TT

Table 2, THE TOXICITY OF CHLORINE TO SELECTED SPECIES OF MARINE PHYTOPLANKTON

(Values are ugs C1,/liter that produced a 50% reduction
in growth rate during a 24-hour exposure period.)

24-hr IC-50 24-hr IC-50

Species ugs/C1/1 Species> ugs/C1/1
Skeletonema costatum 95 Chaetoceros decipiens 140
Rhodomonas baltica 110 Thalassiosira nordensholdii 195
Dunaliella tertiolecta 110 Thalassiosira rotula 330
Monochrysis lutheri 200 Asterionella japonica 250
Thalassiosira pseudonana 75 Chaetoceros didymum 125
200

Detonula confervacea

Temperature 20°C.

bremperature 10°C.


25.

26.

27.

Carpenter, E.J., B.B. Peck, and S.J. Anderson. 1972. Cooling
Water Chlorination and Productivity of Entrained Phytoplankton.
Marine Biology 16: 37-40.

Galtsoff, P.S. 1946. Reaction of Oysters to Chlorination.
Fish and Wildlife Serv., Res. Rep. No. ll.

Muchmore, D. and D. Epel. 1973. The Effects of Chlorination of

Waste Water on Fertilization in Some Marine Invertebrates.
Marine Biology 19: 93-95.

28


detachment and movement of mussels in the direction of water flow
could be achieved with 0.02-0.05 mg/1 residual chlorine levels.

Although various methods for fouling control have been documented
for over two decades the practice has been to adopt chlorination as
method of choice. Interestingly, whereas continuous low level
application has been shown to produce most effective control, the
usual practice in the U.S. is to use high intermittent doses.
Further, until recently, there has been little serious effort to
develop alternatives. This also seems unusual since the use of
recirculating warm water was effectively developed as a primary
control at Redondo Beach twenty years ago. Interest in this type
of system, particularly for condenser slime control, is increasing.
Several northeastern power companies are exploring short duration,
high temperature condenser cycles with good success.

As a result of the widespread use of chlorine in fouling control by
power companies, it was inevitable that concern would develop about
the impact on non-target species. The burgeoning energy needs of
the post-war era has resulted in the proliferation of generating
facilities particularly in coastal areas. The large volumes of
needed cooling water were more readily available from the marine
environment than from the already overburdened fresh surface waters.
By 1980 it is estimated that close to 2.5 x 1013 (9.5 x 1013m3)
gallons of cooling water will be taken yearly from estuarine waters
(6). More than 70% of this will have to be treated to reduce fouling
problems in some manner. It is imperative, therefore, that a data
base be prepared that will allow evaluation of the potential impact
of chlorine to non-target marine and estuarine waters.

FIELD ASSESSMENT

Field investigations at a 650 MW fossil fuel electric generating
facility on upper Narragansett Bay were initiated in May 1970 and
terminated in June 1971. At the time of this study, the cooling
water demand was 6.5 x 10° gpm (2.4 x 103m3/minute) : a AT = 10°C;
and a daily chlorination cycle of 30 minutes/each of three units/day.
Dosing was as NaOCl at an initial concentration of ~10 ppm.
Residuals in the discharge canal ranged from 0.5-3.0 ppm.

The objectives of this program were to develop sampling techniques
for holo- and meroplanktonic forms which would permit the assessment
of thermal, mechanical, and chemical effects to pumped organisms.
Biological information was then integrated with plant operating
modes and water quality data.

Sampling consisted of weekly collections from intake canal and
discharge canal for both chlorination and non-chlorination cycles as
well as from a control station in upper Mt. Hope Bay that was not


ST

CHLORINE - PPM

PERCENT /NHIB/TION
++ 50
or2s
e-0

NG
\

e >

L 1 5

10 10.0 100
EXPOSURE TIME ~- MINUTES

Figure 2. Response isopleths for the marine diatom,
Thalassiosira pseudonana, exposed to chlorine



ABSTRACT

Chlorine has and continues to be the principal biocide in systems
using marine waters for cooling purposes. While considerable
information exists on the role of chlorine applicable to specific
fouling organisms, data on its impact upon non-target marine species
is limited.
Results of a year's field investigations at a power plant on upper
Narragansett Bay indicated that total residual chlorine at >1.0 ppm
was responsible for complete mortality of all pumped phytoplankton
and up to 75% of the zooplankton. In terms of biological impact,
this amounted to approximately 15 tons of primary producer carbon
and 1.6 tons of primary consumer carbon from June to December.

Biological assay systems using indigenous holo- and meroplankton
were designed to model the chlorination patterns of power plants. A
matrix of chlorine concentrations and exposure times permitted the
generation of response isopleths that were then applied to developing
design criteria. This data indicated that certain algal species had
a 50% reduction in photosynthesis at 0.15 ppm after 10 minutes
exposure and complete growth inhibition at 0.3 ppm after 5 minutes
exposure. Microzooplanktonic adults showed 50% mortality after 5
minute exposures to 2.5 ppm total residual chlorine. Furthermore,
chlorinated seawater showed residual toxicity to algae, 100 hrs. post-
dosing, when no detectable residual chlorine was present.

Studies of larval and juvenile fish emphasize that short-term exposure
to chlorine levels <0.2 ppm will produce a significant biological
effect under routine intermittent dosage conditions.

Laboratory bioassay data was verified in a field study where the
researcher was capable of modifying power plant operations. This
study also was used to both develop and verify the use of ATP as a
measure of pumped damage to both zooplankton and phytoplankton.

The above studies, supplemented by existing data on the toxicity of
chlorine to marine organisms, have resulted in a modification of
chlorination practices, more stringent effluent guidelines, and
revised water quality criteria.

iii


10.

11.

REFERENCES

Odum, E.P. 1971. Fundamentals of Ecology, 3rd Ed. W.B.
Saunders Co., Philadelphia, Pa.

McHugh, J.L. 1966. Management of Estuarine Fisheries. In: A
Symposium on Estuarine Fisheries. Am. Fish. Soc. Special Publ.,
No. 6, pp 133-154.

National Estuarine Pollution Study. 1970. Secretary of
Interior In: Document No. 91-58. U.S. Senate, 91st Congress,
2nd Session.

Thorson, G. 1950. Reproductive and larval ecology of marine
bottom invertebrates. Cambridge Philosophical Society Bio-
logical Reviews, Vol. 25, 1-45.

Jeffries, H.P- 1967. Saturation of Estuarine Zooplankton by
Congeneric Associates. In: Estuaries, G.H. Lauff, Ed.,
American Association for the Advancement of Science, Pub.

No. 83, pp 500-508.

Clark, J. and W. Brownell. 1973. Electric Power Plants in the
Coastal Zone: Environmental Issues. American Littoral Soc.,
Special Publ. No. 7.

White, G.C, 1972. Handbook of Chlorination. Van Nostrand,
Reinhold Co., N.Y.

Ingols, R.S., P.E. Gaffney, and P.C. Stevenson. 1966. Bio-
logical activity of halophenols. JWPCF, 38 (4): 629.

Jolley, R.L. 1973. Chlorination Effects on Organic Consti-
tuents in Effluents from Domestic Sanitary Sewage Treatmente
Plants. Water Pollution Control Fed. Mtg., Cleveland, Ohio.

Holland, G.A., J.E. Lasater, E.D. Neumann, and W.E. Eldridge.
1964. Toxic effects of organic and inorganic pollutants on
young salmon and trout. Wash. Dept. Fish. Res. Bull. 5:
203-215.

Arthur, J.W. and J.G. Eaton. 1971. Chloramine toxicity to the
amphipod Gammarus pseudolimnaeus and the fathead minnow
Pimephales promelas. J. Fish. Res. Bd. Canada 28 (12):
1841-1845,

26


the chlorine levels in the test vessels. The original stock solution
(100 ppm) was checked by titration with sodium thiosulfate and appro-
priate dilutions were used for lower levels. In order to determine
if significant amounts of chlorine were lost during the twenty-four
hour period, seawater dosed at 5 ppm was monitored every four hours.
After twenty-four hours this value decreased to 4.3 ppm. In sub-
sequent short term bioassays (<4 hrs) the problem of chlorine loss
was not deemed significant for this system.

The concentrations of chlorine found toxic after twenty~four hours
exposure are lower than those found to be satisfactory for anti-
fouling control. Hydrographic conditions, however, are generally
not favorable to prolonged exposures in power plants unless extensive
cooling or discharge canals are present. Though informative, the
twenty-four hour toxicity studies described above do not reflect
actual in situ exposures and therefore are not predictive for most
operating conditions.

The primary objective of subsequent studies was to examine a
spectrum of chlorine concentrations and exposure times in an effort
to delineate the precise relationship between these factors as they
relate to biological response.

The model developed and described below was applied to four species
of phytoplankton--Detonula confervaceae, Asterionella japonica,
Skeletonema costatum, and Thalassiosira pseudonana. The most
extensive series was performed on T. pseudonana and will be described
in detail.

The test species was cultured in unenriched filtered natural sea-
water collected from the intake. This water contained adequate
nutrients to support excellent growth without additional nutrient
supplementation. Chlorine (NAOC1) was added to a growing culture
of the test species (~5000 cells/ml) and the exposure time with a
stopwatch. Sodium thiosulfate, which was used to stop the action
of chlorine, did not interfere with growth or photosynthesis of the
test species at levels one-hundred times greater than the concen-
trations employed. Post exposure aliquots were removed and incu-
bated for four hours with Nnaci4co,. The remaining cultures were
placed in an incubator and the growth rates measured for 48 hourse
to evaluate permanent damage (Table 3).

The shortest exposure interval was 10 seconds due to manipulative
restrictions. At 1.0 ppm residual chlorine no growth was measured
even at the shortest exposure, although there was some photo-
synthetic activity during the first four hours post exposure. At
0.5 ppm there were significant decreases in both photosynthesis and
subsequent growth after only 15 seconds exposure with no growth
recorded after 30 minutes exposure. As the concentration of
chlorine decreased, longer exposure periods were required to elicit

12


CHLORINE - PPM

8T

PERCENT MORTALITY

+= 100
02 75
e250
Of 25
ao
50+ «
256 SSS

Or se EES e ae +

10.0 (@

Ol 10 10.0 100 1000

EXPOSURE - MINUTES

Figure 4. Response isopleths for the marine calanoid
copepod, Acartia tonsa, exposed to chlorine



a response. At 0.15 ppm only moderate growth inhibition was recorded
even after twenty minutes exposure, but initial photosynthesis was
markedly reduced (48% of control). It is interesting to note that
in several instances there are significant decreases in photosynthe-
sis that are not reflected in corresponding decreases in growth rate.
There was not enough data to thoroughly explore the relationship
between photosynthesis and growth under chlorine stress. The data
does indicate that information based solely upon C-14 assimilation
could be misleading if extrapolation to long term affects were to be
attempted.

The results of this study predict that chlorine concentrations

>0.5 ppm cannot be tolerated by pumped phytoplankton during the usual
1-3 minute plant transit time. Survival and growth at 0.2 ppm is
normal after five minutes exposure and only 26% inhibition is noted
after a 20 minute exposure. It would appear that continuous
chlorination at 0.2 ppm for anti-fouling purposes while having some
impact would not seriously alter the productivity of this trophic
level. The practice of intermittent chlorination at >1.0 ppm will
essentially destroy all phytoplankton pumped during the chlorination
cycles.

From the type of data discussed in Table 3, extrapolated values for
zero, 25, 50, and 100% inhibition of growth can be calculated for
specific exposure time at each chlorine concentration. The isopleths
of response can then be graphically displayed (Fig. 2). Similar,
though less detailed, data was generated for other species.
Asterionella japonica exhibited sensitivity similar to that of T.
pseudonana but Detonula confervaceae was 2-5 times less sensitive

at concentrations <0.5 ppm. Skeletonema costatum (Fig. 3) was
somewhat less sensitive to chlorine than Thalassiosira. S$. costatum,
however, is more sensitive to thermal stress than Thalassiosira with
marked inhibition of growth at 32.5°C. Therefore, S. costatum would
be expected to have a higher response interaction than Thalassiosira
which can tolerate thermal stress exposures at 35-36°C. The graph—
ical representation of response isopleths can be effectively used by
design engineers since it gives precise and easily interpretable
information on the degree of biological impact that will result from
changes in operational mode.

ZOOPLANKTON~MEROPLANKTON

The approach as described above was employed with selected species
of estuarine adult copepods and sand shrimp larvae. All copepod
experiments were performed in filtered natural seawater, 30 o/oo at
15°C. Larval experiments were done at 10°C. The response measured
was mortality 24 hours post exposure.

A detailed study was performed on Acartia tonsa because it is one

14


12.

13.

14,

15.

16.

17.

18.

19.

20.

21.

22.

23.

24,

Richards, A.P. 1953. The use of chlorination and heat in the
control of marine borers. Bull. Sea Horse Inst. 1 (2).

White, H.E. 1947. Control of Marine Fouling in Seawater
Conduits Including Exploratory Tests on Killing Shelled Mussels.
In: Trans. Amer. Soc. Mech. Eng. Symposium on Marine Fouling.

Clapp, W.F. 1947. Some Biological Fundamentals of Marine
Fouling. In: Trans. Amer. Soc. Mech. Eng. Symposium on
Marine Fouling.

Turner, H.J., D.M. Reynolds, and A.C. Redfield. 1948. Chlorine
and sodium pentachlorophenate as fouling preventatives in
seawater conduits. Indus. & Engnr. Chem. 40: 450-453.

James, W.G. 1967. Mussel fouling and use of exomotive chlorina-
tion. Chem. & Ind. 24: 994-996.

Strickland, J.D.H. and T.R. Parsons. 1968. A practical hand-
book of seawater analysis. Fish. Res. Bd. Canada Bull. No.
167, 311 pp.

McLean, R.I. 1973. Chlorine and temperature stress on
estuarine invertebrates. JWPCF 45 (5): 837-841.

Alderson, R. 1970. Effects of low concentrations of free
chlorine on eggs and larvae of plaice, Pleuronectes platessa.
FAO Tech. Conf. Marine Pollution. Effects on Living Resources
and Fishing.

Fairbanks, R.B., et al. 1971. An assessment of the Effects of
Electrical Power Generation on Marine Resources in the Cape
Cod Canal. Mass. Dept. Nat. Res., Div. Marine Fisheries, 39.

Stober, Q.J. and C.H. Hanson. 1974. Toxicity of chlorine and
heat to pink, Oncorhynchus gorbuscha and Chinook salmon,
Q. tshawytscha. Trans. Amer. Fish. Soc. 103 (3): 569-576.

Virginia State Water Control Board. 1974, James River Fish
Kill 73-025. Bureau of. Surveillance and Field Studies,
Div. of Ecological Studies, 61 p.

Gentile, J.H., N. Lackie, and S. Cheer. 1974. Assessment of
effects of entrainment to microzooplankton. In manuscript.

Carpenter, E.J., B.B. Peck, and S.J. Anderson. 1974, Survival

of Copepods Passing Through a Nuclear Power Station on North-
eastern Long Island Sound, USA. Marine Biology 24: 49-55.

27


% MORTALITY

@ ZOOPLANKTON
© CHAETOGNATHS
Q FISH LARVAE
Q FISH ADULTS
@ CHLORINE
Or 9 Oo °° e © fa 75
&
44
75
. 8 43
s s
sob
e es e
e e 42
e es s
° s
25h ce 6 4!
e ee
ol_i ©? 4 4 1 a ae? 1 semen 1 om @)/0
M A M J J A s ° N
MONTH

Figure 1. Seasonal distribution of mortality to entrained
zooplankton at Narragansett Bay power plant

SNIMOTHS Wdd


INTRODUCTION

The importance of estuarine communities to man for both recreation
and sustenance cannot be overemphasized. Estuarine productivity is -
estimated at 20,000 kCal/m2/year compared with 1,000 kCal/m2/year
for the open ocean (1). Productivity alone, however, doesn't truly
describe the importance of estuaries. What must be realized is that
commercially important species of fish, shellfish, and crustaceans
are dependent on the highly productive phytoplankton and zooplankton
populations for food. In addition many of these same species of
macrofauna are dependent upon the water column for spawning, early
development, and growth during portions of their life history.
McHugh (2) reports that 63% of the commercial catch of fish and
invertebrates in the Atlantic consists -of species dependent on
estuaries. The National Estuarine Pollution Survey (3) notes that
65% of marine fish require the rich estuarine environment for some
part of their life history. Thorson (4) estimates that 70% of all
bottom invertebrate species have planktotrophic larvae that inhabit
the water column for a 2-4 week period. Jeffries (5) reports that
meroplankton comprise from 10-80% of the total zooplankton population
collected from three East Coast estuaries.

The salient point from these studies is that the water column
supports a myriad of planktonic forms that represent important life
stages, from a wide variety of commercially and ecologically
important communities. Yet, it is this very component of the
estuarine system that is being used increasingly as a source of
cooling water for a variety of industrial uses. This water contains
a vast array of living forms which are then subjected to mechanical,
thermal, and chemical stress. There are 140 existing or planned
power plants located on marine sites, of which 133 have continuous
flow, once-through cooling (6). The projected cooling water demands
from these plants amount to 1 x 10° cfs (2.8.x 103 m3/sec). This
converts to a yearly consumption of 2.6 x 1013 gallons (“1.0 x

1oll m3).

With this projected usage of nearshore marine waters it is im-
portant that research effort be directed toward identifying the
potential impact of this type of operation to the environment. Since
marine life in water used for cooling purposes is subjected to three
major stress components--mechanical, thermal, and chemical--an
evaluation of the relative importance of these as related to biologi-
cal impact is necessary. The objective of the study reported here
was threefold--to examine an operating facility and focus on one
major stress component (chlorine) in order to determine which portion
of the biotic community is affected; to design and develop laboratory

1


simulate exposure durations at the discharge and canal sampling
points. The ATP value at the discharge was 0.16 and at the canal,
0.05 ugs ATP/liter. This indicated that the through plant damage
was primarily attributable to chlorine.

Attempts to evaluate the effects of these two chlorine regimes on
zooplankton were complicated by the unexpectedly high mortalities
encountered from plant passage during non-chlorination periods.
However, when rates of sinking were compared, the effects of
chlorination were quite evident (Gentile, Lackie, and Cheer, 1974
[23]). The degree to which this response reflected irreversible
damage due to chlorination alone could not be proven since mechanical
damage was simultaneously occurring. When ATP/organism was evaluated
there were no significant differences between chlorination and non-
chlorination cycles. By the time the water mass had reached the end
of the discharge canal, the damaged organisms had settled out of the
water column and only healthy survivors were being sampled. Com-
parison of intake and canal stations by both ATP analysis and micro-
scopic counts revealed a 50-15% loss of zooplankton biomass. This
data supports recent findings by Carpenter et al., 1974 (24).

Investigating the effects of plant passage on productivity at a
Long Island Power station, Carpenter et al. (25) observed a 70%
decrease in productivity at 0.12 ppm continuous chlorination and
25% decrease at 0.2 ppm intermittent. From Table 7, a 30% decrease
in carbon-14 assimilation was noted at 0.2 ppm after 5 minutes
exposure. Post exposure growth rates, however, were normal leading
to the conclusion that the noted effects on productivity might be
transitory. The data from this study indicate that at 0.32 ppm
damage was essentially complete and irreversible.

CONCLUSION

The results of field and laboratory investigations on chlorine
toxicity to marine organisms reported here have been primarily de-
veloped from power plant related activities. These studies deal
with chlorine primarily in the available form and are unlike muni-
cipal waste water systems in which a considerable percentage of the
chlorine is in a combined state. Furthermore, the discharge of
chlorinated water from power plants is of an intermittent nature
rather than continuous as it is in municipal treatment plants.
Although these differences are important in terms of application of
this data for water quality standards, certain general conclusions
emerge.

Chlorine is one of the few elements for which experimentation has
demonstrated specific toxicity of a chemical to marine organisms.
Phytoplankton, juvenile fish, fish larvae, all show demonstrable
impairment of biological function at residual chlorine levels of

24


residual chlorine, respectively (22).

The data presented in this section provides an overview of chlorine
toxicity to a wide variety of organisms that could be impacted by a
power plant. The generalized summary presented in Fig. 5 shows the
distinct response patterns of the major organism groups. By choosing
any combination of chlorine concentration and exposure time one can
determine what group or groups of organisms are to be affected. The
data point represents fifty percent mortality at the respective
concentration and exposure period. The response slope for the algae
and copepods is quite similar though displaced while that of the
ichthioplankton and juvenile fishes is much steeper and covers a
wider range of concentrations. Obviously, intermittent chlorination
which involves high residuals (<5.0 ppm) for exposure periods of up
to 30 minutes will seriously affect phytoplankton, ichthioplankton,
and zooplankton populations. Lower chlorine levels (i.e., 0.25)
continuously applied would almost completely eliminate entrainment
damage and produce discharge residuals <0.1 ppm thus protecting
receiving waters. Still there is the potential hazard that continu-
ous chlorination and its by-products (i.e., chlorinated organics)
could impact larval and juvenile fish populations attracted by the
plume.

FIELD VALIDATION--MORGANTOWN GENERATING STATION

The field and laboratory studies discussed above indicate that
intermittent chlorination as generally practiced would result in
serious damage to a variety of plankton organisms that would be
entrained in cooling water. The laboratory studies, however, indi-
cate that lower levels of chlorine (<0.25 ppm) may show only moderate
damage to algae and be relatively safe for ichthioplankton and cope-
pods if exposures did not exceed one hour. An opportunity to eval-
uate the effects of chlorine levels less than 1.0 ppm in the field
arose and permitted us to verify laboratory studies. The primary
objectives of this effort were to evaluate the biological impact of
plant operational modes (particularly chlorination) as well as to
complete the evaluation and verification of ATP as a field assess-
ment of living biomass. This study was carried out with the
cooperation of Martin-Marrietta and Potomac Electric Power Company.

Sampling stations were set up at the intake, discharge, and terminus
of the canal. The passage of a unit water mass through the plant
requires approximately 2 minutes with an additional 45 minutes to
traverse the length of the canal. Studies were performed in late
spring, May 29-June 6; summer, August 23-28; and September 19-20,
1973. A thermal load of 6°C was typical with chlorination levels
of 0.55 and 0.32 ppm total residual. These residual values were
determined at the point of dosing and were usually reduced to 0.2
and 0.1 within the canal. Laboratory studies would predict that the

21


FIGURES

Seasonal distribution of mortality to entrained
zooplankton at Narragansett Bay power plant

Response isopleths for the marine diatom, Thalassiosira

pseudonana, exposed to chlorine

Response isopleths for the marine diatom, Skeletonema
costatum, exposed to chlorine

Response isopleths for the marine calanoid copepod,
Acartia tonsa, exposed to chlorine

Distribution of 50% response isopleths for marine
phytoplankton

vi

15

16

18

22


CONTENTS

Page
Abstract aii
List of Figures vi
List of Tables vii
Acknowledgments viii
Introduction 1
Chlorination 2
Fouling 3
Field Assessment 5
Bioassay Modeling 10
Field Validation--Morgantown Generating Station 21
Conclusion 24
References 26


BIOASSAY MODELING

Literature describing the toxicity of chlorine to marine organisms
is primarily related to fouling communities. Only limited informa-
tion on ecologically important or indigenous species was available
when this study was initiated. Since our staff has experience in
both the culture and bioassay of holo-, mero-, and ichthioplankton,
which are the major pumped species, a series of experiments was
designed to simulate the effects of chlorine during passage through
the plant and in the plume. A matrix of chlorine concentrations and
exposure times was selected for each species and post exposure
responses were measured periodically. Chlorine dilutions were
prepared in filtered seawater (30 o/oo). Test species were exposed
for varying periods of time and chlorine action was stopped either
by the addition of sodium thiosulfate or transfer of the test
species to clean seawater. Post exposure responses of growth,
photosynthesis, and mortality were monitored for 48-96 hrs.
Thiosulfate was shown to have no effect on the organisms at the
levels used.

PHYTOPLANKTON

Axenic cultures of marine phytoplankton obtained from our culture
collection were selected to include the primary ecological dominants
from both winter and spring. Also included were food organisms
often used in mariculture.

Studies were performed in enriched synthetic seawater (30 0/oo),
2500 lux continuous cool white illumination, at either 10° or 20°C.
Growth rates (k) were determined from daily cell counts using an
electronic particle counter, and the expression

= Nt 24. -

k = logo ie) te to-

Rates of photosynthesis were determined immediately after dosing
ceased by labelling an aliquot of the culture with Nag? C03
(0.1 yCi/2.4 uMc/ml). Triplicate light and duplicate dark exposures
were incubated for four hours, filtered at <-5 psi, the filters
were exposed to HCl fumes for 60 seconds, and the assimilated
radioactivity was counted by liquid scintillation spectrometry.

Since there was no reference data on the sensitivity of marine
phytoplankton to chlorine, routine short term (24 hr) bioassays on
eleven species of algae at two temperatures were performed. The
results (Table 2) indicate that these species are very sensitive to
chlorine. The 24 hr LC-50 values were generally one-tenth the con-
centrations monitored in the discharge canal and one-one hundredth
of that at the maximum initial dose. No attempt was made to monitor

10


ACKNOWLEDGMENTS

The authors would like to thank the following staff members for their
advise and assistance: Drs. S. Cheer, J. Gonzalez, and J. Prager;
Ross Johnson, Neal Lackie and George Morrison. In addition, we
appreciate the cooperation of Milton Anderson and his staff at

New England Power Co.; Drs. L. Bongers and T. Polgar of Martin-
Marrietta and their contractor Potomac Electric Power Company.

vili


oT

CHLORINE-PPM

o7

06

Os

04

0.3

0.2

Ol

PERCENT INHIBITION

r +50
0 +25
@-0
P. ° \
a e \ ° +
\, NX. NN
r e ° +
ee
4 = J
ol 10 10.0 100

EXPOSURE-MINUTES

Figure 3. Response isopleths for the marine diatom,
Skeletonema costatum, exposed to chlorine


Ecological Research Series



Non-nitrogenous organic compounds will also react with chlorine to
produce toxic substances. The mono-, di-, and trichlorophenols
have demonstrated toxicity to aquatic organisms (8). Jolly (9) has
prepared an extensive review of chlorinated organics found in
domestic sewage effluents.

The addition of chlorine, therefore, can result in a variety of
chemical species being formed; the relative proportions of which are
dependent upon pH, qualitative and quantitative composition of nitro-
genous compounds, and other organic material present in the water.
Such a potential complexity of biologically active and inactive
chemical species necessitates some type of classification.

Free residual chlorine is the residual chlorine existing in the
water as hypochlorous acid (HOC1) and hypochlorite ion (0C1~). The
disinfection capabilities of these two forms are quite different.
Because of its neutral charge and small molecular size HOC1 readily
penetrates cell membranes and may exert its effect biochemically
rather than as an oxidizing agent. The OCl” ion, bearing a negative
charge, is impeded in membrane passage. Of further biological
significance is the pH dependent distribution of these forms in
aqueous systems. In the pH range 6.5-7.2 (characteristic of fresh-
water), the dominant form is the more toxic HOC1. While at
estuarine pH's 7.5-8.2 the reverse is true (7).

Combined available residual chlorine is that residual chlorine
existing in water in chemical combination with ammonia and organic
nitrogenous compounds. While having a lower oxidation potential
than free chlorine forms, the chlorine is still available for
chemical reactions. There are reports that chloramine toxicity to
coho salmon and rainbow trout (10) was of the same magnitude as
free residual chlorine. Arthur and Eaton (11) have shown the
chloramine 96-hr Tlm to Gammarus pseudolimnaeus and Pimephales
promelas to be 220 ug/1 and 85-154 ug/1, respectively. Concentra-
tions producing no significant long term effects on these species
were <3.4 ug/l for the amphipod and 16.5 ug/l for the minnow. As in
the case of free residual chlorine, the distribution of mono- and
dichloramines in aqueous systems is strongly pH-dependent (7). At
seawater pH's only 20% of the total chloramine is present as the
toxic dichloramine.

FOULING

With the widespread increase in the use of marine waters for cooling
purposes the problems associated with fouling are increasing pro-
portionally. The following comments are in no way to be construed
as a review of the subject but rather to describe the situation that
has resulted in the widespread use of chlorine as an antifouling
agent.


programs that will determine the tolerance limits of a variety of
organisms to this stress component; and finally to verify laboratory

data in the field.

The results of these investigations will hopefully have multiple
applications. The information can be used to guide the improvement
of operational and design characteristics of power plants, with the
objective of minimizing biological impact. The data will also
contribute to an understanding of stress tolerance in biological
systems and to the establishment of water quality criteria necessary
for the continued vitality of estuarine communities.

CHLORINATION

Although the chemistry of chlorine as a biocide and disinfectant

has been investigated for freshwater systems, particularly in regard
to municipal sewage, less is understood of interactions in seawater.
The following discussion is based upon knowledge obtained from
chlorination of municipal wastes, but is applicable to understanding
the general concepts of (7).

Chlorine gas, when dissolved in water, completely hydrolyzes to form
hypochlorous acid (HOC1).

Cl) + HO Z Hoc] + HY + C17

At concentrations below 1000 mg/1 and above pH 3.0, no chlorine
exists in solution as Clj. The hypochlorous acid then dissociates
to Ht and OCl (hypochlorite). This dissociation is strongly pH
dependent.

Hoc] Z Ht + OC1~ (hypochlorite)

Being a strong oxidizing agent chlorine (HOC1) will readily react
with a variety of organic and nitrogenous compounds. The most
important reactions of chlorine with organic or inorganic nitrogenous
compounds are described in the following equations:

NH3 + HOCL 2 NH2Cl + H20 (monochloramine)

NH)Cl + HOC] 2 NHCly + H)0 (dichloramine)

NHC1) + HOC] 2 NCl3 + Hy0 (trichloramine)

The disinfecting capacity of chloramines is a function of the amount
and rate of hypochlorous acid formation. The hydrolysis constant of
monochloramine is too low for hypochlorous acid to be formed in
significant amounts; dichloramine has a higher hydrolysis constant
and is, therefore, more effective for disinfection.


higher dose level (0.55 ppm) would produce complete destruction of
phytoplankton within the two minute plant transit time. The lower
dose (0.32 ppm) should be effective within 10 minutes. The field
exposures would also include an additional thermal stress component
from plant passage. Temperatures ranged from 18-27°C which were
somewhat higher than those of the laboratory studies.

The data indicate that both chlorination levels produced essentially
complete destruction of phytoplankton ATP (Table 7). Since ATP is

Table 7. THE EFFECTS OF PLANT PASSAGE AND CHLORINATION
TO ESTUARINE PHYTOPLANKTON@

Date Intake Discharge Canal
5-29 0.43 0.38 0.38
5-302 0.42 0.08 0.04
8-22 0.61 0.27 0.14
8-23° 0.43 0.03 0.03
8-28 0.49 0.065 0.03
9-19 0.65 0.40 0.25
9-20> 0.30 0.14 0.10

4Tabular values are ugs ATP/liter of water.
bo, 32 ppm Cl.

£0.55 ppm Clo.

rapidly lost upon cell death these results indicate irreversible

loss of living biomass. Plant passage in the absence of chlorination
resulted in no damage to pumped phytoplankton on 5-29, but show
definite indications of damage on 8-22 and 9-19. The effects of
chlorination are far more severe and appear to be independent of
dosage. This corroborates the laboratory studies in that both levels
produce severe damage. An effort was made to isolate the chlorina-
tion effects on 9-20 by removing a water sample immediately after
chlorination and prior to thermal loading at the condensers. The
samples were held for 2 and 45 minutes at ambient temperatures to

23


(a4

CHLORINE - MG/L

0.01 | 1 i

Ol 10 10.0 100
EXPOSURE- MINUTES

Figure 5. Distribution of 50% response isopleths for
marine phytoplankton

1440


TABLES

Analysis of Chlorophyl-a and Productivity Data Collected
from Intake and Discharge for Both Chlorination and
Non-Chlorination Operational Modes

The Toxicity of Chlorine to Selected Species of Marine
Phytoplankton

The Post Exposure 48 Hour Growth Rates of Thalassiosira
pseudonana

The Acute Toxicity of Estuarine Copepods and Fish
Larvae to Chlorine

The Concentration of Chlorine (mgs/1) Fatal to 50% of
Pleuronectes platessa larvae

The Toxicity of Chlorine to Young of the Year Menhaden,
Brevoortia tyrannus

The Effects of Plant Passage and Chlorination to
Estuarine Phytoplankton

vii

il

13

17

19

20

23


€T

Table 3.

THE POST EXPOSURE 48 HOUR GROWIH RATES OF THALASSIOSIRA PSEUDONANA

(The values in parenthesis are the immediate effects on
photosynthesis as %-control.)

Chlorine (mgs/1)

Exposure-Seconds 1.0 0.5 0.4 0.3 0.2 0.15
Control 1.92 (100) 1.82 (100) 2.44 (100) 2.96 (100) 2.70 (100) 2.42 (100)
10 0.06 ( 16) 1.55 ( 68) 2.30 ( 79)
15 0.90 ( 21) 2.30 ( 67) 2.95 (100)
20 0.03 (14) 0.55 (17) 2.20 ( 65)
30 0.03 (13) 0.01 (14) 2.20 (58) 2.75 (100) 2.60 ( 99)
60 N.G.4( 7) N.G. ( 6) 1.26 ( 30) 2.83 ( 88) 2.50 ( 90)
150 N.G. (24) 0.96 ( 25) 2.70 ( 68)
300 N.G. (0.0) 2.60 ( 70) 2.60 (100)
600 2.10 64) 2.30 ( 62)
1200 1.10 ( 33) 2.10 ( 48)

an.G. indicates no measurable growth.


suffered approximately 75% mortality after 5 minute exposure to
2.5 ppm while similar exposures to the grass shrimp, Paleomenetes
pugio, the amphipods, Melita nitida and Gammarus sp., showed
essentially no mortality.

While not as sensitive as the microalgae, specific species of
microzooplankton do show extensive damage at combinations of chlorine
and exposure times commonly employed to reduce fouling. The problem
appears to be particularly severe for the genus Acartia which consti-
tute a major portion of the microfauna grazed upon by larval fish.

ICHTHIOPLANKTON

Information on the tolerance of larval and juvenile fish indicate
that this group is also very sensitive to chlorine. Two species
were investigated at our laboratory, the winter flounder
(Pseudopleuronectes americanus) and the yellowtail flounder
(Limanda ferruginea). The results indicate that the winter flounder
larvae were in the same sensitivity range as the copepods. Twenty-
four hour exposures of the yellowtail flounder produced an LC-50
of 0.2 ppm and 0.10 ppm on two separate samples of larvae.
Regretably, similar data was unavailable for the winter flounder.
What is significant is that these values are comparable to the
twenty-four hour exposure values derived from the microalgae.
Alderson (19) studied the effects of low concentrations of free
chlorine on the eggs and larvae of plaice (Pleuronectes platessa)
(Table 5). Fairbanks et al. (20) in an investigation of chlorine

Table 5. THE CONCENTRATION OF CHLORINE (mgs/1) FATAL
TO 50% OF PLEURONECTES PLATESSA LARVAE (19)

Chlorine (mgs/1) Exposure time
0.028 96 hrs.
0.050 460 mins.
0.075 175 mins.
0.100 90 mins.
0.130 70 mins.

toxicity to young of the year menhaden (Brevoortia tyrannus) found

19


DISCLAIMER

This report has been reviewed by the Environmental Research
Laboratory, U.S. Environmental Protection Agency, and approved
for publication. Mention of trade names or commercial products
does not constitute endorsement or recommendation for use.

ii


influenced by the plume. In order to reduce sampling variability,
collections made at the intake and discharge stations were time
phased to assure that the same water masses were being compared.

PHYTOPLANKTON

Water samples were collected with a 5 liter non-metallic Van Dorn
sampler from a three meter depth. Four casts were made at five
minute intervals and pooled. The pooled sample was mixed and two
liters were placed in a thermos bottle for transportation to the
laboratory. Replicate 25 ml aliquots were preserved in 1% glutar-
aldehyde for a microscopic examination. Triplicate 250 ml aliquots
were immediately filtered, (-10 psi) frozen over silica gel in the
dark, and analyzed for chlorophyl-a and phaeophytin (17). For
productivity measurements, incubation facilities were set to
simulate ambient temperature and light intensity. Six 125 ml flasks
containing 50 ml of water were incubated with Nag!4co3 (0.1 uc/ug?
final sp. activity) for 12 hours. Four were incubated in the light
while two incubated in the dark. Cellular radioactivity was mea-
sured by liquid scintillation spectrometry.

The results of chlorophyl-a analysis (Table 1) indicate that the
three stations showed highly significant between station variation
when subjected to analysis of variance (F = 4.68; P = 0.05). Sub-
sequent examination using Duncan's Multiple Range Test revealed
intake and discharge without chlorination were homogenous subsets
but that discharge with chlorination was not. While chlorophyl-a
was somewhat lower in the discharge due to mechanical and thermal
stress these differences were not significant. The effect of
chlorination on the other hand is dramatic. On many occasions
chlorophyl was not even detected in the discharge samples implying
total loss of primary producer biomass. Using plant characteristics
and assuming worst case conditions of total kill during the 90
minute/day chlorination cycle, the loss of primary producer carbon
from the food web is ~16 tons (1.45 x 104 kilograms) of carbon from
June-December.

Productivity data (Table 1) further implicates chlorination as the
primary source of biological effect. The data substantiates the
fact that thermal and mechanical stress have little or no impact

on the phytoplankton during the summer-fall months. The interpre-
tation of C-14 uptake data as obtained in this study is somewhat
different from that of in situ studies where short term effects are
measured. Since the photosynthetic system is often subject to
transient effects it can be dangerous to extrapolate to longer term
responses. Carbon-14 uptake as used in this study reflects more
permanent effects since the 24 hr incubation time allowed for
recovery to occur.



stations described above. Sampling employed a modified Clarke-
Bumpus sampler, equipped with a special "cod-end" bucket to reduce
damage, a calibrated TSL flowmeter, and #10 mesh netting (153 micron
apperture). Tows were of varying duration (1-15 minutes) depending
on organism density and current speed. Intake samples were taken
from the three meter depth while discharge samples were taken from
the surface. The discharge canal (300' x 25' x 10') had a mean
flow of 5'/sec (1.52m/sec) and was extremely turbulent and well
mixed. The tow samples were diluted with ambient seawater and
treated as follows: a portion was preserved in buffered formalin
(10%) for microscopic examination and the remainder placed in insu-
lated containers and transported back to the laboratory. In the
laboratory, aliquots were diluted in two liters of filtered seawater.
Since damaged or dead organisms sink faster than living, those
organisms settling to the bottom and unresponsive to touch were
counted as dead and preserved. The samples were then placed at
ambient temperature for twenty-four hours and examined to determine
living and dead. Total mortalities were tabulated and the remaining
living organisms were preserved and counted. The data is presented
as percent mortality (Fig. 1).

Chaetognaths and fish larvae were unable to survive the mechanical
stress of plant passage. Microscopic examination revealed extensive
fragmentation of these forms. Fish adults showed extensive mor-
tality in the discharge area only during periods of chlorination.
These organisms are attracted into the discharge area by the warm
water and are unable to escape when the chlorination cycle is
initiated.

Zooplankton populations are dominated by Acartia tonsa from June to
October and Acartia clausi from November to May. During periods of
chlorination (1-3 ppm total residuals) there is essentially complete
mortality of Acartia tonsa. During non-chlorination periods these
organisms appear to survive plant passage. There are moderate
mortalities of Acartia clausi during April and May due primarily to
the thermal stress. This situation is analogous to that described
for Detonula confervaceae. Acartia clausi will not tolerate
prolonged exposure to temperatures >150C. Therefore when ambient
temperatures reach 10-12°C, the additional rise of 10°C produces
thermal stress above its tolerable limit.

From data on the population densities of Acartia tonsa and Acartia
clausi during June-December (17) and assuming total mortality during
chlorination periods, an estimated 1.6 tons (1.45 x 103 kilograms)
of primary herbivore biomass was destroyed.

From these field studies it was obvious that estuarine populations

of primary producers and primary herbivores were acutely sensitive
to chlorine.


EPA-600/3-76-055
June 1976

POWER PLANTS, CHLORINE, AND ESTUARIES

by

J. H. Gentile, J. Cardin, M. Johnson,
and S. Sosnowski

Environmental Research Laboratory
Narragansett, Rhode Island 02882

U.S. ENVIRONMENTAL PROTECTION AGENCY
OFFICE OF RESEARCH AND DEVELOPMENT
ENVIRONMENTAL RESEARCH LABORATORY
NARRAGANSETT, RHODE ISLAND 02882


TECHNICAL REPORT DATA .
(Please read Instructions on the reverse before completing)

1, REPORT NO. 2. 3. RECIPIENT'S ACCESSIONNO.

5. REPORT DATE
June 1976 (Issuing Date)

POWER PLANTS, CHLORINE, AND ESTUARIES J6. PERFORMING ORGANIZATION CODE

7, AUTHOR(S) lg. PERFORMING ORGANIZATION REPORT NO.
J. H. Gentile, J. Cardin, M. Johnson, S. Sosnowski

i9. PERFORMING ORG ANIZATION NAME AND ADDRESS 10 EOS. ELEMENT NO,
Environmental Research Laboratory
Office of Research and Development 71. CONTRACT/GRANT NO.

U.S. Environmental Protection Agency In-house Project

' Narragansett, Rhode Island 02882

[12. SPONSORING AGENCY NAME ANO ADDRESS 13. TYPE OF REPORT AND PERIOD COVERED
As Above

74, SPONSORING AGENCY CODE

EPA-ORD

15, SUPPLEMENTARY NOTES

16. ABSTRACT

Biological assay systems using indigenous holo- and meroplankton were designed
to model the chlorination patterns of power plants. A matrix of chlorine
concentrations and exposure patterns permitted the generation of response
isopleths that were then applied to developing design criteria. The marine
phytoplankter, Thalassiosira pseudonana showed a 50% reduction in photosynthesis
when exposed to 0.15 ppm Cl, for 10 minutes, and complete growth inhibition
after 5 minutes exposure to'0.3 ppm. Microzooplankton adults were somewhat
less sensitive in that a 5 minute exposure at 2.5 ppm was necessary to produce
50% mortality. Larval and juvenile fish were sensitive to chlorine levels
<0.2 ppm for exposure periods of sixty to ninety minutes.

Two field studies were evaluated and compared to laboratory data with
specific emphasis on the use of ATP to monitor entrainment and damages.
A review of pertinent literature is also included.

H7. KEY WORDS AND DOCUMENT ANALYSIS

ja. ~~ DESCRIPTORS lb, IDENTIFIERS/OPEN ENDED TERMS |c. COSATI Field/Group
Chlorine Ichthioplankton
Bioassay Chlorine Bioassays (Marind) 6F
Marine Biology ATP
Zooplankton ATP Assessment Entrainment
Phytoplankton Power Plants
Entrainment Power Plant Impact
. DISTAIBUTION STATEMENT 19, SECURITY CLASS (This Report) 21, NO. OF PAGES
° UNCLASSIFIED 37
RELEASE TO PUBLIC 20. SECURITY CLASS (This page) 22. PRICE
UNCLASSIFIED
EPA Form 2220-1 (9-73) 29

vir U.S. GOVERNMENT PRINTING OFFICE: 1976-657-659/5450 Region No. 5-11


of the most ecologically important primary herbivores. The results
(Fig. 4) indicate this species to be much less sensitive to chlorine
than the algae but still unable to tolerate chlorine levels above
1.0 ppm without substantial mortality. This study did not attempt
to evaluate the potential long term effects of these exposures on
subsequent survival and reproduction, not the combined effects of
thermal addition and chlorine.

McLean (18) in a study designed to model the effects of the Chalk
Point Power Station exposed A. tonsa at 6°C to 2.5 mgs chlorine/1
for 5 minutes. A consistent mortality at 3 hours post exposure of
90% was recorded. We noted for identical exposure conditions at
15°C a mortality of 49%. Differences could be related to salinity,
temperature, or pH. Of further interest is the occurrence of A.
tonsa, apparently in abundance, at 6-8°C. Our experience would
question this, as A. clausi is the usual congeneric cold water form
which is abundant in the Patuxent River.

Additional species of copepods, Eurytemora affinis and Pseudo-
diaptomus coronatus were somewhat less sensitive than Acartia
(Table 4).

Table 4. THE ACUTE TOXICITY OF ESTUARINE COPEPODS
AND FISH LARVAE TO CHLORINE

Chlorine conc (mgs/1)

Species 1.0 2.5 5.0 10.0
Acartia tonsa 120.0 5.0 2.0 0.7
Eurytemora affinis 360.0 9.0 4.0 2.0
Pseudodiaptomus coronatus -- 45.0 9.8 5.0
Pseudopleuronectes americanus - 15.0 2.5 0.3

@aTabular values are exposure time (minutes) to produce 50%
mortality.

Studies on the larvae of sand shrimp (Crangon septemspinosis)
indicated this organism to be resistant to chlorine. At 10 ppm, 60%
mortality resulted from a 5 minute exposure and at 5 ppm, 42%
mortality was produced from a 10 minute exposure. These results
were almost identical to those reported for Pseudodiaptomus
coronatus (Table 4). McLean (18) reported that barnacle larvae

17


RESEARCH REPORTING SERIES

Research reports of the Office of Research and Development, U.S. Environmental
Protection Agency, have been grouped into five series. These five broad
categories were established to facilitate further development and application of
environmental technology. Elimination of traditional grouping was consciously
planned to foster technology transfer and a maximum interface in related fields.
The five series are:

1. Environmental Health Effects Research

2. Environmental Protection Technology
3. Ecological Research

4. Environmenta! Monitoring

5. Socioeconomic Environmental Studies

This report has been assigned to the ECOLOGICAL RESEARCH series. This series
describes research on the effects of pollution on humans, plant and animal
species, and materials. Problems are assessed for their long- and short-term
influences. Investigations include formation, transport, and pathway studies to
determine the fate of pollutants and their effects. This work provides the technical
basis for setting standards to minimize undesirable changes in living organisms
in the aquatic, terrestrial, and atmospheric environments.

This document is available to the public through the National Technical Informa-
tion Service, Springfield, Virginia 22161.


0.1 ppm. Oysters show reduced pumping rates at <0.05 ppm (26) and
extensive mortalities to plaice larvae occur at 0.028 ppm after
ninety~six hours exposure. Muchmore and Epel (27) demonstrated the
spermicidal effect of 0.05 ppm available chlorine to three marine
species of invertebrates. Holland et al. (10) has demonstrated
that three species of young salmon are sensitive to chlorine at
<O.1 ppm. Research on combined chlorine toxicity in freshwater
systems indicate that these compounds are of comparable toxicity to
available chlorine. Studies at this laboratory indicate that natural
seawater chlorinated (10 ppm initially) for 100 hours and treated
with sodium thiosulfate to eliminate any available chlorine was
still inhibitory to phytoplankton growth.

In developing effluent guidelines and water quality criteria for
chlorine discharges into the marine environment, a conservative
approach is necessary. While considerable information is available
for short term effects of available chlorine, little is known about
the long term exposures that will result from treated wastes discharge
through ocean outfalls. This is an area that deserves immediate
research attention. Nevertheless, the data available does provide

a sound scientific foundation for recommending limits on the concen-
tration, form, and duration of chlorine discharges into marine waters.

In order to assure that indigenous marine populations are protected
from irreversible damage from chlorine and its organic derivatives
such as chlorinated amines, chlorinated phenols, and other potential
unidentified chlorinated derivatives, levels of total residual
chlorine should not exceed 0.01 mg/l for up to 2 hours in any 24 hour
period. This value is in fact not a conservative number, since
examination of Fig. 5 clearly demonstrates that 50% mortality and
growth inhibition occur at levels of 0.075-0.10 ppm for this exposure
time. These are not nebulous biological responses but mortality and
impairment of reproductive function. Therefore, a margin of safety
must be afforded the biota since continued loss of 50% of the
entrained populations and jeopardizing receiving water populations is
an unnecessary risk. Without adequate research into the chronic
effects of continuous chlorination, water quality criteria for this
type of discharge can only be inferred from studies performed in
freshwater systems and from marine short term data.

25


extensive mortalities at chlorine levels less than 1.0 ppm (Table 6).
Comparing data from these studies reveals that the menhaden 60 minute
TLm of 0.22 ppm is remarkably similar to the 70 minute Tlm of 0.13
ppm for plaice larvae (19).

Table 6. THE TOXICITY OF CHLORINE TO YOUNG OF THE YEAR
MENHADEN, BREVOORTIA TYRANNUS (20)

Exposure (min.) LCs (mgs/1)
10 0.70
15 0.64
30 0.27
60 0.22

These larval studies emphasize that short term exposure to chlorine
levels of >0.1 ppm would produce a significant biological effect
under routine intermittent dosage conditions. Of further concern is
the potential damage to receiving water populations of these species
inhabiting the environs of the discharge canal where discharge
residuals often reach 0.1 ppm.

Holland et al. (10) investigated the toxicity of chlorine and
chloramines to three species of salmon in seawater of 18 o/oo
chlorinity between 6-9°C. Forty percent of Chinook salmon (365 day
old) were killed after 24 hrs exposure to 0.05 ppm Cla. Pink salmon
showed decreasing sensitivity to chlorine with age. Thirty-two day
old pink salmon had a 72 hr LC-100 of 0.084 while 61 day old
specimens had a 72 hr LC-50 of 0.91 with only 13% mortality noted
after 72 hrs exposure at 0.13 ppm. Silver salmon showed complete
mortality after 72 hrs exposure to 0.10 ppm. More recent studies
on pink and Chinook salmon (21) demonstrate the interaction of
temperature and chlorine. The most toxic effect for juveniles of
these species occurred at a temperature of 10.0°C. The lethal
time for 50% mortality ranged from 10 minutes at 0.5 mg/1 total
residual for Chinook and 80 minutes at 0.5 mg/l total residual for
pink.

Though not originally related to a power plant problem, investi-
gations on chlorine tolerance of juvenile spot (Leiostomus xanthurus)
produced a 96 hr LC-50 of 0.09 mg/1 total residual chlorine.
Estimated 24 and 6 hr LC-50's were 0.14 mg/l and 0.28 mg/1 total

20


Among the marine organisms often classified as major fouling types,
the marine borers and mussels appear to be the most abundant and
difficult to control. To further place the problem in perspective
consider that studies at a Northeast Coast power station reveal an
annual crop of 1000 tons/acre/year (220 kilograms/m2/year) of the
fouling mussel, Mytilus edulis (12).

Control methods for marine fouling organisms include: properly
located revolving screens, predetermined increments in water
velocity, use of elevated temperature, and the chlorination of
intake water. Recently, combinations of temperature and chlorine
have been investigated as have: mechanical condensor scouring
systems (i.e. Amertap) and anodic introduction of copper and other
biocides.

Early studies by White (13) detail the effect of elevated tempera-
tures with and without additions of chlorine on the survival of
Mytilus edulis. These studies were done on organisms from Lynn
Harbor with continuous chlorination at 0.3 to 3.0 ppm for tempera-
tures above 85°F (29.5°C) and with intermittent chlorination at
lower temperatures. For this group of test organisms, temperatures
>840F (>29.0°C) the addition of chlorine did not appreciably decrease
the time necessary to kill the mussels.

Mussels, unlike other molluscs, possess a gland in their foot which
secretes a thread used to anchor the organism in place. This byssus
gland appears to be particularly sensitive to chlorine. Clapp (14)
investigated the effects of various chlorine concentrations and
exposure regimes on the ability of Brachydontes exustus to remain
attached to a substratum. His results indicated that continuous
chlorination at 0.25 ppm-0.50 (nominal) was sufficient to cause all
exposed mussels to loose their holdfasts and their shells to open.
Intermittent chlorination of 2 hr duration, at 1.5 and 3.0 ppm with
2 hr off and 6 hr off also resulted in loss of attachment but not
death, Return to undosed water after six days exposure revealed
that the continuously dosed organisms did not recover while those
with intermittent doses did recover and reattach. In addition,
slime, barnacles, and Bryozoa were totally eliminated by continuous
but not by intermittent chlorination.

Richards (12) using an approach similar to that of the Clapp studies,
found that 0.25 ppm chlorine or a temperature of 110°F for 30
minutes/week was effective in preventing colonization by marine
borers. Intermittent chlorination at 1.00 ppm for 1 hr/12 hrs in
combination with 110°F for 30 minutes/week was also effective whereas
chlorine alone in the above dosing regime was not effective.

Turner (15) found that continuous chlorination at 0.25 mg/l pre-
vented fouling over a 90 day interval, yet intermittent treatment at
10 mg/1 for 8 hrs per day was ineffective. James (16) found that


Table 1. ANALYSIS OF CHLOROPHYL-A AND PRODUCTIVITY DATA
COLLECTED FROM INTAKE AND DISCHARGE FOR BOTH
CHLORINATION AND NON-CHLORINATION
OPERATIONAL MODES

Treatment Mean Std. error N F(0.05)4
Chlorophyl~a

Intake 9.22 1.26 25 4.688
Discharge 7.72 1.23 25

Discharge + C12 3.41 0.87 14

Productivity

Intake 39.99 1.45 8 58.00
Discharge 36.91 2.18 8

Discharge + Cl,

uncan's Multiple Range (Alpha 0.05). Intake and discharge are
homogeneous subsets. Chlorinated discharge is significantly
different.

Microscopic examination indicated that during periods of the year
when chain forming diatoms such as Detonula confervaceae and
Skeletonema costatum were at peak abundance there was extensive
fragmentation of these chains. In addition, thermal stress was noted
during March 1970 when Detonula was dominant. This species has an
upper temperature range of 10-12°C. Since ambient water temperatures
were at this level the resulting thermal load (10°C) stressed this
species as was indicated by markedly depressed rates of photosynthe-
sis. Such a phenomenon is likely to occur for many species during
transitional periods of both spring and autumn if exposure times in
the plume are long enough.

In summary these studies indicate that chlorination as practiced at
this plant was responsible for severe damage to primary producer

populations. Only under the specifically mentioned circumstances
was either thermal or mechanical damage observed.

ZOOPLANKTON

Zooplankton samples were collected for the same sample dates and