RELATIONSHIP BETWEEN POLLUTION AND SUSCEPTIBILITY TO INFECTIOUS-DISEASE IN THE EASTERN OYSTER, CRASSOSTREA-VIRGINICA

Infectious disease epizootics seriously affect many populations of marine organisms. Pollution has been hypothesized to contribute to some aquatic epizootics, although this link has not been adequately examined To further evaluate this hypothesis, the effect of a complex mixture of sediment derived pollutants on the susceptibility of the eastern oyster, Crassostrea virginica, to an infectious disease was investigated. The disease studied is caused by the protozoan parasite Perkinsus marinus (Dermo) and results in significant oyster mortalities in the mid-Atlantic region of the United States. Oysters were exposed to 0, 15 and 30% dilutions of water soluble fractions, generated from sediments collected from the Elizabeth River, a heavily, polluted subestuary of the Chesapeake Bay, USA. Oysters were then challenged with P. marinus meronts. Pollutant exposure enhanced preexisting P. marinus infections and increased the oysters' susceptibility to experimentally induced infection, in a dose-dependent manner.