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 cont aminated sediments (CSs) and related water-soluble fractions (WSFs) on haem ocyte function/activity and the onset and progression of an infectious dise ase caused by the protozoan parasite, Perkinsus marinus (Dermo) in the east ern oyster, Crassostrea virginica. Sediments used to generate WSFs and sedi ments used for the whole CS exposure experiments were collected in differen t areas of the southern branch of the Elizabeth River, a heavily polluted s ub-estuary of the Chesapeake Bay, USA. The WSFs were dominated by low molec ular weight polycyclic aromatic hydrocarbons (PAHs). The CSs used for whole CS exposure experiment had elevated concentrations of high molecular weigh t PAHs. Polychlorinated biphenyls (PCBs) and metals were also present in th e CSs. No PCBs were detected in the WSFs. In vitro exposure of haemocytes t o 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 H-3-leucine incorporation in haemocytes. Exposure of oysters to 0, 15, 30% WSFs increased the oysters' susceptibility to laboratory-induced infect ion caused by P. marinus. Exposure of oysters to 15, and 30% dilutions of W SFs for 33 days or to 1.0, 1.5, and 2.0 g CSs for 30 days significantly ele vated the expression/progression of latent P. marinus infection in oysters in a dose-dependent manner.