Limitation of Primary Productivity in a Southwestern

Home , Thermal pollution

MO i

LIMITATION OF PRIMARY PRODUCTIVITY IN A SOUTHWESTERN

RESERVOIR DUE TO THERMAL POLLUTION

THESIS

Presented to the Graduate Council of the

North Texas State University in Partial

Fulfillment of the Requirements

for the Degree of

MASTER OF SCIENCE

Tom J. Stuart, B.S.

Denton, Texas

August, ]977 Stuart, Tom J., Limitation of Primary Productivity in a Southwestern Reseroir Due to Thermal Pollution. Master of

Sciences (Biological Sciences), August, ]977, 53 pages, 6 tables, 7 figures, 55 titles.

Evidence is presented to support the conclusions that

(1) North Lake reservoir is less productive, contains lower standing crops of phytoplankton and total organic carbon than other local reservoirs; (2) that neither the phytoplankton nor their instantaneously-determined primary productivity was detrimentally affected by the power plant entrainment and (3) that the effect of the power plant is to cause nutrient

limitation of the phytoplankton primary productivity by long- term, subtle, thermally-linked nutrient precipitation activities.

ld" TABLE OF CONTENTS Page

iii LIST OF TABLES...... ------iv LIST OF FIGURES ...... - --

ACKNOWLEDGEMENTS .-...... v

Chapter

I. INTRODUCTION...... 1

II. METHODS AND MATERIALS ...... 5

III. RESULTS AND DISCUSSION...... 11

Phytoplankton Studies

Primary Productivity Studies

IV. CONCLUSIONS...... 40

APPENDIX...... 42

REFERENCES...... -...... 49

ii LIST OF TABLES

Table Page

1. Selected Comparative Data from Area Reservoirs Near North Lake...... 18

2. List of Phytoplankton Observed in North Lake .. 22

3. Percentage Composition of Phytoplankton in North Lake...... 28

4. Values of H.Computed for Phytoplankton Volumes and Cell Numbers for North Lake ...... 31

5. Primary Production Values Observed in Various Lakes of the World in Comparison to North Lake...... 35

6. List of Variables Used in Correlation and Stepwise Multiple Linear Regression Analyses of Primary Productivity in North Lake 36

iii LIST OF FIGURES Page- Figure

1. Morphometric Features of North Lake Including . Numbered Locations of Sample Sites7...... Zone 2. Mean Water Temperatures in the Euphotic of North Lake at Pelagic Sites of Maximum and Minimum Effects of Power Plant 14 Entrainment and Discharge Temperatures ....

3. Total, Organic (diagonals) and Inorganic 17 Carbon Values in North Lake, 1973-74 3 4. Phytoplankton Volumes in ml/m as Observed at Stations 2 and 5 in North Lake, ...-.-.-. 21 September 1973 through August 1974... 2 5. Phytoplankton Standing Crop per m Euphotic Zone in North Lake. (Numbers indicate number of genera present)...... -.-.-.-.-.-.24

6. Community Composition of Phytoplankton in North Lake, 1973-74...... -- ..--..-. 27 2 the C Photosynthetically fixed/hr/m in 7. mg 33 Euphotic Zone of North Lake, 1973-74 .0.0.*.0.0.0

iv ACKNOWLEDGEMENTS

This research was supported by a grant to the Depart- ment of Biological Sciences, North Texas State University, from the United States Environmental Protection Agency

(Training in Water Supply, Water Quality and Pollution

Control, T - 900115).

V CHAPTER I

INTRODUCTION

Planktonic primary producers are one of the fundamental units of aquatic communities and they are a major source of biologically important, labile, organic carbon (Wetzel, 1975).

Because phytoplankton perform such an important function at

the base of the aquatic food web, they serve as a significant

focal point for research on the effects of thermal pollution

(Patrick, 1969; Coutant, 1969, 1970, 1971, 1973; Coutant and

Goodyear, 1972; Coutant and Talmage, 1976; etc.). One method

of assaying the impact of thermal pollution on algal communities

has involved the study of periphyton colonizing glass slides

(diatometers) incubated in situ (Patrick, 1969; Patrick, Hohn

and Wallace, 1954; Patrick, Crum and Coles, 1969; Cairns,

Kaesler and Patrick, 1970; Merriam, 1970; Trembley, 1969; and

others). Different approaches to assaying the effects of

thermal pollution on phytoplankton populations and productivity

have been taken by other investigators.

Gurtz and Weiss (1972) reviewed published literature

dealing with the effects of temperature elevations and power

plant condensor entrainment in the populations and photo-

synthetic activities of natural phytoplankton from marine,

estuarine, river and reservoir systems. Photosynthetic rate

1 2

changes in the studies they reviewed ranged from 94 percent inhibitions to 969 percent stimulations. Degrees of photosynthetic rate changes in these studies varied with the type of phytoplankton community, the absolute temperature increase to which plankters were subjected, the initial environmental temperature, the maximum temperature reached, the environment from which they were entrained, etc. Several of the reviewed studies reported photosynthetic inhibition due to chlorination while others failed to even include chlorination as a possible inhibitor. Little similarity was noted between experimental techniques and much of the testing was done 'in vitro, often without regard to "natural" cooling rates of thermal discharges. Gurtz and Weiss (1972), in their own in vitro study of phytoplankton productivity after condensor passage at the Allen steam-electric generating plant on Lake Wylie, North Carolina, found relatively constant photosynthetic inhibitions occurring for a 50 or 10 C rise in temperature, regardless of the initial temperature. Greater inhibitions occurred when initial temperatures were greater than 210 C. Temperature changes of 170 C produced successively greater inhibitions with increasing initial temperatures on the 6 sampling dates throughout their year of study. Their results suggested that maximum photosynthetic inhibition occurred in the first 1 to 2 hours after condensor passage and that no further inhibition or recovery of photosynthesis occurred during a 26 hour 3

"simulated-natural" cooling period. They also found that the

final yield of thermally-stressed phytoplankton grown in nutrient-

enhanced laboratory conditions for 2 weeks was directly related

to the magnitude of their initial thermal stress. Although the

results of in vitro studies are useful, there is difficulty in

applying them to real situation. The need for in situ studies

has been noted by several workers (Patrick, 1969; Coutant, 1970; Vollenweider, 1974).

The supply of water in the southwestern United States is

finite and relatively limited (Geraghty, et al., 1973) and the

demands placed on it for all uses are constantly increasing.

Surface reservoirs in the southwestern United States are the

major source of water for all purposes and most electric power

plant cooling water comes from and is returned to them.

Although the electric power industry's use of water is largely

non-consumptive, there is concern that it may detrimentally

affect the quality of aquatic environments (Scott, 1973; U. S.

Federal Power Commission, 1971; Nassikas, 1971; Steiglemann,

1969; Wilson, 1970; Barton, 1970; Belter, 1969; Singer, 1969;

Hogerton, 1968; Healy, 1973; Carlson, 1969; Geraghty, et al.,

1973; Krenkal and Parker, 1969). Nevertheless, little pub-

lished information exists concerning the effects of thermal pollution on phytoplankton populations and their ecologically

important photosynthetic activities in southwestern reservoirs.

The site of the present study was a small, southwestern

reservoir with a relatively large usage demand for the purpose 4

of cooling a steam-electric generating plant. It was originally felt that the naturally warm surrounding climate coupled with the intense demands on this reservoir for cooling purposes might be producing a situation where stresses on the phytoplankton and their photosynthetic metabolism would be measur- able. Previous investigations of higher trophic levels of the biotic community at this stie had revealed reduced species diversity, lower condition coefficients, low standing crops and altered distribution and behavioral patterns of several organisms (Searns, 1972; Hobson, 1973; McNeely and Pearson, 1974; Jones, 1976; Venables, et al., 1977; Durett and Pearson, 1975; Yeh, 1972) . Historical chemical data together with a comprehensive chemical analysis of the reservoir were avail- able (Sams, Silvey and Stanford, 1976) . The present study sought to elucidate the general trophic status of this thermally altered reservoir. The study also examined the effects of power plant entrainment and thermal discharge on the extant phytoplankton population and its in situ determined primary productivity. CHAPTER II

METHODS AND MATERIALS

North Lake is a small (330 ha. surface area) reservoir in northeast Dallas County, Texas. It is owned and operated by the Dallas Power and Light Company which maintains a

700 M.We. fossil-fueled, thermal electric power plant on the northeast shore. Subsurface water is entrained immediately south of the plant, passed through condensors and returned to the northwest corner of the reservoir via a 1500 m-long effluent canal (Figure 1) . Maximum pumping capacity of the plant is 1559 m3 min-1 and total entrainment time from initial uptake of phytoplankton until discharge at the mouth of the canal varies with the pumping rate, but is approximately 1 to

2 hours during routine operation.

Reservoir volume was maintained at approximately 2.25 x 7 3 10 m throughout the study; at maximum pumping rates, an equivalent volume of water was recirculated in approximately 10 days. However, this did not mean that the entire reservoir water volume passed through the condensor at 10-day intervals.

In fact, observations of currents and temperature plumes created by the thermal discharge indicated the possibility of considerable short-circuiting of discharged waters. Realtively static conditions were noted at the southeastern corner of the reservoir (Figure 1).

5 6

Figure 1. Morphometric features of North Lake including numbered locations of sample sites. 7

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Five reservoir stations were selected and sampled at meter intervals from surface to bottom on 16 dates from Sep- tember through August, 1973 - 74. Stations 1 through 5 were

3, 5, 5, 11 and 9 meters deep, respectively. Stations 2 and

5 were selected during preliminary reconnaissance to represent thermal extremes observed in the reservoir.

The plankton populations at Station 2 (i.e., at the Canal mouth) and Station 5 (i.e., in the area of the reservoir least

affected by thermal discharge) received critical study. Plank-

ton populations were sampled from each station with an opaque,

non-metallic, 4-liter Kemmerer bottle from each meter in the

water column. Phytoplankters were concentrated 25 to 50 times

by centrifugation and preserved with a water:alcohol:formalin

(6:3:1) solution recommended by Prescott (1973). Lugol's iodine

solution was also used as an aid to preservation and identifi-

cation (Vollenweider, 1974). Phytoplankton in these samples

were counted, identified to the generic level and their volumes

estimated with the aid of a Whipple Occular Micrometer and a

nannoplankton counting slide (Palmer and Maloney, 1954) at

200x and 430x magnification by standard, phase-contrast and

dark-field microscopy techniques.

Water samples for chemical analyses were collected as

described above and initially stored and transported to the

laboratory in 1-liter polyethylene bottles on ice and/or

under refrigeration. Temperature, pH and dissolved oxygen

were determined electrometrically either in situ or as soon 9

as possible after samples were collected. Conductivity was determined electrometrically (YSI,. Model 31 Conductivity

Bridge) at room temperature within a few hours of sample collection. Alkalinity, chlorides, total ortho-phosphates

(Ascorbic Acid Modification) and total NO -nitrogen (Brucine

Modification) were determined according to A.P.H.A. Standard

Methods (1971). Sulfates, total iron and hardness were determined by the use of prepared chemicals and reagents produced by the Hach Chemical Company (Ames, Iowa). Carbon analyses were made with a Beckman 915 Total Carbon Analyzer within 12 hours of collection, the samples having remained sealed and refrigerated until analyzed.

Total phytoplankton primary productivity was estimated simultaneously at Station 2 and 1600 meters away at Station 5.

Primary productivity was determined by 14C isotope techniques similar to those proposed by Schindler, Schmidt and Reid (1972) as modified by Stuart and Stanford (in preparation). The relative light penetration at each station and depth was determined with a submarine photometer (G. M. Instruments, Model

310). The euphotic zone (to a depth permitting 1 percent light transmission) extended to approximately 5 meters at all stations throughout the study. Three representative depths of 1, 3 and

5 meters were selected for simultaneous in situ phytoplankton incubations at Stations 2 and 5. Productivity values from these photic zone depths were plotted against depth and the integrated area under the resulting photosynthesis curve was 10

used to estimate productivity values of the euphotic zone per square meter of surface area (Vollenweider, 1974).

Simple correlation analysis was used to study the covariance of 20 separate biotic and abiotic limnological parameters observed throughout the study period. Stepwise multiple regression analysis was used to study similarities in covariance of 19 biotic and abiotic limnological parameters with the measured primary productivity rates that occurred for corresponding depths at Stations 2 and 5 during the year-long sampling program. CHAPTER III

RESULTS AND DISCUSSION

Water temperatures were determined immediately prior to productivity studies. At midday, when chlorination was not practiced, entrainment of plankters subjected them to mechan- ical disturbances associated with pumping activity and a rapid temperature rise of up to 100 C, but averaging about 5.50 C. Water temperatures slowly declined with passage down the effluent canal but were still several degrees higher than the main reservoir surface temperature at the point of discharge from the canal mouth. Entrained waters experienced maximum temperature increases of nearly 100 C on two sampling dates during the study (1/26/74 and 8/22/74). On these two dates, the mean water column temperatures at Station 5 were observed to be the minimum and near maximum recorded temperatures for the study period, respectively, On two sampling dates (12/3/73 and 3/10/74), no change in temperature occurred upon entrainment and the entire reservoir was observed to be homeothermous. The mean water column temperature for the euphotic zone at Station 2 averaged 1.60 C warmer than the corresponding water column at Station 5. Examination of temperature data from all stations revealed that while Station 2 was warmer than the rest of the reservoir, the additional heat had been substan-

11 12

tially transferred to the atmosphere and diluted by the reservoir by the time the canal discharge had traveled a few hundred meters. Maximum temperatures of 410 C were recorded just prior to the beginning of this study at the condensor discharge exit site. However, the maximum discharge temperature observed during the study was 39.50 C (Figure 2). The limited drainage and relatively high evaporation rates of North Lake during its 19-year history have caused a 3 to 7- fold increase of many dissolved solids. Certain essential biotic macronutrients were observed in relatively low levels compared to the Elm Fork Trinity River, the major North Lake water supply. Suspected reasons for low macronutrient levels in North Lake, and possible mechanisms for phosphorus precipitation in particular, have been discussed by Sams (1976). He also discussed the chemistry of North Lake in detail and demon- strated Phosphorous-limitation of the alga Selenastrum capricornutum when grown in North Lake water collected in Spring 1975.

During this study, total orothphosphate measurements were made on five separate, seasonally representative sampling dates. All samples from all stations on each sampling date contained less orthophosphate than the lowest standard (0.010 mg/l PO-P) used for test 4 calibration. Total soluble nitrate nitrogen measurements were made on four seasonally representative sampling dates. The tests indicated that all samples for all stations on each sampling date contained 13

Figure 2. Mean water temperatures in the euphotic zone of North Lake at pelagic sites of maximum and minimum effects of power plant entrainment and discharge temperatures. 14

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concentrates of NO 3 -N equal to or less than the lowest standard

(0.040 mg/i NO-N) used for test calibration. The low concentrations of Nitrogen (N) and Phosphorus (P) existing in North

Lake precluded their accurate measurements because of test limitations. Subsequent analyses by different test methods confirmed the low levels of N and P observed (Sams, 1976).

In general, either no differences or insignificant ones were found between stations and depths for other physico- chemical parameters measured. During this study, the mean reservoir values of pH = 8.62; conductivity = 875 umhos/cm2 total alkalinity = 103 mg/l; chlorides = 105 mg/l; total soluble reactive Fe = 0.02 mg/l; sulfates = 265 mg/l and total hardness = 224 mg/l were measured.

Inorganic, organic and total carbon values were identical for all depths of all stations on each sampling date; a three- fold variation in concentrations occurred during the annual cycle (Figure 3). Organic carbon concentrations were relatively low in comparison to other local reservoirs (Table 1).

During this study and a previous one (McNeely and Pearson,

1974), dissolved oxygen concentrations were never observed to be less than 6.0 mg/l in the 5-meter deep euhotic zone.

During a subsequent study, dissolved oxygen concentrations approached zero on one occasion, near the bottom (15 m depth) of a midlake station. Lack of anaerobic conditions, a common occurrence in nearby area reservoirs, can be attributed to adequate 02 influx due to power plant and wind induced 16

Figure 3. Total, organic (diagonals) and inorganic carbon values in North Lake, 1973 - 74. 17

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circulation combined with low levels of phytoplankton standing crop and organic carbon.

Phytoplankton Studies

Phytoplankton populations for all stations were similar and a two-way analysis of variance indicated no significant differences (P = 0.1) between total standing crops at Stations

2 and 5. Total phytoplankton standing crop, based on the mean values of samples collected at meter intervals from the

photic zones of Stations 2 and 5 varied between 1.2 ml/m2 and

12.5 ml/m2 throughout the study period. Phytoplankton

standing crop expressed on a cubic meter basis for Stations

2 and 5 varied between 0.23 ml/m3 and 2.47 ml/m3 for the study

period (Figure 4). The smallest volumes of phytoplankton

appeared during the coolest periods of the year and maximum

volumes were observed during the warmest months of the year

(Figure 4). Total phytoplankter cell numbers varied in a manner similar to the phytoplankton standing crop, with a mid- winter minimum of 495 cells ml~ and a mid-summer maximum of -1 5672 cells ml

Phytoplankton populations comprised representatives from

5 algal divisions and 36 genera (Table 2). The fluctuations

of Cyanophyta standing crop (mostly Anabaena) can be observed

from Figure 5. Blue-green algae never dominated the phyto-

plankton standing crop (Figure 6), but did account for 40 to

50 percent of the total phytoplankton cells on 3 sampling dates. 20

Figure 4. Phytoplankton volumes in ml/m 3 as observed at Stations 2 and 5 in North Lake, September 1973 through August 1974. 21

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Table 2. List of Phytoplankton Observed in North Lake,

Euglenophyta Cyanophyta Chlorophyta ChrysophytajPYrrophyta

Euglena Anabaena Ankistro- Fr agilleria Ceratium Phacus Anacystis desmus Synedra Glenodin- Aphanothece Chlamydo- Unknowns ium Chroococcus monas Meris- Closterip.- mopedia sis Unknowns Closterium Coelastrum Cosmarium (2 species) Crucigenia Dictyosphae- rium Elakatothri Euastrum Franceia Gloeocystis Goelenkinia Kirchner- iella Lagerhaemia Qocystis Pandorina Pediastrum Scenedesmus Sphaerocys- tis Staurastrum (2 species) Treburia Tetraedron Unknowns

4- ______23

Figure 5. Phytoplankton standing crop per m2 euphotic zone in North Lake. (Numbers indicate number of genera present.) 24

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In terms of volume of the total phytoplankton population,

Cyanophyta were practically absent from mid-winter through late spring. Chlorophyta were consistently represented by present 7 to 16 small, nannoplankton-sized genera which were of throughout most of the year. On an annual basis, genera total Chlorophyta comprised an average of 29.5 percent of the genera phytoplankton standing crop (Table 3). Chlorophyta species which were almost always present in samples included two

of Cosmarium, one species each of Tetraedron, Scenedesmus,

Staurastrum, Ankistrodemus, Curcigenia, Sphaerocystic and

Oocystic and small, unidentifiable green algae. The Chrysophyta genera present were all small diatoms.

order Pennales was represented on most occasions by members

of the genus Fragillaria and an occasional Synedra sp. The

remaining populations of Chrysophyta were comprised of members

of the order Centrales. Annual fluctuations of Chrysophyta

populations can be observed (Figure 5). Diatoms comprised

an average of 33.2 percent of the total phytoplankton standing

crop for the annual cycle of sampling (Table 2). Diatoms

dominated the phytoplankton population, at least on the basis

of cell volumes, on two sampling dates (Figure 5).

Euglenophyta populations were comprised of only two genera organisms. (Euglena and Phacus) of large, infrequently encountered of the total Euglenophyta never represented a large percentage proportions phytoplankton cell numbers but did represent large

of the phytoplankton population standing crop in the spring due 26

Figure 6. Community composition of phytoplankton in North Lake, 1973 - 74. 27 4 4 H

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to their relatively large individual size (Figure 6).. Eugleno- counts phyta genera were not represented in the phytoplankton during the late fall and winter months (November through

February) (Figure 5).

Ceratium hirudenellia and a single species of Glenodinium were encountered in plankton samples. No representatives of the phylum Pyrrophyta were encountered during late fall and winter months (Figure 5).. Even though members of Pyrrophyta were present in relatively low numbers, because of their large

size they constituted the dominant volume of phytoplankters

on two occasions (Figure 6).

Diversity (H) indices (Odum, 1971) for the phytoplankton

community were computed on the basis of cell number and cell

volume. Large differences between H computed on cell number

data and H computed on cell volume data existed when phytoplankton

populations were not dominated with respect to both cell number

and volume by the same algal genera (Table 4). Maximum values

of H, when computed on the basis of relative cell numbers or

on the basis of relative cell volumes per unit volume of reser-

voir water, were observed for the same sampling date (5/8/74).

On this sampling date, the phytoplankton population was

composed of at least 26 different genera representing 5 algal

divisions. Also, the phytoplankton community was not dominated

with respect to relative cell number or volume by any single

algal genus. A low E-volume value of 0.46 was calculated for

the phytoplankton population on 9/22/73. The phytoplankton 30

population on this date was dominated with respect to relative cell volumes by a single, relatively large species of Gleno- dinium. On a relative volume basis, Glenodinium represented

91 percent of the total phytoplankton standing crop observed for this sampling date. The phytoplankton community on

8/22/74 was dominated with respect to relative cell numbers by a single alga. Samples for this date had total cell counts of 3451 ml1 , 41 percent of which were a single, small species of Anabaena. The minimum H-cell number value (1.50) for the entire study period was observed for this date (Table 4).

Primary Productivity Studies

Rates of phytoplankton primary productivity simultaneously measured at the two major study sites (i.e., Stations 2 and 5) followed similar annual trends (Figure 7). It should be noted that, with a few exceptions, there was good precision (average variance - 5 percent of mean) in estimating the primary productivity rates occurring at each station on any given sampling date. On 3 sampling dates (10/6/73, 5/8/74 and 6/4/74) independently determined primary productivity rates were greater at Station 5 than at Station 2. On two of these three dates, the range of duplicate primary productivity estimates at Station 5 overlapped the range of estimates for Station 2.

A two-way analysis of variance revealed significantly greater

(P = 0.01) primary productivity rates occurring at Station 2 versus Station 5 for 15 sampling dates analyzed. In comparison 31

Table 4. Values of H computer for phytoplankton volumes and cell numbers for North Lake,

Date H by volume/m 3 H by cell number/ml

9/22/73 0.46 1.87 10/06/73 1.26 2.10 10/22/73 2.60 2.43 11/03/73 2.33 2.22 11/17/73 1.81 2.19 12/03/73 1.85 2.16 1/08/74 1.47 1.93 1/26/74 1.21 1.69 2/11/74 1.49 1.97 2/22/74 1.22 1.60 3/10/74 2.09 1.59 4/06/74 1.71 2.28 5/08/74 2.46 2.59 6/04/74 1.61 2.27 7/16/74 1.71 1.34 8/22/74 2.27 1.50

-4 - - -. - .------32

Figure 7. mg C fixed/hr/m2 in the euphotic zone of North Lake, 1973-74. 33

N~No

low 8 9

o W O oto N 3NOZ Zl1OHdf3 NI g..Wul .44 Q3XIJ D Bw 34

to primary production values measured in various other reservoirs

and lakes, productivity was relatively low in North Lake (Table

5).

Simple correlations were calculated in a multiple linear

regression analysis for each of 19 different variables (Table 6)

against the observed primary production rates on 15 sampling

dates at the 1, 3 and 5-meter depths at both Station 2 and

Station 5. One parameter, H-by relative cell numbers, was

correlated significantly with the primary productivity rates

observed on 15 sampling dates at the 1 meter depth. H-by

relative cell numbers was significantly correlated with the

1 meter primary productivity rates observed at Station 5 but

not with primary productivity rates observed at Station 2. In

fact, none of the 19 parameters was significantly correlated with the 1 meter primary productivity rates observed at both

stations. At the 3 meter depth, conductivity was the only parameter significantly correlated with primary productivity rates at both Station 2 and Station 5 (significant at Station 2; highly significant at Station 5). No parameters were significantly correlated with the primary productivity rates observed at both Station 2 and Station 5 at the 5 meter depth for the

15 sampling dates.

Stepwise multiple linear regression analyses of the same

19 parameters regressed against primary productivity rates yielded multiple R-square values in excess of 90 percent from

8 or less variables at each depth and at each station. In one 35

Table 5. Primary production values observed in various lakes of the world in comparison to North Lake.

Mean Net Primary Production -2-@-ow Body of Water mg Cm day TmgCm day

Lake Vanda, Antarctica 14 0.24 Lake Tahoe, Cal. - Nev. 28 - 133 1.65 Brooks Lake, Alaska 158 3.5 Lake Superior 16.6 Lake Huron 23.0 Crooked Lake, Indiana 469 31.0 Lake Michigan 37.6 Martin Lake, Indiana 561 56.0 North Lake, Texas 521 104.0 Clear Lake, Cal. 438 146.0 Lake Erie 175.2 Waco Reservoir Texas 857 390.0 Sylvan Lake, Indiana 1564 489.0 Lake Erken, Sweden 40 - 2205 730.0 Lake Esrom, Denmark 1600.0 Lake Furese, Denmark 2100.0

-I.

Modified after Kimmel and Lind (1972) . 36

Table 6. List of variables used in correlation and stepwise multiple linear regression analyses_ of primary productivity in North Lake.

Parameter Unit of Measure Variable Number

1 Productivity Rate ug C 1 1hr "lY" Temperature OC 1 pH 2 Conductivity umhos 3 Percent Light Trans. 4

Total Phytoplankton -3 Volume m 3 mlmim 5 Cyanophyta Volumes 6 I Chlorophyta Volumes 7 it Chrysophyta Volumes " 8 if Pyrrophyta Volumes 9 if Euglenophyta Volumes 10 H-by Relative Volumes 11 Total Phytoplankton Numbers cells ml 1 12 Cyanophyta Numbers i" 13 Chlorophyta Numbers i 14 Chrysophyta Numbers i 15 Pyrrophyta Numbers i 16 Euglenophyta Numbers if 17 Inorganic Carbon mgl 1 18 H-by Relative Cell Numbers 19 37

case (Station 5, 3 meter depth), only 4 variables (conductivity,

H-by cell numbers, Chrysophyta volumes and pH) were necessary to achieve an R-square value of 92 percent. Comparison of the variables explaining the variance in primary productivity rates at corresponding depths of different stations showed little similarity. Likewise, little similarity existed between the variables explaining up to 90 percent of the primary productivity variance at different depths at the same station.

The foregoing analyses indicated that the variability of

observed primary productivity at any of the depths of either

station was not directly related to any single physico-

chemical or biotic parameter compared with it, nor was it

directly related to any small group of the aforementioned

parameters. It is assumed that a much more complex relation-

ship exists between primary productivity, at least as measured

in this study, and the environmental factors I compared it

with.

Primary productivity measured on an instantaneous basis

was not observed to be inhibited by power plant entrainment

during this study; in fact, productivity stimulation was

observed at Station 2. Furthermore, productivity stimulus

was observed on 2 dates (12/3/73 and 3/10/74) when no change

of temperature resulted from power plant entrainment and the

entire reservoir was homeothermous (Figures 2 and 7). Perhaps

the observed stimulus of productivity at Station 2 was due to

enhanced diffusion rates between phytoplankton and their exter- 38

nal environment caused by the relatively turbulent discharge stream. Other workers have noted positive effects on algal metabolism caused by environmental turbulence (Doty, 1971;

Gessner and Hammer, 1968; McIntire, 1968; Schumacher and

Whitford, 1965; Rodgers and Harvey, 1976). Obviously, similar static conditions occurred inside in situ 1C produc-- tivity flasks during incubations at Station 2 and 5, but the phytoplankton at Station 2 may have been more "charged" and potentially photosynthetically active due to turbulence enhanced nutrient and waste diffusion rates immediately prior

to the collection.

Failure to observe instantaneous inhibition of photo-

synthesis at Station 2 could also be due to my method of measuring primary productivity. In this study, I employed

Non-Filtration 14C techniques and thus estimated total photo-

synthetic carbon assimilation. Other workers have used more

conventional Filtration techniques and have not attempted

to estimate photosynthetically fixed carbon which may have been

released to the extracellular environment. It is well known

that a variety of different conditions which might be

considered stressful can cause variable amounts (up to 90

percent) of photosynthetically fixed organics to be released

by phytoplankton (Fogg, Nalewajko and Watt, 1965; Watt, 1965;

Anderson and Zeutschell, 1970). "Apparent" instantaneous

photosynthetic inhibition might be observed if photosynthetically

fixed but extracellularity released organics are not estimated. 39

Examination of data collected during the latter part of this study (7/20/74 and 8/22/74) at first appeared to suggest some degree of thermally-induced photosynthetic inhibition occurring on a reservoir-wide basis. It can be seen that on these two dates the highest temperatures and near maximum observed phytoplankton standing crops coincided with the near minimum primary productivity values observed during this study (Figures 2, 4 and 7). However, it should be noted that even for these two dates, the productivity at Station 2 was greater than at Station 5 (Figure 7), which suggests that high temperature was not the cause of any instantaneous photosynthetic inhibition at Station 2, much less the entire reservoir. It is likely that the explanation for the preceeding coincidental, yet apparently contradictory, facts

(high standing crops but low productivity of phytoplankton) lies in the acknowledged inability of visible phytoplankton counts to accurately reflect the true phytoplankton biomass. Indeed, no significant correlation was found between phytoplankton standing crop estimates and primary productivity in this study. CHAPTER IV

CONCLUSIONS

of In general, abiotic parameters (with the exception in temperature) were essentially identical at all stations

North Lake, including Stations 2 and 5. Phytoplankton

standing crops were not significantly different at Stations

2 and 5 which indicated there was no wholesale destruction

of cells due to power plant entrainment. The fact that 2 could photosynthetic metabolism was stimulated at Station

merely be a reflection of "Q10 laws" which generally call for

increased rates of all metabolism (anabolic and catabolic) of with increases in temperature. Since no measurements cannot phytoplankter or community metabolism were made, I

confirm the foregoing hypothesis. However, productivity

stimulus at Station 2 could also have been due to turbulence

enhanced nutrient diffusion rates which caused photosynthetic

activity to be temporarily stimulated. Lack of metabolis

inhibition and/or wholesale destruction of phytoplankton

cells by power plant entrainment at North Lake might, after and all, be expected since this reservoir is 19 years old

its phytoplankton population has probably been somewhat

selected for its "power plant tolerance". It is certainly

biologically interesting that Cyanophyta, and algal division

40 41

noted for its high thermal tolerances and predisposition for dominating thermally and otherwise stressed aquatic environments are conspicuously "non-dominate" in North Lake.

The primary productivity, algal standing crop and organic carbon in North Lake were all conspicuously low when compared to other nearby southwestern reservoirs probably as a result of nutrient limitation aggravated by power plant usage-caused evaporation and consequent concentration of dissolved solids.

Precipitation of incoming dissolved nutrients such as P and N by excessively concentrated cations could be the ultimate cause of low primary production in North Lake.

Thus the effect of the power plant entrainment at North

Lake is possibly to limit primary production -- the basic link in the food chain -- not by immediate or instantaneous entrainment-linked inhibition, but rather by long-term, subtle, thermally-linked precipitation activities causing nutrient limitation. APPENDIX

The Significance of the Thermal Pollution Problem

Thermal pollution is a problem receiving significant

attention in the recent era of environmental awareness. One

form of thermal pollution, heated aquatic effluent, is often

produced in large quantities from point sources and discharged

into relatively confined aquatic ecosystems. The aquatic

ecosystems receiving these discharges are often extremely

important to man. Their importance is related to the quality

of water they supply for floral and faunal habitat, for various

human activities and needs and for their intrinsic aesthetic

properties.

Growth in the Electfic Power Industry

Industry, specifically the electrical power industry, is

the Largest man-made sour-ce of thermal pollution (Scott, 1973).

Electrical power generation has doubled every ten years since

1945. The installed thermal electrical generating capacity

in this country in 1970 was approximately 300 million kilowatts

(300,000 megawatts) (Wilson, 1970). Estimates in 1970 by

Mr. Fred H. Warren, Advisor on Environmental Quality of the

Federal Power Commission, pointed out that by 1980 the United

States will have a generating capacity of 668,000 megawatts

(Barton, 1970). Estimates for generating capacity in 1990

42 43 are approximately 1,261,000 megawatts (Steigelmann, 1969).

The increasing demand for electrical power is due to several factors. Population growth is important in increasing demand but the usage rate per person is increasing much faster.

Between 1950 and 1968 the United States' population increased by one-third -- but the United States' consumption of electrical energy quadrupled. Per capita consumption during this period rose from 2,000 kilowatt hours to 6,500 killowatt hours per year. The estimated per capita consumption in 1980 is 11,500 kilowatt hours and for the year 2000 will be approximately 25,000 kilowatt hours (Belter, 1969).

Several methods for electrical power generation exist today: hydroelectric, thermal-electric (conventional fossil fueled or nuclear fussion fueled), gas turbine and diesel driven generators, magnetohydrodynamics, geothermal, solar and fuel cells (Scott, 1973). Nuclear fussion technology offers hope for future power generation but is unlikely to be a significant power source in this century (Scott, 1973).

Hydroelectric and thermal-electric processes supply virtually all of our nation's electric power at present.

Hydroelectric power generation supplied approximately 33.4 percent of this nation's electricity in 1940, approximately

16.3 percent in 1970 and is predicted to supply ever decreasing percentages in the future. In contrast, thermal-electric power supplied approximately 66.6 percent of our electrical power in

1940, approximately 83.7 percent in 1970 and is predicted to 44

supply ever increasing percentages in the future (U. S. Federal

Power Commission, 1970). The steady decline in hydroelectric power importance is due to the lack of suitable sites for this type of power generation. Hydroelectric generation, whether by hydroelectric dam, pumped-storage facilities or tidal current developments, is relatively clean and generally produces thermal pollution problems of a different nature from the heated thermal effluents of thermal-electric power generation.

In 1967 conventional fossil-fueled (coal, fuel oil, natural gas) generators produced nearly 99 percent of our thermal-electric power. Nuclear fueled plants produced the remaining 1 percent (Hogerton, 1968). In 1973 nuclear fueled thermal electric plants produced 3 to 4 percent of our electrical energy (Healy, 1973). About 50 percent (120) of the power plants now proposed or under construction are atomic power plants (Carlson, 1969) .

It is estimated that by the years 1980 and 2000, 25 percent of the estimated 668,000 M.W.and 69 percent of the

estimated 1,852,000 M.W., respectively, of our total electrical power generating capacity will come from atomic power plants

(Belter, 1969).

In addition to the foregiong facts about the future

upsurge in atomic powered electrical energy production, the

following facts are important to an understanding of the magnitude of possible thermal pollution problems. 45

At present the best, most modern fossil-fueled plants

are about 40 percent efficient. That is, they discard about

60 percent of the thermal energy they produce to their immediate

environment (approximately 10 percent to the air through stack

emissions and approximately 50 percent to their condensor cooling

waters) (Scott, 1973; Belter, 1969). Modern atomic plants -

because of limitations on pressures - have peak steam tempera-

tures of about 3400 C (versus 5400 C for fossil-fueled plants)

and yield maximum thermal efficiencies of about 33 percent.

Virtually all thermal wastes from atomic plants (77 percent)

are released through the condensor cooling waters. The result

is that atomic plants emit nearly 50 percent more waste heat

into aquatic thermal effluents and require correspondingly greater amounts of cooling water than comparably sized fossil fueled plants. Future improvements in nuclear reactors (fast- breeder types - predicted availability in 1980's) should make them comparably efficient with the best fossil-fueled plants

(Scott, 1973; Belter, 1969). However, until this improvement occurs, waste heat problems will continue to worsen as nuclear- fueled power generation increases.

The Need for Cooling Water

Thermal-electric power stations produce electricity by driving generators with high pressure steam turbines. They require water to cool and condense the steam before recycling it back to the heat source. The cooling water is generally heated 2 to 150 C above ambient water temperatures and then 46

returned to its original environment (sometimes with added disinfectant chemicals).

It has been estimated that 75 percent of all the water withdrawn for industrial cooling uses in 1968 -- 204,300 billion liters (559.8 x 109 liters/day) -- was passed through power plant condensors (Steigelmann, 1969). Estimated condensor cooling water needs for 1980 are 1,135 x 109 liters/ day -- 908 x 109 liters of which will be fresh water (Geraghty, Miller, VanderLeedon and Troise, 1973). This amount is roughly equivalent to one-fifth of all the fresh surface water runoff in the United States (Geraghty, Miller, Vanderleedon and Troise,

1973; Krenkal and Parker, 1969). The total national daily fresh water runoff is about 5,448 billion liters. Morevoer, if one discounts flood flows which occur through about one- third of the year and account for about two-thirds of the total runoff, it becomes apparent that by 1980 the electric power industry will require about half the total daily runoff for the remaining two-thirds of the year (Singer, 1969). Recent projections for cooling water needs by the year 2000 indicate the requirement for cooling water will equal about two-thirds of the total daily national runoff (Belter, 1969; Singer, 1969).

Two-Fold Concentration Problems

The real reason for thermal pollution's coming to the forefront of environmental awareness is that the problems are constantly getting more concentrated. Geographically and perhaps 47 biologically significant levels of pollution are occurring.

Geographical Concentration

There is often efficiency in bigness. The power industry of the United States is no exception to the "bigness" trend

in our society. Capital investment per unit of electrical

power produced usually decreases with increasing plant size --

up to a point. Generally maximum efficiency is reached around

400 M.We. for nuclear fueled plants. Efficiency can be further

increased by locating multiple plants at the same installation

site (Wilson, 1970). The present trend is toward construction

of large generating complexes composed of several units of

about 1000 M.W. capacity (Belter, 1969; Steigelmann, 1969;

Carlson, 1969; Singer, 1969; Wilson, 1970).

Thus, the trends in future electric power production are

increasing production from less efficient nuclear fueled power

plants; increases in the size of electric power generating

complexes; increases in total number of electric power generating

complexes; increases in the amount of water needed for cooling

and in thermal waste discarded to the environment; and

increases, often in the maximum temperature, of thermal effluents

released.

Biologically Significant Concentration

It is a technological fact that 60 to 75 percent of the

energy used in thermal electric power generation must be

discarded as heat. Although there are many different methods 48

for dealing with waste heat, once through cooling by fresh water and its immediate return to its original environment is by far the most economical and prevalent method (Scott,

1973). The heated aquatic effluent from thermal electric power stations is 2 to 150 C warmer than ambient water temperatures. After its discharge, the less dense, heated water floats and spreads as a plume over the receiving water.

Heat dispersal by radiation, evaporation, etc. depends on such

factors as currents, turbulence of receiving waters, air temperatures and wind speeds.

Aquatic ecosystems are delicately balanced combinations of biotic and abiotic components. The biomass of the system

affects and is effected by the abiotic factors in the surrounding environment. The quality of water in an aquatic ecosystem is related to the needs of the biomass which lives in or depends on that water. Man is only part of the biomass which depends

upon the quality of water in aquatic ecosystems.

The biomass of an aquatic ecosystem can be divided into

three basic types of organisms: primary producers, secondary producers and consumers. The primary producers, which perform

the fundamental activity of photosynthesis, are perhaps the most important type of organisms in most aquatic ecosystems.

The euphotic zone (where photosynthesis occurs) of an aquatic

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