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The effects of free chlorine and chloramine on growth and respiration rates of larval lobsters (Homarus Americanus)
Water Research Vol. II, pp. 1021 to 1024, Pergamon Press 1977. Printed in Great Britain.
THE EFFECTS OF FREE CHLORINE A N D CHLORAMINE ON GROWTH A N D RESPIRATION RATES OF LARVAL LOBSTERS
(HOMARUS AMERICANUS) JUDITH M. CAPUZZO Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, U.S.A. (Received 21 Feburary 1977; in revised form 10 June 1977) Abstract--The length, dry weight and standard respiration rate of larval lobsters (Homarus americanus) were monitored for 19 days following a 60 rain exposure at 25°C to 1.0 mg 1-1 applied free chlorine and 1.0 mg 1-t applied chloramine. Compared to control organisms, significantly lower increases in dry weight (P < 0.05) and significant reductions in standard respiration rates (P < 0.01) were measured among exposed organisms; greater differences were detected among chloramine exposed organisms. From these results it can be concluded that acute exposure to either free chlorine or chloramine results in subsequent reductions in growth and metabolic activity of larval lobsters.
INTRODUCTION Interest in chlorine toxicity is a result of its extensive use for fouling control at coastal power stations. Chlorination of seawater may result in the formation of halogen toxicants in addition to free chlorine including chloramine (Lewis, 1966), organochlorine compounds (Jolley, 1975) and bromine compounds (Dove, 1970). The nature of the halogen toxicants produced during chlorination of sea-water in both a power plant and an experimental situation varies with the relative concentrations of bromide, ammonia and organic compounds. Wong & Davidson (1977) have confirmed that in the presence of low ammonia concentrations, chlorine (as OC1- or HOC1) reacts with the bromide ions of sea-water to form hypobromite (HOBr or OBr-). Johannesson (1958) suggested that in the presence of high ammonia concentrations in sea-water chloramine formation would be favored, but this halogen species could exist in equilibrium with bromamine compounds as well. In a previous study (Capuzzo et al., 1976) the differential effects of applied free chlorine and chloramine on stage I larvae of the American lobster Homarus americanus were investigated. F r o m the results of our earlier study, there was an indication that chloramine was more toxic than free chlorine and that exposure to low levels of either toxicant resulted in significant survival but decreased respiration rates. Standard respiration rates are indicative of the physiological condition of an organism, thus changes in respiration rates of early larval stages could result in subsequent changes in growth and development and increased susceptibility to other environmental stresses. The objective of the present study was to determine the long term effects of acute exposure to free chlorine or chloramine on growth and standard respiration rates of larval lobsters. W.R, I1/12--A
MATERIALS A N D M E T H O D S
Stage I larvae of the American lobster were hatched at 20°C from eggs held by female lobsters and used in experiments within 24 h. Before the bioassays were begun, the average length (mm), dry weight (mg) and standard respiration rate (#1 02 h- 1 mg- 1 dry weight) of test organisms were monitored. Lobster larvae were dried at 60°C for 24h; respiration rates were measured using microrespirometers as previously described by Capuzzo et al. (1976). Test organisms were selected randomly and 12 replicate samples of 10 animals each were exposed to either 1.0 mg 1- t applied free chlorine (NaOC1) or 1.0 mg 1- t applied chloramine (equimolar concentrations of NH4OH and NaOC1) for 60 min at 25°C in the continuous flow bioassay apparatus described earlier (Capuzzo et al., 1976); control organisms (6 replicates of 10 animals each) were maintained at 25°C during the 60 rain exposure period. Before use in the assays, sea-water (salinity = 30-31%o; pH = 7.8-8.1) was filtered through activated charcoal and 1.2/~m membrane filters and aerated for 48h with ammonia free air for removal of organics and ammonia; ammonia levels were reduced to <0.5/~g-atom NH4-N/I. Chlorine and chloramine were measured as total C12 by amperometric titration (Fischer and Porter Model 17T1010; APHA, 1971; pH 4 oxidant, lmg1-1 total C12 = 0.028 mN total oxidant species; accuracy = +0.02 mg 1-1). Seawater and toxicants were equilibrated for 12 h before the addition of test organisms and the resulting residual toxicant levels were 15% of the applied levels due to the chlorine demand of sea-water. Total residual chlorine concentrations include all chlorine and bromine species measurable by amperometric titration. The temperature was reduced to 20°C after the 60min exposure to free chlorine or chloramine; the halogen toxicants were chemically removed by the addition of sodium thiosulfate after the designated exposure period. Per cent mortality and standard respiration rates of exposed organisms were compared to those of control organisms held in the same bioassay apparatus until 48 h after exposure. After 48 h, the three groups of lobster larvae (control, chlorine exposed and chloramine exposed) were transferred to three 401 fibreglass aquaria supplied with filtered (20/tm) flowing seawater at 20°C and constant aeration. Test organisms were maintained in the three aquaria for 1021
1022
JUDITH M. CAPUZZO
17 days until all larvae had developed to the last larval stage (stage IV). Lobster larvae were fed 10 mg dry weight of frozen brine shrimp Artemia salina per animal per day during the experimental period. The total length of lobster larvae, excluding claws (tip of rostrum to tail fin), was measured within 12 h after each molt and the time between molts recorded. It was observed that in the three test groups molting activity was quite uniform among both control and exposed organisms and that all of the test organisms within a group would molt within 6-12h of one another. Sub-samples of 8 organisms were taken periodically from each test group (day 3, or 48 h after exposure, day 5, 12 h after completion of the molt to stage II in the three test groups, and day 19, at the termination of the experiment and 12h after attainment of stage IV in chloramine exposed animals) for dry weight and respiration rate measurements. Respiration rates of stage I (initial, day 3) and stage II (day 5) larvae were measured using microrespirometers; oxygen consumption rates of stage IV larvae were measured using a Gilson differential respirometer. In both instances, individual larvae were placed in respirometer flasks with filtered seawater; fluted filter paper soaked with 10% KOH was used as the CO2 absorbent. Oxygen uptake was measured at 22°C at 15 min intervals for 2 h and is reported as pl O2 h- ~ mg- ~ dry weight, adjusted to #1 of dry gas at standard temperature and pressure. Organisms were not fed for at least 4h prior to respiration rate measurements and were allowed to acclimate to test conditions for 15 min before oxygen uptake was measured. Values of length, dry weight and standard respiration rate are mean values + 1 standard error. Significant differences in these parameters between control and exposed organisms were determined by analysis of variance. The relationship of dry weight and standard respiration rate of control organisms was analyzed by log-log linear regression analysis.
RESULTS
The concentrations tested (1.0 mg 1-1 applied free chlorine and 1.0 mg 1-1 applied chloramine) cannot be considered strictly to be sublethal levels, since an increase in mortality compared with control organisms did occur with exposure to these concentrations (Table 1). However, the values are significantly lower than LCso values reported earlier (16.30 mg1-1 applied free chlorine and 2.02mg1-1 applied chloramine; Capuzzo et al., 1976) and a significant percentage of the test population survived these stresses. The mortaility rate appeared to stabilize 48 h after exposure; no increase in mortality during the remainder of the experimental period could be attributed to toxicant exposure, although some mortality did occur ( ~ 10%) in the three test groups due to cannibalism. Table 1. Per cent mortality of larval lobsters (stage I) 48 h after 60min exposure at 25°C to free chlorine and chloramine
i
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I00
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II
50 I
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DAYS
Fig. l. Length (mm) of larval lobsters, stage I-IV; circlescontrol organisms, triangles-chlorine exposed organisms, squares-chloramine exposed organisms; values are mean values from each group + 1 standard error. The average length and dry weight of the larval stages from the three test groups are presented in Figs. 1 and 2 and Table 2. Significantly lower increases (P < 0.05) in length and dry weight compared to control organisms were observed with the first molt (stage I to stage II) of organisms exposed to free chlorine and chloramine; lesser increases in length and dry weight were measured among chloramine exposed organisms. Subsequent molts resulted in no significant difference in length increases per molt between chlorine exposed and control animals ( 1 . 5 m m m o l t -1) but significant differences in dry weight increases were observed (control = 2.3mg m o l t - 1, chlorine exposed = 1.9 mg m o l t - 1). Length and dry weight increases of chloramine exposed animals remained significantly lower with each molt (1.0 mm m o l t - 1 and 0.9 mg m o l t - 1). N o significant difference in molting time of the first two molts was observed between control and exposed organisms, however, a slight delay in molting to the fourth larval 8.0
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1.0 Toxicant Control Free chlorine Chloramine
Concentration mg 1- z Total C l 2 applied residual 1.00 1.00
0.15 0.15
I
% Mortality 10 15 25
O.C
I/ I
I
I
5
I0
15
lV 20
DAYS
Fig. 2. Dry weight (rag) of larval lobsters, stage I-stage IV; circles-control organisms, triangles-chlorine exposed organisms, squares-chloramine exposed organisms; values are mean values from each group + 1 standard error.
Effects of free chlorine on H. americanus
1023
Table 2. Length, dry weight and standard respiration rate measurements of larval lobsters exposed to free chlorine and chloramine and maintained at 20°C Toxicant
Length* (mm)
Dry wt.* (mg)
/11 0 2 h - 1 mg- 1,
I
control
6.8 + 0.1
1.7 + 0.1
1.1 ___0.1
I
control free chlorine chloramine control free chlorine chloramine control free chlorine chloramine control free chlorine chloramine control free chlorine chloramine
1.7 1.7 1.7 1.7 1.7 1.7 2.6 2.4 1.9
+ 0.1 + 0.1 ___0.1 + 0.1 4- 0.1 + 0.1 + 0.1 + 0.1 ___0.1 -
1.1 + 0.1 0.9 + 0.2 0.5 + 0.1 1.1 ___0.1 0.5 + 0.1 0.3 + 0.2 1.8 4- 0.1 1.2 ___0.1 1.0 ___0.1
7.2 + 0.5 6.2 4- 0.4 3.6 4- 0.5
3.4 + 0.2 2.5 ___0.2 1.8 4- 0.1
Day
Stage
1 (pre-exposure) 1 (post-exposure) 3
I
5
II
11
III
19
IV
6.8 6.8 6.8 6.8 6.8 6.8 7.8 7.3 6.8 9.6 8.5 7.9 10.8 10.2 8.8
4- 0.1 + 0.1 ___0.1 4- 0.1 4- 0.1 4- 0.l 4- 0.2 4- 0.2 4- 0.1 4- 0.2 4- 0.3 + 0.1 + 0.2 ___0.3 4- 0.3
-
* All values are mean values _+ 1 standard error.
stage was detected a m o n g chloramine exposed organisms (Table 3). All length a n d dry weight measurements were made within the first 12 h following completion of the molt from one stage to the next except in the case of stage IV larvae; measurements of control a n d chlorine exposed stage IV larvae were m a d e 48 h after completion of the molt to correspond with completion of the molt in chloramine exposed organisms. Standard respiration rates of exposed lobster larvae were significantly lower (P < 0.01) than those of control organisms t h r o u g h o u t the experimental period (Fig. 3 a n d Table 2). The greatest differences in oxygen uptake were measured 48 h after exposure with a 55% reduction a m o n g chlorine exposed organisms a n d a 73% reduction a m o n g chloramine exposed organisms. Older lobster larvae h a d a higher energy d e m a n d than stage I larvae as indicated by the higher weight specific standard respiration rates detected. This trend was observed in b o t h control a n d exposed organisms. It is possible that the respiration rates of stage II a n d stage IV larvae from b o t h control a n d exposed groups only reflect differences in the size of the Table 3. Days between each molt of larval lobsters exposed to free chlorine and chloramine and maintained at 20°C Toxicant
Stage
Control
I II III I II III I II III
Free chlorine Chloramine
organisms. The relationship of dry weight a n d standard respiration rate of control animals is represented by the following equation: log Y (respiration r a t e ) = 0.75 log X (dry weight) + log 0.80 r = 0.987, N = 24. Values for respiration rates of stage II a n d stage IV larvae from the chlorine exposed group a n d the chloramine exposed group are less than values predicted from this equation, suggesting that exposure to the toxicants has resulted in significant differences in respiration rates. DISCUSSION The impact of chlorinated cooling waters on marine ecosystems is a problem of great concern with 4.0
,
,
,
~
,
3.0
/~// %,
s ~I~
~'~
I It
Days before molt to next stage 4 5 6 4 5 6 4 5 8
I
3
5
t0
I~
20
DAYS
Fig. 3. Standard respiration rate (#1 02 h -1 mg-1 dry weight) of larval lobsters, stage I-stage IV; circles-control organisms, triangles-chlorine exposed organisms, squareschloramine exposed organisms; values are mean values from each group + 1 standard error.
1024
JUDITH M. CAPUZZO
the extensive use of chlorine for fouling control at coastal power plants. The halogen compounds formed upon chlorination of sea-water are dependent on the relative concentrations of bromide, organic matter, ammonia and other nitrogenous compounds. Thus toxic effects of chlorinated cooling waters may vary from one power plant site to another because of the relative concentrations of different halogen compounds. An understanding of the comparative toxicity of these halogen compounds is needed to adequately assess the potential effects of power plant chlorination on marine organisms. The toxicity of chlorinated cooling waters to marine organisms has been the subject of several studies, recently reviewed by Davis & Middaugh (1976). The major environmental variables affecting toxicity are temperature and exposure time, as well as the available form of chlorine or other halogen compounds. Few studies have focused on the long term effects of acute short term exposures to chlorinated cooling waters on survival and growth of marine invertebrates. Waugh (1964) exposed naupliar larvae of the barnacle Elminius modestus to chlorine doses ranging from 0.5 to 5.0mg1-1 for 10min and monitored survival, development and growth for periods up to 6 days after exposure. He concluded that concentrations in excess of 0.5 mg l - 1 caused significant mortality and reductions in growth rates of surviving organisms. Growth may be defined as the net balance between food supply and metabolic expenditures. Logan (1976) observed exponential growth rates among larvae of the American lobster and noted that a high percentage of energy intake was directed towards growth during larval development. Any interference with metabolic processes could result in inefficient utilization of food and subsequent reductions in growth. In our previous study (Capuzzo et al., 1976), lobster larvae exposed to free chlorine and chloramine for 60 rain showed significant reductions in metabolic activity 48h after exposure; greater reductions were observed among chloramine exposed animals. The effects of both halogen toxicants appeared to be irreversible with exposed organisms being unable to maintain the standard respiration rate of control organisms. In the present study, the effects of the halogen toxicants on growth of larval lobsters provide evidence that longer-lasting metabolic disturbances may result from acute exposure to chlorinated seawater. The exponential growth pattern was evident among the three test groups of lobsters but the resulting size of stage IV larvae was significantly reduced among chlorine exposed and chloramine exposed organisms. The apparent effect of the toxicants on lobster larvae was an interference with energy utilization as evidenced by lesser dry weight increases and decreased metabolic activity. These findings were detected at residual levels of
0.15 mg 1-1 of either toxicant; this value is within the range of commonly detected residual levels in cooling waters discharged from coastal power stations (0.05-5.00mg1-1; Brungs, 1973; Marshall, 1971). If large numbers of lobster larvae become entrained in these cooling waters or reside in adjacent receiving waters, serious consequences for populations of this valuable commercial species could result, particularly where chloramine is the major halogen toxicant. Therefore, the use of chlorine for fouling control at coastal power plants should be executed with great care and dechlorination of cooling waters should be considered before discharge into marine ecosystems. Acknowledoements--This research was supported by U.S.
Energy Research and Development Administration Contract No. E (11-1)-2532. The author wishes to thank John Hughes of the Massachusetts State Lobster Hatchery for providing egg-bearing lobsters. Woods Hole Oceanographic Institution Contribution No. 3926. REFERENCES
APHA (1971) Standard Methods for Examination of Water and Wastewater, 13th edn, Am. Public Health Assn., New York. Brungs W. A. (1973) Effects of residual chlorine on aquatic life. J. War. Pollut. Control Fed. 45, 218022193. Capuzzo J. M., Lawrence S. A. & Davidson J. A. (1976) Combined toxicity of free chlorine, chloramine and temperature to stage I larvae of the American lobster Homarus americanus. Water Res. 10, 1093-1099. Davis W. P. & Middaugh D. P. 0976) A review of the impact of chlorination processes upon marine ecosystems. In The Environmental Impact of Water Chlorination, Proceedings (Edited by R. L. Jolley), pp. 299-325. Oak Ridge Nat. Lab., Oak Ridge, Tenn. Dove R. A. (1970) Reactions of small dosages of chlorine in sea water. Central Electricity Generating Board, Research Report 42/70, File No. 0.3070/ID, Job No. 10665. Univ. of Southampton, England. Johannesson J. K. (1958) The determination of monobromamine and monochloramine in water. Analyst 83, 155-159. Jolley R. L. (1975) Chlorine containing organic constituents in chlorinated effluents. J. Wat. Pollut. Control Fed. 47, 601-6t 8. Lewis B. G. (1966) Chlorination and mussel control. I: The chemistry of chlorinated sea water: A review of the literature. Central Electricity Research Laboratories, Laboratory Note No. RD/L/N 106/66, Leatherhead, England. Logan D. T. (1976) A laboratory energy balance for the larvae and juveniles of the American lobster Homarus americanus. P h . D . Thesis, University of Delaware, Lewes, Delaware. Marshall W. L. (1971) Thermal discharges: characteristics and chemical treatment of natural waters used in power plants. Oak Ridge Nat. Lab, Report No. 4652, Oak Ridge, Tennessee. Waugh G. D. (1964) Observations on the effects of chlorine on the larvae of oysters (Ostrea edulis (L.)) and barnacles (Elminius modestus (Darwin)). Ann. appl. Biol. 54, 423-440. WoN~ G. T. F. & DAVIDSOSJ. A. (1977) The fate of chlorine in seawater-A preliminary review. Water Res. 11, 971 978.
THE EFFECTS OF FREE CHLORINE A N D CHLORAMINE ON GROWTH A N D RESPIRATION RATES OF LARVAL LOBSTERS
(HOMARUS AMERICANUS) JUDITH M. CAPUZZO Woods Hole Oceanographic Institution, Woods Hole, Massachusetts 02543, U.S.A. (Received 21 Feburary 1977; in revised form 10 June 1977) Abstract--The length, dry weight and standard respiration rate of larval lobsters (Homarus americanus) were monitored for 19 days following a 60 rain exposure at 25°C to 1.0 mg 1-1 applied free chlorine and 1.0 mg 1-t applied chloramine. Compared to control organisms, significantly lower increases in dry weight (P < 0.05) and significant reductions in standard respiration rates (P < 0.01) were measured among exposed organisms; greater differences were detected among chloramine exposed organisms. From these results it can be concluded that acute exposure to either free chlorine or chloramine results in subsequent reductions in growth and metabolic activity of larval lobsters.
INTRODUCTION Interest in chlorine toxicity is a result of its extensive use for fouling control at coastal power stations. Chlorination of seawater may result in the formation of halogen toxicants in addition to free chlorine including chloramine (Lewis, 1966), organochlorine compounds (Jolley, 1975) and bromine compounds (Dove, 1970). The nature of the halogen toxicants produced during chlorination of sea-water in both a power plant and an experimental situation varies with the relative concentrations of bromide, ammonia and organic compounds. Wong & Davidson (1977) have confirmed that in the presence of low ammonia concentrations, chlorine (as OC1- or HOC1) reacts with the bromide ions of sea-water to form hypobromite (HOBr or OBr-). Johannesson (1958) suggested that in the presence of high ammonia concentrations in sea-water chloramine formation would be favored, but this halogen species could exist in equilibrium with bromamine compounds as well. In a previous study (Capuzzo et al., 1976) the differential effects of applied free chlorine and chloramine on stage I larvae of the American lobster Homarus americanus were investigated. F r o m the results of our earlier study, there was an indication that chloramine was more toxic than free chlorine and that exposure to low levels of either toxicant resulted in significant survival but decreased respiration rates. Standard respiration rates are indicative of the physiological condition of an organism, thus changes in respiration rates of early larval stages could result in subsequent changes in growth and development and increased susceptibility to other environmental stresses. The objective of the present study was to determine the long term effects of acute exposure to free chlorine or chloramine on growth and standard respiration rates of larval lobsters. W.R, I1/12--A
MATERIALS A N D M E T H O D S
Stage I larvae of the American lobster were hatched at 20°C from eggs held by female lobsters and used in experiments within 24 h. Before the bioassays were begun, the average length (mm), dry weight (mg) and standard respiration rate (#1 02 h- 1 mg- 1 dry weight) of test organisms were monitored. Lobster larvae were dried at 60°C for 24h; respiration rates were measured using microrespirometers as previously described by Capuzzo et al. (1976). Test organisms were selected randomly and 12 replicate samples of 10 animals each were exposed to either 1.0 mg 1- t applied free chlorine (NaOC1) or 1.0 mg 1- t applied chloramine (equimolar concentrations of NH4OH and NaOC1) for 60 min at 25°C in the continuous flow bioassay apparatus described earlier (Capuzzo et al., 1976); control organisms (6 replicates of 10 animals each) were maintained at 25°C during the 60 rain exposure period. Before use in the assays, sea-water (salinity = 30-31%o; pH = 7.8-8.1) was filtered through activated charcoal and 1.2/~m membrane filters and aerated for 48h with ammonia free air for removal of organics and ammonia; ammonia levels were reduced to <0.5/~g-atom NH4-N/I. Chlorine and chloramine were measured as total C12 by amperometric titration (Fischer and Porter Model 17T1010; APHA, 1971; pH 4 oxidant, lmg1-1 total C12 = 0.028 mN total oxidant species; accuracy = +0.02 mg 1-1). Seawater and toxicants were equilibrated for 12 h before the addition of test organisms and the resulting residual toxicant levels were 15% of the applied levels due to the chlorine demand of sea-water. Total residual chlorine concentrations include all chlorine and bromine species measurable by amperometric titration. The temperature was reduced to 20°C after the 60min exposure to free chlorine or chloramine; the halogen toxicants were chemically removed by the addition of sodium thiosulfate after the designated exposure period. Per cent mortality and standard respiration rates of exposed organisms were compared to those of control organisms held in the same bioassay apparatus until 48 h after exposure. After 48 h, the three groups of lobster larvae (control, chlorine exposed and chloramine exposed) were transferred to three 401 fibreglass aquaria supplied with filtered (20/tm) flowing seawater at 20°C and constant aeration. Test organisms were maintained in the three aquaria for 1021
1022
JUDITH M. CAPUZZO
17 days until all larvae had developed to the last larval stage (stage IV). Lobster larvae were fed 10 mg dry weight of frozen brine shrimp Artemia salina per animal per day during the experimental period. The total length of lobster larvae, excluding claws (tip of rostrum to tail fin), was measured within 12 h after each molt and the time between molts recorded. It was observed that in the three test groups molting activity was quite uniform among both control and exposed organisms and that all of the test organisms within a group would molt within 6-12h of one another. Sub-samples of 8 organisms were taken periodically from each test group (day 3, or 48 h after exposure, day 5, 12 h after completion of the molt to stage II in the three test groups, and day 19, at the termination of the experiment and 12h after attainment of stage IV in chloramine exposed animals) for dry weight and respiration rate measurements. Respiration rates of stage I (initial, day 3) and stage II (day 5) larvae were measured using microrespirometers; oxygen consumption rates of stage IV larvae were measured using a Gilson differential respirometer. In both instances, individual larvae were placed in respirometer flasks with filtered seawater; fluted filter paper soaked with 10% KOH was used as the CO2 absorbent. Oxygen uptake was measured at 22°C at 15 min intervals for 2 h and is reported as pl O2 h- ~ mg- ~ dry weight, adjusted to #1 of dry gas at standard temperature and pressure. Organisms were not fed for at least 4h prior to respiration rate measurements and were allowed to acclimate to test conditions for 15 min before oxygen uptake was measured. Values of length, dry weight and standard respiration rate are mean values + 1 standard error. Significant differences in these parameters between control and exposed organisms were determined by analysis of variance. The relationship of dry weight and standard respiration rate of control organisms was analyzed by log-log linear regression analysis.
RESULTS
The concentrations tested (1.0 mg 1-1 applied free chlorine and 1.0 mg 1-1 applied chloramine) cannot be considered strictly to be sublethal levels, since an increase in mortality compared with control organisms did occur with exposure to these concentrations (Table 1). However, the values are significantly lower than LCso values reported earlier (16.30 mg1-1 applied free chlorine and 2.02mg1-1 applied chloramine; Capuzzo et al., 1976) and a significant percentage of the test population survived these stresses. The mortaility rate appeared to stabilize 48 h after exposure; no increase in mortality during the remainder of the experimental period could be attributed to toxicant exposure, although some mortality did occur ( ~ 10%) in the three test groups due to cannibalism. Table 1. Per cent mortality of larval lobsters (stage I) 48 h after 60min exposure at 25°C to free chlorine and chloramine
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II
50 I
~
In"
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20
DAYS
Fig. l. Length (mm) of larval lobsters, stage I-IV; circlescontrol organisms, triangles-chlorine exposed organisms, squares-chloramine exposed organisms; values are mean values from each group + 1 standard error. The average length and dry weight of the larval stages from the three test groups are presented in Figs. 1 and 2 and Table 2. Significantly lower increases (P < 0.05) in length and dry weight compared to control organisms were observed with the first molt (stage I to stage II) of organisms exposed to free chlorine and chloramine; lesser increases in length and dry weight were measured among chloramine exposed organisms. Subsequent molts resulted in no significant difference in length increases per molt between chlorine exposed and control animals ( 1 . 5 m m m o l t -1) but significant differences in dry weight increases were observed (control = 2.3mg m o l t - 1, chlorine exposed = 1.9 mg m o l t - 1). Length and dry weight increases of chloramine exposed animals remained significantly lower with each molt (1.0 mm m o l t - 1 and 0.9 mg m o l t - 1). N o significant difference in molting time of the first two molts was observed between control and exposed organisms, however, a slight delay in molting to the fourth larval 8.0
t
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M" 5.0
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////"i
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2.0
1.0 Toxicant Control Free chlorine Chloramine
Concentration mg 1- z Total C l 2 applied residual 1.00 1.00
0.15 0.15
I
% Mortality 10 15 25
O.C
I/ I
I
I
5
I0
15
lV 20
DAYS
Fig. 2. Dry weight (rag) of larval lobsters, stage I-stage IV; circles-control organisms, triangles-chlorine exposed organisms, squares-chloramine exposed organisms; values are mean values from each group + 1 standard error.
Effects of free chlorine on H. americanus
1023
Table 2. Length, dry weight and standard respiration rate measurements of larval lobsters exposed to free chlorine and chloramine and maintained at 20°C Toxicant
Length* (mm)
Dry wt.* (mg)
/11 0 2 h - 1 mg- 1,
I
control
6.8 + 0.1
1.7 + 0.1
1.1 ___0.1
I
control free chlorine chloramine control free chlorine chloramine control free chlorine chloramine control free chlorine chloramine control free chlorine chloramine
1.7 1.7 1.7 1.7 1.7 1.7 2.6 2.4 1.9
+ 0.1 + 0.1 ___0.1 + 0.1 4- 0.1 + 0.1 + 0.1 + 0.1 ___0.1 -
1.1 + 0.1 0.9 + 0.2 0.5 + 0.1 1.1 ___0.1 0.5 + 0.1 0.3 + 0.2 1.8 4- 0.1 1.2 ___0.1 1.0 ___0.1
7.2 + 0.5 6.2 4- 0.4 3.6 4- 0.5
3.4 + 0.2 2.5 ___0.2 1.8 4- 0.1
Day
Stage
1 (pre-exposure) 1 (post-exposure) 3
I
5
II
11
III
19
IV
6.8 6.8 6.8 6.8 6.8 6.8 7.8 7.3 6.8 9.6 8.5 7.9 10.8 10.2 8.8
4- 0.1 + 0.1 ___0.1 4- 0.1 4- 0.1 4- 0.l 4- 0.2 4- 0.2 4- 0.1 4- 0.2 4- 0.3 + 0.1 + 0.2 ___0.3 4- 0.3
-
* All values are mean values _+ 1 standard error.
stage was detected a m o n g chloramine exposed organisms (Table 3). All length a n d dry weight measurements were made within the first 12 h following completion of the molt from one stage to the next except in the case of stage IV larvae; measurements of control a n d chlorine exposed stage IV larvae were m a d e 48 h after completion of the molt to correspond with completion of the molt in chloramine exposed organisms. Standard respiration rates of exposed lobster larvae were significantly lower (P < 0.01) than those of control organisms t h r o u g h o u t the experimental period (Fig. 3 a n d Table 2). The greatest differences in oxygen uptake were measured 48 h after exposure with a 55% reduction a m o n g chlorine exposed organisms a n d a 73% reduction a m o n g chloramine exposed organisms. Older lobster larvae h a d a higher energy d e m a n d than stage I larvae as indicated by the higher weight specific standard respiration rates detected. This trend was observed in b o t h control a n d exposed organisms. It is possible that the respiration rates of stage II a n d stage IV larvae from b o t h control a n d exposed groups only reflect differences in the size of the Table 3. Days between each molt of larval lobsters exposed to free chlorine and chloramine and maintained at 20°C Toxicant
Stage
Control
I II III I II III I II III
Free chlorine Chloramine
organisms. The relationship of dry weight a n d standard respiration rate of control animals is represented by the following equation: log Y (respiration r a t e ) = 0.75 log X (dry weight) + log 0.80 r = 0.987, N = 24. Values for respiration rates of stage II a n d stage IV larvae from the chlorine exposed group a n d the chloramine exposed group are less than values predicted from this equation, suggesting that exposure to the toxicants has resulted in significant differences in respiration rates. DISCUSSION The impact of chlorinated cooling waters on marine ecosystems is a problem of great concern with 4.0
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,
,
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,
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Days before molt to next stage 4 5 6 4 5 6 4 5 8
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Fig. 3. Standard respiration rate (#1 02 h -1 mg-1 dry weight) of larval lobsters, stage I-stage IV; circles-control organisms, triangles-chlorine exposed organisms, squareschloramine exposed organisms; values are mean values from each group + 1 standard error.
1024
JUDITH M. CAPUZZO
the extensive use of chlorine for fouling control at coastal power plants. The halogen compounds formed upon chlorination of sea-water are dependent on the relative concentrations of bromide, organic matter, ammonia and other nitrogenous compounds. Thus toxic effects of chlorinated cooling waters may vary from one power plant site to another because of the relative concentrations of different halogen compounds. An understanding of the comparative toxicity of these halogen compounds is needed to adequately assess the potential effects of power plant chlorination on marine organisms. The toxicity of chlorinated cooling waters to marine organisms has been the subject of several studies, recently reviewed by Davis & Middaugh (1976). The major environmental variables affecting toxicity are temperature and exposure time, as well as the available form of chlorine or other halogen compounds. Few studies have focused on the long term effects of acute short term exposures to chlorinated cooling waters on survival and growth of marine invertebrates. Waugh (1964) exposed naupliar larvae of the barnacle Elminius modestus to chlorine doses ranging from 0.5 to 5.0mg1-1 for 10min and monitored survival, development and growth for periods up to 6 days after exposure. He concluded that concentrations in excess of 0.5 mg l - 1 caused significant mortality and reductions in growth rates of surviving organisms. Growth may be defined as the net balance between food supply and metabolic expenditures. Logan (1976) observed exponential growth rates among larvae of the American lobster and noted that a high percentage of energy intake was directed towards growth during larval development. Any interference with metabolic processes could result in inefficient utilization of food and subsequent reductions in growth. In our previous study (Capuzzo et al., 1976), lobster larvae exposed to free chlorine and chloramine for 60 rain showed significant reductions in metabolic activity 48h after exposure; greater reductions were observed among chloramine exposed animals. The effects of both halogen toxicants appeared to be irreversible with exposed organisms being unable to maintain the standard respiration rate of control organisms. In the present study, the effects of the halogen toxicants on growth of larval lobsters provide evidence that longer-lasting metabolic disturbances may result from acute exposure to chlorinated seawater. The exponential growth pattern was evident among the three test groups of lobsters but the resulting size of stage IV larvae was significantly reduced among chlorine exposed and chloramine exposed organisms. The apparent effect of the toxicants on lobster larvae was an interference with energy utilization as evidenced by lesser dry weight increases and decreased metabolic activity. These findings were detected at residual levels of
0.15 mg 1-1 of either toxicant; this value is within the range of commonly detected residual levels in cooling waters discharged from coastal power stations (0.05-5.00mg1-1; Brungs, 1973; Marshall, 1971). If large numbers of lobster larvae become entrained in these cooling waters or reside in adjacent receiving waters, serious consequences for populations of this valuable commercial species could result, particularly where chloramine is the major halogen toxicant. Therefore, the use of chlorine for fouling control at coastal power plants should be executed with great care and dechlorination of cooling waters should be considered before discharge into marine ecosystems. Acknowledoements--This research was supported by U.S.
Energy Research and Development Administration Contract No. E (11-1)-2532. The author wishes to thank John Hughes of the Massachusetts State Lobster Hatchery for providing egg-bearing lobsters. Woods Hole Oceanographic Institution Contribution No. 3926. REFERENCES
APHA (1971) Standard Methods for Examination of Water and Wastewater, 13th edn, Am. Public Health Assn., New York. Brungs W. A. (1973) Effects of residual chlorine on aquatic life. J. War. Pollut. Control Fed. 45, 218022193. Capuzzo J. M., Lawrence S. A. & Davidson J. A. (1976) Combined toxicity of free chlorine, chloramine and temperature to stage I larvae of the American lobster Homarus americanus. Water Res. 10, 1093-1099. Davis W. P. & Middaugh D. P. 0976) A review of the impact of chlorination processes upon marine ecosystems. In The Environmental Impact of Water Chlorination, Proceedings (Edited by R. L. Jolley), pp. 299-325. Oak Ridge Nat. Lab., Oak Ridge, Tenn. Dove R. A. (1970) Reactions of small dosages of chlorine in sea water. Central Electricity Generating Board, Research Report 42/70, File No. 0.3070/ID, Job No. 10665. Univ. of Southampton, England. Johannesson J. K. (1958) The determination of monobromamine and monochloramine in water. Analyst 83, 155-159. Jolley R. L. (1975) Chlorine containing organic constituents in chlorinated effluents. J. Wat. Pollut. Control Fed. 47, 601-6t 8. Lewis B. G. (1966) Chlorination and mussel control. I: The chemistry of chlorinated sea water: A review of the literature. Central Electricity Research Laboratories, Laboratory Note No. RD/L/N 106/66, Leatherhead, England. Logan D. T. (1976) A laboratory energy balance for the larvae and juveniles of the American lobster Homarus americanus. P h . D . Thesis, University of Delaware, Lewes, Delaware. Marshall W. L. (1971) Thermal discharges: characteristics and chemical treatment of natural waters used in power plants. Oak Ridge Nat. Lab, Report No. 4652, Oak Ridge, Tennessee. Waugh G. D. (1964) Observations on the effects of chlorine on the larvae of oysters (Ostrea edulis (L.)) and barnacles (Elminius modestus (Darwin)). Ann. appl. Biol. 54, 423-440. WoN~ G. T. F. & DAVIDSOSJ. A. (1977) The fate of chlorine in seawater-A preliminary review. Water Res. 11, 971 978.