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

Infectious disease epizootics seriously affect many populations of mar ine organisms. Pollution has been hypothesized to contribute to some a quatic 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 oy ster, Crassostrea virginica, to an infectious disease was investigated . The disease studied is caused by the protozoan parasite Perkinsus ma rinus (Dermo) and results in significant oyster mortalities in the mid -Atlantic region of the United States. Oysters were exposed to 0, 15 a nd 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 i nfection, in a dose-dependent manner.