A field experiment was conducted from 1991 to 1992 to examine induction and impact of hematopoietic neoplasia on the marine bivalveMya arenariain southeastern Massachusetts. Clams were collected from Little Buttermilk Bay and separated into three size classes (20–29, 30–39, and 40–49 mm shell length) in the laboratory. These sizes span the range of adults found in the population. A random subsample of these clams was taken to estimate disease prevalence at the start of the experiment, and this was found to be ≤10% in all size classes. Remaining clams were assigned randomly to two groups: Control and Treated. “Controls” were injected with filtered seawater, while “Treated” clams were injected with hemocytes extracted from diseased individuals. Injection of diseased hemocytes was performed to increase disease prevalence in the Treated group. Clams were returned to New Bedford Harbor, a more contaminated field location, where hematopoietic neoplasia is more prevalent, in January 1991, and characteristics of both groups were monitored for 555 days. Among Controls, probability of survival was size-dependent, with higher survival rates in larger clams. Treated clams had a lower probability of survival than Controls, and the magnitude of treatment effect increased with size class. The impact on survival was evident after 89 days, but it was first shown to be statistically significant after 189 days. Among Controls, probability of disease was strongly season-dependent, increasing in the large size class from 0.19 in spring to 0.50 in summer. During summer, Treated clams had a higher probability of being diseased than Controls. Among survivors, no significant sublethal effects due to treatment were detected in the field experiment. Experimental manipulation of disease prevalence may be a useful tool in future studies. In addition to results pertaining to disease, this study obtained long-term growth information, by size class, on somatic and reproductive tissue and shell size.

Activities of digestive protease, lipase, and amylase from the foregut and midgut gland were measured during the course of early development in the American lobster Homarus americanus Milne Edwards. Total enzyme activities were very low among embryos sampled 3 days prior to hatching. Protease and amylase activities increased slightly at the time of hatching and again during larval Stage I; lipase activity did not change. Activity of the three enzymes more than doubled among Stage II larvae and although there were slight increases in enzyme activities during Stage III, they were not significant. Protease activity peaked during Stage IV, whereas lipase and amylase activities were greatest among Stage V juveniles. Different patterns were observed when specific enzyme activities (normalized on the basis of protein) are examined. Specific activities of the three enzymes were very low in embryos just prior to hatching and increased slightly during the hatching process. During Stage I, the specific activity of protease doubled, lipase specific activity increased by a factor of 10, and that of amylase increased slightly. Activities of both protease and amylase more than doubled in Stage II larvae; in general, there were no significant differences in specific activities measured in Stages II through V. Lipase specific activity did not change significantly among Stages I through V. The increase in enzyme activities among the hatching stages correlates well with morphological changes observed in the midgut gland (hepatopancreas), specifically in regard to the presence of enzyme-producing B-cells. Changes in enzyme activities among the postmetamorphic Stages IV and V may be related to changes in body form, habitat, or patterns of energy storage and utilization. Lobster larvae normally hatch during early summer but embryonic development can be accelerated in the laboratory by maintenance at high (21°C) rather than ambient temperature. Temperature conditions during embryonic development, however, had no effect on digestive enzyme activities of larvae that were induced to hatch out of season.

The biochemical composition of a subtropical bivalve, the turkey-wing mussel Arca zebra, was examined in specimens deployed along two contaminant gradients (Castle Harbour and Hamilton Harbour) in Bermuda. Pooled homogenized samples of the mussel were analysed for protein, ash, total lipid and lipid-class composition. The biochemical composition of A. zebra was similar to that observed in other bivalves that rely on glycogen as their primary energy substratum. Differences were noted in the lipid content and composition in mussels deployed in the two harbours. These differences suggest that Hamilton Harbour has higher food availability than Castle Harbour and so the A. zebra from Hamilton Harbour were in better physiological condition as indicated by higher lipid levels, primarily neutral lipids. The biochemical composition of the mussels provides no evidence that Castle Harbour is impacted by contaminants at a local dumpsite. Mussels deployed at Hamilton Harbour had increasing neutral lipid levels along an increasing contaminant gradient, a pattern observed previously in bivalves impacted by anthropogenic inputs to their environment. These changes may indicate impaired mobilization of free fatty acids from the neutral to polar lipid pools, or possible gonadal resorption following exposure to lipophilic contaminants.

Protozoa are an important component of both the nano- and microplankton in marine and freshwater environments and are preyed upon by zooplankton, including suspension-feeding cope pods, some gelatinous zoopiankters and some first-feeding fish larvae. The clearance rates of suspension-feeding zooplankton for ciliates, in particular, are higher than for most phytoplankton. For at least some suspension-feeding zooplankton, protozoans are calculated to be quantitatively an important component of the diet during certain seasons. In laboratory studies, protozoan components in the diet appear to enhance growth and survival of certain life-history stages or enhance fecundity. These data suggest that protozoans are qualitatively as well as quantitatively important in the diets of marine zooplankton. Most studies of predation on Protozoa have focused on the euphotic zone in nearshore waters. Predation on Protozoa is expected, however, to be particularly important both quantitatively and qualitatively in marine environments and seasons in which primary production is dominated by cells <5 μm in size, such as nearshore environments after the spring phytoplankton bloom, in oligotrophic waters, and in environments dominated by detritus-dominated food webs, such as the deep sea. In detritus-dominated food webs, Protozoa may be a source of essential nutrients and may thus facilitate utilization of bacterial and detrital carbon by metazoan plankton.

1.1. Digestive protease, lipase, and amylase of Stage I larvae of the American lobster Homarus americanus are characterized.2.2. A sensitive method for detection of crustacean lipase was developed using an latroscan which combines thin-layer chromatography and flame ionization detection to quantify free fatty acids generated by lipase digestion.3.3. pH optima of the three enzymes occurred at or near the pH of gastric fluid.4.4. A time course study demonstrated slight increases in protease and amylase activities during the first larval stage, regardless of whether the lobsters were fed or not, whereas lipase activity was constant.

The concentrations of individual chlorobiphenyl congeners were measured in the mussel Mytilus edulis transplanted to several stations in Buzzards Bay and Nantucket Sound, MA (USA). Individual stations represented a gradient of chemical contamination and the sampling period extended over a complete annual cycle. Fluctuations in concentrations of some chlorobiphenyl congeners were apparent at all stations during the late spring and early summer with a marked decline occurring during autumn; this pattern was correlated with the seasonal cycle of gametogenesis and spawning activity. Relative redistribution and release of individual chlorobiphenyl congeners associated with spawning is not consistent, suggesting differential partitioning of specific congeners in different tissues or lipid pools. These patterns are consistent with our general view of the bioconcentration of organic contaminants in marine organisms. The major factors controlling the distribution of PCBs in mussels appear to be the relative concentrations of individual contaminants in ambient waters, modified to some extent by differences in partitioning between organisms and water (as indicated by differences in Kow), and seasonal variations in lipid content.

The objective of the physiological studies at the GEEP Workshop was to assess the following responses to field and experimental pollutant gradients: (1) bioenergetic parameters, such as scope for growth, as an integrative measure of energy allocation to somatic and reproductive processes; (2) specific components of a bioenergetic budget, such as respiration and excretion;(3) larval viability from controlled spawnings; (4) lipid composition of digestive gland in relation to nutrient storage and turnover.

In field stuhes for the GEEP Workshop in Langesundfjord.Norway, changes in lipid content and lipid : protein ratios of digestive glands of Mytilus edulis and Carcinus maenas were reflected along the pollution gradient, with populations of M. edulis showing elevations in both parameters at the 3 most contaminated Sites (2, 3 and 4) in comparison to the reference site (l), and populations of C. maenas showing elevations only at Site 3. In mesocosm experiments only M. edulis from the high dose basin showed elevationsin lipid content and lipid : protein ratios; C. maenasin the medium dose basin showed a decrease in both parameters.Analysis of lipid class composition for field and mesocosm samples of M. edulis reveal differences in response to contaminant gradients that reflect alterations in mobilization of triacylglycerols to phospholipid pools, reductions in phospholipid content, and nutritional condition.Changes in lipid class distributions of M. edulis from both field and mesocosm experiments correlate well with body burden data for tissue concentrations of aromatic hydrocarbons and/or polychlorinated biphenyls.Lipid class dstributions of field samples of C. maenasindicate alterations in the mobilization of triacylglycerols, sterol turnover, and reductions in phospholipid content.The responses, which suggest that crabs from Site 3 are the most impacted, are not consistent with contaminant data from the field sites.Crabs from mesocosm expenments show no evidence of alterations in lipid class distribution in spite of a consistent trend in aromatic hydrocarbon tissue concentrations along the gradient.Differential responses of field and mesocosm populations of M edulis and C. rnaenas are possibly the result of metabolic capacity for detoxification and differences in trophic transfer.

The degree to which toxicity testing can lead to predictions of long-term environmental consequences of contaminant exposure has been widely debated. Laboratory approaches designed to address both chemical concerns of contaminant bioavailability and persistence in addition to biological concerns of sublethal effects on marine organisms would be most useful in providing the linkage between laboratory and field evaluations. Examples of bioenergetic, developmental, and reproductive abnormalities observed with exposure to lipophilic organic contaminants are discussed in reference to consequences at higher levels of biological organization. Alterations in bioenergetics linked with observations of reduced fecundity and viability of larvae, abnormalities in gamete and embryological development, and reduced reproductive effort provide a strong empirical basis for examination of population responses. Such empirical data can be incorporated into population models to assess the effects of energetic, reproductive and developmental aberrations on population success and provide the basis for further examining the predictive value of toxicity testing.