The persistence of chronically accumulated hydrocarbons in the hard shell clam Mercenaria mercenaria

Hard shell clams, Mercenaria mercenaria, from the chronically polluted environment of the Providence River, USA, were transferred to a clean laboratory system located in lower Narragansett Bay, Rhode Island. The hydrocarbon contents of these transplanted clams were monitored for 120 days after transfer. After this period only slight depuration had occurred. A 41.9 g g wet weight^-1 average initial hydrocarbon burden decreased to 29.3 g g^-1, a decrease that became statistically significant (P<0.1) only after 120 days. At most, only 30% of the clams' hydrocarbons were lost. These findings indicate that the duration of the exposure period and the chemical nature of the source hydrocarbons are both instrumental in determining the persistence of these compounds in filter-feeding bivalves. Chronically accumulated petroleum hydrocarbons are strongly retained by the organisms and are only very slowly depurated.     

Effects of kelthane on the estuarine shrimp Crangon tranciscorum

The chlorinated hydrocarbon pesticide Kelthane was assayed for effects on food consumption, molting rate, cannibalism, respiration, mortality and behavior of the estuarine shrimp Crangon franciscorum Stimpson. The test system was a single-pass pulse-flow apparatus employing a modified Mount-Brungs style diluter. Treatment levels were 0, 14, 33 and 81 g l^-1 Kelthane at 16.6°C and 19 S over an exposure period of 317 h. Exposure to Kelthane reduced food consumption, molting rate, cannibalism, and respiration. Behavior also was abnormal in exposed shrimp. They spent more time swimming, were less coordinated and had feeble escape reactions. Kelthane was very toxic to C. franciscorum with LT₅₀ values of 163, 196 and 264 h for shrimp exposed to 81, 33 and 14 g l^-1 respectively. The incipient lethal level of Kelthane is probably below 14 g l^-1.     

Growth response of Chaetoceros calcitrans (Bacillariophyceae) in batch culture to a range of initial silica concentrations

Batch cultures of the marine unicellular centric diatom Chaetoceros calcitrans (Paulsen) Takano were maintained by serial subculturing every 4 d into nutrient-enriched natural sea-water medium supplemented with 350, 950 and 1 400 g-at Si l^-1. The diatom cultures removed initial silica concentrations of 350 and 950 g-at l^-1 from the medium within 2 and 3 d, respectively. About 30 g-at l^-1 of the highest initial concentration remained in the medium after 4 d. The mean final cell density with an enrichment of 350 g-at Si l^-1 was 3.43±0.26×10⁴ cells l^-1 (median cell volume = 77.5±5.0 m³); with 950 g-at Si l^-1, 8.55±0.55×10⁴ cells l^-1 (50.0±4.5 m³); and with 1 400 g-at Si l^-1, 9.72±0.48×10⁴ cells l^-1 (37.3±5.0 m³). There was no significant difference in the final total organic weight of cells produced, which was in the range of 170 to 190 mg per 250 ml culture. This consisted of proportionately more lipid and carbohydrate and less protein from the treatment with 350 g-at Si l^-1 than from the 1 400 g-at Si l^-1 treatment.     

Feeding,growth and bioluminescence of the heterotrophic dinoflagellate Protoperidinium huberi

Feeding, growth and bioluminescence of the thecate heterotrophic dinoflagellate Protoperidinium huberi were measured as a function of food concentration for laboratory cultures grown on the diatom Ditylum brightwellii. Ingestion of food increased with food concentration. Maximum ingestion rates were measured at food concentrations of 600 g C l^-1 and were 0.7 g C individual^-1 h^-1 (1.8 D. brightwelli cells individual^-1 h^-1). Clearance rates decreased asymptotically with increasing food concentration. Maximum clearance rates at low food concentration were ca. 23 l ind^-1 h^-1, which corresponds to a volume-specific clearance rate of 5.9x10⁵ h^-1. Cell size of P huberi was highly variable, with a mean diameter of 42 m, but no clear relationship between cell size and food concentration was evident. Specific growth rates increased with food concentration until maximum growth rates of 0.7 d^-1 were reached at a food concentration of 400 g C l^-1 (1000 cells ml^-1). Food concentrations as low as 10 g C l^-1 of D. brightwellii (25 cells ml^-1) were able to support growth of P. huberi. The bioluminescence of P. huberi varied with its nutritional condition and growth rate. Cells held without food lost their bioluminescence capacity in a matter of days. P. huberi raised at different food concentrations showed increased bioluminescence capacity, up to food concentration that supported maximum growth rates. The bioluminescence of P. huberi varied over a diel cycle, and these rhythmic changes persisted during 48 h of continuous darkness, indicating that the rhythm was under endogenous control.     

Cadmium accumulation,LC50 and oxygen consumption in the tropical marine amphipod Elasmopus rapax

Adult Elasmopus rapax, collected from the eastern coast of Venezuela in 1990, were exposed to seawater containing various CdCl₂ concentrations ranging from 0.25 to 5.5 mol l^-1. The 48-h and 96-h LC₅₀ values obtained were 4.0 and 1.6 mol Cd l^-1, respectively. In amphipods exposed to 1 mol Cd l^-1 for up to 240 h, the apparent rate of cadmium uptake was higher in dead animals (most of which had molted during the preceding 24 to 48 h) than in those which survived throughout the treatments without molting. Thus, whole-body cadmium content reached 1.74 mol g^-1 dry weight (dw) in the former and only 0.85 mol g^-1 dw in the latter; the higher body Cd-load may have caused the increased mortality observed in molters. On exposure to cadmium levels above 0.5 mol l^-1 the oxygen consumption rate of non-molters decreased from 2.2 to about 1.5 ml O₂ g^-1 dw h^-1 over the first 24 h, remaining unchanged thereafter. The results place E. rapax among the most sensitive marine organisms yet studied concerning cadmium toxicity, and emphasize the usefulness of the Amphipoda as bioindicators and research tools for bioassays.     

Toxicity of the fungicide captan to the Dungeness crab Cancer magister

Captan did not affect the survival of Dungeness crab (Cancer magister Dana) zoea exposed to 30 g l^-1 during a chronic toxicity test lasting 69 days, but larvae were quickly killed (mean survival time = 9 days) in the same test by exposure to 450 g l^-1 of the fungicide. Delay of molting occurred, however, for later stages at 30 g l^-1. Survival of juvenile crabs was not reduced by exposure to captan for 36 days at 510 g l^-1 or, in a second test, for 80 days at 290 g l^-1. No deaths of adults exposed for 75 days to 340 g l^-1 of captan were observed. Captan appeared to accelerate hatching of eggs at all concentrations tested from 100 to 10,000 g l^-1. The development from prezoeae during a 24-h period was not inhibited by the fungicide, but at 3,300 and 10,00 g l^-1, the two highest concentrations tested, developing zoeae exhibited a morphological deformity and were largely inactive. Under the prevailing conditions in the toxicity tests, the half-life of captan was estimated to be from 23 to 54 h. Because of the relatively low toxicity of captan to crab stages and its high rate of degradation in sewater, it is suggested that the agricultural application of captan near marine waters is not likely to affect natural crab populations or crabs in laboratory culture. Further-more, the prophylactic use of captan as a fungicidal treatment for Lagenidium sp. in larval crab cultures is considered safe when used at recommended dosages.Technical Paper No. 4131, Oregon Agricultural Experiment Station.     

Acute toxicity of mercury and selenium to Crassostrea gigas embryos and Cancer magister larvae

The possible modification of mercury toxicity by selenium in embryos of the Pacific oyster Crassostrea gigas and the larvae of the crab Cancer magister was investigated. Mercury concentration eliciting abnormal development in 50% of the oyster embryos (EC₅₀) was 5.7 g l^-1 (48 h) and mortality in 50% of the crab larvae (LC₅₀) occurred with 6.6 g l^-1 (96 h). The 48 h EC₅₀ for selenium was greater than 10,000 g l^-1 for oyster embryos and the 96 h LC₅₀ for crab zoeae was 1040 g l^-1. The response from each species, when exposed to both toxicants, revealed, that a high level of selenium (5,000 g l^-1) increased mercury toxicity. Moderate selenium concentrations (10 to 1,000 g l^-1) tended to decrease mercury toxicity, although no statistical verification could be made. The order of administration of toxicants had no effect on the response of Crassostrea gigas embryos. Early developmental stages (8 h) of C. gigas embryos were most sensitive to dissolved Hg; toxicant administration 24 h after fertilization resulted in no apparent abnormalities in development.     

Nutrient enrichment and the ultrastructure of zooxanthellae from the giant clam Tridacna maxima

The separate and combined effects of ammonium (10M) and phosphate (2M) on the ultrastructure of zooxanthellae (Symbiodinium sp.) from giant clams, Tridacna maxima, were examined in the field. Nitrogen addition significantly changed the ultrastructure of the zooxanthellae inhabiting the clams. After 9 mo exposure, the cross-sectional area of zooxanthellae from N-treated clams was significantly lower than that from other treatments [N=39.3 m²; C=47.9 m²; P=43.2m²; N+P=44.5 m²; (P=0.001)]. There was also a significant decrease in the size of starch bodies, especially around the pyrenoid of the zooxanthellae from N and N+P treatments [N=1.2 m²; C=2.0 m²; P=1.8 m²; N+P=1.2 m²; (P=2.08E-11)]. This presumably occurs as a result of the mobilization of organic carbon stores in response to stimulated amino acid synthesis under enriched nutrient conditions. These data strongly suggest that the symbiotic zooxanthellae of clams are limited to some extent by the availability of inorganic nitrogen, and that relatively minor changes to the nutrient loading of the water column can have substantial effects on the biochemistry of symbioses such as that which exists between clams and zooxanthellae.     

Mytilus edulis planulatus: an “integrator” of cadmium pollution?

Mussels, Mytilus edulis planulatus, were collected from Port Phillip Bay, Victoria, Australia, in February 1984, to test the assumption that they are integrators of cadmium pollution. Groups of mussels were subjected to the same average dose of cadmium (21 g l^-1), administered according to different dosing regimes over 4 wk (Regimes 1, 2, 3, 5); other groups received twice the average dose (42 g l^-1) in half the time (Regime 4). During each regime, the mussels were exposed to the different cadmium concentrations for one week at each concentration. Nominally, the regimes were: (1) 36 g (Wk 1) to 26 g (Wk 2) to 16 g (Wk 3) to 6 g (Wk 4) Cd l^-1; (2) 6 to 16 to 26 to 36 g Cd l^-1; (3) 21 to 21 to 21 to 21 g Cd l^-1; (4) 42 to 42 g Cd l^-1; (5) 42 to 42 g Cd l^-1 to background (<0.5 g) to background. Differences in cadmium accumulation by mussels from Regimes 1 and 4 were not statistically significant, nor were differences in accumulation between mussels from Regimes 2 and 3. However, mussels from Regimes 1 and 4 had accumulated significantly more cadmium than had mussels from Regimes 2 and 3. Accumulation by mussels from Regime 5 was not significantly different from that by mussels from any of the other regimes. These results suggest that, at least for cadmium, the assumption that mussels are integrators of pollution should be treated with caution. They also have implications with regard to the quantitative biological monitoring of pollution. For example, even in a carefully controlled monitoring program, using mussels of standard size and condition, significant differences in cadmium content between mussels need not indicate exposure to different levels of contamination. Rather, these differences could reflect differences in the regime by which the contamination was received.     

Effect of pentachlorophenol (PCP) on meiobenthic communities established in an experimental system

Aquaria containing clean sand received a continuous supply of seawater from Santa Rosa Sound, Florida, USA, mixed with known concentrations (7, 76 and 622 g l^-1) of pentachlorophenol (PCP). After 9 weeks, nematodes accounted for 87% of the total meiofauna. Nematode biomass and densities were greatest in aquaria exposed to 76 g PCP l^-1 and were least in aquaria exposed to 622 g PCP l^-1. Epistrate feeders were abundant in control aquaria and aquaria exposed to 7 and 76 g PCP l^-1, but not in aquaria exposed to 622 g PCP l^-1. Selective deposit feeders were not abundant in the control aquaria and aquaria exposed to 7 g PCP l^-1, but comprised 19% of the nematodes in aquaria exposed to 76 g PCP l^-1 and 61% in aquaria exposed to 622 g PCP l^-1.     

Effect of cadmium on survival and osmoregulation of various developmental stages of the shrimp Penaeus japonicus (Crustacea: Decapoda)

The object of this study was to evaluate the acute toxicity of cadmium in different post-embryonic stages of the penaeid shrimp Penaeus japonicus (Bate, 1888) and to determine the effect of sublethal cadmium on the osmoregulatory capacity used as an indicator of physiological condition. Tolerance to cadmium increases with the developmental stage. The least tolerant stages are the nauplii (48 h LC₅₀: 124 g Cd l^-1) and the zoeae (96 h LC₅₀: 10 to 30 g Cd l^-1). The most tolerant stages are the postlarvae (96 h LC₅₀: 200 to 3500 Cd l^-1) and juveniles (96 h LC₅₀: 5500 g Cd l^-1). In juvenile shrimp, 2000 g Cd l^-1 significantly reduce hypo- and hyper-OC. The effect of cadmium on hypo- and hyper-osmoregulatory capacity illustrates a dose- and time-dependent response. Surviving shrimp recover their hypo-osmoregulatory capacity after 6 d of readaptation in cadmium-free seawater.     

Effect of the hard clam Mercenaria mercenaria on benthic fluxes of inorganic nutrients and gases

The effect of the hard clam Mercenaria mercenaria (L.) on the exchange of dissolved nutrients (silicate, phosphate, ammonium, nitrate+nitrite) and gases (oxygen, carbon dioxide) across the sediment-water interface was examined in 1983 and 1984 using experimental mesocosms (13 m³), designed to simulate a shallow coastal ecosystem, that allow for reciprocal biogeochemical interactions between water column (5 m) and bottom sediments (30 cm deep). Benthic, fluxes, measured during a spring-summer warming period, were compared for mesocosms maintained either with added M. mercenaria (16 per m², treatment) or without M. mercenaria (control) as a component of the benthic community. Fluxes were within the range observed for the (control) community in situ in mid-Narragansett Bay and exhibited the pattern of increasing flux with increasing temperature observed in nature. For dissolved inorganic (DIN=ammonia+nitrate+nitrite), analytical problems allowed comparison of fluxes only at the higher temperatures (17° to 22°C); average DIN fluxes were 57% higher in mesocosms with clams. Fluxes of other nutrients and gases were modelled as exponential functions of temperature (9° to 22°C) using a linear regression of the natural logarithm of flux upon temperature in both treatment and control situations. Differences between regression slopes and intercepts for conditions with and without clams were assessed by analysis of covariance. Slopes of the linearized temperature-flux relationships were not significantly different between treatments for any flux measured, suggesting that presence of the clams did not alter the basic relationship of flux and temperature normally observed with this community. For oxygen consumption and silicate production, the regression intercepts were significantly higher in the clam treatment, suggesting that the level of flux was generally elevated in the presence of M. mercenaria by about 20% (oxygen) and 86% (silicate) at any given temperature. Data for carbon dioxide and phosphate showed similar trends to oxygen and silicate, but the variance in fluxes was larger and regression intercepts for the two treatments were not significantly different.     

Effects of suspended and sedimented clays on juvenile hard clams,<Emphasis Type="Italic"> Mercenaria mercenaria</Emphasis>, within the context of harmful algal bloom mitigation

Increased interest in using ecologically inert clays to flocculate, sediment, and thus mitigate harmful algal blooms at nearshore mariculture sites has prompted studies on the effectiveness of this method on prolific blooms, such as those caused by the neurotoxic dinoflagellate Karenia brevis in the Gulf of Mexico. Potential repercussions of this control strategy revolve around the increased flux of suspended particles to the benthos. Juvenile suspension-feeding bivalves are potentially vulnerable as they could suffer burial, a decrease in clearance rates, and/or an increase in pseudofeces production in response to suspended clay, leading to reduced growth and delay in attaining size refuge from predators. Here we assess lethal and sublethal effects on juvenile hard clams, Mercenaria mercenaria, in a 2-week flume application of phosphatic clay to simulated blooms of the nontoxic dinoflagellates Heterocapsa triquetra and Prorocentrum micans. Flow regimes simulated two contrasting, worst-case field conditions where (1) low flow allowed complete sedimentation and formation of a benthic sediment layer, and (2) high flow allowed complete particle suspension. No clam mortalities occurred in either treatment. The sedimentation treatment showed variable growth inhibition in shell and/or tissue, but effects were not apparent compared to controls (no sediment layer), and clams rapidly resumed siphon contact with the overlying water column. In contrast, a strong growth effect (~90% reduction in shell and tissue growth) occurred in particle-suspension trials compared to no-clay controls. These results suggest that repeated clay applications in the field are likely more detrimental to clams in a high-energy environment leading to prolonged in situ resuspension of clay than in an environment favoring sedimentation.Communicated by R.J. Thompson, St. Johns     

Modification of the feeding behavior of marine copepods by sub-lethal concentrations of water-accommodated fuel oil

The feeding behaviors of Acartia clausi and A. tonsa were measured in samples of water containing low levels of a water-accommodated fraction of No. 2 fuel oil. The copepods fed normally at a hydrocarbon concentration of 70 g l^-1, but their feeding behavior was altered both quantitatively and qualitatively at a concentration of 250 g l^-1. Three types of response to the higher oil level were found. The first was total suppression of feeding. Both other types involved suppression of feeding on particles between 7 and 15 m diameter, but one showed no change in the ingestion of larger particles, whereas the other displayed increased feeding on particles larger than 15 m diameter. These results suggest that the species of Acartia studied use three different modes of feeding, each on a different size range of particulate material. Low-level hydrocarbon pollution affects each feeding mode differently.Contribution No. 973, Center for Environmental and Estuarine Studies of the University of Maryland     

Acute and chronic toxicity of tributyltin (TBT) to pediveliger larvae of the bivalve Scrobicularia plana

A static renewal test was run for 30 d to assess the effects of the antifoulant tributyltin (TBT, nominal concentrations of 50, 125, 250 and 500 ng Sn l^-1) on the survival and growth of 240 m-long pediveliger larvae of the bivalve Scrobicularia plana (da Costa) settling in fine sand. Exposure to nominal TBT levels of 125 ng Sn l^-1 (actual range of 37 to 102 ng Sn l^-1, as analysed) resulted in substantial mortalities and negligible shell growth of individuals. More importantly, larval shell growth at the lowest concentration tested (i.e. nominal 50 ng Sn l^-1 or 14 to 32 ng Sn l^-1, as analysed) was significantly reduced (by a factor of 4) and grossly abnormal. In contrast, some control postlarvae had begun developing siphons as they attained a length of 600 to 700 m by the end of this test, thereby completing metamorphosis and becoming juveniles. The results are discussed in relation to the widespread disappearance of S. plana in North Atlantic European estuaries during the 1980s and the concurrent TBT pollution in their waters. It is inferred that TBT is likely to have contributed to the reported demise of clam populations by preventing the successful and timely progress of their pediveliger larvae.     

Comparison of the scope for growth with the growth performance of Ostrea edulis seed reared at different food concentrations in an open-flow system

Oyster (Ostrea edulis L.) seed was reared on five rations of Isochrysis galbana Parke: 10, 30, 100, 200 and 300 cells l^-1, in an open-flow system. Physiological parameters such as clearance, ingestion, absorption and respiration rates were measured, and the scope for growth (SFG) calculated from these parameters was compared with actual growth over 20 d. Actual growth was negligible at 10 cells l^-1 (daily maintenance ration=2.5% organic wt) and maximum (growth rate=13.64 d^-1) at 200 cells l^-1 (daily ration=43% organic wt), which also supported the maximum gross and net growth efficiencies (K ₁=50%, K ₂=85%). Ingestion rate was directly correlated to cell concentration up to maximum of 100 cells l^-1, but further increases failed to support higher ingestions. Absorption efficiency decreased with increasing algal concentration from 95% down to 60%. Due to the costs of growth, respiration rate significantly increased when food was added above maintenance levels; however, metabolic costs associated with feeding activity were undetectable. The scope for growth calculated from these physiological parameters agreed with the long-term growth performance, validating the physiological energetics method as a valuable tool for predicting long-term growth performance under constant environmental conditions.     

Copper effects on reproductive stages of Baltic Sea Fucus vesiculosus

Copper is an active ingredient in many antifouling products, and pleasure boats are estimated to be the major single source of copper pollution in Swedish coastal waters. For this reason, the effects of copper were studied on egg volume, fertilization, germination and development of apical hairs of Baltic Sea Fucus vesiculosus L. Germination was the most sensitive stage and was studied at different concentrations of copper, different salinities and different ages of zygotes. Low concentrations of copper, 2.5 g Cu l^-1, added to natural brackish water before fertilization, adversely affected germination at the ambient, suboptimal salinity of 6, suggesting that as little as a doubling of the copper levels in the studied area will severely affect the germination frequency of F. vesiculosus. The addition of 20 g Cu l^-1 caused about 70 to 80% decline in germination at 6S but also at 20S which is higher than optimum. At a salinity close to optimum (14S) no negative effect was noticed on germination when 20 g Cu l^-1 was added. The results suggest that the degree of salinity stress acting upon the zygotes is a more important factor for the response to copper than the influence of salinity on metal availability. When 2.5 to 60 g Cu l^-1 was added to the medium 24 h after fertilization, the zygotes were more resistant, resembling the response of adult marine fucoid tissue.     

The composition and biosynthesis of lipids in Thysanoessa raschi from the Clyde Estuary,Scotland

The lipid composition and biosynthesising activity of Thysanoessa raschi collected from the Clyde Estuary, Scotland, in May 1981 were examined. Triacylglycerols were the major lipid class present, although 16.7% of the total lipid were wax esters in which phytol was the dominant fatty alcohol. The thoracic contents (hepatopancreas) of the krill were capable of biosynthesising lipids in vitro from various labelled substrates. Radioactivity from [1-¹⁴C] palmitic acid was incorporated into lipids in the order phospholipids>triacylglycerols>wax esters; the bulk of the radioactivity was present in all cases in the fatty acyl moieties of the lipids. [U-¹⁴C] glucose labelled lipids in the order phospholipids>triacylglycerols>free fatty acids> was esters; in the first two lipids the radioactivity was mainly in the glycerol moieties, whereas in was esters it was solely in the fatty acyl moieties. The extent of labelling of these lipids from [U-¹⁴C] alanine was less than that from [U-¹⁴C] glucose, but the pattern of labelling was generally similar. More than 90% of the radioactivity incorporated into total lipid from ³H₂O was present in free fatty acids from which it was calculated that the hepatopancreas of T. raschi can synthesise 2.5 g of fatty acid per hour at 15°C. This value is approximately three times lower than that previously determined for T. inermis from Balsfjorden, northern Norway. The results are discussed in terms of the sources of the dietary lipids of krill and the role of endogenous biosynthesis in contributing to its lipid reserves.     

Lead Contamination of Topsoil and Vegetation in the Vicinity of a Battery Factory in Nigeria

Levels of Pb, Zn, Cu, Cr, Ni and Cd were determined in topsoil and vegetation in the vicinity of a factory manufacturing lead- batteries in Ibadan, Nigeria. The samples were collected along five transects in different directions, and varying distances up to 1000m from the factory. Soil lead levels were found to be elevated around the factory, with average levels of about 2000mgkg^–1 close to the fence that declined gradually to about 50mgkg^–1 some 750m away. Soil-lead level around a primary school located about 500m from the factory was as high as 1450mgkg^–1. Lead levels were equally elevated in the vegetation, though average levels in vegetation were slightly lower than in the soil. Cadmium concentrations in soil and vegetation, though low, were more positively correlated with lead levels than any of the other metals are with lead.     

Effects of copper and cadmium on growth,swimming and predator avoidance in Eurytemora affinis (Copepoda)

In this study we demonstrate the sensitivity of swimming behavior and predator-escape responses of nauplii of the estuarine copepod Eurytemora affinis to sublethal doses of Cu and Cd. Behavior was generally altered at metal doses below those affecting growth rates or survival of the copepods. Swimming velocities of Cu-dosed nauplii were different from controls at all concentrations of Cu tested (10–50 g l^-1 total Cu) after 24- to 48-h exposure, whereas development rate of nauplii was significantly reduced only after 96 h at 25 g l^-1. The 96 h LC50 for Cu was approximately 30 g l^-1 Cu. Naupliar swimming velocity was also affected by Cd. Swimming speeds were reduced after 24 h at 130 g l^-1, and development was slowed after 48 h at 116 g Cd l^-1. The 96-h LC50 was >120 g l^-1. Little is known of the adaptive role of specific motile behaviors in the success of larval copepods. We investigated the relationship of swimming speed to predator — prey interactions of the nauplii using both real and simulated predators. Nauplii exposed to Cu for 24 h were observed to be generally hyperactive, a condition which could increase their encounter frequency with predators. Reduced numbers of escape responses of nauplii to a simulated predator, another indication of increased vulnerability to predation, were observed only after 48-h exposure to Cu. Nevertheless, feeding rates of non-dosed larval striped bass on dosed nauplii (24 h at 25 g Cu l^-1) were significantly higher than on control nauplii. Feeding rates of larval mysid shrimp, however, were not higher on similarly dosed nauplii; 24 h exposure of nauplii to >30 g Cu l^-1 did result in increased predation by mysids.Contribution No. 272 of the US EPA Environmental Research Laboratory, Narragansett, Rhode Island 02882, USA