Uptake and depuration of organochlorine compounds in Sydney rock oysters (Saccostrea commercialis)

Abstract

Field experiments were done to determine the rates of uptake and depuration of chlordane, dieldrin, heptachlor epoxide, PCBs, DDT, DDD and DDE in Sydney rock oysters (Saccostrea commercialis). Oysters from a clean source were placed in a contaminated location and concentrations of organochlorines determined in samples collected at a number of times during the deployment. After 209 days (which was long enough for equilibrium to have been reached), the oysters were moved to an uncontaminated location and concentrations of the compounds were determined at various times. Mean weight of the oysters changed during the study, but not in any consistent manner. Mean content of lipids did not change significantly during the study. Detectable concentrations of all organochlorines were present after 3 days. Times to equilibrium and biological half-lives were calculated using kinetic models. Generally, rates of depuration were of the same order, but slower, than rates of uptake. There was a strong correlation between percentage lipid and organochlorine concentration, but little difference in times to equilibrium and biological half-lives derived from concentrations per wet weight and those per weight of lipid. The experiments show that times to equilibrium for each compound differ and that this should be taken into account when designing a programme to monitor these compounds.