COMPARATIVE BIOACCUMULATION OF POLYCYCLIC AROMATIC-HYDROCARBONS FROM SEDIMENT BY 2 INFAUNAL INVERTEBRATES

Bioaccumulation of polycyclic aromatic hydrocarbons (PAHs) from field- contaminated sediments by 2 infaunal invertebrates, Rhepoxynius abroni us (a non-deposit feeding amphipod) and Armandia brevis (a non-selecti ve, deposit-feeding polychaete), was examined. Sediments were selected over a large geographical area of the Hudson-Raritan estuary (New Yor k, USA) to assess the potential for bioaccumulation from a typical urb an estuary. Assessment of bioaccumulation in these invertebrates is im portant because of the need to understand their health and role in eco system functioning and because they are vectors of sediment-associated contaminants to demersal fish. Our study compared the response of the se 2 species over a wide range of PAH concentrations to learn how feed ing mode may affect contaminant accumulation. After 10 d of exposure t o sediments, we assessed the tissue concentrations of 24 PAHs and foun d no significant differences for the low molecular weight PAHs (LPAHs) between R. abronius and A, brevis. There was, however, a large differ ential observed between species for bioaccumulated high molecular weig ht PAHs (HPAHs). Because we assumed that the amphipod was not feeding and most of its tissue burden was received through ventilation of inte rstitial water (IW), we concluded that IW was probably the major route of uptake for the LPAHs for both species and that sediment ingestion was a much more important uptake route of HPAHs for the polychaete. An alysis of correlations between amphipod and polychaete tissue burdens found that the species were responding similarly to a gradient of PAH concentrations in sediment; however, when the associations between con centrations in tissue and exposure matrix (e.g. sediment, IW) were exa mined the interpretations were less clear. Concentrations of PAHs in I W and sediment indicated that the partition coefficient (K-oc) was gen erally 2 orders of magnitude higher than expected for LPAHs and highly variable between sites for HPAHs. When K-oc was re-calculated using f ree PAH, it became much less variable and was uniformly elevated above the predicted values. The BAF(loc) (lipid/organic carbon normalized b ioaccumulation factor) in the polychaete was generally consistent over the series of PAHs, as expected, and when metabolism and pre-steady s tate conditions were considered, partitioning of PAHs between tissue a nd sediment was relatively close to the theoretical maximum. Despite m uch lower than predicted IW concentrations, the LPAH bioconcentration factors (BCF) for the amphipod were close to expected, but the HPAH BC Fs were close to the predicted values only when expressed in terms of the free PAH. From these data, and previous studies, we conclude that there was a significant reduction in bioavailability of HPAHs to R. ab ronius due to partitioning of HPAHs to dissolved organic carbon.