National Status and Trends: Mussel Watch Program - Resurrection Bay Database

In response to the growing concerns among Native communities about the safety of subsistence shellfish, this project assessed the health risks associated with consuming softshell clams, mussels and cockles. The aforementioned shellfish were collected in traditional harvest area in Resurrection Bay, AK and analyzed for contaminant body burdens and for occurrences of pathogens and diseases. A broad suite of contaminants were analyzed including 55 Polycyclic Aromatic Hydrocarbons (PAHs) , 27 chlorinated pesticides including DDT and its break-down products, 37 Polychlorinated Biphenyls (PCBs), 16 major and trace elements (Ag, Al, As, Cd, Cr, Cu, Fe, Hg, Mn Ni, Pb, Sb, Se, Sn and Zn), and tributyl-tin and its break-down products. The health of the subsistence shellfish were further characterized based on the presence an array of about 30 parasite taxa (e.g. bucephalus, chlamydia, ciliates, cestodes and nematodes) and occurrence of 11 diseases (e.g. MSX, tumors, neoplasm, edema and necrosis), which were quantified using prevalence and intensity computation. Results indicated that: - A great variation in metal body burdens among the different subsistence shellfish studied. Mercury was measured in all shellfish, but with the maximum value (0.2 ppm) found in blue mussels. Maximum tissue concentration for toxic metals such as chromium and Nickel were recorded in cockles. Maximum values for cadmium were found in mussels and softshell clams, while that of lead was found in the blue mussels. - Organic contaminants were detected in all subsistence shellfish although many of these compounds were banned more than three decades ago. - Metal and organic contaminant body burden were in general very low relatively to U.S. Food and Drug Administration guidelines for seafood safety. - Among the parasites assessed only large gill ciliates, small gill ciliates and gut rickettsia were detected in clam and blue mussels. - Among the bivalve diseases and tissue pathologies characterized in this study, digestive tubule atrophy was the most prevalent with 100% occurrence in cockles and mussels and about 96% in clams. Disease, such as ceroid bodies and histological condition such as diffuse and focal inflammations were also measured, but at relatively lower count than the digestive track atrophy. - In general, all infections and tissue pathology in the shellfish were minor and the conditions do not appear to be either a threat to the health of the shellfish or to humans that consume them. As a part of this study interspecies concentration factors (ICFs) that relate chemical concentrations in mussels to those in subsistence shellfish, were determined. The intent is to use ICFs as factor to evaluate contaminant concentrations in a wide range of Alaskan shellfish based upon measurements obtained for one species, thereby eliminating the need to monitor all species. Concentration values for many compounds were low or not detected, but where possible ICFs were calculated. This project provides invaluable baseline chemical body burden data on shellfish species that is geo-referenced and posted on the internet through the NOAA's National Status and Trends data portal.