Importance of interstitial, overlying water and whole sediment exposures to bioaccumulation by marine bivalves

During the performance of contaminated sediment studies using nonpolar pollutants, like polyclorinated biphenyls (PCBs), with marine organisms, the routes of exposure can include whole sediment, overlying waters and interstitial waters (assuming no feeding). These routes can be further subdivided into particulate, colloidal and dissolved aquatic phases. Currently, the dissolved phase is believed to be the primary bioavailable exposure phase. In this investigation, two (i.e. interstitial water) and three phase (i.e. whole sediment) exposures were performed to determine the relative importance of each phase to the accumulation of PCBs from environmentally contaminated sediments. PCB concentrations in each exposure were separated into dissolved, colloidal and particulate phases, quantified and compared to concentrations accumulated by two exposed bivalve species: the filter-feeder Mulinia lateralis and the deposit-feeder Yoldia limatula. Identifying specific sources of bioavailable PCBs was hampered by the high level of correlation amongst all phases. However, differences between species were apparent, possibly reflecting bivalve-specific behavioral strategies. Also, overlying water contaminant distributions were often better correlated to organism accumulation than interstitial water dissolved phase contaminant distributions. ©