i t y . The results also serve to define roughly the non&lethal limits of temperature and salinity that specimens from each of the locations could withstand. In order to account for possible differences -34-resulting from changes in seasonal states of acclimation to temperature, experiments were carried out on specimens captured in both summer and winter. The results of this part of the study indicate that with E_. pacifica the action of stresses ensuing on changes in temperature and salinity may be additive, _i._e- the total effect from stress simultaneously applied by changes in both temperature and salinity may be greater than for either property separately. This is a reflection of the fact that the animals' reactions are to the sum of a l l stresses imposed on i t by the environment. The results further show that animals from the coastal population of E. pacifica possess a greater capacity to resist stress from temperature and salinity -A changes than animals from cthecuoteanlcapopulation. Materials and Methods. Because of limitations in ship time and the possible problem of obtaining sufficient experimental animals, and efficient experimental design was required. A three-factor factorial experiment with five replicates in each c e l l was chosen as the basic design. The three factors were: I. Seasons - 2 levels (winter and summer); II. Temperature - 3 levels (5°, 10°, 15° C); III. Salinity - 4 levels (full-strength sea water, 27, 24, 21 o/oo). The data from these experiments were subjected to analysis of variance in order to test the significance of the main effects of each of the factors as well as the significance of the interactions between the effects of the factors. The factorial design sacrifices some detail in order to obtain an over-a-111 indication of the animals' reactions to -35-variations of temperature and salinity. Therefore, whenever time and material allowed, this basic design was augmented by adding more levels of salinity. Because the range 5° to 15° C approximates to the seasonal variation i n temperature that the animals might encounter, i t was thought that the three levels of temperature would give an adequate picture of the temperature responses of animals from the three locations. The specimens and water used in the experiments were obtained by the procedures described i n Part II at stations Pac. 1, J.F. 9 and SAA 4. Results. A graphic presentation of the results of the experiment performed with animals from Saanich Inlet is shown in Fig. 11a. The data are plotted as respiration-salinity (R-S) curves, data from June 1969 (summer animals) and February 1969 (winter animals) being plotted separately. It is important to note that there is a general, but small decrease in respiration with decreased salinity. It should also be observed that animals from Saanich Inlet could withstand a salinity of 21 o/oo at 5°, 10° and 15° C in summer and at 5° and 10°Gi±nwinter with no large reduction i n respiration rate. Fig. l i b shows R-S curves obtained using animals captured in summer and winter at the mouth of Juan de Fuca Strait. It appears from these that there is a slight immediate reduction in respiratory rate with the i n i t i a l dilution from 34 o/oo and then no further reduction in respiratory rate un t i l some c r i t i c a l low salinity is reached at which respiration is -36-Figure 11. (a-e)_ (facing) Respiration-salinity curves for Euphausia pacifica under various combinations of temperature and salinity. a. Specimens from Saanich Inlet, data collected in February and June 1969. b. Specimens from Juan de Fuca Strait, data collected in November 1968 and July 1969. c. Specimens from the Pacific Ocean, data collected in February and June 1969. SALINITY % SALINITY % -37-rapidly reduced. Because the R-S curves are essentially ' f l a t ' between 34 and 24 o/oo i t appears that in this range the animals' respiration rate is independent of salinity changes. Another important result is that the lowest salinity that animals from the mouth of Juan de Fuca Strait could tolerate under a l l temperature conditions was 24 o/oo. A salinity of 21 o/oo proved fatal to a l l experimental animals acclimated at 15° C. Results.obtained using animals from the open ocean west of the Queen Charlotte Islands appear in Fig. 11c. It should be noted that, for these animals too, respiration was independent of changes in salinity between 34 and 24 o/oo. There are indications (reduction in respiratory rate) that for the winter animals 24 o/oo might be too dilute at 15°C and perhaps also at 10°. None of the animals could survive a salinity as low as 21 o/oo regardless of the temperature of acclimation, or the season. Results of analysis of variance performed on the data obtained with summer and winter animals from Saanich Inlet are shown in Table 2. Significant main effects are obtained for temperature, sali n i t y , and seasons; of the possible interactions only the temperature x seasons interaction is significant. These results indicate that the respiration rate of Saanich animals is influenced not only by the temperature and salinity of the treatment, but also by seasonal differences in the animals. The temperature x seasons interaction is a reflection of the differing responses to changed temperature seen in February -38-TABLE 2 Results of analysis of variance: Reactions of Euphausia pacifica from Saanich Inlet to changes in temperature and s a l i n i t y , data from February 1969 and June 1969 combined. Source of Variation Sum of Squares Mean Square df F-ratio Temperature 41.438 20.719 2 70.22** Salinity 7.5904 3.7952 2 12.86** Seasons 6.1429 6.1429 1 20.82** Temperature x salinity interaction 1.3094 0.32734 4 1.11 Temperature x seasons interaction 17.222 8.6112 2 29.18** Salinity x seasons interaction 0.068188 0.034094 2 0.12 Temperature x salinity x seasons interaction 2.22894 0.57234 4 1.94 Error 21.24525 0.29507 72 Total 98.398 89 Note: The probability of obtaining an F -ratio larger than the one observed i s indicated by asterisks. No asterisk indicates that the probability i s greater than 0.05; one asterisk indicates that the probability of observing a larger F-ratio is less than 0.05; two asterisks indicates that the probability i s less than 0.01. -39-TABLE 3 Results of analysis of variance: Reactions of Euphausia pacifica from Juan de Fuca Strait to changes in temperature and sali n i t y , data from November 1968 and July 1969 combined. Source of Variation Sum of Squares Mean Square df F-ratio Temperature 4.3301 2.1650 2 24.44** Salinity 17.413 4.3531 4 49.15** Seasons 1.8062 1.8062 1 20.39** Temperature x salinity interaction 4.3672 0.54590 8 6.16** Temperature x seasons interaction 0.065029 0.032514 2 0.37 Salinity x seasons interaction 1.8146 0.45365 4 5.12** Temperature x salinity x seasons interaction 1.0908 0.13635 8 1.54 Error 10.62939 0.08857 120 Total 41.516 149 -40-TABLE 4 Results of analysis of variance: Reactioncof Euphausia  p a c i f i c a from the P a c i f i c Ocean to changes i n temperature and s a l i n i t y , data from February 1969 and June 1969 combined. Source of V a r i a t i o n Temperature S a l i n i t y Seasons Temperature x s a l i n i t y i n t e r a c t i o n Temperature x seasons i n t e r a c t i o n S a l i n i t y x seasons i n t e r a c t i o n Temperature x s a l i n i t y x seasons i n t e r a c t i o n Error T o t a l Sum of Squares 3.3785 55.359 0.3224 1.8723 0.19685 1.584 0.93924 19.7529 83.370 Mean Square 1.6892 18.453 0.3224 0.31205 0.098427 0.51630 0.15654 0.20575 df 2 3 1 6 F- r a t i o 8.92** 101.48** 1.57 1.57 0.48 2.51 0.76 96 119 -41-and June 1969 (see Fig. 11a). At the same time, the non-significant interaction of temperature and salinity suggests that the effects of these factors operated independently., Table 3 shows the results of analysis of variance carried out on the data obtained using animals from the mouth of Juan de Fuca Strait. Once again, significant main effects are obtained for temperature, salinity, and seasons. The significance of the temperature x salinity interaction indicates that the effects of temperature and salinity are no longer independent. Also the salinity x seasons interaction suggests that responses to salinity per se changed significantly between November 1968 and July 1969. Results of an analysis of variance performed on the data obtained using Pacific Ocean animals (Table 4) indicate that only the main effects of temperature and salinity are significant. Neither the main effect of seasons, nor any of the interactions are significant. Thus i t appears that the animals' overallI respiratory rate did not change from February 1969 to June 1969 and that the effects of temperature and salinity were independent. Discussion. The primary object of these three series of experiments was to investigate the effects of stress, ensuing on changes in temperature and/or sa l i n i t y , on the respiration of euphausiids from several locations. The effects of stress arising from changes i n a single factor are best seen in the results obtained with animals from the mouth of Juan de Fuca Strait (Fig. l i b ) . -42-Here, respiration tends to be only slightly affected by changes in the salinity of the external medium unti l some c r i t i c a l , j L . j i . stressing, lower value of salinity is reached, whereupon the animals' respiration rate is sharply reduced. Similar responses to changes in salinity have been reported for Calanus plumchrus from B.C. waters by Topping (1966) and for Calanus finnmarchicus from the Woods Hole region by Anraku (1964). If the stress is prolonged or increased, death ensues. The cause of the apparent upward shift of the lower c r i t i c a l salinity between November 1968 and July 1969 (Fig. lib) is unknown; i t appears in the s t a t i s t i c a l analysis of the results as a significant salinity x season interaction (Table 3), which indicates that the response to lowered salinity changed between November and July. The effects of reduced salinity on the respiration of specimens caught in the Pacific Ocean (Fig. 11c) show a similar pattern of response. That i s , the effect of stress from reduced salin i t y is to reduce the respiration rate of E. pacifica. Because no sharp reduction in respiratory rate was observed in the results obtained with specimens from Saanich Inlet, i t appears that the lower c r i t i c a l value of salinity for these animals is less than 21 o/oo. This agrees with the results obtained by Regan (1968). He found that, for animals from Indian Arm, both survival and vertical migration were affected by reduced salinity; the pattern of response was similar to the effect of reduced salinity on the respiration of animals from Juan de Fuca Strait. In brief, Regan showed -43-that, there was a lower c r i t i c a l salinity below which both survival and migration were severely affected. Regan's (1968) results show that the lower c r i t i c a l salinity for migration and survival li e s between 15 and 20 o/oo. It is possible then that animals from Saanich Inlet and Indian Arm may have similar tolerances to reduced salinity. The patterns .of response to reduced salinity shown by E_. pacifica suggest that, some sort of internal mechanism exists to compensate for changes in external sal i n i t y , but that this mechanism breaks down at the lower c r i t i c a l s alinity. The very slight slope of the R-S curves seems to indicate that this mechanism requires a minimal expenditure of energy. If so the mechanism is presumably a passive one. Possibly i t is similar to theoone reported by Shaw (1958) for muscle cells of Carcinus maenas. Shaw found that the osmotic activity of the muscle cells was adjusted by varying the internal concentration of amino acids and short-chain peptides. Winter oceanic animals did not show as large an increase in respiratory rate in full-strength sea water for a rise in temperature from 10° to 15° C as did the summer animals (Fig. 11c). This, combined with a general opaque appearance of the winter animals after the period of acclimation at 15° C indicated that they had been stressed. Otherwise, none of the specimens appeared to be stressed.byOiSerGiwhile in full-strength sea water. -44-Only the animals from Saanich Inlet appeared to change their respiratory response to increased temperature from February (winter) to June (summer). This change is shown by the much larger increase in respiration between 10° and 15° C in winter opposed to that i n summer. The significant temperature x seasons interaction in the s t a t i s t i c a l analysis of the data (Table 2) points up the fact that the animals' responses to changed temperature are not the same in summer and winter. Paranjape (1967) reports on the relation between respiration and temperature for summer E_. pacifica from Saanich Inlet. In most instances the values for respiration reported by Paranjape are smaller than those obtained in the present study by a factor of two or more. During the course of this study tests were made on the effect of using as the experimental medium a r t i f i c i a l l y oxygenated water from the anoxic, deep water in Saanich Inlet. The results of this experiment are not reported elsewhere in this presentation, but they indicated that the re-oxygenated deep water could depress the respiratory rate of E. pacifica by a factor of two or more, a result closely resembling Paranjape's. Paranjape '(1967) does not say from what depth he collected the water used as an experimental medium. It appears, however, as though the discrepancy between Paranjape's results and those of the present study could be explained i f he had inadvertently collected water which had originated in the lower zone of Saanich Inlet. -45-Analysis of the results obtained with specimens collected at the mouth of Juan de Fuca Strait (Table 3) indicates that the overall! respiratory rate increased between November 1968 and July 1969 (significant main effect for seasons). No explanation for this increase is offered. At the same time, s t a t i s t i c a l analysis of results obtained using animals from the Pacific Ocean (Table 4) indicated that no seasonal changes occurred in their respiratory rate. Small and Hebard (1967) found no seasonal change in the respiratory rate of E_. pacifica from Oregon; the respiratory rates obtained in the present study for oceanic animals are comparable with those reported by Small and Hebard. They are also comparable with those reported for E_. pacifica from the San Diego area by Lasker (1966). The R-S curves for animals from Juan de Fuca Strait (Fig. lib) indicate that as the temperature increases the lower c r i t i c a l salinity increases. For winter animals the lower c r i t i c a l salinity lies below 21 o/oo for 5° and 10° C, but at 15° C i t li e s between 24 o/oo and 21 o/oo. In summer, the lower c r i t i c a l salinity lies between 24 o/oo and 21 o/oo at a l l three temperatures, but the degree to which respiration is reduced increases as the temperature increases. Both of these sets of results appear to indicate that stresses resulting from changes in temperature and salinity are not independent i n their effect on E_. pacifica. The significant temperature x salinity interaction observed in the s t a t i s t i c a l analysis of the above data (Table 3) is another manifestation of the interdependence of the effects of temperature and salin i t y . -46-A similar interaction between the effects of temperature and salinity is visible in the R-S curves for Pacific Ocean winter animals (Fig. 11c); the summer animals give no indication of any interactions. The results of s t a t i s t i c a l analysis (Table 4) give no indication of a temperature x salinity interaction, presumably because only one of the six R-S curves considered in the analysis demonstrates an interaction. Data obtained for Saanich Inlet animals (Fig. 11a) indicate that the lower c r i t i c a l s a l i n i t y is less than 21 o/oo at a l l three temperatures. Therefore no interaction between the effects of temperature and salinity could be demonstrated. The results of analysis of variance (Table 2) confirm the independence of the effects of temperature and salinity (temperature x salinity interaction is non-significant). It appears, however, from the results of experiments using Juan de Fuca Strait animals (Fig. lib) that stresses resulting from variations in temperature and salinity interact in their effects on IS. pacifica. Thus , the combination of an otherwise tolerable tempera tare; (15° C) with an equally tolerable salinity (21 o/oo) may become intolerable. The interaction appears to come into play when the limits of tolerance of temperature and salinity (extreme values) are approached. In the data from the oceanic animals (Fig. 11c) there is only a slight indication of a temperature x salinity interaction (additive effect of stress from changes i n temperature and salinity) at 24 o/oo; a l l animals subjected to 21 o/oo died. These results suggest that the range of salinity over which -47-interaction occurs may be quite narrow. Regan (1968) using E_. pacifica from Indian Arm showed that there was an interaction between the effects of temperature and salinityoon both vertical migration and survival. Like-wise McLeese (1956) who observed the effects of temperature, salinity and dissolved oxygen content on the survival of Homarus  americanus found that these three factors interacted strongly as lethal values were approached. Brenko and Calabrese (1969) and Manzi (1970) studied the effects of various temperature-salinity combinations on adult and larval molluscs and found that stress from changes in temperature and salinity was additive at extreme values. Costlow et al (1960) also obtained a strong interaction between the effects of temperature and salini t y oil the survival of crab larvae. Thus i t appears that theiinteraction of the effects of temperature and salin i t y observed i n the course of this study is a manifestation of a general property of organisms, jL.ja. that they react to the sum of a l l stresses imposed on them by the environment. In general the experimentally obtained respiratory rates (Figs. 11a, b, c) suggest that the animals from different locations have differing tolerances to changes in the temperature and salinity of their environment. That i s , animals from the Pacific Ocean were more stressed by 'changes in temperature and salini t y than the animals from the mouth of Juan de Fuca Strait, which, in turn, were more stressed by the same changes than animals from Saanich Inlet. -48-It is possible that the intermediate tolerances of the specimens from Juan de Fuca Strait might be a result of employing a mixture of oceanic and coastal animals as experimental subjects. If this were so i t could be expected that size of the residual mean square in the analysis of the data from Juan de Fuca Strait would be increased over that of the analyses for the data from- the oceanic animals or the Saanich Inlet animals as a result of the inhomogeneous reactions of the experimental material. A comparison of error mean squares (Tables 2, 3, 4) shows that there is no indication that the animals from Juan de Fuca Strait were less homogeneous in their reactions to experimental conditions than those from the Pacific Ocean or Saanich Inlet. Therefore, they may be presumed to be from a homogeneous population of _E. pacifica. In sum, therefore, these three homogeneous groups of _E. pacifica show large differences in their resistance to experimental changes i n temperature and salinity. These differences in reactions to temperature and salinity may represent a progressive extention of the absolute limits of tolerance to changes i n temperature and salinity as a result of genetic adaptation to changed environmental conditions. On the other hand, the observed extention of the tolerable ranges of temperature and salini t y may reflect acclimitization of specimens to the warmer, more dilute, coastal environment. The experiments required to determine which of the two alternatives referred to above is correct were beyond the scope of this investigation. If, however, the differences between these three groups of E. pacifica can be shown to have a basis i n genetic change, then the groups could justifiably be termed physiological races. -49-V. THE EFFECT OF SEVERAL NATURAL SEA WATERS ON TOLERANCE TO TEMPERATURE AND SALINITY VARIATIONS. Introduction. Wilson and Armstrong (1952, 1954, 1958, 1961) have shown that some natural sea waters are more favorable for the development of echinoderm larvae than others. Regan (1968) found also that some sea waters from the local, British Columbia, area were more conducive to the survival of E_. pacifica than others. These observations, and others, lead to the hypothesis that some sea waters can exert a deleterious effect, or stress, on some species while others might exert a neutral, or even a beneficial effect on the same species. The above hypothesis suggests, moreover, that zooplanktonic organisms can be limited in their distribution to water bodies which have a neutral or beneficial effect on them as has been proposed by Bary (1963d). This concept of 'water body control! of a species' distribution is basic to the concept-of indicator species. The object of this portion of the experimental program was to see whether any differences in 'other' water properties could affect, adversely or otherwise, the metabolism of adult E_. pacifica, i.e. to investigate the effects on the animals of stress from undetermined and therefore non-measurfah'lee properties of sea water. The hypothesis was that i f there werea-anyvldeleteriidus effects on the animals' metabolism as a result of differences in 'other' properties, the interaction of stresses resulting from changes in temperature and salinity would be affected. The -50-interdependence of the effects of stresses resulting from changes in temperature, salinity and oxygen concentration has been demonstrated by McLeese (1956) using Homarus americanus, and by Haefner (1970) using Crangon septemspinosa. A similar interdependence of the effects, but of temperature, salinity and toxic substances, has been demonstrated by Alderdice (1963) for young salmon; Wohlschlag and Cameron (1967) demonstrated a deleterious effect on the respiration-temperature relations of pinfish resulting from the presence of low concentrations of petrochemical wastes. Basically the experimental design was to subject the animals to sublethal combinations of temperature and salinity, in media made from sea waters of different origins. It was expected that i f the animals were stressed by differences i n 'other' properties between sea waters, there would be an interaction between their responses to extremes of temperature and salinity and the source of the sea water used to make up the media. The results of these experiments indicate that the source of the experimental medium can have a significant effect on the amount of stress the experimental animals can support. The results also indicate that, when tested i n a standard set of conditions, the animals' respiratory response to a series of sea waters may provide an index of the comparative amount of stress an animal liv i n g i n each of them can support. -51-Materials and Methods. The experimental procedure was a standard three-factor factorial experiment with five replicates i n each c e l l . One of the advantages of this design is that the results lend them-selves to analysis of variance. In a l l , three experiments were performed. The f i r s t of the three factors considered was temperature of which there were two or three levels depending on the particular experiment. A l l experiments included 10° which was regarded as non-stressful and 15° C which was considered to be moderately stressful. The August 1969 experiment included measurements made at 20° C which was highly stressful and appeared to be near the animals' upper lethal limit. Salinity was the second factor. Two or three levels were employed. Each of the experiments included measurements made in full-strength sea water and in sea water diluted to 21 o/oo. In July 1969 measurements were obtained at 18 o/oo, but 18 o/oo proved to be below the level of tolerance for most of the specimens. The effects of changes i n 'other' water properties were included at four levels i n a l l experiments, and at an additional level in July 1969. The four standard levels corresponded to water collected at two depths at each of two locations, one in the Strait of Georgia and the other i n Indian Arm (Fig. 3). The shallower depth was the depth having the greatest concentration of the euphausiid population, as determined by st r a t i f i e d plankton tows, and the other was a depth close to the bottom at each location. -52-A series of three experiments was carried out in May, July, and August 1969. None of the experiments was precisely the same because of progressive changes i n the detailed design, but those of July and August included the same set of treatments as used in the May experiment. In May the experimental animals were collected at the surface at night at station G.S.-l (see Part II for the collecting and handling techniques). Two levels of temperature were used, 10° and 15° C. Particulars of the experimental waters used are shown in Table 5. Undiluted (full-strength) sea water and water diluted to 21 o/oo with Barnstead-distilled water were the two levels of salinity. The experimental animals were acclimated for 12 hours to each treatment and then their respiration was measured (see Part II). Results of the May experiment suggested that perhaps the experimental animals had not been sufficiently stressed to show adequately the effects of differences in water properties. Therefore, the July experiment included a lower level of sali n i t y , 18 o/oo, to provide greater stress. The same two temperatures used in May, 10° and 15° C, were employed. From the results of the July experiment i t appeared that 18 o/oo was below the lethal limit for most animals. Thus, i t appeared that the lower c r i t i c a l salinity was quite sharply defined and i t was decided to increase the stress from temperature. In the August experiment in addition to 10° and 15° C a third temperature, 20° C was included. Only two s a l i n i t i e s , f u l l -strength sea water and 21 o/oo, were used. -53-TABLE 5 • The depth of collection and the salinity of sea-water samples from Indian Arm and the Strait of Georgia used in the experiments carried out in May, July and August 1969. U i Geographic Area \~ Indian Arm Georgia Strait upper water lower water upper water lower water depth So/oo depth So/oo depth Sjo/oo depth So/oo May 75 27.04 200 27.18 100 29.91 350 30.80 July 75 26.87 200 27.14 75 29.73 350 30.96 Augus t 75 26.78 200 27.12 75 29.88 350 30.96 The water from Juan de Fuca Strait which was used in July was collected from a depth of 250 m and had a salinity of 33.80 o/oo. -54-Statis t i c a l Analysis. Ordinarily seven animals were acclimated in each bottle. This allowed for accidental loss during handling. In non-stressful treatments mortality during acclimation was rare. During acclimation to more stressful treatments mortality became more frequent. The purpose of the experiments was to determine the animals' reactions to the experimental conditions. Therefore, i t was f e l t that some account should be taken of the mortality, presumed to have resulted from stress imposed by the treatment; otherwise information would be lost. Because the respiratory rates of stressed E_. pacifica generally decreased with increased stress in experiments where no mortality occurred,it was f e l t that entry of zero values for the respiration of those animals which died before measurement was not unreasonable/ At the same time i t should be kept in mind that there is a qualitative difference betwen a live and a dead animal. It is possible that this qualitative difference might introduce a non-orthogonal component into the analysis. However, because highly stressed, but alive, specimens yield low respiratory rates, the effect of using zero values for dead animals is not considered to be serious. The technique that evolved was that when five or more of the seven original animals survived to have their respiration rates determined, five animals were tested and their respiration rates entered into the analysis. When less than five animals survived the respiratory rates of the survivors were included, along with zero values for the dead animals. The s t a t i s t i c a l analysis of the results was carried out -55-using multifactor analysis of variance. Replication was treated as a factor to simplify the preparation of the data for analysis. A l l possible interaction terms were computed. The n u l l hypothesis was that none of the factors had any effect on the respiration rates of the experimental animals. In the analysis of the results of the July experiment a significant main effect for replication (Table U) was obtained as well as a significant salinity x replication interaction. In this instance replication is purely nominal and refers to the order in which the data were punched on computer cards. This result obtains because most bf the animals in the treatments involving I 8 0 / 0 0 s a l i n i t y , as well as many in 21 0 / 0 0 , died. Replication was purely nominal, and therefore when the data were punched on the cards no effort was made to randomize the order of the zero entries corresponding to the respiration rates of the dead animals. It was fe l t that this non-random distribution of zero values would not affect the accuracy of the analysis. For the July analysis the non-significant interaction sums of squares and degrees of freedom for replication effects have been pooled with the error sum of squares. In the analysis for May and August no significant effects were observed for replication, so a l l sums of squares and degrees of freedom for replication, have been pooled with the error term. Results. Assuming there was no interaction between the source of the water used to make up the experimental media ('water properties') and the effects of temperature and sali n i t y , the expected result of -56-the experiments, i f there were significant effects of water properties, would be eight parallel R-S curves (four waters at two temperatures). If there were no effect of water properties, two parallel R-S curves would be expected. An interaction between factors would cause the R-S curves to be non-parallel. The results of the May experiment (Fig. 12a) are represented by eight non-parallel R-S curves, thus indicating that not only is there an effect of 'water properties' on respiration rate per se, but that there is also an interaction of these effects with the effects of temperature and salinity. The s t a t i s t i c a l analysis of the results of the May experiment (Table 6) shows that, while the main effects of both temperature and water properties are significant, the main effect of salinity is not significant. This would appear to indicate that salinity per se had no effect on the euphausiids' respiration. However, there is a large water properties x salinity interaction which indicates that the effect of variations in salinity depends upon the type of water the animal is in. The temperature x salinity interaction is non-significant which suggests that the main effects of temperature and salinity are independent and that the higher temperature and lowered salinity used in this experiment were not sufficiently stressful, even in combination, to affect.the animals. The temperature x water properties interaction is significant which suggests that the effect of temperature changes with the source of water used as an experimental medium. There i s , however, l i t t l e indication that any of the waters has particularly deleterious or beneficial effects on the animals. -57-Figure 12. (a-c) (facing) Respiration-salinity curves for Euphausia pacifica from the Strait of Georgia while in media made from 4 sea waters collected at differing depths and locations. a. Data from the experiment performed in May 1969. b. Data from the experiment performed in July 1969. c. Data from the experiment performed in August 1969. -58-TABLE 6 Results of analysis of variance: Reaction of Euphausia  pacifica from the Strait of Georgia to changes in temperature, salinity and 'other' water properties; data from the experiment performed in May 1969. Source of Variation Sum of Squares Mean Square df F-ratio Temperature 5.6743 5.6743 1 8.809** Salinity 1.3225 1.3225 1 2.05 Water properties 6.3539 2.1180 3 3.288* Temperature x salinity interaction 0.02178 0.02178 1 0.0 34': Temperature x water property interaction 5.7477 1.9159 3 2.974* Salinity x water property interaction 9.9497 3.3166 3 5.149* Error 43.157 0.6441 67 Total 72.227 79 -:59-The graphic representation of the results of the July experiment (Fig. 12b) shows two 'families' of R-S curves, designated 'a' and 'b'. R-S curves i n the 'a' group demonstrate less reduction in respiration between full-strength sea water and 21 o/oo than those in the 'b' group. Presumably these different responses are mediated by differences i n water properties. The 'a' group of R-S curves includes measurements made at 10° and 15° C i n both shallow and deep waters from Indian Arm and the 10° C measurements i n Strait of Georgia upper water. The 'b' group of curves includes both the 10° and 15° C measurements in Strait of Georgia lower water and the 15° C measurements in Strait of Georgia upper water. It should be noted that respiratory rates determined at 10° C in Indian Arm waters are higher than those i n Georgia Strait waters. The s t a t i s t i c a l analysis of the results of the July experiment (Table 7) shows that the main effect of temperature is non-significant; the main effects of salinity and water properties are significant. There is a significant temperature i x salin i t y interaction suggesting that the effects of temperature and salin i t y are no longer independent, presumably as a result of adding a lower level of salinity (18 o/oo). The lack of-a significant temperature x water properties interaction (Table 7) indicates that the effects of temperature on the animals' metabolism may not be influenced by the source of the water used as the experimental medium. This situation probably results from the fact that any stressing effect of water properties on these animals seems to be small. Thus, -60-TABLE 7 Results of analysis of variance: Reactions of Euphausia  pacifica from the Strait of Georgia to changes in temperature, salinity and 'other' water properties, data from the experiment performed i n July 1969. Source of Variation Temperature Salinity Water properties Temperature x salini t y interaction Temperature x water property interaction Salinity x water property interaction Temperature x salinity x water property interaction Replication Salinity x replication Error Total Sum of Squares 0.54397 131.07 9.0340 7.9987 2.3188 5.2293 5.2443 4.1901 5.9650 31.979 203.57 Mean Square df 0.54397 1 65.533 2 2.2585 4 3.9994 2 0.5797 4 0.65366 8 0.65553 8 1.0475 4 0.74563 8 0.29610 108 F-ratio 1.83 221.32** 7.62** 13.51** 1.96 2.21* 2.21* 3.53** 2.51** -61-since the higher of the two temperatures used was not stressing to these particular animals, the two effects operated independently. The significant salinity x water properties interaction probably is a reflection of the additive nature of stress from low salinity and from changes i n water properties. The same causes likewise probably act to produce the significant temperature x salinity x water property interaction. The causes of the significant replication effect have been described in the section on s t a t i s t i c a l analysis and need not be discussed here. The graphic presentation of the results of the August experiment (Fig. 12c) shows a strong interaction between the effects of temperature and 'water properties' in that a l l specimens in the shallow and deep water from Indian Arm died at 20° C regardless of the salinity. At the same time a l l those i n both upper and lower water from the Strait of Georgia at full-strength and some of those in G.S. upper water at 21 o/oo, lived. There are no clearly defined groupsoof water property interactions such as were present in July. On the whole, the respiration rates in August in Indian Arm waters have decreased.while those in waters from the Strait of Georgia have increased from those observed in July. In August there is some indication, in that the R-S curves obtained at 10° and 15° C are nearly parallel, that Strait of Georgia lower water is the one in which the experimental animals exhibit the most 'normal' responses. This is the same water in which the highest respiratory rate was obtained when measurements made at 10° C i n f u l l -strength sea water are compared (Fig. 12c). -62-Results of the s t a t i s t i c a l analysis of the data from the August experiment are shown i n Table 8. They are s i m i l a r to the res u l t s of the July experiment except that the main e f f e c t of temperature i s s i g n i f i c a n t , presumably because a higher l e v e l of temperature (20° C) has been included. A l l int e r a c t i o n s are s i g n i f i c a n t which indicates a large degree of interdependence i n the e f f e c t s of temperature, s a l i n i t y , and water properties. Discussion. The hypothesis used i n the formulation of the three experiments was that any differences i n 1 vitifae.v& properties of sea waters acting d e l e t e r i o u s l y on the experimental animals, would add to the s t r e s s i n g e f f e c t s of lowered s a l i n i t y and elevated temperature. That i s , there should be an i n t e r a c t i o n between stresses r e s u l t i n g from reduced s a l i n i t y and elevated temperature and stresses r e s u l t i n g from differences i n 'other' properties between sea waters. This hypothesis was based on the assumption that stress from a l l sources would be additive i n i t s e f f e c t on the metabolism of E. p a c i f i c a , i n the same fashion as has been shown with stress from changes i n temperature and s a l i n i t y i n Part IV. The s i g n i f i c a n t main e f f e c t s of water properties (Tables, 6, 7, and 8) indic a t e that sea water from diverse sources can a f f e c t the r e s p i r a t i o n rate of E. p a c i f i c a . The res u l t s of a l l three experiments show s i g n i f i c a n t i n t e r a c t i o n s between water properties and temperature and/or s a l i n i t y e f f e c t s on the animals' r e s p i r a t i o n . This indicates that whatever property of sea water i t i s that i s being referred to as 'water properties', can a f f e c t the experimental animals' a b i l i t y to withstand TABLE 8 Results of analysis of variance: Reactions of Euphausia  pacifica from the Strait of Georgia to changes in temperature, salinity and 'other' water properties, data from the experiment performed in August 1969. Source of Variation Temperature Salinity Water properties Temperature x salinity interaction Temperature x water property interaction Salinity x water property interaction Temperature x salinity x water property interaction Error Total Sum of Squares 50.650 12.006 11.870 9.3282 15.316 4.6595 18.199 46.9642 168.99 Mean Square 25.325 12.006 3.9565 4.6641 2.5526 1.5532 3.0332 df 2 1 3 2 F-ratio 51.75** 24.54** 8.07** 9.52** 5.21** 3.16*1-'-6.20** 0.4892 96 119 -64-stress from other sources. There remains, however, the question of what is_ being referred to as water property effects. It is possible that differences in the i n i t i a l s a l i n i t i e s of the full-strength sea waters used in the three experiments (Table 5) might have affected the results. A l l of these s a l i n i t i e s , however, lay well within the 'f l a t ' part of the R-S curves obtained for euphausiids from Saanich Inlet and from Juan de Fuca Strait. (Figs. 11a, b). Therefore i t appears likely that differences in i n i t i a l salinity probably do not affect the results. Evidence supporting this is found i n the fact that when the effects of waters from Indian Arm and the Strait of Georgia changed i n a complementary fashion between July and August (Figs. 12b, c), the sa l i n i t i e s of the four waters hardly changed at a l l between the two months. Both of these pieces of evidence appear to indicate that the i n i t i a l s a l i n i t i e s are not appreciably affecting the results and thus that the source of the water property effects w i l l have to be sought elsewhere. Possibly the dilution of the sea waters with water d i s t i l l e d in a metal (tin) s t i l l might have had some effect on the animals' respiration other than that of reduced osmotic pressure as a result of contamination. Gostlow (1969, p. 306) has suggested that there was an appreciable difference in the time to the f i r s t zoeal moult for crab larvae maintained in Instant Ocean, medium made up with tap water, metal d i s t i l l e d water, and glass d i s t i l l e d water. These results indicate that contamination in the d i s t i l l e d water used i n this study might -65-have been a source of error. On the other hand, in the same report Provasoli (p. 306) states that any tin residue in Bams tead-dis t i l l e d water is not deleterious for culturing experiments. Presumably, i f traces of tine were harmful, the water requiring the greatest dilution to reach 21 o/oo would consistently exert the most deleterious effects. This is not the case in the results of the present study. Strait of Georgia upper and lower water require a greater dilution to reach 21 o/oo than either Indian Arm upper or lower water; yet? ?they are not consistently the least beneficial waters. On the contrary, in August the Strait of Georgia waters were by far the most beneficial. : Therefore, i t seems like l y , that the varying amounts of d i s t i l l e d water introduced no systematic error in the animals' respiration and thus that the d i s t i l l e d water used was not deleterious in its effects on the animals. It is also possible that the combination of 20° C and the s a l i n i t i e s of the two waters from Indian Arm (Table 5) might be lethal to the animals as a result of the interaction of temperature and salinity effects alone with no added effect of 'water properties'. The fact that some animals survived at a salinity of 21-o/oo i n Strait of Georgia upper water, however, indicates that, i f there were no effect from 'water properties', some animals should have survived in full-strength sea water from Indian Arm because i t had a salinity higher than 21 o/oo (Table 5). It is also unlikely that any of the laboratory procedures could have biased the results i n favor of any of the waters, because a l l waters were treated as nearly alike as possible in -66-both collecting and laboratory techniques. Therefore i t seems that whatever is causing the effects classfied under general heading of 'water properties' is an actual property or properties of the water, distinct from i t s salinity and not an artifact of either collecting or laboratory technique. Thus, the interaction of effects of 'water properties' with stress resulting from changes in temperature and salinity are indicative of changes in the suit a b i l i t y of different sea waters as media for £-. pacifica. These results are similar inppattern to those reported by Wilson and Armstrong (1952, 1954, 1958, 1961) who investigated the su i t a b i l i t y of various natural sea waters as culture media for echinoderm larvae. They are also similar to the results obtained by Regan (1968) in his series of experiments on the ab i l i t y of E_. pacifica from B.C. coastal waters to survive i n waters collected from various local areas. Wilson and Armstrong, and Regan, found that there were appreciable differences in the survival rates of their experimental animals in sea waters from different geographic areas; these differences were interpreted as stemming from differences in 'other' properties of sea water. The graphical respresentation of the results of the July experiment (Fig. 12b), indicates that some of the waters may be more beneficial in their effects on the animals than others, in that the reduction in respiration between full-strength sea water and 21 o/oo was less. The Indian Armuupper and lower waters allow the experimental animals to withstand more stress from temperature and salinity changes than either water from -67-the Strait of Georgia. It is also clear that Strait of Georgia upper water is superior to the lower water. This is approximately the order in which the waters would appear i f ranked from highest to lowest on the basis of the respiration i n them of E_. pacifica in full-strength sea water at 10° C. Results of the August experiment (Fig. 12c) again show that one group of waters is more beneficial in i t s effects on the animals than another. In this instance the two waters from Strait of Georgia are the most beneficial, as shown by the fact that i t is not unt i l 20° C that the effect of 21 o/oo becomes greatly deleterious. In Indian Arm upper water 21 o/oo reduces the animals' respiration rate at a l l three temperatures. Indian Arm lower water appears to be slightly more beneficial in i t s effects but no animals were able to survive at 20° C even in full-strength sea water. Again, there is an indication that the amount of stress that an animal can stand in a given water may be indicated by the relative respiration rates in f u l l -strength sea water at 10° C. The results of a l l three experiments show that sea waters from various sources can affect the respiration rate of _E. pacifica. For reasons given above i t appears unlikely that differences in the in s i t u salinity of the sea waters or the handling after collection could have caused the observed differences. The implication i s , therefore, that the factors causing the differences in respiratory rates are the i n t r i n s i c , 'other' properties of the sea waters used i n the experiments^ not their in situ temperature and/or salinity. -69-VI. ANNUAL CHANGES IN THE REACTIONS OF TWO COASTAL POPULATIONS OF EUPHAUSIA PACIFICA TO NATURAL SEA WATERS. Introduction. Lewis and Ramnarine (1969) present evidence that sea water from a constant depth at one station varies from month to month in i t s su i t a b i l i t y as a culture medium for copepod larvae. Further they show that sea water, which may be poor as a culture medium, can be improved by adding small amounts of chelated trace elements, in particular cobalt and zinc (Lewis, 1967). Lewis and Ramnarine infer from these findings that at some times of the year the natural sea water they collected was deficient in cobalt and/or zinc, or i n chelation. Further evidence (Lewis, MS i n prep.) indicates that seasonal variations i n the effect of enrichment of sea water are related to changes in physical oceanographic processes. The greatest influence on these processes appears to be the amount of runoff from the Fraser River and the upwelling off the mouth of Juan de Fuca Strait (see Part III of this report). Regan (1968) carried out a series of experiments using E_. pacifica from Indian Arm in which the survival of specimens in sea waters from several local areas was compared. The results of these experiments were reported as an 'order of preference', the most highly preferred water being that having the highest survival rate. Water from Indian Arm ('home water') was always most preferred, but after that the order changed from one experiment to another. The survival rate i n 'home water' also varied from experiment to experiment. Regan suggested that these changes in order of preference were related to -70-changes i n the hydrography of the areas. Regan proposed the hypothesis that specimens of _E. p a c i f i c a indigenous to Indian Arm had adapted to the 'other' properties of the water at intermediate depths i n such a way as to react against the 'other' properties of waters from another area. He also suggested that reactions toward and against 'other' properties affected the d i s t r i b u t i o n of _E. p a c i f i c a i n Indian Arm. Thus, the absence of specimens i n the deep wate rs resulted from "... an adverse reaction of specimens towards the 'unique ('other') properties' of deep water" (Regan, 1968, p. 157). The re s u l t s obtained by Lewis and Ramnarine (1969) andby Regan (1968) in d i c a t e that the d i s t r i b u t i o n of water properties which might a f f e c t the s u r v i v a l of E_. p a c i f i c a or copepod larvae varies with the geographic area and with time. Regan's res u l t s also i n d i c a t e that E_. p a c i f i c a from Indian Arm may have become adapted to the conditions there; h i s order of preference indicates that specimens are stressed by being placed i n water from any other source. I f specimens of E. p a c i f i c a can adapt to the p e c u l i a r water properties of one p a r t i c u l a r environment as i t appears the specimens from Indian Arm used by Regan may have done, i t may be presumed that they can adapt to another. I f so, i t i s possible that there w i l l e x i s t a number of populations, each of which would react d i f f e r e n t l y i f presented to one p a r t i c u l a r environment and i t s 'other' properties. -71-The r e s u l t s of the previous p a r t of t h i s study (Part IV) i n d i c a t e that animals l i v i n g i n some sea waters are able to support more s t r e s s from changes i n temperature and s a l i n i t y than those i n others. The r e s u l t s a l s o i n d i c a t e that the r e l a t i v e order of the r e s p i r a t o r y r a t e s , from highest to lowest, obtained w i t h E. p a c i f i c a i n a s e r i e s of sea waters under standard c o n d i t i o n s could i n d i c a t e the r e l a t i v e amounts of s t r e s s from grea t e s t to l e a s t that could be withstood by specimens i n each of these waters. The o b j e c t of t h i s p o r t i o n (Part VI) of the research p r o j e c t i s to study v a r i a t i o n s i n the d i s t r i b u t i o n of 'other' p r o p e r t i e s . I t was approached by usin g the r e s p i r a t i o n of specimens of E_. p a c i f i c a as an index of ' d e s i r a b i l i t y ' . I t was expected that the use of specimens from two c o a s t a l l o c a t i o n s (Indian Arm, the S t r a i t of Georgia) would give an i n d i c a t i o n of whether separate populations of _E. p a c i f i c a , c h a r a c t e r i z e d by t h e i r d i f f e r e n t r e a c t i o n s to water p r o p e r t i e s , e x i s t . I t was a l s o expected that the r e s u l t s would i n d i c a t e whether the d i s t r i b u t i o n of E_. p a c i f i c a i n Indian Arm or i n the S t r a i t of Georgia was a f f e c t e d by d i f f e r e n c e s i n 'other' p r o p e r t i e s . The r e s u l t s of t h i s study i n d i c a t e that.the ' d e s i r a b i l i t y ' of sea water c o l l e c t e d at a given s t a t i o n and depth, changes throughout the year i n a s s o c i a t i o n w i t h changes i n oceanographic processes. The, . r e s u l t s a l s o i n d i c a t e that the two populations of E. p a c i f i c a used had c h a r a c t e r i s t i c , but d i f f e r e n t , r e a c t i o n s to the same sea waters. There was, however, no i n d i c a t i o n that 'other' p r o p e r t i e s were e f f e c t i v e i n determining the d i s t r i b u t i o n -72-of E_. p a c i f i c a within e i t h e r Indian Arm or the S t r a i t of Georgia, although they may be e f f e c t i v e i n maintaining separate populations i n Indian Arm and the S t r a i t of Georgia. Materials and Methods. The aim of this part of the study was two-fold; f i r s t l y , to examine e f f e c t s on specimens of E_. p a c i f i c a of v a r i a t i o n s i n water properties on a yearly basis i n r e l a t i o n to hydrographic conditions, and secondly, to determine whether geographically separate populations of E_. p a c i f i c a react d i f f e r e n t l y to waters with s i m i l a r properties. The experiment which was designed to examine these questions was a standard three-factor f a c t o r i a l design with f i v e r e p l i c a t e s i n each c e l l . Specimens of E. p a c i f i c a from two areas, the S t r a i t of Georgia and Indian Arm (G.S.-l, F i g . 3; I.A.-9, F i g . 3), comprised the two l e v e l s of the f i r s t f a c t o r . The second fa c t o r , water properties, was represented by four l e v e l s , namely an 'upper' water at each of the two stations c o l l e c t e d at the l e v e l of the greatest concentration of the euphausiid population, and a 'lower' water c o l l e c t e d from a depth near the bottom at each s t a t i o n . Table 9 gives the depth from which the- two waters were c o l l e c t e d i n Indian Arm as w e l l as t h e i r i n s i t u temperatures and s a l i n i t i e s . Table 10 gives the same information f o r the two waters c o l l e c t e d i n the S t r a i t of Georgia. Time, the t h i r d factor, was represented by 13 of the 14 months between August 1968 and September 1969. There are no observations f o r March 1969 and only p a r t i a l observations f o r a few months preceding August 1968. TABLE 9 Temperatures, s a l i n i t i e s , and depths from which the two waters used in experiments were collected from Indian Arm Month August 1968 September 1968 October 1968 November 1968 December 1968 January 1969 February 1969 March 1969 April 1969 May 1969 June 1969 July 1969 August 1969 September 1969 Indian Arm Upper Water z T S 125 8.34 26.574 75 10.28 26.031 100 8.48 26.338 100 8.73 26.351 100 9.10 26.280 100 8.06 26.464 100 6.17 26.739 100 6.51 27.136 100 6.49 27.199 75 6.46 27.044 100 6.53 27.091 75 6.63 26.870 75 6.85 26.717 75 7.21 26.715 Indian Arm Lower Water z T S 200 8.35 26.678 200 8.34 26.644 200 8.37 26.618 200 8.36 26.607 200 8.41 26.592 200 7.04 26.446 200 6.28 26.824 200 6.57 27.204 200 6.57 27.186 200 6.59 27.175 200 6.58 27.171 200 6.60 27.140 200 6.58 27.121 200 6.59 27.108 TABLE 10 Temperatures, sa l i n i t i e s , and depths from which the two waters used i n experiments were collected in the Strait of Georgia Month Strait of Georgia Upper Water z T S August 1968 100 8.60 30 .221 September 1968 125 9.10 30 .544 October 1968 100 9.26 30 .341 November 1968 125 9.29 30 .570 December 1968 100 9.28 30 .295 January 1969 75 8.28 29 .684 February 1969 100 7.19 29 .850 March 1969 100 7.00 29 .925 April 1969 100 7.25 29 .776 May 1969 100 7.32 29 .910 June 1969 75 8.25 29 .665 July 1969 75 7.89 29 .728 August 1969 75 8.82 29 .710 September 1969 75 9.37 30 .158 Strait of Georgia Lower Water z T S 350 8.70 30.926 350 8.88 31.107 350 9.04 31.118 350 8.98 31.138 350 9.05 31.066 350 9.01 310014 350 9.00 31.028 350 9.02 30.950 350 8.90 30.852 350 8.62 30.799 350 8.47 30.770 350 8.58 30.756 350 8.'80 30.831 350 9.13 31.057 75 The e f f e c t of water properties was assessed by measuring r e s p i r a t i o n of specimens i n each of the four waters at 10° C using the techniques outlined i n Part I I . The s t a t i s t i c a l analysis of the r e s u l t i n g data was c a r r i e d out by means of mu l t i f a c t o r analysis of variance with r e p l i c a t i o n treated as a factor. In reporting the r e s u l t s a l l r e p l i c a t i o n sums of squares and degrees of freedom have been pooled with the error term. The r e s u l t s are reported as analysis of variance tables 11 to 18 and g r a p h i c a l l y i n Figures 13a and 13b. Results. Results of an-;analysis of a l l data obtained over 13 months using animals from both Indian Arm and the S t r a i t of Georgia in the four waters are shown i n Table 11. Of the three sources of v a r i a t i o n considered, time (months), source of experimental animals (area), and water properties, only months and area show s i g n i f i c a n t main e f f e c t s ; the main e f f e c t of water properties i s n o n - s i g n i f i c a n t . These r e s u l t s indicate that the o v e r a l l r e s p i r a t i o n of specimens changed from one month to the next and that animals from Indian Arm demonstrated a d i f f e r e n t o v e r a l l r e s p i r a t i o n rate from those the S t r a i t of Georgia. The r e s u l t s also indicate that e i t h e r within each of the two areas, or between them, there was no e f f e c t of water properties, or that these e f f e c t s were not the same i n each area. The s i g n i f i c a n t i n t e r a c t i o n between areas and months suggests that the r e s p i r a t i o n of animals from Indian Arm changed d i f f e r e n t l y with time from that of the animals from the S t r a i t of Georgia. Because of the s i g n i f i c a n t main e f f e c t of area i n the o v e r a l l analysis (Table 11), r e s u l t s obtained with specimens from the S t r a i t of Georgia and from Indian Arm are treated separately i n the rest of the analyses. •-75A-Figure 13a. (facing) Respiration of Euphausia pacifica from the Strait of Georgia in Strait of Georgia upper and lower water and in Indian Arm composite from April 1968 to September 1969 (Indian Arm composite from August 1968 to September 1969 only). Figure 13b. (facing) Respiration of Euphausia pacifica from Indian Arm in Strait of Georgia upper and lower and i n Indian Arm Composite from March 1968 to September 1969. 1968 1969 I.A. composite — — • — - G .S . upper water G.S. lower water -76-The results of an analysis (Table 12) of the reactions of specimens from Indian Arm to Indian Arm and lower waters over 13 months indicate that there was an overall change in respiration rate with time (months) , but that there' were no consistent differences between responses to the two waters. Therefore, the results obtained with the two waters have been combined in the graphic presentation of the data as 'Indian Arm composite water' (Figs. 13a, 13b). The respiration of E_. pacifica from the Strait of Georgia in the three waters over 13 months is shown in Fig. 13a. An obvious feature of the results shown is that respiration i s a l l three waters declines from a higtt i n April-May 1968 to a low in November-December 1968 and then increases u n t i l August-September 1969. The fact that the high respiratory rate obtained in April-May 1968 was not maintained through July-August 1968 as i t was in 1969 may be an indication of a cycle having a period of more than one ytear. Superimposed on the overall seasonal variation in respiratory rate (Fig. 13a) is a cycle of the 'desirability' of Strait of Georgia upper and lower waters. With the exception of June 1968, from April to September 1968 respiration in Strait of Georgia upper is higher, although at times only slightly higher, than i n Strait of Georgia lower water; from October 1968 to March 1969 the reverse is true. From April 1969 to July 1969 upper water is again more 'desirable' than lower, but in August 1969 the 'desirability' of the two waters reverses again. This cycle appears to have a seasonal basis; i n winter lower water is more 'desirable' than upper; i n summer the reverse is true. -77-Results of an analysis designed to test whether there was any difference between the reactions of specimens from the Strait of Georgia to the Strait of Georgia upper and lower during April-May 1968 and May-June 1969 are shown in Table 13. They indicate that there was a significant effect of water properties, and that this effect was consistent from month to month and between 1968 and 1969. The four months included i n the analysis were the two from each year in which the 'summer' response to water properties was most fully developed, if-e? the months showing the'greatest difference in respiration rate between-Straitaof Georgia upper and lower waters. Table 14 shows the results of analysis of variance performed on the data obtained using animals from the Strait of Georgia in Strait of Georgia upper and lower water for months when the 'winter' response to water properties obtained (October, November, and December 1968; January 1969). In the results of this analysis neither of the two sources of variation considered, water properties and months, showed any significant main effects. The probability of obtaining a larger F-ratio than was obtained for water properties (3.89) by chance lie s hetween 0.10 and 0.05. Such a result indicates that water properties may have had an effect on the respiration of the animals but that i f so, experimental error was too great to allow i t to be dis tinguished. Figure 13b gives a graphic presentation of the respiration of animals from Indian Arm in the three waters (Strait of Georgia upper and lower; over 13 months Indian Arm composite). -78-As i n the r e s u l t s obtained with specimens from the S t r a i t of Georgia (Fig. 13a), an important feature i s the decline i n r e s p i r a t i o n from July 1968 to December 1968 followed by a r i s e i n r e s p i r a t i o n rate between January 1969 and July 1969. Superimposed on t h i s general seasonal cycle are other e f f e c t s . During July, August, and September 1969 r e s p i r a t i o n of Indian Arm animals i n Indian Arm composite water i s consistently higher than for the same period i n 1968. There appears to be a c y c l i c change i n the r e l a t i v e ' d e s i r a b i l i t y ' of S t r a i t of Georgia upper and lower water. In July and August 1968, and i n A p r i l , May, June, July and August 1969 S t r a i t of Georgia lower water i s more 'desirable' than upper water. From September 1968 to A p r i l 1969 S t r a i t of Georgia upper water i s more 'desirable' than lower. This cycle is the reverse of the one observed i n the r e l a t i v e ' d e s i r a b i l i t y ' of the same two waters using S t r a i t of Georgia animals. With few exceptions, i n months when Indian Arm animals found S t r a i t of Georgia upper water more 'desirable', animals from the S t r a i t of Georgia preferred the lower water. Results of an analysis of the reactions of Indian Arm animals to the three experimental sea waters during August, September and October 1968 and during July, August and September 1969 are shown i n Table 15. This analysis was designed to test whether the in t r u s i o n of outside sea water into Indian Arm (January-March 1969, see section III) affected either the animals' o v e r a l l r e s p i r a t i o n rate or t h e i r reactions to water properties. The large main e f f e c t of years indicates that specimens' o v e r a l l r e s p i r a t o r y rate changed -79-between 1968 and 1969. At the same time the s i g n i f i c a n t i n t e r a c t i o n between years and water properties indicates that the animals reacted i n 1968 d i f f e r e n t l y from i n 1969 to waters from the same depths and l o c a l i t i e s . The graphic presentation of the data (Fig. 13b) suggests that the i n t e r a c t i o n arises from the fact that Indian Arm water i s least 'desirable' i n August 1968 and the most 'desirable i n July and September 1969. The other two waters, S t r a i t of Georgia upper and lower water, have the same r e l a t i v e ' d e s i r a b i l i t y ' i n August and September of both years. The r e s u l t s shown i n Figure 13b suggest that Indian Arm animals reacted to S t r a i t of Georgia upper and lower water i n the period January to A p r i l 1969, d i f f e r e n t l y from what they did i n the period May to August 1969. Tables 16 and 17 present the r e s u l t s of an analysis designed to test this hypothesis. In each instance s i g n i f i c a n t main e f f e c t s are obtained for months and water properties. These r e s u l t s suggest that specimens from Indian Arm do react d i f f e r e n t l y to S t r a i t of Georgia upper and lower waters during the two periods. Monthly estimates of the abundance of adult and juvenile E. p a c i f i c a at s t a t i o n I.A.-9 are shown in Table 19. These estimates were obtained by summing the numbers of E, p a c i f i c a 3 per m for the various depths at which they were caught. The small Clarke-Bumpus plankton samplers used to c o l l e c t the samples are quite l i k e l y i n e f f i c i e n t with respect to the fast swimming euphausiids, but there i s no reason to suppose that they were any more i n e f f i c i e n t i n one month than i n another. -80-Therefore, although the absolute abundances shown in Table 19 are probably incorrect, the relative comparison of abundances from one month to another is probably valid. The most important points to notice are that the I 3 abundance of adult _E. pacifica ranges between 10.6 and 1.5/m from September 1968 to January 1969. In February 1969 no E_. pacifica were caught, and from April to June 1969 only a few were caught; in May 1969 juvenile E. pacifica appear and from July to September 1969 the numbers of adult _E. pacifica present are considerably higher than from February to June 1969. Discussion. One of the salient features of the results obtained with specimens from both Indian Arm and the Strait of Georgia is that there is a large seasonal variation i n respiratory rate, the summer rate being higher than the winter rate. Similar seasonal variation in respiratory rates has been reported for calanoid copepods by Marshall and Orr (1958) , Anraku (1964) , Topping (1966) and by Haq (1967). Small and Hebard (1967)>however, report no seasonal variation in respiration of an oceanic population of E. pacifica. It was suggested by Small and Hebard that perhaps the relatively unchanging thermal environment of the oceanic animals might have resulted in their having l i t t l e or no seasonal changes in their respiratory rate. In the present study the respiratory rate of both coastal populations of E. pacifica increases in January, long before the surface temperature increases appreciably in April-May. Therefore, i t appears unlikely that the seasonal changes in respiratory rate reflect seasonal changes in the -81-TABLE 11 Results of analysis of variance: Analysis of a l l data obtained over 13 months using Euphausia pacifica from both Indian Arm and the Strait of Georgia in four sea waters. Source of Variation Sum of Squares Mean Square df F-ratio Months 80.520 6.7100 12 48.45** Populations 1.8961 1.8961 1 13.69** Water properties 0.019426 0.006475 3 0.05 Months x populations interaction 5.8027 0.48356 12 3.49** Months x water properties interaction 5.7891 0.16081 36 1.16 Populations x water properties interaction 0.17679 0.058929 3 0.42 Months x populations x 9.7701 water properties interaction 0.27139 36 1.96** Error 57.61184 0.13849 416 Total 161.58 519 -82-TABLE 12 Results of analysis of variance: Reaction of Euphausia  pacifica from Indian Arm to Indian Arm upper and" lower water over 13 months. Source of Variation Mon ths Water properties Months x water properties interaction Error Total Sum of Squares 17.361 0. 01223 1. 7977 12.86375 32.035 Mean Square df F-ratio 1.4468 12 11.70** 0.01223 1 0.10 0.14981 12 1.21 0.125689 104 129 -83-TABLE 13 Results of analysis of variance: Reactions of Euphausia  pacifica from the Strait of Georgia to Strait of Georgia upper and lower water during 'low salinity' conditions in 1968 i A p r i l , May) and in 1969 (May, June). Source of Variation Sum of Squares Mean Square df F-•ratio Years 0.066178 0.066178 1 0. 206 Months 0.029214 0.029214 1 0. 09 Water properties 2.5427 2.5427 1 7. 93** Years x months interaction 0.17200 0.17200 1 0. 54 Years x water properties interaction 0.060451 0.060451 . 1 0. 19 Months x water properties interaction 0.015406 0.015406 1 0. 05 Years x months x water properties interaction 0.00002722 0.00002722 1 0. 00 Error 10.25728 0.32054 32 Total 13.143 39 -84-TABLE 14 Results of analysis of variance: Reactions of Euphausia  pacifica from the Strait of Georgia to Strait of Georgia upper and lower waters during 'high salinity' conditions, winter 1968 - 1969 (November, December, January, February). Source of Variation Months Water properties Months x water properties interaction Error Total Sum of Squares 0.49837 0.34708 0.091657 2.8528 3.7901 Mean Square 0.16612 0.34708 0.030552 0.08915 df 3 1 3 32 39 F-ratio 1.86 3.89 0.34 -85-TABLE 15 Results of analysis of variance: Reactions of Euphausia  p a c i f i c a from Indian Arm to S t r a i t of Georgia upper, S t r a i t of Georgia lower and Indian Arm composite waters during August, September and October 1968 compared with those during July, August and September 1969. Source of V a r i a t i o n Sum of Squares Mean Square df F - r a t i o Years 4.2376 4.2376 1 50.29** Months 0.18021 0.090106 2 1.07 Water properties 0.077720 0.038806 2 0.46 Years x months i n t e r a c t i o n 0.34969 0.17484 2 2.08 Years x water properties i n t e r a c t i o n 0.70957 0.35479 2 4.21* Months x water properties i n t e r a c t i o n 0.59620 0.14905 4 1.77 Error 6.40407 0.08426 76 Total 12.555 89 -86-TABLE 16 Results of analysis of variance: Reactions of Euphausia  pacifica from Indian Arm to Strait of Georgia upper, Strait of Georgia lower, and Indian Arm composite waters during February, March, April and May 1969. Source of Variation Months Water properties Months x water properties interaction -Error Total Sum of Squares 1.4265 1.3870 1.0572 5.14896 9.0198 Mean Square 0.47549 0.69349 0.17620 0.10727 df 3 2 6 48 59 F-ratio 4.43** 6.46** 1.64 -87-TABLE 17 Results of analysis of variance: Reactions of Euphausia  pacifica from Indian Arm to Strait of Georgia upper, Strait of Georgia lower, and Indian Arm composite waters during June, July, August and September 1969. Source of Variation Months Water properties Months x water properties interaction Error Total Sum of Squares 1.65255 0.68686 0.23414 5.0712 7.6179 Mean Square 0.54183 0.34343 0.039024 0.10565 df 3 2 6 48 59 F-ratio 5.12** 3.25* 0.37 -88-TABLE 18 Results of analysis of variance: Reactions of Euphausia  pacifica from Indian Arm to Strait of Georgia upper, Strait of Georgia lower, and Indian Arm composite waters during the period of February, March, April and May 1969 compared with their reactions to the same waters during the period June, July, August, and September 1969. Source of Variation Sum of Squares Mean Square df F-ratio Seasons 0.71441 0. 71441 1 6.81** Months 1.5493 0. 51643 3 4.91** Water properties 0.14895 0. 074477 2 0.71 Seasons x months interaction 1.5027 0. 50089 3 4.77** Season x water properties interaction 1.9249 0. 96244 2 9.17** Months x water properties interaction 0.81032 0. 13505 6 1.30 Error 10.70160 0. 10491 102 Total 17.352 119 -89-TABLE 19 Abundance of adult and j u v e n i l e Euphausia p a c i f i c a as 3 numbers/m a t Indian Arm Station 9: data from plankton samples c o l l e c t e d using the Clarke-Bumpus Plankton samplers. Month 3 no. adults/m no. juvs September 1968 10.6 0 October 1968 1.66 0 November 1968 1.50 0 December 1968 4.00 0 January 1969 2.50 . 0 February 1969 0 0 March 1969 no sample no s A p r i l 1969 0.2 0 May 1969 0.2 10.3 June 1969 0.14 12.1 July 1969 2.6 0 August 1969 1.2 8.8 -90-envlronmental temperature. The beginning of the increase, i n January, coincides neither with the change in relative 'desirability' (Figs. 13a, 13b) nor with the change from 'high sa l i n i t y ' to 'low salinity' hydrographic conditions i n the Strait of Georgia (see section III for a definition of 'high salinity' and 'low sa l i n i t y ' conditions). Therefore the increase in respiration rate does not appear to be a result of changes in water properties. The time of the beginning of the increase i n respiratory rate, January, does coincide with the increase i n the daily photoperiod. Pearcy et a l (1969), however, were unable to demonstrate any effect of light on the respiration of E_. pacifica. They did not attempt any long term photoperiod experiments. LIttlepage (pers. comm.)"'" has found that E_. pacifica from the local area dp not appear to store food i n a seasonal cycle. That i s , their chemical composition does not change appreciably over a yearly cycle. Therefore, the animals' energy expenditure, which is ultimately equivalent to i t s respiration rate, may be dependent on the amount of food available to i t . Conover (1959) reports that the spring increase in the respiration of Acartia discaudata, which has a seasonal cycle of respiration similar to that observed for E_. pacifica, was related to the increased availability of food in the spring; Conover and Corner (1968) report a similar relation between respiration and feeding for several species of copepods. Therefore, i t appears li k e l y that the seasonal variation in the respiratory rate of _E. pacifica from both areas-1 Dr. J.L. Littlepage, University of Victoria, Victoria, British Columbia. -91-may result from seasonal variations in their food supply. If this is true, the increase in respiratory rate in the early spring might be related to the appearance of large numbers of copepod nauplii in the water column (Stephens et a l , 1969). The seasonal cycle of high respiration i n summer and low respiration i n winter is the only feature that is common to the results obtained with animals from both the Strait of Georgia and Indian Arm. The results of the s t a t i s t i c a l analysis of the data (Table 11) indicate that not only are the overall respiratory rates of specimens from the two areas different (significant main effect of areas), but also that their reactions to seasonal changes and to water properties are not the same (significant interactions for months x areas and months x area x water properties). Because of the apparent differences between reactions of specimens from the two areas, results from each w i l l be discussed separately. An interesting aspect of the results obtained with specimens from the Strait.of Georgia is the cycle of relative 'desirability' of Strait of Georgia upper and lower water (Fig. 13a). This cycle appears to be related to changes in hydrographic conditions in the Strait. When 'high salinity' hydrographic conditions prevail in the Strait of Georgia, then lower water is more 'desirable' than the upper water"; in 'low salinity' conditions the opposite situation holds. In Fig. 13a 'low salinity' conditions are shown as obtaining i n the Strait of Georgia between April 1968 and September 1968; regular sampling of temperature and salinity was not begun u n t i l August 1968, but data available for May and July 1968 -92-indicate that 'low sa l i n i t y ' conditions obtained at those timesi Therefore, i t has been presumed that 'low salinity' conditions were continuous from April 1968 to September 1968. An analysis of the data for the two months in which the maximum response (greatest difference between respiration in Strait of Georgia upper and lower water) of Strait of Georgia animals to 'low salinity' conditions in each of 1968 and 1969 (Table 13) indicates that the magnitude of the responses to Strait of Georgia upper and lower waters did not change from 1968 to 1969, and that the differences in respiratory rates obtained were real. At the same time, inspection of Fig. 13a suggests that, although there are differences i n the specimens' reactions between the two years, the pattern of response to Strait of Georgia upper and lower waters during 'low salinity' conditions is consistent i n both years. I n i t i a l l y (April, May 1968; May, June 1969) Strait of Georgia upper water is appreciably more 'desirable' than lower; this period i s followed by one in which the two waters are equally 'desirable' (June, July, August, 1968; July, August 1969); fi n a l l y the transition to the 'high sa l i n i t y ' response takes place (October 1968; September 1969). The above pattern of response suggests that the difference between the two waters arises as a result of some event and that the property causing the difference is then slowly' equalizedbbetween them. One event which occurs during May and June each year is the time of the peak runoff from the Fraser River (Waldichuck, 1957). Thus i t is possible that the observed pattern of response is a result of the addition at the -93-surface of the Strait of Georgia of some 'desirable' property in the runoff water. Analysis of the respiration of specimens from the Strait of Georgia in Strait of Georgia upper and lower water during the period when 'high salinity' conditions obtain (Table 14) is inconclusive. The probability of obtaining a larger F-ratio than that observed for water .properties is less than 0.10% and greater than 0.05%; perhaps the results of this analysis can be said to suggest that the observed differences in the effects of Strait of Georgia upper and aioweriwaters (Fig. 13a) on the euphausiids' respiration may be. real, but not to prove the point conclusively. In any event the pattern of response to 'high salinity' hydrographic conditions, the greater 'desirability' of Strait of Georgia lower water, is consistent from October 1968 to February 1969. The primary feature of the results obtained with specimens of ji . pacifica from Indian Arm is an overall seasonal cycle of respiration with the winter respiratory rates being less than, those in summer; this cycle possibly results from the same causes as the one discussed above for Strait of Georgia animals. The results of the analysis of the Indian Arm animals' reactions to water from the upper zone, where they li v e , and from the lower zone (Table 12) show that there is no detectable difference i n their reaction to the two waters. The one month interval between sampling used i n this study, of course, w i l l not, allow fluctuations having a period of less than one, or possibly two months,to be detected. At the same time i t is reasonable to assume that any persistent differences between waters would have been detected. Regan (1968-)1 did not include water from the deep zone in his experiments so i t is not possible to say what effect i t might have had on the animals' survival. It does not appear, from the present results, however, that there are any differences in 'other-' propertie's' between the two waters. One of the more interesting features of the results is that, on the whole, respiration in Indian Arm composite water (Fig. 13b, Table 1!5>) is higher in August and September of 1969 than in the same period of 1968. A notable incident which occurred between 1968 and 1969 was the intrusion of outside water into Indian Arm in February-March 1969. It is possible that higher respiration rates observed for Indian Arm animals in July and August 1969 as opposed to the same months of 1968 result from changes in the hydrography of the fjord. It appears, too, that, far from reacting adversely to intruding water as suggested by Regan (1968), the animals react favorably to i t as shown by their increased respiratory rates. It is possible that the increased respiration and changed reactions to Indian Arm composite water result from the use i n experiments of E_. pacifica recruited into Indian Arm along with the intruding water. Regan (1968), however, considers the population of E_. pacifica living i n Indian Arm to be indigenous and suggests that, rather than there having been a large influx of E_. pacifica at the time of the intrusion which occurred during his study, specimens were lost from the inlet with the water displaced by the intrusion. The same - 9 5 -course of events appeared to take place at the time of the i n t r u s i o n i n February-March 1969, the population density of E_. p a c i f i c a at s t a t i o n 9 (Table 19) dropped sharply i n February 1969 and remained low u n t i l breeding began i n May 1969. Thus i t appears l i k e l y that at l e a s t a majority of the specimens from Indian Arm employed i n the experiments were from the indigenous population. i The s i g n i f i c a n t seasons x water properties i n t e r a c t i o n seen i n Table 18 suggests that, although the main e f f e c t of water properties i s n o n - s i g n i f i c a n t , the Indian Arm animals' reaction to water properties d i f f e r s i n winter from i n summer. The s i g n i f i c a n t e f f e c t s f o r water properties observed i n the r e s u l t s of the analysis shown i n Tables 13 and 17 confirm that there are e f f e c t s on the r e s p i r a t i o n of animals caused by differences i n water properties. In general, during the po s t - i n t r u s i o n period Indian Arm composite water i s always about the same i n i t s e f f e c t s on E_. p a c i f i c a from Indian Arm as the more preferred of S t r a i t of Georgia upper or lower water ( F i g . 13b). Indian A"rm:'uahimals i n S t r a i t of Georgia upper water give higher respiratory rates than those i n S t r a i t of Georgia lower water from October 1968 to May 1969. From June to August S t r a i t of Georgia lower water i s preferred to upper water. In September 1969 the order of preference changes again. With small discrepancies (one month at most) the timing of the changes i n the order of preference, the preference shown by the Indian Arm animals f o r S t r a i t of Georgia upper lower water i s the inverse of the cycle seen i n the re s u l t s obtained with animals from the S t r a i t of Georgia ( F i g . 13a). Because of the correspondence of the -96-dates of changing preference, i t appears that both populations are responding to changes in the same properties in a different way. In sum, the results of this experiment show that specimens of E_. pacifica from the Strait of Georgia and from Indian Arm can detect and react to differences in 'other' water properties. It has also been shown that specimens from Indian Arm and the Strait of Georgia do not react to 'other' properties in the same way: changes in 'other' properties have been related to changes in oceanographic processes. -9 7-VII. GENERAL DISCUSSION. The presence or absence of a species i n an area or water is probably a result of the action of a limiting factor. Such a limiting factor may be presumed to operate through stresses i t imposes. The overall object of the present research was to gain an insight into the effects on Euphausia  pacifica of factors; that might act to limit the distribution of the species. To this end the effects of changes in the temperature, salinity and 'other' properties of sea water on the animals' respiration have been investigated. The results reported i n Part IV provide an estimate of the ranges of values of temperature and salinity that are tolerable to E_. pacifica; they suggest that, as Regan (1968) proposed, these two factors w i l l only be important in limiting the distribution of E. pacifica in B.C. coastal waters near the surface where the temperature of the water may become high, or low, and i t s salinity low. Results reported in Part V demonstrated that changes in 'other' properties between sea waters could exert stress on E_. pacifica and, further, provided a means, through, comparing respiratory rates obtained at 10° C, of assessing differences in the 'other' properties of a series of sea waters. The question remains as to what causes the different responses to the various waters. Because a l l the animals used in this study were treated alike, except for the water that they were placed i n , i t is unlikely that the observed differences between sea waters were an artifact of experimental technique. At the same time, although the in s i t u temperature and salinity -98-of the water varied over a year's time (Tables 9 and 10) i t seems likely that measuring the animal's respiration after acclimation at a constant temperature eliminated any effects of differing in situ temperatures. The changes in salinity at any one depth do not exceed 1 o/oo, and are generally less (Tables 9 and 10). Changes in salini t y of less than 1 o/oo affect the respiration of E_. pacifica only at values of salinity much lower than any encountered in the f i e l d away from the surface. Also, when the relative 'desirability' of upper and lower water from the Strait of Georgia to specimens from each of the two populations changes, the relative s a l i n i t i e s of the two water do not (Table 10). These results suggest that the differMg.g responses to various sea waters do not ensue on changes in i n s i t u s a l i n i t y . It appears, rather, that the differing responses result from changes in other, but undefined, properties of the water. Because of the close coincidence of the changes in the 'desirability' of Strait of Georgia upper and lower water with changes from 'high sa l i n i t y ' to 'low sal i n i t y ' oceanographic conditions in the Strait (see Part III for a definition of these conditions), the changes in 'other' properties of these two waters may be linked to the origins of the waters (Part III). Further evidence of the close correlation of changes in 'other' properties with changes i n the origins of water is furnished by the fact that Indian Arm composite (see Part VI for a definition of Indian Arm Composite) appears to have been more 'desirable' to specimens from Indian Arm after the intrusion than before. From this i t may be deduced that 'other' properties -99-are at least quasi-conservative properties of sea water. Lewis and Ramnarine (1969) and Lewis (pers. comm.) have found that by enriching Strait of Georgia lower water with chelated cobalt and zinc during 'low salinity' hydrographic conditions i t s value as a culture medium for copepod larvae is enhanced, presumably by supplying or making available, needed trace elements. During 'high salinity' conditions, however, enrichment of Strait of Georgia lower water either provides no benefit, or is harmful to the copepod larvae. Lewis and Ramnarine interpret this result as indicating that the trace elements were already present in sufficient quantities and that the enrichment, or the added chelation, raised the usable trace element concentration to a toxic level. Thus, i t can be inferred that the contentlofietrace elements in Strait of Georgia lower water when 'high salinity' conditions prevail is higher than when 'low salinity' conditions obtain. Because animals from the Strait of Georgia find Strait of Georgia lower water more 'desirable' when it s trace element content can be inferred to be high, perhaps Strait of Georgia upper water can be inferred to have a higher trace element content than the lower water when i t is more 'desirable' than lower water (during 'low salinity' conditions). If the above reasoning is valid the cycle of the relative 'desirability' of Strait of Georgia upper and lower water to specimens from the Strait of Georgia could be explained i f both upwelled oceanic water and Fraser River runoff were sources of trace elements. Thus, the lower water would be the most 'desirable' to animals from the Strait of Georgia in late summer and early winter when the bottom waters are -100-displaced by water containing recently upwelled water ('high salinity conditions'); the upper water would be most 'desirable' i n late spring and early summer when trace elements were added at the surface by the influx of Fraser River runoff. The water resident i n Indian Arm is ultimately derived from the water i n the upper zone of the Strait of Georgia, and probably always in late winter. Thus, i f as has been proposed, the trace element content of the water i n the upper zone of the,Strait of Georgia is low in late winter, the waters resident , in Indian Arm could be expected to have a low trace element content. Specimens of E. pacifica from Indian Arm react more favourably to whichever of Strait of Georgia upper or lower water that can be inferred at that time to have the lower ' trace element content. This situation implies! that the optimum concentration of trace elements for specimens from Indian Arm is lower than for specimens from the Strait of Georgia. Such a situation could be expected to arise i f the trace element content of the water in Indian Arm were lower than that of the water in the Strait of Georgia. From this i t seems necessary to postulate that the Indian Arm population has become adapted to a particular set of 'other'properties (low trace element concentration?) of the water in Indian Arm. Thus these specimens reacttoo outside, properties (higher concentrations of trace elements?) differently from another population (from the Strait of Georgia) that has become adapted to the latter conditions. The fact that -101-the intrusion of outside water did not appear to affect the characteristic response of the Indian Arm animals to Strait of Georgia upper and lower water suggests that the adaptation may be genetically fixed and not just an acclimatization. If so, i t would suggest that free passage of E_. pacifica between the Strait of Georgia and Indian Armmmay be limited by stresses arising from the persistent differences in 'other' properties between the waters of these two areas. A genetic adaptation would also suggest that these two groups form two separate physiological races of E_. pacifica which differ with respect to their reactions to 'other' properties of sea water. This bears out Regan's (1968) hypothesis that the Indian Arm E_. pacifica might comprise a separate population, distinct from specimens in EheaStrait of Georgia. The results of Part V~suggest that the water yielding the higher respiration rate under a standard set of experimental conditions permits the animals to support a greater amount of stress. Therefore, i t is possible that the changes in the relative 'desirability' of Strait of Georgia upper and lower water represent changes in the relative suitability for E. pacifica of the two waters. . The occurrence of euphausiids in the Strait of Georgia as revealed by horizontal plankton tows were usually confined to two or three of the depths sampled with one of the samples containing the majority of the specimens captured. Strait of Georgia upper water was always collected from the depth of greatest abundance of euphausiids. It seems therefore either that changes in the relative -102-s u i t a b i l i t i e s of Strait of Georgia upper and lower water were not great enough to affect the vertical distribution of E_. pacifica in Georgia Strait or that such changes in distribution were not detected. The absence of similar differences in the su i t a b i l i t y of the upper and lower waters from Indian Arm an specimens from there suggests that there are no such differences in 'other' properties as exist between Strait of Georgia upper and lower waters between the upper and lower waters from Indian Arm. This result implies that the occurrences of _E. pacifica at mid-depth in Indian Arm observed by Regan (196801 as well as in the result of this study probably do not result from an avoidance of deleterious 'other' properties of deep water in Indian Arm. The above arguments concerning the distribution of E. pacifica do not rule out the possibility that differences in 'other' properties between Indian Arm and the Strait of Georgia might limit the free passage of animals from the Strait of Georgia into Indian Arm. In fact, the inverse (Part VI) reactions of specimens from the two areas to the same water properties suggests that free passage between the two areas may be limited. The above arguments concerning the distribution of E. pacifica are based on i t s observed distribution. The methods and equipment used to determine the distributionoof euphausiids, namely s t r a t i f i e d tows with Clarke-Bumpus samplers leave much to be desired ,nneve r the les ss, used consistently , they w i l l provide a reasonably accurate estimate of the depth of maximum abundance of specimens. The author believes that more -103-efficient sampling equipment would have yielded essentially the same picture of the distribution of the euphausiids. In summary, temperature, salinity and 'other' water properties are a l l capable of exerting stress on specimens of E_. pacifica and thus are potentially capable of acting to limit the species' distribution of occurrences. At the same time, from the observed tolerances of coastal euphausiids (Part IV) to changes in temperature and salinity i t appears that these two factors could affect distribution of E_. pacifica only at or near the surface. Thus i t i s a reasonable deduction that any effects of water properties on E. pacifica's'idistribution away from the surface in the local area w i l l be a result of the action of 'other' properties. In neither Indian Arm nor i n the Strait of Georgia was there a demonstrable effect of 'other' properties on E_. pacifica's distribution. However, differences between the areas were such that there may be some limitation of free passage of specimens between Indian Arm and the Strait of Georgia as a result of theaaction of the 'other' properties. At the same time i t is not d i f f i c u l t to see how a species which was less tolerant to changes i n 'other' properties could be limited in i t s distribution of occurrences by the observed distribution of the 'other' properties either in the Strait of Georgia or between Indian Arm and the Strait of Georgia. The results of the present study indicate that the effect of 'other' properties on the distribution of planktonic animals may be greater, and the effect of temperature and -104-salinity less than has been previously considered (Kinne, 1964)., A deeper insight into the ecology of plankton animals would seem to await a greater knowledge of 'other' properties and their effects on zooplanktonic organisms. - 1 0 5 -VIII. SUMMARY AND CONCLUSIONS. Temperature and salinity and other unidentified properties have been suggested asffactors acting to limit the distribution of planktonic organisms through the stresses they impose. The objective of this study was to examine experimentally the effects of stress on the respiration of E. pacifica. Both immediate and long term effects were examined by means of acute measurements of the effects of the property(ies) in question on specimens from populations of E) pacifica resident in areas that differed, or could be presumed to d i f f e r , with respect to the property(ies) under investigation. The f i r s t properties whose effects were investigated were temperature and salini t y ; not only can these properties be measured in the f i e l d , but they can also be readily manipulated in the laboratory. At the same time waters differing in their characteristic values of temperature and salinity and having resident populations of IS. pacifica were available for s tudy. The results of the experiments using specimens of E. pacifica resident in oceanic, mixed oceanic-coastal, and coastal waters show that large, and consistent differences occur in j their tolerances of changes in the temperature and salinity of their environment. These differences are correlated with the characteristic temperatures and s a l i n i t i e s of the waters in which the animals were li v i n g . Specimens from the warmest and most dilute water (coastal) showed the greatest tolerances to changes in temperature and s a l i n i t y ; animals from the cooler -106-and less dilute oceanic water had the least tolerance. Specimens from mixed oceanic-coastal water possess tolerances intermediate between those of the above groups. These results suggest that the long term effects of liv i n g i n environments which demonstrate progressively greater "changes in temperature and salinity has been to expand the tolerances of specimens living in the more variable environments; the three populations of _E. pacifica employed in this study may constitute separate physiological races of E_. pacifica. The results of the investigation into the acute effects of changed temperature and salinity demonstrated that a sharp reduction in respiratory rate could be used as an indication of stress. At the same time, the results of these experiments showed that as the values of temperature and salinity approach the limits of tolerance the effects of stress from these sources interact. Experiments taking advantage of the interaction between the effects of temperature and salin i t y were used to establish that differences in the non-measurable, 'other' properties between sea waters could impose additional stress on adult E_. pacifica. At the same time a simple method of assessing the effects of differences in 'other'pproperties between sea waters through a comparison of respiratory rates obtained i n a number of sea waters under standard experimental conditions was developed. The experiment designed to investigate the long term effects of changes in 'other' properties of sea water used sea water and specimens of E_. pacifica from two areas, Indian Arm -107-and the Strait of Georgia. The reactions of these two groups of specimens to water from two depths in each area was observed over a period of 14 months. The results of the survey indicated that the 'other' properties of a given sea water appeared to depend on the origin of the water; changes in the distribution with time and with depth of 'other' properties are correlated with changes in oceanographic conditions. The equally close correlation of the results of enrichment studies using trace elements suggest that observed changes in 'other' properties may be related to changes in the trace element content of the sea waters. There were opposite reactions of E_. pacifica from the Strait of Georgia and from Indian Arm to two waters that can be inferred to have different trace element contents. This inference suggests that E_. pacifica resident in Indian Arm may be adapted to a lower concentration of trace elements than E_. pacifica resident i n the Strait of Georgia. In neither Indian Arm nor in the Strait of Georgia is there any evidence to show that differences i n 'other' properties (possibly the concentration of trace elements) as shown by this study affects the distribution of E. pacifica. The results of this study do not, however, rule out the possibility that free passage of specimens of E. pacifica between Indian Arm and the Strait of Georgia might be limited by differences in 'other' properties between the areas. - 108-Th e results of this study show that changes in temperature, sa l i n i t y , and 'other' properties can a l l exert stress on adult E_. pacifica; animals from areas that differ with respect to the various properties have been shown to adapt to those differences. It is also indicated that the animals are reacting to the sum of a l l stresses imposed on them. A better under-standing of the ecology of marine zooplanktonic organisms w i l l have to involve identifying and elucidating the mode of action of what have been loosely called 'other' properties in the course of this study. -109-IX. REFERENCES ALDERDICE, D.F. 1963. 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U.K., 41: 663-680. WOHLSCHLAG, D.E. and J.N. CAMERON, 1957. Assessment of a low level stress on the respiratory metabolism of the pinfish (Lagodon rhomboides). Contrib. mar. Sci. Univ. Texas, 12: 160-171. 115 APPENDIX 1 RESPIRATION RATES OBTAINED FOR SPECIMENS OF EUPHAUSIA PACIFICA DURING THE COURSE OF THE EXPERIMENTAL PROGRAM. Respirationcrates obtained under a v a r i e t y of conditions of temperature and s a l i n i t y for specimens captured at Stn. Pac.-l i n February 1969. S a l i n i t y Temperature 5°CZ 10°C 15°C d d d d d d Zl%<, d d d d d d d d d 0.758 1.823 1.822 1.291 1.117 2.151 24&> 0.906 1.526 d 1.147 0.985 d. 0.776 d rid 1.298 1.885 2.740 2.146 1.768 3.240 Zl%o 1.145 2.281 1.383 1.220 2.161 1.973 1.456 0.869 . 1.528 1.016 1. I l l 34& 1.139 1.029 0.686 1.518 1.182 1.171 2.362 2.089 1.438 1.347 2.916 1.986 1.155 Respiration rates obtained under the above', conditions of temperature and s a l i n i t y f o r specimens captured at Stn. Pac.-l i n June 1969. d d d d d d lit, d d d d d d d d d 1.154 1.217 24&> 0.934 0.569 0.852 1.015 1.350 1.686 1.288 1.425 1.353 1.516 1.574 1. 965 1.669 * specimen died i n acclimation 116 Iff™ 5°C 10°C 15°C 1.624 1.254 1.771 0.945 2.137 2.013 1.076 1.727 1.591 1.270 1.864 1.844 1.592 1.027 2.088 1.016 1.610 2.013 1.162 1.172 1.856 1.251 2.149 3.102 1.338 2.075 1.404 2.206 1.756 2.267 Respiration rates obtained underaa variety of conditions of temperature and salinity using specimens captured at Stn. J.F.-9 in November 1968. 0.568 0.881 d 0.262 0.741 d 21& 0.342 0.730 d 0.389 0.444 d 0.326 0.498 d 0.453 0.533 1.505 0.592 0.752 1.139 24l 0.463 0.629 1.379 0.748 0.911 1.425 0.541 0.527 1.162 0.697 1.688 0.993 ZTfoo 0.645 1.086 1.270 0.269 1.405 1.656 0.514 0.800 0.922 0.559 0.801 1.126 0.585 0.645 1.024 3lto 0.592 0.909 0.766 0.473 1.134 1.272 0.427 0.872 1.442 0.567 0.999 1.334 0.573 0.898 1.549 3$o 0.865 0.782 1.529 0.950 0.584 1.570 1.190 0.813 0.969 Respiration rates obtained under the above conditions < and salinity for specimens captured at Stn. J.F.-9 in , 0.382 0.582 d 0.652 0.542 d d d d d d d d d d 117 5°C 0.364 0.797 24& 0.955 0.689 1.375 10°C 1.218 1.203 1.431 1.308 1.057 15°C 1.551 1.459 1.962 0.964 d 27& 1.017 1.091 0.966 0.973 0.788 3l%o 0.951 0.574 0.708 1.536 1.253 1.134 1.286 0.811 1.047 1.274 1.505 1.229 1.486 1.234 0.708 1.659 2.139 0.995 1.223 1.778 1.461 1.584 1.284 1.279 1.300 1.184 1.683 1.370 1.027 1.672 1.361 0.825 0.766 1.274 1.731 0.985 2.342 2.054 1.621 2.022 Respiration rates obtained under a variety of conditions of temperature and salinity using specimens captured at Stn. SAA.-4 in February 1969. 1.133 1.633 1.954 0.739 1.630 3.421 21& 0.723 1.906 3.108 0.729 1.223 2.960 0.830 1.339 2.720 0.898 2.034 3.811 2.291 1.317 4.348 27& 0.847 1.663 4.104 1.309 1.381 3.403 0.542 1.997 2.682 1.357 0.987 6.703 1.645 2.341 3.085 30l 0.813 1.120 4.785 1.539 1.527 3.893 1.338 1.590 3.498 118 Respiration rates obtained under the above conditions and salinity for specimens captured at Stn. SAA.-4 in . 5°C 10°C 15°C 1.027 0.650 1.090 0.859 1.665 1.708 0.830 1.246 1.542 0.693 1.439 1.661 0.860 1.154 1.800 1.424 2.270 0.934 0.978 1.179 2.087 1.152 1.273 1.866 0.826 2.173 2.416 1.246 2.056 1.825 1.508 2.602 2.432 1.965 1.742 2.321 3 (Zoo 1.963 2.257 23394 0.598 1.908 1.226 1.193 2.636 2.823 Respiration rates obtained under a variety of conditions of temperature and salinity in four different sea waters using specimens captured at Stn. G.S.-l, May 1969. water f u l l strength sea water d i l -sea water uted to ZlXo measurements at 10°C G.S. upper 1.744 1.807 (GSU) 2.382 1.268 1.830 1.361 1.665 1.934 1.488 1.593 G.S. lower 1.730 3.673 (GSL) 1.495 1.410 1.281 1.698 1.495 3.207 1.469 1.807 I.A. upper 1.169 1.162 (IAU) 2.331 1.683 3.288 1.221 2.088 2.061 3.018 1.635 119 f u l l strength sea water d i l -sea water uted to Zlto I. A. lower 2.080 1.344 (IAL) 2.151 1.986 2.821 1.809 2.126 1.979 1.674 1.778 measurments at 15°C GSU 1.688 2.304 2.139 2.089 3.043 3.331 2.935 2.396 1.766 2.228 GSL 2.778 1.674 2.863 2.378 2.479 2.780 2.683 2.899 2.708 2.802 IAU 3.922 1.814 3.014 1.833 3.960 1.956 2.683 1.855 3.655 1.875 IAL 2.029 2.271 2.820 2.039 d 1.976 d 2.010 d 1.717 Respiration rates obtained under a variety of conditions of temperature and salinity in five different sea waters using specimens captured at Stn. G.S.-l, July 1969. water f u l l strength sea water d i l - sea water d i l -sea water uted to 2l%o uted to 1$4 measurements at 10°C GSU 1.936 1.347 d 1.924 1.759 d 1.665 1.266 d 2.592 1.388 d 1.504 1.427 d 120 f u l l strength sea water d i l - sea water d i l -sea water uted to Zl%0 uted to GSL 1.987 1.448 d 1.656 1.725 d 1.599 d d 1.958 d d 1.681 d d IAU 2.397 0.995 1.335 2.028 1.532 d 2.062 1.311 d 1.624 1.871 d 2.580 1.528 d IAL 2.092 2.057 d 1.471 1.734 d 2.310 1.361 d 1.444 1.412 d 2.262 1.526 d J.F. 250* 2.399 1.620 1.518 1.949 1.508 d 1.779 1.479 dd 2.309 1.897 d 2.109 1.445 d measurements made at 15°C GSU 3.096 1.800 d 2.976 d d 3.242 d d 2.646 d d 2.456 d d GSL 2.422 2.036 d 1.587 d d 1.954 d d 1.719 d d 2.148 d d IAU 3.425 2.724 d 3.806 2.155 d 2.500 2.124 d 3.200 2.616 d 2.222 d d IAL 1.978 1.690 d 2.486 2.832 d 3.067 3.045 d 4.389 2.419 d 3.423 d d * water collected at a depth of 250m at Stn. J.F.-9. 121 f u l l strength sea water d i l - sea water d i l -sea water uted to 21%o uted to 18&> J.F. 250 1.990 2.130 d 2.232 1.988 d 2.929 d d 3.098 d d 3.139 d d Respiration rates obtained under a variety of conditions of temperature and salinity in four different sea waters using specimens captured at Stn. G.S.-l, August 1969. water f u l l strength sea water d i l -sea water uted to 21^ o GSU GSL IAU IAL GSU measurements made at 10°C 1.793 1.885 1.799 1.852 1.857 2.251 1.657 1.837 2.256 1.868 2.880 1.431 1.554 1.893 2.063 1.724 2.584 1.918 2.270 1.741 2.312 1.924 1.488 1.073 2.168 1.223 1.793 1.626 1.940 1.518 1.605 1.295 1.839 0.969 1.677 2.052 2.322 1.820 1.860 1.617 measurements made at 15°C 1.393 2.348 1.571 1.511 2.486 2.576 2.138 2.165 2.046 3.451 122 f u l l strength sea water d i l -sea water uted to ZlXo GSL 3.074 3.567 2.402 2.228 2.070 3.209 2.684 2.405 3.434 d IAU 1.685 3.747 1.692 4.081 2.787 d 2.079 d 3.188 d IAL 1.933 1.367 2.403 2.075 1.930 2.817 3.152 2.512 3.079 4.555 measurements made at 20°C GSU 3.197 2.190 2.910 d 2.857 d 3.094 d 2.512 d GSL 2.805 d 2.901 d 2.584 d 2.856 d 3.135 d IAU d d d d d d d d . d d IAL d d d d d d d . d d d Respiration rates obtained for specimens from Indian Arm i n f u l l strength sea water c o l l e c t e d from two depths i n each of the S t r a i t of Georgia and Indian Arm, A p r i l 1968 to September 1969. 123 month IAU A p r i l 1968 1.780 1.602 1.482 1.528 2.106 May 1968 no data f o r June 1968 J u l y 1968 1.135 1.442 0.770 August 1968 0.878 0.653 0.770 0.850 0.680 September 1968 1.409 1.803 1.293 1.175 1.366 October 1968 0.930 0.533 1.154 0.632 0.863 November 1968 1.563 1.139 0.530 0.795 1.007 December 1968 0.858 1.016 0.911 1.011 0.975 January 1969 0.938 1.148 1.072 1.132 0.928 IAL GSU GSL 1.700 1.184 2.550 1.544 1.841 1.832. 1.918 2.202 2.351 1.952 2.088 1.453 2.060 1.956 2.183 2.955 2.160 2.246 2.890 1.814 1.566 2.107 1.683 2.201 2.837 1.092 1.483 1.356 1.287 1.441 1.502 0.807 0.792 1.562 1.426 1.456 1.401 1.173 1.229 1.443 1.120 1.250 1.610 1.862 2.024 1.124 1.174 0.733 1.197 1.298 1.308 0.991 0.713 0.789 1.496 1.432 2.190 1.530 0.839 0.970 0.850 0.730 0.611 0.766 1.303 0.779 0.822 1.239 0.617 0.715 0.679 0.780 0.768 0.795 1.078 1.161 0.696 1.127 0.743 1.071 1.398 0.939 0.895 0.864 0.919 0.805 0.925 0.875 1.003 0.643 0.802 0.886 0.785 0.643 0.787 0.645 0.596 0.861 0.612 0.773 0.885 1.143 0.564 1.182 1.888 0.952 1.463 1.721 1.391 1.626 0.944 1.118 0.838 1.840 0.968 1.056 1.194 1.107 124 month February 1969 March 1969 A p r i l 1969 May 1969' June 1969 July 1969 August 1969 September 1969 IAU IAL 1.602 1.122 2.028 1.615 1.076 1.272 1.740 1.271 1.522 1.740 1.505 1.502 1.676 1.552 2.196 2.225 1.421 1.641 2.515 1.998 1.563 2.093 1.015 2.174 1.568 2.592 0.900 0.646 1.662 0.802 1.514 1.409 1.052 1.837 1.878 1.431 2.321 1.573 2.183 1.324 1.742 1.468 1.483 1.545 2.339 1.320 1.492 1.699 1.467 0.983 2.230 1. 943 1.910 2.027. 1.981 2.043 1.724 2.233 2.001 1.993 1.574 1.306 1.479 1.448 1.505 1.873 2.122 1.328 1.831 1.995 1.560 1.536 1.696 1.682 1.938 2.063 1.768 1.876 1.988 1.973 GSU GSL 2.098 1.285 1.196 1.154 1.765 1.280 1.901 1.466 1.809 1.688 .1.752-- 1.322 1.682 1.420 2.037 1.098 1.429 1.280 1.725 1.311 1.623 1.367 2.024 1.616 2.265 1.044 1.089 1.375 1.750 1.439 1.559 1.890 1.578 1.713 2.043 1.683 1.603 1.229 1.232 1.629 1.301 1.542 1.182 1.198 1.422 1.234 0.977 1.799 1.139 2.023 1.772 0.774 1.471 2.396 1.778 2.508 1.674 1.893 1.667 1.903 1.310 1.684 1.212 l.Z©0 1.732 1.677 1.600 • 1.843 1.463 1.661 1.581 1.539 2.052 1.712 1.501 1.538 1.523 1.162 1.827 1.522 125 Respiration rates obtained for specimens from the Strait of Georgia in f u l l strength sea water collected from two depths in each of Indian Arm and the Strait of Georg ;ia, April 1968 to September month IAU IAL GSU GSL April 1968 1.770 2.115 2.243 1.770 1.913 1.202 2.178 1.318 2.239 2.610 May 1968 1.857 1.102 2.890 1.460 1.721 1.849 1.888 1.219 June 1968 1.856 1.84*2 1.503 1.562 1.058 1.832 2.502 1.969 1.652 1.600 July 1968 1.738 2.037 0.888 2.170 1.351 1.126 1.417 0.943 1.189 1.389 August 1968 1.130 1.322 1.606 0.802 1.469 1.216 1.257 0.836 1.8632 1.002 1.026 0.843 1.303 1.296 1.277 1.019 1.214 1.100 1.291 0.874 September 1968 1.046 1.325 1.625 1.286 1.289 1.698 1.026 1.470 1.118 1.335 1.455 1.244 1.357 1.530 1.671 1.340 1.274 1.299 1.550 0.878 October. 1968 1.141 1.129 1.462 0.899 1.053 1.107 1.311 1.858 1.667 0.535 0.955 1.798 0.966 0.814 0.846 0.795 1.268 1.129 1.088 1.187 November 1968 1.439 1.064 1.048 1.080 0.648 0.791 0.740 0.788 0.793 1.185 0.922 0.934 1.028 0.880 0.891 0.920 0.976 0.979 1.006 0.850 126 month IAU IAL GSU GSL December 1968 0. 643 0. 542 1. 243 1. 087 0. 388 0. 628 1. 289 1. 081 0. 451 0. 709 0. 572 1. 070 0. 651 0. 709 0. 712 0. 963 0. 415 0. 323 0. 660 1. 361 January 1969 1. 045 0. 719 1. 229 0. 780 0. 882 0. 845 0. 892 0. 810 1. 071 0. 962 0. 996 1. 264 0. 732 0. 949 0. 904 1. 483 0. 968 0. 609 0. 958 1. 721 February 1969 1. 313 1. 072 2. 303 1. 165 1. 530 2. 588 1. 397 1. 995 1. 391 1. 381 1. 908 1. 646 1. 912 1. 430 1. 809 1. 565 1. 536 1. 616 1. 856 1. 366 no data for March 1969 April 1969 1. 175 2. 881 2. 077 1. 308 1. 628 2. 284 1. 865 1. 356 0. 843 1. 359 1. 131 2. 033 0. 754 1. 433 1. 823 1. 501 1. 239 1. 989 1. 009 1. 302 May 1969 1. 679 2. 080 1. 744 1. 730 2. 331 2. 151 1. 819 1. 493 3. 288 2. 821 2. 382 1. 281 2. 088 2. 126 1. 665 1. 495 3. 018 1. 674 1. 488 1. 465 June 1969 2. 257 1. 541 1. 757 1. 304 1. 729 1. 564 2. 458 1. 741 1. 340 1. 563 1. 394 1. 398 ' 2. 596 l . , 971. 977 1. 876 1. 610 1. 637 1. 962 2. 644 0. 963 July 1969 2. 397 20092 1. 936 1. 987 2. 028 1. 471 1. 924 1. 656 2. 062 2. 310 1. 665 1. 599 1. 624 1. 444 2. 592 1. 958 2. 580 2. ?,62 1. 504 1. 681 August 1969 1. 946 1. 605 1. 793 2. 880 2. 312 1. 839 1. 799 1. 554 1. 488 1. 860 1. 857 2. 063 2. 168 1. 677 1. 657 2. 584 1. 7 93 2. 322 2. 256 2. 270 September 1969 1. 931 2. 058 1. 592 2. 381 1. 716 2. 609 1. 346 1. 659 1. 759 2. 694 1. 622 2. 195 1. 672 1. 695 1. 868 2. 201 1. 718 1. 792 1. 607 2. 424 

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