Parasites of sentinel bivalves in the NOAA Status and Trends Program: Distribution and relationship to contaminant body burden

The National Status and Trends Mussel Watch data for 1997 were used to comp are the distribution of parasites between sentinel bivalves of the East, We st, Gulf and Great Lakes coasts of the USA and to assess the relationship o f parasitism to contaminant body burden. Overall, five patterns dominated t he geographic distribution of the parasite fauna. (1) Certain parasites, su ch as Nematopsis, were principally associated with oysters from the southea st and Gulf coasts. (2) Discounting Nematopsis, oysters and mussels did not differ significantly in total parasite infection intensity (3) West coast mussel populations were always lower in infection intensity than East coast mussels and rarely showed anything but a sporadic pattern of infection. (4 ) East coast mussels typically had a focus of infection in the Boston Harbo r region. (5) With the exception of Nematopsis, mussels on the West coast, Mytilus edulis and Mytilus californianus, did not differ significantly in t heir parasite fauna. The geographic distributions of most parasites and dis ease-causing organisms varied independently. Any two parasites rarely co-oc curred predictably over wide areas and never on more than one coast. Certai n contaminants were correlated with certain parasites on one coast but not the other or in one bivalve type but not another. Statistics that emphasize d infection intensity found significant relationships between parasitism an d contaminant body burden most often in East and Gulf coast oysters and Wes t coast mussels and, in most cases, higher body burdens were associated wit h lower infection intensities, Statistics that emphasized prevalence also i dentified significant relationships most often in East and Gulf coast oyste rs and West coast mussels, In contrast to infection intensity, most signifi cant results occurred because parasites were observed more often in locales characterized by higher contaminant body burdens. In no case was a parasit e/contaminant pair significant for both infection intensity and prevalence. (C) 1998 Elsevier Science Ltd. All rights reserved.