Group Title: Growth, reproduction and survival of some marine copepods subjected to thermal and mechanical stress /
Title: Growth, reproduction and survival of some marine copepods subjected to thermal and mechanical stress
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Title: Growth, reproduction and survival of some marine copepods subjected to thermal and mechanical stress
Physical Description: xii, 339 leaves : ill. ; 28 cm.
Language: English
Creator: Alden, Raymond W
Publication Date: 1976
Copyright Date: 1976
 Subjects
Subject: Copepoda   ( lcsh )
Zoology thesis Ph. D
Dissertations, Academic -- Zoology -- UF
Genre: bibliography   ( marcgt )
non-fiction   ( marcgt )
 Notes
Thesis: Thesis--University of Florida.
Bibliography: Bibliography: leaves 333-338.
Additional Physical Form: Also available on World Wide Web
General Note: Typescript.
General Note: Vita.
Statement of Responsibility: by Raymond William Alden III.
 Record Information
Bibliographic ID: UF00097496
Volume ID: VID00001
Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
Resource Identifier: alephbibnum - 000172566
oclc - 02975366
notis - AAT9004

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GROWTH, REPRODUCTION AND SURVIVAL
OF SOME MARINE COPEPODS SUBJECTED TO THERMAL
AND MECHANICAL STRESS






By




RAYMOND WILLIAM ALDEN Ill


A DISSERTATION PRESENTED TO THE GRADUATE
COUNCIL OF THE UNIVERSITY OF FLORIDA IN PARTIAL
FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY


UNIVERSITY OF FLORIDA
1976












ACKNOWLEDGMENTS


It is impossible to acknowledge individually all the staff members,

fellow students and friends who contributed in one way or another to

the successful completion of this research.

I would like to express my sincere appreciation to Dr. Frank J. 5.

Mature, Jr. for his enthusiasm, criticism and able direction during

the research and the writing of this manuscript. I am also obliged to

Dr. Frank Nordlie and Dr. Jackson Fox for their critical and editorial

review of this manuscript.

Special thanks are due to Mr. William Ingram who provided

invaluable assistance with the statistical analysis and computer

programming; and to Mr. Richard Drew who diligently shared in the

field work despite often adverse conditions.

Gratitude is expressed to Dr. Paul Hargraves of the University of

Rhode Island and to Mr. Donald Wilson of the Naval Research

Laboratories for providing the various algae cultures used during the

course of the study.

Would especially like to thank my wife, Becky, for her unending

patience, and the help and inspiration she provided during the research

and the preparation of the manuscript.

This study was supported by a research grant from the Florida

Power Corporation, through the University of Florida Marine Laboratory.

The computing facilities and analysis packages utilized were supplied

by the Center for Instructional and Research Computing Activities

(CIRCA) of the University of Florida.











TABLE OF CONTENTS


SECTION


ACKNOWLEDGMENTS.


LIST OF TABLES

LIST OF FIGURES.

ABSTRACT

I. INTRODUCTION

II. METHODS AND MATERIALS.

Field Studies.

Description of Field Site.

Experimental Design

Laboratory Studies

Growth Studies.

Reproduction Studies

Analysis of Long-Term Survil

II I. RESULTS

Field Studies

Acart la tonsa.

Oithona spp.

Paracalanus crassirostris

Euterpina acutifrons

Pseudodiaptomus coronatus

Labidocera spp.

Tortanus setacaudatus

Total Copepod Population


: : : : : I I










































































. . 296


333


Appendix C Survivorship Curves ..


REFERENCES . . .- - -


SECTION


Laboratory Studies

Growth Studies of Acartia tonsa

Growth Studies of Oithona brevicornis.

Reproductive Studies of Acartia tonsa

Long-Term Survival of Acartia tonsa
Juveniles.


Long-Term Survival of Oithana
brevicornis Juveniles.


Long-Term Survival of Acartia tonsa
Adults . . . . . . .

IV. DISCUSSION ... ..

Field Studies . . .. . .

Copepod Species of the Crystal River
Area . . .. . .

Factors Involved in Entrainment


. .


.

.

.



.



.


135

142

142



142



149

160

170

170

176


180


Mortality ..


Biological and Ecological

Laboratory Studies .....

Effects of Entrainment on

Effects of Entrainment on

Effects of Entrainment on
Survival . . .

V. SUMMARY AND CONCLUSIONS .....

Appendices ......

Appendix A Grow~th Curves

Appendix B Population Age


Impl ications ....




Growth . . . .


Reproduction ....

Long-Term


. . 182

. . 187

. . 188


Structure


Histog rams












LIST OF TABLES


TABLE PAGE


1. Comparison of the Growth Rates of Intake and
Discharge Acartia tonsa Juveniles .. .. .. .. 109

2. Comparison of the Growth Rates of Intake and
Discharge Oithona brevicornis Juveniles .. .. .. 121

3. Comparison of the Mortality Rates of Intake and
Discharge Acartia tonsa Juveniles . .. .. . .. 134

4. Comparison of the Mortality Rates of Intake and
Discharge Oithona brevicornis Juveniles . .. .. .. 136

5. Comparison of the Mortality Rates of Intake and
Discharge Acartia tonsa Adults . . . ... 137

6. Average Percent Mortality/Day Calculated for
Acartia tonsa Adults in Reproductive Experiments .. 138
















FIGURE PAGE


1. Seasonal variation in temperature in intake and
discharge canals of the Crystal River power
generating plant .. . .. .... .. 6

2. Seasonal variation in salinity in intake and
discharge canals of the Crystal River power
generating plant . .. ... . .. 7

3. Schematic diagram of study site indicating
designation and purpose of experimental field
treatments. . . .. ... . .. 11

4. Seasonal variation in numbers of Acartia tonsa . .. 22

5. Seasonal variation in percent of total copepod
population represented by Acartia tonsa . ... .. 23

6. Seasonal variation in mortality of Acartia tonsa
exposed to treatment IDO .. .. .. ... . .. 25

7. Seasonal variation in mortality of Acartia tonsa
exposed to treatment ID2 .. . .. .. .. 26

8. Seasonal variation in mortality of Acartia tonsa
exposed to treatment DSO .. .. . .. .. . 27

9. Seasonal variation in mortality of Acartia tonsa
exposed to treatment DS2 .. .. . . . .. 29

10. Entrainment mortality as a function of discharge
temperature .... . .. . . 31

11. Response surface estimates of mortality as a
function of discharge temperature and salinity
for populations of Acartia tonsa exposed to
various conditions ... .. .. . 35

12. Seasonal variation in numbers of Oithona spp. .. .. 37

13. Seasonal variation in percent of total copepod
population represented by Oithona spp. . .. .. 39

14. Seasonal variation in mortality of Oithana spp.
exposed to treatment 100 .. .. .... .~ 40


LIST OF FIGURES









FIGURE PAGE


15. seasonal variation in mortality of Oithona spp.
exposed to treatment ID2 . .. .. .. .. . 41

16. Seasonal variation in mortality of Oithona spp.
exposed to treatment DSO . . . .. 42

17. Seasonal variation in mortality of Oithona spp.
exposed to treatment DS2 . . . .. ... 44

18. Response surface estimates of mortality as a
function of discharge temperature and salinity
for populations of Oithona spp. exposed to
various conditions ..... .... . .. 46

19. Seasonal variation in numbers of Paracalanus
crassirostris .. .. .. . 48

20. Seasonal variation in percent of total copepod
population represented by Paracalanus
crassirostris .. .. . .. . . 49

21. Seasonal variation in mortality of Paracalanus
crassirostris exposed to treatment 100 . . . . 50

22. Seasonal variation in mortality of Paracalanus
crassirostris exposed to treatment ID2 . .. . 52

23. Seasonal variation in mortality of Paracalanus
crassirostris exposed to treatment DSO . . . . 53

24. Seasonal variation in mortality of Paracalanus
crassirostris exposed to treatment DS2 . . . 54

25. Response surface estimates of mortality as a
function of discharge temperature and salinity
For populations of Paracalanus crassirostris
exposed to various conditions .. . . . 56

26. Response surface estimates of mortality as a
function of discharge temperature and salinity
for entrainment populations at different
densities .. . 60

27. seasonal variation in numbers of Euterpina
acutifrons .. 61

28. Seasonal variation in percent of total copepod
population represented by Euterpina acutifrons 2

29. Seasonal variation in mortal ity of Euterpina
acutifrons exposed to treatment 10 .. 64









FIGURE PAGE


30. Seasonal variation in mortality of Euterpina
acutifrons exposed to treatment ID2 .. ... .. 65

31. Seasonal variation in mortality of Euterpina
acutifrons exposed to treatment DSO ....... 66

32. Seasonal variation in mortality of Euterpina
acutifrons exposed to treatment DS2 .. .. .. .. 67

33. Response surface estimates of mortality as a
function of discharge temperature and salinity
for populations of Euterpina acutifrons
exposed to various conditions .. .. . .. .. 69

34. Seasonal variation in numbers of Pseudodiaptomus
coronatus .. .. .. ... . .... .. 72

35. Seasonal variation in percent of total copepod
population represented by Pseudodiaptomus
coronatus . .. . .... . . ... . 73

36. Seasonal variation in mortality of Pseudodiaptomus
coronatus exposed to treatment 100 .. ... .. 75

37. Seasonal variation in mortality of Pseudodiaptomus
coronatus exposed to treatment ID2 ... .. .. 76

38. Seasonal variation in mortality of Pseudodiaptomus
coronatus exposed to treatment DSO .. ... .. 77

39. Seasonal variation in mortality of Pseudodiaptomus
coronatus exposed to treatment DS2 ........ 78

40. Seasonal variation in numbers of Labidocera spp. .. 81

41. Seasonal variation in percent of total copepod
population represented by Labidacera spp. .. .. 82

42. Seasonal variation in mortality of Labidocera spp.
exposed to treatment 100 .. .. .. . . . 83

43. Seasonal variation in mortality of Labidocera spp.
exposed to treatment ID2 . .. .. .. .. 84

44. Seasonal variation in mortality of Labidocera spp.
exposed to treatment DSO . ... . .. . 85

45. Seasonal variation in mortality of Labidocera spp.
exposed to treatment DS2 . . .. .. .. .. .. 87








FIGURE


PAGE


46. Seasonal variation in numbers of Tortanus
setacaudatus . . . . 88

47. Seasonal variation in percent of total copepod
population represented by Tortanus setacaudatus . .. 90

48. Seasonal variation in mortality of Tortanus
setacaudatus exposed to treatment 100 . .. .. 91

49. Seasonal variation in mortality of Tortanus
setacaudatus exposed to treatment ID2 .. . ... 92

50. Seasonal variation in mortality of Tortanus
setacaudatus exposed to treatment DSO .. .. .. 93

51. Seasonal variation in mortality of Tortanus
setacaudatus exposed to treatment DS2 .. .. .. 94

52. Seasonal variation in numbers of the total
copepod population .... .... .. . 96

53. Seasonal variation in mortality of the total
copepod population exposed to treatment 100 . ... 98

54. Seasonal variation in mortality of the total
copepod population exposed to treatment ID2 .. .. 99

55. Seasonal variation in mortality of the total
copepod population exposed to treatment DSO .. .. 100

56. Seasonal variation in mortality of the total
copepod population exposed to treatment DS2 .. . 101

57. Response surface estimates of mortality as a
function of discharge temperature and salinity
for the total copepod population exposed to
various conditions . .. .. .. 104

58. Seasonal variation in numbers of early instars
of Acartia tonsa found in samples at the
beginning of growth experiments .. . . .. 106

59. Seasonal variation in growth rates of intake and
discharge populations of Acartia tonsa .. .. .. 108

60. Growth rate ratio of Acartia tonsa as a function
of discharge temperature . . . ... . 112

61. Histogram series for Acartia tonsa in growth
experiment started on September 3, 1974, showing
changes in population structure with time . .. .. 114









FIGURE


PAGE


62. Seasonal variation in numbers of early instars
of Oithone brevicornis found in samples at the
beginning of growth experiments . . . .. . 117

63. Seasonal variation in growth rates of intake
and discharge populations of Oithona brevicornis .. 119

64. Growth rate ratio of Oithona brevicornis as a
function of discharge temperature . ... . .. 123

65. Histogram series for Oithona brevicornis in
growth experiments started on August 20, 1974.
showing changes in population structure
with .time .. ... . . .. 125

66. Seasonal variation in reproductive rate for
intake and discharge populations of Acartia tonsa . 129

67. Reproductive rate ratio of Acartia tonsa as a
function of discharge temperature .. ... .. 133

68. Mortality rate of Acartia tonsa adults as a
function of culturing temperature . . .. 141











Abstract of Dissertation Presented to the Graduate Council
of the University of Florida in Partial Fulfillment of the Requirements
for the Degree of Doctor of Philosophy


GROWTH, REPRODUCTION AND SURVIVAL OF 50ME MARINE COPEPODS
SUBJECTED TO THERMAL AND MECHANICAL STRESS



Raymond William Alden Ill

March, 1976

Chairman: Frank J. S. Mature, Jr.
Major Department: Zoology

A study was made of the lethal and sublethal effects of power

plant entrainment and thermal stress on the copepods of the Crystal

River estuary on the west coast of Florida. The important copepod

species that were observed for entrainment mortality listed in order

of abundance were Oithona spp., Acartia tonsa, Paracalanus

crassirostris, Euterpina acutifrons, Pseudodiaptomus coronatus,

Tortanus setacaudatus and Labidocera spp. Experimental field treat-

ments employing circulating system drift bottlee devices were set up to

test the relationships between entrainment mortality and such variables

as temperature, salinity, length of exposure to the heated effluent,

mechanical damage, seasonal factors, density (numbers/m ) and sex or

age class of the various species. Temperature, salinity, and

temperature-salinity interactions were seen to be among the most

important factors influencing mortality. Under conditions of low

temperature and moderate salinities, mechanical damage was the major

lethal entrainm~ent effect for mo~st species, but produced relatively

low mortal ities compared to those found with other temperature-salini ty








regimes. Each species had unique response patterns to temperature-

salinity effects, as well as to combinations of other variables, but

virtually all exhibited rapidly increasing mortalities as temperatures

rose above 350C

Laboratory studies were carried out to observe the subtler biolo-

gical aspects of entrainment and thermal stress: the effects on

reproduction of copepods surviving entrainment; the effects on growth

of entrained juveniles; and the long-term effects occurring over a

period of time following entrainment. Sublethal entrainment effects

were negligible until summer conditions caused discharge waters to rise

above 350C. Above this temperature, fecundity rates declined and

growth rates of juveniles dropped below those of control populations.

Long-term mortality rates of copepods surviving entrainment were not

significantly different from those of controls, although the mortality

rates of both populations were shown to be accelerated by increasing

culture temperatures.

Possible biological and ecological implications of entrainment

and thermal stress are discussed in light of the findings of the

present study.















SECTION

INTRODUCTION


The important role of copepods in the sea has been long recognized.

These holoplankters dominate the zooplankton in most estuarine and

marine environments and play the principal "middle man" in the transfer

of energy from primary producers to higher trophic levels (Clarke and

Gellis, 1935). The importance of these organisms is especially

apparent in estuaries, where ecological adaptations allow certain

species to utilize the energy from these nutrient-rich ecosystems to

form blooms of vast numbers. Migrating species of higher trophic

levels make efficient use of this food supply by utilizing estuaries

as breeding and nursery areas. It has been repeatedly demonstrated

that copepods play the major food item for most of the young and at

least some adult fishes (Grice, 1957).

The vital role that copepods play in the functioning of estuarine

ecosystems makes the knowledge of the biological responses of these

organisms to environmental factors extremely important. Both drastic

and subtle responses to environmental changes may affect the survival,

distribution, and productivity that make the copepods so important to

the system. The ability to predict the biological reaction of

important copepod species to environmental stress, either natural or

man-made, may be the first step in the effective management of food

chains that support a sizable portion of the world's fisheries.








Planktonic organisms are subjected to many environmental stresses

that may be actively avoided by the nekton as well as many benthic

animals. It is for this reason that much interest has been focused

on the resistance of the planktonic forms to such factors as thermal

stress (Strickland, 1969). Recently, studies in this area have shown

a trend away from the univariate analysis of temperature tolerance and

towards a multiple factor approach. Interactions of temperature with

such factors as salinity, dissolved oxYgen and duration of exposure

have been seen, under many conditions, to be as important in shaping

the tolerance pattern of a species as the primary response to tempera-

ture (Alderdice, 1972). Laboratory studies have been performed in an

attempt to define the effects of such interactions on the thermal

tolerance levels of planktonic larvae of crustaceans (Costiow et al.,

1960, 1962, 1966), molluscs (Kennedy et al., 1974; and Lough, 1975),

and fishes (Alderdice, 1963; and Alderdice and Forrester, 1968). These

studies have utilized multiple regression analysis and response surface

techniques to define the tolerance patterns of the experimental

organisms to various environmental factors. The methodology of such

an approach has been reviewed and the biological applications discussed

in detail by Alderdice (1972).

A related area of study, prompted by growing concern over indus-

trial thermal pollution, is that of the effects of entrainment of

zooplankton in the cooling systems of power generating plants. There

are recent reviews of such entrainment studies by Raney (1973) and

Coutant and PFuderer (1974), as well as the proceedings of a symposium

on the state of the art edited by Jensen (1974). Entrainment studies

usually involve on-site field work, since exact conditions experienced








by organisms pumped through a power plant cannot be artificially

reproduced under laboratory conditions. As a result of the limitation

on experimental design, statistical treatment of entrainment mortality

is generally simpler and less descriptive than that of laboratory

thermal tolerance studies. Zooplankton mortality is usually related

by linear regression analysis to the single independent variable of

discharge temperature (Icanberry and Adams, 1974) or to the combination

of discharge temperature and thermal rise (Davies and Jensen, 1974).

Interactions of environmental factors and entrainment effects of the

type described by response surface methodology, for the most part, have

not been examined by entrainment studies.

Another area that is generally overlooked by entrainment studies

is that of sublethal entrainment effects. Subtle post-entrainment

changes in important processes such as growth, reproduction and long-

term survival could have nearly as significant an effect on the

zooplankton population as immediate mortality (Levin et al., 1972; and

Strickland, 1969). Heinle (1969) studied the effects of entrainment

on growth of copepods and reported a depression in growth rate for the

populations going through the power plant. This indication of signi-

ficant sublethal entrainment effects suggests that all biological

processes that might affect the productivity of a species should

be studied.

The present study was designed to examine lethal and sublethal

effects of entrainment and thermal stress on estuarine copepods. The

investigation can be divided into two basic sections: an experimental

field study designed to analyze the environmental factors that deter-

mine the mortality suffered by entrained species of copepods, and a








laboratory study that was set up to observe subtle post-entrainment

effects on various biological processes. Considered in the field study

of entrainment mortality were such factors as intake and discharge

temperature, salinity, mechanical damage, delayed thermal effects,

seasonal effects, and density, sex and age class of each of the major

species of copepods. These variables were analyzed to observe how

various combinations of factors shaped the response patterns of the

entrained organisms. The laboratory study supplemented this informa-

tion by observing entrainment and thermal effects on the reproduction,

growth and long-term survival of selected species of copepods. The

study was designed not only to assess the impact of a specific power

plant, but also to observe general biological responses of the species

of copepods to thermal stress and the environmental factors that

influence these patterns.














SECTION I I

METHODS AND MATERIALS


Field Studies


Description of Field Site


Research was conducted at the Florida Power Corporation steam

generating plant which is located between the Withlacoochee and Crystal

Rivers on the west coast of Florida. This area represents the typical

shallow water, middle salinity estuary found along the Gulf coast of

the state. Water temperatures generally range annually from 14 to

300C (Figure 1) and salinities range from 17 to 28 ppt. (Figure 2).

Seasonal freshwater runoff from surrounding terrestial and marsh areas

during rainy seasons causes fluctuations in salinity, detrital content,

and organic and inorganic constituents of the water. The spring-fed

rivers of the area, however, provide a constant stabilizing force not

found in many northern estuaries.

The two steam generating units now in operation at Crystal River

have a combined electrical capacity of 897 megawatts and use up to

640,000 gallons of water per minute from the estuary for cooling

purposes. The power plant raises the temperature of the cooling waters

passing through it an average of 5.88 C (Figure 1). This thermal

increase (AT) is quite constant because environmental laws prohibit AT

values above 6-50C and plant operation efficiencies prevent minimum AT

values much below the mean value. Surface salinities are generally


















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-- OISCHARGE


LU
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W
a.

W3
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NOV; DEC JRN FEB MIAR APR NAT JUNI JUL AUG SEP

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Fig. 1. Seasonal variation in water temperature in intake and
discharge canals of the Crystal River power generating
plant.


















































NOV DEC JRNI FEB MAR RPR MATY JUNI JUL AUG SEP

DATE






Fig. 2. Seasonal variation in salinity in intake and discharge
canals of the Crystal River power generating plant.


INTAIKE
--- DISCHARGE


O













CI

V1








raised by 1.12 ppt. (Figure 2) in going through the plant because the

higher salinity oceanic water from the bottom, is mixed with lower

salinity surface waters when the cooling water is taken from the

partially stratified estuary. The heated effluents are channeled away

by a miile-long discharge canal, which takes the water exiting the plant

approximately two hours to traverse during normal operations. During

the passage of the discharge waters down this canal, temperatures

remain relatively unchanged until they are released into the open bay

area of the'estuary.

A proposed nuclear-powered generating unit now under construction

at the Crystal River site will approximately double the electrical

capacity and the maximum flow of cooling water of the power plant. The

new unit is designed to prevent increase in AT values, but will

increase the area of thermal impact due to the larger volume of heated

discharge waters. The numbers of planktonic animals entrained would

also approximately double with the increased demand for cooling waters.



Experimental Design


Copepods were collected utilizing a 64 micron mesh 0-5 meter plank-

ton net fitted with a digital flow meter. Samples were taken biweekly

from intake and discharge areas From November 1973 through September

1974. The number and length of net tows were adjusted so that approxi-

mately equal volumes were sampled from each area and so that the mini-

mum amount of mortality was caused by collection techniques. A pump-

net filtration system based on that described by Icanberry and

Richardson (1973) was tested as a sampling device designed to reduce








collection mortality, but was shown statistically to be avoided by

escape mechanisms of certain types of zooplankters (Maturo et al.,

unpublished data). Thus, the pump system was abandoned for net

collection. Temperature and salinity measurements were taken with a

Beckman salinometer at each area during every sampling period.

Six experimental field treatments were set up to attempt to

separate various factors involved in entrainment mortality (Figure 3).

Two controls were made utilizing copepod populations from the intake

area. The initial control (INO) is a population that has been

collected and analyzed immediately for mortality by vital stain bio-

assay (Dressel et al., 1972). The second intake treatment (IN2)

subjects an intake population to 2 hours of incubation in a circulat-

ing system drift bottle apparatus of the type described by Gonzalez

(1973). This device is placed in the intake waters and the sample,

which is treated for bioassay after the incubation, acts as a control

for the delayed thermal exposure treatments described below.

A third intake population of copepods (100) is brought to the

discharge area, placed in a screened PVC container and submerged in

the heated effluent until it has been brought up to discharge tempera-

tures (approximately 5 minutes). The sample is then treated for blo-

assay and the mortality above control (INO) values are assumed to be

due to the effects of immediate thermal shock. A discharge sample

(DSO) is also assayed immediately for mortality, this population having

undergone the turbulence, shearing forces and mechanical damage asso-

ciated with passage through the condenser system of the power plant.

Since the only difference between the 100 and the DSO populations is

that the latter has been subjected to the mechanical effects of









































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entrainment, the damage caused by the physical factors of plant passage

can be assessed by regression analysis.

Delayed thermal effects associated with the amount of time that

the population spends in the heated effluent of the discharge canal

are also examined. An intake population (ID2) and a discharge popula-

tion (DS2) are placed in a drift-bottle apparatus similar to that used

in the IN2 treatment and are allowed to drift down the length of the

discharge canal for 2 hours. These organisms experience an exposure to

the heated canal waters similar to that experienced by a natural popu-

lation going through the power plant. The ID2 population, however,

has not experienced the mechanical effects of entrainment and might

more closely represent a population entrained into the thermal plume

by tidal recruitment. The results of these treatments allow the

assessment of the delayed thermal effects of entrainment encountered

within the thermal plume.

Samples from each field treatment were preserved in 5% formalin

and kept cold to preserve stain intensity until counts were made

(Dressel et al., 1972). Immediately before counting, the samples were

sieve-fractionated into three size classes by pouring them through a

series of geological sieves (300, 150 and 75 micron mesh) that were

clamped to a "wrist-action" shaker. This method allowed each size

class to be split down separately for counting with a Folsom Plankton

Splitter so that the large, rarer animals were not "lost" in the split-

ting of a sample to countable size. The neutral red stain in the

organisms was "fixed" by titration with an acetic acid-sodium acetate

mixture (SN). This method of acidification to bring out the red

coloration immediately prior to counting was found to be far superior








to that of using acidified formalin during preservation (Dressel

et al., 1972) because the acid tends to cause the neutral red to leach

from the bodies of the copepods, reducing the amount of time that the

samples can be sorted before the stain fades to an undetectable inten-

sity. The samples were counted under a dissecting microscope at 25X

or 50X, depending on size class. The copepods were identified to

species and sex and notations made as to whether they were alive or

dead upon sampling.

Mortality values for the control populations (INO, IN2) were

assumed to be baseline levels and were thus subtracted from those of

the populations that were subjected to the experimental field treat-

ments (100 and DSO, ID2 and DS2) to obtain values For mortality caused

by the various factors associated with entrainment. On those sampling

dates that the experimental population of any given species reached

100%, entrainment-induced mortality was assumed to be 100% and control

values were not subtracted. The entrainment mortality data for each

species subjected to the various field treatments were analyzed by

multiple regression analysis. Predictive regression models for

entrainment mortality under various conditions were formed by the

Stepwise MAXR Regression computer program from the Statistical Analysis

System (SAS) contained in the CIRCA Computing Library at the

University of Florida. The independent variables tested were tempera-

ture, salinity, delayed thermal, mechanical and seasonal effects,

along with effects associated with the sex, age class and density

(numbers/m ) of the species of copepod being observed. Fourth order

temperature and salinity terms were included in the statistical model.

Preliminary regress ions indicated that the increase in the amount of








variation explained (R2) ceased to be significant for terms beyond the

fourth degree. All reasonable interactions between the independent

variables were also tested. The stepwise regression program was of

the type described by Lough (1975) and the predictive model selected

from the sequence was the one that produced the greatest values of R2

for the most parsimonious model. More complex models were observed to

make sure no major increases in R2 values occurred with the addition of

various combinations of variables.

The regression equation for each species was used to plot response

surfaces for various entrainment conditions utilizing the SYMVU three-

dimensional plotter routine from the CIRCA Computing Library. Tempera-

ture and salinity, being the major physical factors, were plotted on

the X and Y axes, while the predicted mortality values were plotted on

the Z axis in the third dimension. All other factors were then varied

one at a time to observe their effects on the response of the species

for the salinity and temperature conditions. The predicted mortality

values were rounded up to the nearest 10% level so that all trends

would be clearly discernable on the graphed surfaces.





Laboratory Studies


Growth Studies


To determine the effects of entrainment on growth of juveniles, a

method modified from that used by Heinle (1969) was employed. During

the biweekly sampling period, juvenile Acartia tons and Oithona

brevicornis, the two dominant copepods of the area, were collected for









the growth experiments. The waters from intake and discharge areas

were bucketed through a 73 micron mesh 0.2 meter diameter plankton net

that was clamped into the mouth of a large, perforated PVC container.

The perforations in the PVC container were screened with 5 micron

filter bag material and the entire apparatus was suspended vertically

in the water during the sampling procedure. Approximately 80 gallons

of water were filtered from each canal by this method, although high

densities of juveniles during the summer months allowed the volume

sampled to be cut in half. The 73 micron net filtered out all but the

smaller naupliar stages, while the PVC container retained and concen-

trated these early istars.

The concentrated samples of juveniles were kept in insulated

containers filled with sea water from the collection areas for trans-

port back to the laboratory. In the laboratory, the intake and dis-

charge samples were each split into eight equal subsamples with a

Folsom Plankton Splitter that had been darkened to prevent phototrophic

clumping on either side of the divider. The subsamples were placed in

culture dishes containing 1 liter of fresh sea water to which had been

added a mixed algal diet. The concentration of this food mixture was

adjusted to give a final concentration in the cultures of 60,000

cells/ml.: 24,000 cells/m1. of Rhodomonas baltica; and 12,000 cells/mi.

each of Isochrysis gaftgga_, Monochrysis lutheri and Thallasiosira

pseudonana. The algae were grown in pure cultures, utilizing Guillard's

f/2 media (Guillard and Rhyther, 1962) and concentrations were deter-

mined by counting fixed cells from a serial dilution in a hemacytometer.

A few drops of a culture of large marine ciliates (probably Euplates

sp.) were routinely added to the food culture before feeding. These








organisms help eliminate excess buildup of bacteria and algal detritus

in the bottom of the culture dishes and provide a secondary food

source for the older stages of the copepods (Zillioux, 1969). The

developing juveniles were further protected from being entangled in

this algal detritus layer by blackening the bottom of the culture

dishes to cause phototrophic attraction away from the area where the

debris settles.

One culture from each population was stained and preserved imme-

diately, while the remaining cultures were kept in an illuminated

B.0.D. box set at intake photoperiod and temperature conditions.

Cultures from each population were then chosen randomly at predeter-

mined time intervals, stained, and preserved. The time interval chosen

depended upon the development time for the particular season: every

other day in winter, and every day in summer when higher temperatures

caused accelerated growth. Remaining cultures were fed every other

day, w~ith the mixed algal diet being added to bring the concentrations

in the culture dishes up to proper levels.

The samples wrere counted under a dissecting microscope at 50X and

the Acartia tonsa and Oithone brevicornis naupl ii and copepodites wrere

identified as to stage of development. The mean stage was then calcu-

lated for each day that a culture was sampled by the following equation:




T:N XN
N

E XNr


N is the mean stage for any given day, N is the stage number up to









the 12th or adult stage and XN is the number of individuals counted in

any stage N.

Growth curves for intake and discharge populations were graphed

for each experiment by plotting mean stage versus day. Linear regres-

sion analysis of the curves produced "B" values or slopes which are

the growth rates for each population of each species. These rates were

then compared with a T-test designed to compare slopes. Thus. the

growth rates of intake and discharge populations for each date were

compared statistically to determine any significant differences due to

the effects of entrainment.

The growth rates for all experiments were plotted against date to

look for any visible trends in divergence among the populations.

Regression analysis was performed to test the relationship of growth

rate to the area from which the juveniles were collected, to the date

on which they wrere collected and to the interaction of these factors.



Reproduction Studies


In order to determine the effects of entrainment on reproduction,

intake and discharge populations of copepods were collected in a 202

micron plankton net and transported to the laboratory in insulated

containers. Male and female Acartia tonsa were sorted out under a

dissecting microscope, utilizing a large bore pipette with a mouth

tube. Generally, females without attached spermatophores were selected

in an attempt to start all cultures at the same point and to test male

fertility. Two males and two females were placed in one-liter

containers of fresh sea water and fed the mixed algal diet every other








day. The cultures were kept in a B.0.D. box set to simulate intake

temperatures and photoperiod for 5 to 7 days. The populations were

then prepared with vital stain and preserved for counting. The adults,

copepodids, nauplii, and eggs from each container were counted under a

dissecting microscope. An eggs/female-day ratio was then computed

from the total reproductive products and the number of living females.

It became apparent that this experimental design was not very

efficient, since all cultures in which a female had died during the

culturing period had to be discarded as it was impossible to ascertain

how many, if any, productive days there were before mortality. A

change in method was therefore made and the cultures were set up as

pair-mating experiments, with a single male and a single female Acartia

tonsa being placed in half liter containers. These cultures were then

observed daily for any mortality. When a female was found dead, the

male was transferred to a fresh container and the eggs and juveniles

were immediately stained and counted. In cultures where the male was

found dead, it was replaced with a live male from the stock sample and

note made as to the day on which the mortality occurred. To calculate

the eggs/female-day ratio for these pair-mating experiments, the day

number was assumed to be that of the day on which the female was last

observed to be alive. Any discrepancies between the estimated produc-

tive time and the amount of productive time that the female might have

actually had before the observation of mortality were assumed to

average out between the populations.

Multiple regression analysis was used to test the relationship of

the rate of egg production to the area from which the adults were taken,

the date on which they were collected and the interaction of these








factors. A Duncanls Multiple Range test from the Statistical Analysis

System (SAS) computer program package was performed to determine the

dates on which the reproductive rate of the entrained population

differed from that of the control.



Analysis of Long-Term Survival


The culturing of copepods for the growth and reproductive studies

provided data for the observation and testing of differential survival

between intake and discharge populations for a relatively long period

of time following entrainment. The comparisons, although dealing with

laboratory conditions, were assumed to show any drastic differences

that may occur between the populations in nature.

The growth experiments provided estimates of the total number of

juvenile Acartia tonsa and Oithona brevicornis alive on each day of

observation. Such data allowed the plotting of survivorship curves of

the juveniles from intake and discharge populations for each sampling

period. The slopes of the curves were determined by linear regression

analysis and compared by a T-test.

Data from the pair-mating experiments produced the daily observa-

tions of adult Acartia tonsa mortality during the 5 to 7 days following

collection. Survivorship curves for the populations in each experiment

were constructed, plotting the percentage of the adults remaining alive

on each day. The slopes for these curves were also determined by linear

regression and compared with a T-test.

As a second test of long-term adult survival, the total amount of

mortality found during each reproductive experiment was used to





20


calculate an average percent mortality/day value for the period.

Values calculated in this manner were rougher estimations of mortality

rates than those obtained by the regressional fitting to daily data,

but such calculations allowed inclusion of data which were collected

before daily observations were established (December 1973 to April

1974). Regress ion anal ys is of mor tal ity rates from the per iod from

April to August when both estimations could be made showed no signifi-

cant differences (at 0.05 level) between the methods, so it is assumed

that the rough estimations adequately show trends in survival.














SECTION Ill

RESULTS


Field Studies


Acartia tonsa


Acartia tonsa seems to be the major year-round component of

secondary production in the zooplankton community of the Crystal River

area. The numbers of this species were exceeded only by those of the

Oithona spp., which, because of their smaller size, probably do not

contribute nearly as much to the biomass production of the area. The

numbers of adult A. tonsa ranged from 10/m3 to 1,208/m3 for males and

from 43/m to 1,835/m3 for females, with mean values of 283/m and

444/m3 respectively (Figure 4). Numbers of juvenile A. tonsa ranged

from 1,127/m3 to 14,371/m3 with a mean of 5,795/m3. Peak numbers

occurred in December, late February to early April, July and

September. This species annually comprises 10 to 50% of the total

copepod population with values of 30 to 40% for most of the y'ear

(Figure 5).

Acartia tonsa that were exposed to discharge temperatures and

sampled immediately (treatment 100) generally had low mortality values.

Mortality for the species as a whole for the IDO treatment ranged from

0 to 32%, with a mean value of 6.9%. Males exhibited higher mortali-

ties than females, while juveniles generally showed lower mortalities
















--- FEMRLES
--- JUVENILES


AAR APR MAY JUN JUL AUG SEP
DATE


Fig. 4. Seasonal variation in numbers of Acartia tonsa.
















---- MALES
----- FEMALES
--- JUVENT LES


LLS








DAT


Fi.5 esn lvra in i ecn fttlcppdpp lto
rersne yAatatna








than either adult (Figure 6). There was a trend of low mortalities

in the winter and generally higher mortalities in the warmer months.

Populations of Acartia tonsa that were exposed to thermal shock

and then allowed to remain in the heated discharge water (treatment

ID2) exhibited greater mortalities than those experiencing only the

thermal shock. The mortality for the species as a whole ranged from

0 to 80% with a mean of 15.6%;. Again, males tended to be the most

sensitive to mortality, while juveni les wdere the least sensitive

(Figure 7).' The trend through the year at ID2 was for mortalities

around 10% through most of the winter and spring months, with a rise

through the latter part of the spring and a sharp increase in

mid-summer.

The Acartia tonsa population that has been sampled immediately

upon leaving the plant (treatment DSO) generally showed higher morta-

li ties than those experiencing only the thermal shock (100). The

range of mortality values for the species as a whole exposed to treat-

ment DSO was from 5 to 40% with a mean value of 12.4%. The males had

almost consistently higher mortalities than females, while the juveni le

values were nearly always lower (Figure 8). Mortalities were

moderately low~ throughout the year, with a slight trend to higher

values in the summer.

Acartia tonsa that were entrained through the power plant and then

allowed to drift down the discharge canal (treatment DS2) exhibited the

largest mortality values. Mortalities for the population as a whole

ranged from 5 to 80% and had a mean of 16-7%. A clear trend can be

seen, w~ith mortalities being moderately lowJ throughout the winter and

spring, gradually rising through the early summer and then sharply















100 -- MRLES
__ FEM1RLES
,o --- JUVENILES


DATE


Fig. 6. Seasonal variation in mortality of Acartia tonsa exposed to
treatment 100.

















MRLES
--- FEMAILES
JUVENILES


DATE


Fig. 7. Seasonal variation in mortality of Acartia tonsa exposed to
treatment ID2.


















MPRLES
--- FEMPILES
--- JLIVENILES


OATE


Fig. 8. Seasonal variation in mortality of Acartia tonsa exposed to
treatment DSO.








rising in mid-summer. Males appear more sensitive than females, with

mortalities rising faster than those of the females, while juvenile

values lagged behind those of the adults (Figure 9).

Figure 10a shows how the Acartia tonsa mortalities for treatment

OS2 are related to discharge temperatures. Mortalities are generally

low for discharge temperatures below 350C and rise with higher

temperatures. The increase in mortality appears to be exponential

above this temperature.

The predictive regression model chosen by the stepwise process for

Acartia tonsa was significant at the .0001 level (F = 30.87, 17df;

R2 = .74). The response surfaces that were plotted from the regression

equation for various conditions are shown in Figure 11.

The response patterns for Acartia tonsa exposed only to thermal

shock showed some interesting temperature-sal inity interactions. Male

A. tonsa (Figure 11a) exhibited higher mortalities than the females

(Figure llb), which in turn were more sensitive than the juveniles

(Figure Ilc). Similar trends were seen for each category, however,

with salinities between 19 and 23 ppt. allowing survival over a broad

range of temperature (20 to 350C). Relatively low mortalities are

seen for combinations of high salinities and moderately high tempera-

tures (30 to 350c). Temperature increases above 350C, however, are

positively correlated with great increases in mortality of the entire

range of salinities.

Exposure to the delayed thermal effects caused predicted mortali-

ties to rise slightly in all areas except for conditions of temperature

less than 350C and salinities of 20 to 25 ppt. (Figure 11d). The

temperature level at which the exponential rise in mortalities occurs

















. ..- MALES
--- FEMAILES
JUVENILES


DATE


Fig. 9. Seasonal variation in mortality of Acartia tonsa exposed to
treatment DS2.



































O




UCCO




O





ID C ~0 (1

- O ---



LI -- IO
U U


0 .0


O IO
ECr

C s.0 o
arDUlCl


DE c Dll~
C~OUUOI
L IUl~

O~aai


LL. ~ l

























On







I I I II I -i l l -
N
O O O O OO O O O O O O O O S
w e a a w e r e m m e c















N

- 1 1 1 ll l -l l l -
0 0 0 0 0 0 0 0 0 0 0 0 0 0
m e < o m o r e o w




































Fig. 10. Continued
(g) Tortanus setacaudatus; (h) total
copepod population.


















































TEMPERATURE, *C


1 I I I I I I I I

-

-


-

-


1 I .1 .1 I I I I


100


80

60


40


20


_1
(g) ~
(1:
O
r


S20 22 24- 26- 28 30 32 34 36


0


O


20 22 24 26 28 30 32 34 36 38































Fig. 11. Response surface estimates of mortality
as a function of discharge temperature and
salinity for populations of Acartia tonsa
exposed to various conditions: ? male,
(b) female and (c) juvenile immediate
response to thermal shock; (d) female
response to extended exposure to elevated
temperatures; (e) female response to
mechanical damage in addition to delayed
thermal effects; and (f) female response
to the same conditions in spring.
























(b)

-.--- --


() E
o


















(c)


(d) Ir
ob
It
oP `... ~,
~, *j
c.' b
'L.
1 --~
'''


~zo\e








~YO

~Jo
tr, X

,o
,o


~"P zD~~;
,z
.p~2 20 5"~~
~~c to \B








is lowered below 350C in areas of higher salinities and the range of

temperatures at which 100% mortality occurs has been broadened.

When mechanical effects are considered into the entrainment condi-

tions (Figure 11e), a rise in mortality of 3 to 5% occurs in all areas

except those of optimum conditions (20 to 35oC, 20 to 23 ppt.). The

Acartia tonsa male response pattern (not shown) exhibits a similar

trend except increases in predicted mortality are nearer 10%.

The addition of seasonal effects associated with spring produces

a response pattern for Acartia tons (Figure 11f) that looks identical

to those for other seasons (Figure 11e), except that all predicted

mortality values are approximately 10% higher.



01thona spp.


Oithona spp. is a category made up of at least three species of

the genus Oithona: 0. brevicornis, 0. nana and 0. simpllex. Species

identification was not feasible for the males and juveniles of this

genus under the magnifications used for counting. Positive species

identification involves dissection of the mouth parts and observation

under a compound microscope (Grice, 1960a). Oithone brevicornis was,

however, by far the most dominant of these species whenever identifi-

cations were made. Therefore, it is assumed that this species makes up

a majority of the category throughout the year.

Oithona spp. are the numerically dominant species of copepod in

the Crystal River area. Females of these species ranged in numbers

from 492/m3 to 17,819/m3 with a mean of 5,298/m3 (Figure 12). The

males were much rarer, with numbers from 61/m3 to 1.151/m3 and a mean
















a
O


2 FEMARLES
o -- JUVENlLE~S
O


O-
O








CD







NO E R E A P A U U U E
0AT


Fig. 12. Seasonal variation in numbers of Oithona spp.








of 477/m3. Juveni les ranged in numbers from 341/m3 to 22,067/m with

a mean of 7,136/m Peak numbers occurred in December, March and

September, with a fairly steady increase in numbers from June to the

time of highest densities at the end of the summer. Oithona spp., as

a whole, represents from 20% to nearly 80% of the total population of

copepods (Figure 13). Females and juveniles of these species nearly

always accounted for at least 50% of the numbers of the total copepod

population.

Mortalities for Oithona spp. which had undergone the thermal shock

of the 100 treatment were from 0 to 52%, with a year-round mean of

6.55%. On the dates that showed peak mortalities, male mortality

values were higher than those of females or juveniles (Figure 14).

The 01thona spp. populations that had traveled down the discharge

canal following the initial thermal shock (treatment ID2) exhibited an

average mortal ity of 13.4% wi th a range from 0 to 74%. Mortal ity

values remained relatively low until mid-summer when they rose rapidly

to the highest levels (Figure 15). Again, males showed higher mortali-

ties than females or juveniles, rising to the 100% level by mid August.

Populations of Oithona spp. sampled immediately upon leaving the

power plant (treatment DSO) had mortalities from 0 to 44% with a mean

of 8.6%. Mortality values fluctuated around a relatively low level

until mid-summer, when they rose (Figure 16). Differential mortality

due to sex or age class was only observed during these warmer months

when male mortalities were greater.

Oithona spp. that were exposed to the full effects of entrainment

through treatment DS2 had a range of mortalities from 0 to 80% and a

mean of 16%. Mortalities remained low until April, after which time




















































_ I I _I


---- MLES
--- FEMALES
--- JUVENILES


Q


NOV DEC JAN FEB MAR RPR MYJUN JUL AUG SEP

DATE






Fig. 13. Seasonal variation in percent of total copepod population
represented by 01thona spp.
















MALES
--- FEMPLESS
JUVENILES


DATE


Fig. th. Seasonal variation in mortality of Oithona spp. exposed to
treatment IDO.

















- --- MALES
----- FE1R LES
-- JUVENILES


DATE


Fig. 15. Seasonal variation in mortal ity of Oithona spp. exposed to
treatment ID2.
















10 -- FMRLES
,,, FE_.MRLES
-- JUVENILES


DATE


Fig. 16. Seasonal variation in mortal ity of Oithona spp. exposed to
treatment DSO.








there was a gradual rise through the month of June (Figure 17). In

July there was a sharp increase in mortality, ending with the highest

values by the end of summer. Males showed greater sensitivity to

mortality than females or juveniles when exposed to this treatment.

The relationship of the entrainment mortality of Oithona spp. to

discharge temperatures is shown in Figure 10b. Consistently low mortal-

ity values were seen until the discharge temperatures rose above 350C

Above the 350C level, mortalities increased rather rapidly with rising

temperatures.

The predictive regression model for Oithona spp. was significant

at the .0001 level (F = 44.25, 12df; R2 = .74). The response surfaces

that were plotted from the regression equation for various conditions

are shown in Figure 18.

Female and juvenile Oithona (Figure 18a) show low (0 to 20%)

mortalities when exposed to thermal shock if the discharge temperatures

are below 350C. Higher salinities apparently buffer the effects of

moderately high temperatures (20 to 350C). Above 350C, however, mortal-

ities rise exponentially with small increases in temperature, regard-

less of salinities. Male Oithona (Figure 18b) exhibit similar patterns,

but appear to be more sensitive to the thermal shock than females or

juveniles, having slightly higher mortality values for all conditions

except for the very lowest temperatures (20 to 22oC).

The extended exposure (2 hours) to the heated effluents in the

discharge canal causes the male (Figure 18c) and female-juvenile

(Figure 18d) response patterns to change. Mortalities rise for condi-

tions of higher temperature (above 32oC), especially with low salini-

ties, since the high salinity-high temperature resistance synergism is














10---- MARLES
SFEMRLES
-"" JUVENILES


DATE


Fig. 17. Seasonal variation in mortality of Oithona spp. exposed to
treatment DS2.

































Fig. 18. Response surface estimates of mortality as
a function of discharge temperature and
salinity for populations of Oithona spp.
exposed to various conditions:7a female
and (b) male immediate response to thermal
shock; (c) male and (d) female response to
extended exposure to elevated temperatures.






































- -- p


~I
_I
(b) c
O
I


F
C

(ol Ir
o
I
re


~/O- "

(c)- - -


Id) h
B

P
i'
~ i'
''L ~
i 5e
hi ;

~c 2 j
'czO\B








still somewhat evident. The temperature where 100% mortality occurs

has also been lowered because of these delayed thermal effects within

the discharge canal.

Mechanical, seasonal and density dependent factors were shown to

be insignificant in relation to entrainment mortality for Oithona spp.



Paracalanus crassirostris


Paracalanus crassirostris is a small calanoid copepod that was the

third most abundant copepod in the Crystal River area. Males of this

species ranged from 13/m3 to 1,037/m3 with a mean value of 422/m3 for

the year (Figure 19). Females were generally more abundant, with a

range of from 40/m3 to 2,793/m3 and a mean of 848/m Juvenile

P. crassirostris ranged in numbers from 35/m3 to 4,382/m3 and had a

mean value of 2,583/m3. Peak numbers of this species occurred in March,

May, June and September. Paracalanus crassirostris represents between

5 to 48% of the copepods of the area throughout the year and generally

accounts for 10 to 20% of the total population (Figure 20).

The population of Paracalanus crassirostris exposed to treatment

100 had mortality values from 0 to 78% and a mean value of 18.2%.

Mortalities were low from January through May, then increasingly rose

to high levels by mid August (Figure 21). No trends in differential

mortality attributable to sex or age class were observed for this

treatment.

Paracalanus crassirostris that were left in the heated effluent

for several hours following the initial shock (treatment ID2) showed

higher mortality values, with a range from 0 to 87% and a mean of 22.7%.














- ---- MRLES
--- FEMALES
--- JUVENILES


NOV DEC JAN FEB MAR APR

ORTE


Fig. 19. Seasonal variation in numbers of Paracalanus crassirostris.

















MARLES
--- FEHALES
--- JUV~ENILES


CT






LL.








ORT


Fi.2. Saoa a ito nprcn fttlcppdpplto
rersne yPrclnscasrsrs

















MFLES
--- FENIRLES
--- JUVENILES


DATE


Fig. 21. Seasonal variation in mortality of Paracalanus crassirostris
exposed to treatment 100.








The same general trend in mortality was seen for this treatment, with

low mortalities through the winter and spring seasons, followed by a

rise in early summer and a very rapid rise by mid-summer (Figure 22).

With this treatment, males tended to have higher mortalities during

the warmer months than females or juveniles.

Immediate bioassay of Paracalanus crassirostris leaving the power

plant (treatment DSO) showed an annual mean mortality of 24.7% and a

range of values from I to 83%. Mortalities fluctuated within the

15 to 20% rdnge for most of the winter and spring, then began to rise

after mid April (Figure 23). A peak in mortalities was observed in

July.

The populations of Paracalanus crassirostris subjected to two

hours in the heated waters of the discharge canal following entrainment

(treatment DS2) had a mean mortality of 31% and a range of 0 to 100%.

Mortalities fluctuated at a low level through Mlarch, then rose at an

increasingly rapid rate to highest values by early summer (Figure 24).

Males appeared to be slightly more sensitive than females or juveniles

during this period of rising mortalities.

Entrainment mortality of Paracalanus crassirostris is shown in

relationship to discharge temperatures in Figure 10c. Mortalities

increased gradually up to 31oC and then exhibited a progressively

steeper rise to high levels with higher temperatures.

The predictive regression model for Paracalanus crassirostris

was significant at the .0001 level (F = 38.97, Ildf; R2 = .76). The

response surfaces plotted from the regression equation for various

conditions are shown in Figure 25.


















MRLES
----- FEMALES
--- JUVENILES


I_____


DATE


Fig. 22. Seasonal variation in mortality of Paracalanus crassirostris
exposed to treatment ID2.














100-- MRLES
--- FEM1RLES
'" JUVENILES


DATE


Fig. 23. Seasonal variation in mortality of Paracalanus crassirostris
exposed to treatment DS0.














100 - - MRLES
-- FEMRLES
,, JUVENILES


0ATE


Fig. 24. Seasonal variation in mortal ity of Paracalanus crassi rostr is
exposed to treatment DS2.
































Fig. 25. Response surface estimates of mortality
as a function of discharge temperature and
salinity for populations of Paracalanus
crassirostris exposed to various conditions:
(a) male and (b) female-juvenile immediate
response to thermal shock; (c) female
response to extended exposure to elevated
temperatures; (d) female response to mecha-
nical damage in addition to delayed thermal
effects; and (e) female response to the
same conditions in spring.



















(b) n~~
02, ~ =
I
z o .-
BP
,o Z-
P
a
L
Z i~Z~~
'r. ,,
~,~~.:" L
c ~ ~' 3"
C~0\8


.i-.





(dl n JO
oZ
Z O
,o
i'
G V
' ~ r

~a~`~r~~
czo\e


Jo









> b





a _~- -- o


~YO

(sl ~
OzJ
O
bCI: ,~


;
Q
~ 20~;e








Paracalanus crassirostris males (Figure 25a) showed slightly lower

mortalities than did the females and juveniles (Figure 25b) when

exposed to thermal shock. The response patterns show a gradually

increasing rise in mortalities with increases in temperature. A slight

temperature-salinity interaction is evident throughout the range of

conditions with higher salinities producing lower mortalities for any

temperature. Mortality values for P. crassirostris do not rise much

above 70%, even for highest temperatures (400C) during this short-term

exposure to'thermal stress.

Extended exposure to the heated effluent (Figure 25c) causes

Paracalanus crassirostris mortality values to rise rapidly for tempera-

tures above 300C. For temperatures below this point, higher salinities

continue to produce lower mortalities. Mortalities of the males

subjected to extended exposure were 10 to 15% higher than those of

females and juveniles.

When the mechanical effects of entrainment are included in the

Paracalanus crassirostris response surface equation (Figure 25d),

mortalities are only slightly increased for temperatures below 300C.

Above this point, the rise to the 100% mortality level occurs more

rapidly and for lower temperature values than would be seen for a popu-

lation not subjected to the physical factors involved in passage

through the plant (Figure 25c).

The Paracalanus crassirostris populations observed during the

spring (Figure 25e) had mortalities approximately 10% lower than would

be expected for all conditions, except the most extreme temperatures

(above 37 C).








Paracalanus crossirostris response patterns are significantly

affected by the density (numbers/m ) of the species at the time of

entrainment. When numbers per cubic meter are low (Figure 26a),

entrainment mortalities are generally higher than when the numbers are

high (Figure 26b). This effect is particularly evident for the more

lethal conditions, where the temperature at which the 100% mortality

level occurs may be changed several degrees by the density factor.



Euterpina acutifrons


Euterpina acutifrons is a pelagic harpacticold that was the fourth

nost abundant species in the Crystal River area. Females ranged in

numbers from 5/m3 to 857/m3 and had a mean of 177/m3 (Figure 27). Male

E. cutfros ererarrranging in abundance from 0/m to 184/m and

having a mean value of 60/m Numbers for juveniles of this species

ranged from 0/m3 to 2,617/m with a mean of 944/m3. There were three

obvious peak periods for this species: one in December, a second at

the end of February, and the third at the beginning of June. By mid-

summer months, however, E. acutifrons had become scarce in the samples.

The trend toward the decreasing importance of this species with the

warmer months is reflected in the percent of the total population that

it represented through the year (Figure 28). Through most of the

winter and spring months this species accounted for 5 to 10% of the

copepods of the area but gradually decreased in importance until, by

mid-summer, it represented only a fraction of a percent of the total

populat ion.































Flg. 26. Response surface estimates of mortality
as a function of discharge temperature and
salinity for entrainment populations at
different densities: (a) female Paracalanus
crassirostris at lowest numbers per ml DECr
female Paracalanus crassirostris at highest
numbers per m3; -(c) female Euterpina acutifrons
at lowest numbers per m3; (d) female Euterpina
acutifrons at highest numbers per m3.







































(a)













o -


o

( b












(d)

0 --















- MRLES
--- FEMRL~ES
--- JUVIEN1lLES


NOV DOEC JRN FEB MAR APR MAY JUN JUL AUG SEP
DATE


Fig. 27. Seasonal variation in numbers of Euterpina acutifrons.















------ MRLES
-- FEMFILES
-- JUVENILES


O
















DAT

Fi.2 Saoa a ito nprcn fttlcppdpp lto
rereene byEte-n auifos








Euterpina acutifrons exposed to treatment 100 exhibited mortality

values from 0 to 100% with a mean of 27.7%. Mortalities were generally

low until May, when a peak in mortalities occurs (Figure 29). Values

then rose again in mid-summer, though scarcity in the numbers of this

species after this time prevented further calculations of mortalities.

The mortalities of Euterpina acutifrons subjected to prolonged

exposure to the heated effluent (treatment ID2) ranged from 0 to 100%

with a mean value of 25%. Mortalities were generally low until mid-

spring when they rose steeply to highest levels (Figure 30). Females

appeared more sensitive than juveniles to the warmer temperatures, with

female mortalities rising to high levels a month earlier in the spring.

The trend in male mortality could not be discerned because dwindling

numbers with the coming of spring provided only a few data points.

Euterpina acutifrons sampled for bioassay immediately upon leaving

the powJer plant (treatment D50) showed mortalities that ranged from

0 to 100%, with a mean value of 20%. Mortalities fluctuated at a low

level until May when they rose to higher levels (Figure 31). Values

rose to the 100% level by the beginning of July, after which no further

calculations could be made due to low numbers.

Euterpina acutifrons populations left in the heated waters of the

discharge canal following entrainment (treatment DS2) showed a mean

mortality value of 33% and a range from 0 to 100%. Mortalities remained

quite low through April, but then steeply rose to the 100% level in

July (Figure 32). Males showed the increase in mortalities earliest in

the spring, followed by the females and then the juveniles.

The relationship of Euterpina acutifrons entrainment mortality to

discharge temperatures is shown in Figure 10d. N(ortalities were low

















MRLES
---- FEEHRLES
--- JUVENILES


100p


N D


DATE


Fig. 29. Seasonal variation in mortality of Eute~rpina acutifrons
exposed to treatment 100.

















MARLES
--- FENIRLES
--- JUIVENILES


DATE


Fig. 30. Seasonal variation in mortal ity of Euterpina acutifrons
exposed to treatment ID2.

















...--- MALES
--- FEMALES
--- JUVENILES


0 4


DA~TE


Fig. 31. Seasonal variation in mortality of Euterpina acutfrons
exposed to treatment DSO.

















-- MRLE S
---- FENRILES;
--- JUV1EN]JLES


DATE


Fig. 32. Seasonal variation in mortal ity of Euterpina acutifrons
exposed to treatment DS2.
































Fig. 33. Response surface estimates of mortality
as a function of discharge temperature and
salinity for populations of Euterpina
acutifrons exposed to various conditions:
(a) male, (b) female and (c) juvenile imme-
diate response to thermal shock; (d) female
response to extended exposure to elevated
temperatures; (e) female response to
mechanical damage in addition to delayed
thermal effects and (f) female response
to same conditions in spring.























- i
-- -


I


,o -


(a) aP J
o O

a 9



b##










'bP 2 4








and only slightly increased with temperatures up to 300C but then rose

steeply to the 100% level by 350c.

The predictive regression equation for Euterpina acutifrons

was significant at the .0001 level (F = 9.49, 24df; R2 = .71). The

response surfaces that were plotted from the regression equation for

various conditions are shown in Figure 33.

In response to short-term thermal stress, male Euterpina

acutifrons (Figure 33a) are less sensitive to the various temperature

and salinity combinations than are females (Figure 33b). Juveniles

(Figure 33c) appear more resistant than adults, except for conditions

of high salinity. The response surfaces for Euterpina acutifrons

exhibit a stronger temperature-sal inity interaction than do those of

the other species. High salinities and low temperatures produce low

mortalities, while low salinities and high temperatures produce high

mortalities. The effects of this interaction on the immediate response

to thermal shock appear more important than do either of the factors

considered alone.

When discharge canal effects are considered (Figure 33d), mortali-

ties rise, especially with high temperatures (above 350C). Male

Euterpina acutifrons have mortal ity levels 10 to 15% higher than the

females, while juvenile mortalities are 10 to 15% lower. The tempera-

ture-salinity interaction remains evident but extended exposure to the

heat makes the factor of temperature relatively more important in its

upper range.

Mechanical effects cause mortality values in the response pattern

for Euterpina acutifrons (Figure 33e) to rise slightly, the effect

being especially evident in areas of low temperatures and high salinity








where mortalities were previously low. Most of the temperature-

salinity interaction disappears and the temperature of the discharge

canal becomes the dominant factor in entrainment mortality.

As with Paracalanus crassirostris, populations of Euterpina

acutifrons entrained during the spring had significantly lower mortali-

ties than would be expected (Figure 33f). Except at temperature above

350C, mortalities are 10 to 20% lower throughout the range of

conditions.

Euterpina acutifrons also showed response surface changes due to

density factors. Conditions where this species had low numbers per

cubic meter (Figure 26c) were related to higher mortalities, while

those with high densities showed low mortalities (Figure 26d).



Pseudodiaptomus coronatus


Pseudodiaptomus coronatus is a fairly large calanoid copepod that

is at times epibenthic. This species was the fifth most common copepod

in the sampling area, but adults were quite rare. Male P. coronatus

ranged in numbers from 0 to 41/m3 and had a mean value of 8/m3

(Figure 34). Females were not much more abundant, ranging in numbers

from 0 to 47/m3 and having a mean value of 13/m3. Juveniles were at

times quite common, however, ranging from 8/m3 to 934/m3 and having a

mean value of 202/m'. Peak numbers occurred in December, March, June

and September, though the winter peak was by far the greatest. The

importance of this species, as indicated by the percent of the total

population that it represented, fell from a high of 4% in December to

a fraction of a percent by mid-spring (Figure 35).



























































-- -
--- -*


I I I 1 I
NOVY DEC JRN FEB MAR


--- M- RLES
- FEMARLES
-- JUVENILES


CO


U o-



uLD


o


APR MAY JUNI JUL AUG SEP

DATE


Fig. 34. Seasonal variation in numbers of Pseudodiaptomus coronatus.
















------ MRLES
-- FEMIRLES
-- JUVENILES


.J
CE:















DAT


Fi.3 Saoa a ito nprcn fttlcppdpp lto
rersne yPeddatmscrnts








Pseudodiaptomus coronatus populations exposed to the thermal shock

of discharge temperatures (treatment IDO) exhibited a range of mortali-

ties from 0 to 15% and had a mean value of lt%. The low numbers of this

species in the control and experimental samples prevented mortality

calculations for the adults subjected to this treatment. Juveniles

exhibited low mortalities until mid August when this category also

became too rare in the samples to permit further calculations

(Figure 36).

Pseudodiaptomus coronatus subjected to treatment ID2 exhibited

mortalities from 0 to 100% with a mean value of 11%. Juvenile mortali-

ties were the only values calculated for this treatment due to the

scarcity of adults. Mortalities for the juveniles P. coronatus were

low through the year until they suddenly rose to the 100% level in

August (Figure 37).

Populations of Pseudodiaptomus coronatus sampled immediately

following entrainment (treatment DSO) had mortality values that ranged

from 0 to 100% with a mean of 18%. Mortalities of juvenile P. coronatus

fluctuated at moderately low levels through the year until August when

values jumped to 100% (Figure 38). There were too few data points,for

adult P. coronatus subjected to this treatment,to discern any trends.

The discharge population of Pseudodiaptomus coronatus that was

left in the heated waters for two hours prior to sampling showed mortal-

ities from 0 to 100% and a mean value of 23%. Juvenile P. coronatus

had moderately low mortalities until the beginning of summer when

values rose to higher levels (Figure 39). By September, mortalities

for the juveniles jumped to the 100% level. Although there are only a

few data points available for observation, female P. coronatus seem
















MRLES
~- FEMALES
--- JUVENILES


DATE


Fig. 36. Seasonal variation in mortality of Pseudodiaptomus coronatus
exposed to treatment 100.

















----- MRLES
--- FEMRLES
--- JUVENILES


0ATE


Fig. 37. Seasonal variation in mortality of Pseudodiaptomus coronatus
exposed to treatment ID2.
















M1RLES
---- FEIHRLES
--- JIUVENILES


DATE


Fig. 38. Seasonal variation in mortality of Pseudodiaptomus coronatus
exposed to treatment DS0.

















MRLES
--- FEMALES
--- _IIJUENILES


DATE


Fig. 39. Seasonal variation in mortality of Pseudodiaptomus coronatus
exposed to treatment DS2.









to generally follow the same trend, though the 100% mortality level is

reached in July.

Figure 10f shows the relationship between entrainment mortality

of Pseudodiaptomus coronatus and the temperature of the discharge

waters. Mortalities remained below the 20% level for observations

below 350C. Observations for temperatures around 350C showed that

mortalities had risen to the 40% level. By the time the temperature

reached 370C, mortalities went to 100%.

Multiple regression analysis and the creation of response surfaces

were not attempted for Pseudodiaptomus coronatus due to the relatively

low numbers of observations for each treatment. Such statistical

treatment requires many observations for each of the various conditions

in order to be considered valid.



Labidocera spp.


Labidocera spp. is a category made up of two species of the genus

Labidocera: L. aestiva and L. scottl. These two species were counted

together for two reasons. First of all, the numbers of either species

alone were quite low, so that in order to obtain enough observations to

analyze trends in mortality, the counts were combined. Secondly,

although the species identification of these large calanoids was rela-

tively easy as adults, the identification of juveniles to species was

not feasible under the magnification used for counts. It was assumed

that the effects of entrainment on the Labidocera species were more

similar within the category than they would be to species of other

genera.








Numbers of Labidocera spp. females ranged from 0 to 60/m with a

mean of 8/m3 (Figure 40). Males of these species were rarer, ranging

in numbers from 0 to 23/m3 and having a mean value of 3/m3. Juveniles

were by far the most abundant, ranging from 0 to 567/m3 and averaging

25/m3. Peak numbers occurred in January, June and September.

Labidocera spp. represented between 0 and 2.7% of the copepod popula-

tion of the sampling area, generally accounting for only about 0.2% of

the total (Figure 41).

Populations of Labidocera spp. subjected to treatment 100 exhibi-

ted mortality values that ranged from 0 to 40%, with a mean value of

13.2%. As can be seen in Figure 42, low numbers in experimental and

control samples for this treatment allowed only a few data points to be

plotted when the species are broken down by sex and age class. About

the only trend that can be seen is that mortality values were fairly

low for this treatment.

Labidocera spp. populations that were left in the heated effluent

following thermal shock (treatment ID2) showed mortalities of 0 to 100%

with a mean value of 49%. Mortalities were generally low until May

(Figure 43). The coming of the warmer months brought consistently high

mortalities except for a single dip in values at the end of June.

Discharge populations of Labidocera spp. sampled immediately

following entrainment showed rather high mortality values ranging from

20 to 100% and having a mean value of 68%. Mortality values for adults

were higher during the warmer months, remaining at the 100% level

(Figure 44). Juvenile mortality fluctuated through the year, remaining

at the 100% level only after mid-summer.
















O
0






(o






O

(D






LD


-- MRLES
--- FEMRLES
-- JUVENILES


NOV DOEC JRN FEB MAR APR MAY JUN JUL AUG SEP

DATE


Fig. 40. Seasonal variation in numbers of Labidocera spp.
















----- MRLES
--- FEHRLES
--- JUVENILES


-1.


DATE


Fig. 4l. Seasonal variation in percent of total copepod population
represented by Labidocera spp.
















MPLES
--- FEMALES
--- JLIVENIJLES


DATE


Fig. 42. Seasonal variation in mortality of Labidocera spp. exposed
to treatment IDO.

















- MRLES
-- FEMALES
-- JUVENILES


DATE


Fig. 43. Seasonal variation in mortality of Labidocera spp. exposed
to treatment ID2.











































-- MRLES
-- FEMALES
-- JUVENILES


DATE


Fig. 144. Seasonal variation in mortality of Labidocera spp. exposed
to treatment DSO.








Mortalities for Labidocera spp. subjected to treatment DS2 were

high throughout the year, with a range of 75 to 100% and a mean value

of 88%. Adult values fluctuated at high levels until May, then remained

at the 100% level for the rest of the summer months (Figure 4S).

Juvenile mortalities showed greater fluctuations, but rose to 100% by

mid-summer.

The relationship between the entrainment mortality of Labidocera

spp. and discharge canal temperatures is shown in Figure 10e. Mortali-

ties were high throughout the range of temperature, without an apparent

trend. The only possible exception was that mortalities seemed to rise

to higher levels and attain the 100% level more consistently with

temperatures above 350c.

Multiple regression analysis and the creation of response surfaces

were not attempted for Labidocera spp. due to the low number of obser-

vations that could be made for the various conditions.



Tortanus setacaudatus


Tortanus setacaudatus is a fairly large calanoid copepod that was

moderately abundant from time to time in the Crystal River area. Male

7. setacaudatus ranged in numbers from 0 to 612/m3 and averaged 49/m3

(Figure 46). Females of this species numbered From 0 to 380/m3, with

a mean value of 43/m Juveniles ranged in numbers from 0 to 845/m3

and had a mean of 127/m3. The major portion of the rather high mean

numeric values of this species can be accounted for by three peak

periods: one in April, one in August, and the last in September.

During the April peak, this species represented 9% of the copepods of











































MFILES
---- FEHRLES
--- JUVENILES


DATE


Fig. 45. Seasonal variation in mortal ity of Labidocera spp. exposed
to treatment DS2.

















O




D


O
O

t"







Uo

(1.
UO

SO

Do








70


-- -- MALES
--- FEMARLES
--- JIUVEN MILES


NOV DEC JAN FEB HAIR APR MAY~ JUN JUL AUC SEP

ORTE



Fig. 46. Seasonal variation in numbers of Tortanus setacaudatus.




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