Marine Biology 22, 37--44 (1973) 9 by Springer-Verlag 1973 Accumulation, Release and Retention of Petroleum Hydrocarbons by the Oyster Crassostrea virginica* J. J. Stegeman and J. M. Teal Department of Biology, Woods Hole Oceanographic Institution; Woods Hole, Massachusetts, USA Abstract Two Crassostrea virginica populations, differing in fat content, were experimentally exposed to a complex petroleum- hydrocarbon fraction. The hydrocarbons in this mixture were accumulated by both groups of oysters, and their lipid content, as well as the concentration of hydrocarbon in the water, were found to affect the rate and extent of accumulation. Hydro- carbons accumulated were rapidly, although incompletely, discharged when the oysters were transferred to an uncon- taminated system, Amounts of hydrocarbons discharged and amounts retained efter discharge are probably related to the level of contamination. The data can be interpreted as in- dieating that equilibration and the occurrence of multiple compartments where hydrocarbons can reside are factors in- volved in the uptake and retention of nonbiogenic hydrocar- bons by oysters. The petroleum hydrocarbons contained in the oysters differed from the contaminating oil by displaying a greater aromatic content. In addition, gas-liquid ehromato- grams of aliphatic fractions of the hydrocarbons in the oysters rapidly showed a degraded appearance; the possibility that the oysters themselves are modifying the oil cannot be excluded. Introduction The sedentary habit of most filter-feeding bivalve molluscs makes them extremely vulnerable to both acute and chronic exposure to environmental conta- minants such as petroleum hydrocarbons. 0il spills have resulted in large-scale mortality among marine shellfish (Nelson-Smith, 1970). Marine molluscs ex- posed to sub-lethal concentrations of hydrocarbons contain these hydrocarbons in their lipid pools (Cahn- mann and Kuratsune, 1957; Blumer et al., 1970c; Burns and Teal, 1971 ; Ehrhardt, t972). In this respect, they dearly differ from organisms harvested from uncontaminated areas, the latter containing primarily what are assumed to be biogenie rather than petro- leum-derived hydrocarbons (Blumer et al., 1970@ The occurrence of carcinogenic aromatic compounds in petroleum oils and oil products (Carruthers et al., 1967) makes petroleum-hydrocarbon contamination of commercial shellfish such as oysters of particular concern, especially in light of the suggestion that non- * Contribution No. 3098 from the Woods Hole Oceano- graphic Institution. biogenie hydrocarbons in shellfish are retained for long periods (Blumer et al., t970c). Whether the primary mechanism concerned in uptake of non-biogenic hydrocarbons by marine bi- valves involves consumption of contaminated food or equilibration with hydrocarbons in the water is not yet established. It is beginning to appear that parti- tioning across the outer membrane, particularly gill, surfaces is an important means of uptake (Lee et al., 1972). What determines the levels to which hydro- carbons accumulate in these organisms is not well known. Results with aquatic animals on the uptake of chlorinated hydrocarbon pesticides (tIamelink et al., t97t) suggest that the concentration of chlorinated hydrocarbons in the water and the character of the lipids play significant roles. In this paper, we describe experimental uptake and accumulation of petroleum hydrocarbons by oysters, and relate these processes to the hydrocarbon concentration in the water, and the lipid content of the animals. Materials and Methods Oysters Groups of Crassostrea virginica, averaging 5 cm in length, were obtained from trays in a local harbor (Group l) and from stocks in fiberglass aquaria with running seawater (Group 2). Prior to the experiments, the ambient water temperatures for the oysters were those normally encountered in the Woods Hole region between April and January (Group i) or September and January (Group 2). When oysters were removed to the experimental system at various times between January and May, they were reproductively inactive and essentially dormant. Experimental Procedure Oysters marked as to group were placed together in a fiberglass tray, 38 x 55 x 10 cm deep, containing 6 1 of seawater. In all experimental procedures, sea- water which was filtered to 1 ~ and maintained at