Effects of field-contaminated sediments and related water soluble components on haemocyte function and Perkinsus marinus susceptibility and expression in oysters

This paper reviews and discusses our recent findings on the effects of contaminated sediments (CSs) and related water-soluble fractions (WSFs) on haemocyte function/activity and the onset and progression of an infectious disease caused by the protozoan parasite, Perkinsus marinus (Dermo) in the eastern oyster, Crassostrea virginica. Sediments used to generate WSFs and sediments used for the whole CS exposure experiments were collected in different areas of the southern branch of the Elizabeth River, a heavily polluted sub-estuary of the Chesapeake Bay, USA. The WSFs were dominated by low molecular weight polycyclic aromatic hydrocarbons (PAHs). The CSs used for whole CS exposure experiment had elevated concentrations of high molecular weight PAHs. Polychlorinated biphenyls (PCBs) and metals were also present in the CSs. No PCBs were detected in the WSFs. In vitro exposure of haemocytes to WSFs derived from CSs reduced to haemocytes' chemotaxic, phagocytic, and chemiluminescent responses to some extent. Exposure of oysters to suspended CSs stimulated neutral red uptake, mitochondrial dehydrogenase production and ³H-leucine incorporation in haemocytes. Exposure of oysters to 0, 15, 30% WSFs increased the oysters' susceptibility to laboratory-induced infection caused by P. marinus. Exposure of oysters to 15, and 30% dilutions of WSFs for 33 days or to 1.0, 1.5, and 2.0g CSs for 30 days significantly elevated the expression/progression of latent P. marinus infection in oysters in a dose-dependent manner.