Distribution of Chlorinated Organic Contaminants in Dreissenid Mussels Along the Southern Shores of the Great Lakes

Abstract

Samples of dreissenid mussels were collected from 21 sites along the U.S. shores of the southern part of the Great Lakes and their connecting channels. These samples were analyzed for tissue levels of 16 chlorinated organic compounds, mostly pesticides, as well as for lipid levels. Aldrin, endrin, and lindane were found above detection levels at less than one-half of the sites, primarily at sites in Lake Michigan. Mirex was detected at nine sites mostly in Lake Ontario and the Niagara River, but also near Detroit and in Saginaw Bay. Heptachlor was detected at only two sites, both in Lake Erie. Cis-chlordane, dieldrin, hexachlorobenzene, heptachlor, trans-nonachlor, and total DDTs were detected at all or almost all of the sites. Except for hexachlorobenzene, which was highest near Buffalo, these chemicals were found at higher concentrations in Lake Michigan, especially near Milwaukee, than in the other areas studied. A comparison of the concentrations of chlorinated organic compounds to the levels of lipids showed that differences in dreissenid lipid levels among sites were not the major cause of the observed differences in concentrations in the chlorinated organic compounds. At most sampling locations, the category total DDTs was composed primarily of the DDT breakdown products DDD and especially DDE. However, a substantial percentage of the total DDTs detected at sites in eastern Lake Erie and western Lake Ontario was composed of the parent DDT compounds, suggesting the presence of a relatively recent input of this compound in this area. Comparison of the concentrations of chlorinated organic compounds measured in Great Lakes dreis-senids with concentrations of these compounds in marine mussels and oysters found generally similar levels for most of the compounds. Exceptions to this were hexachlorobenzene and mirex which had mean concentrations more than 5 times greater in mussels from the Great Lakes than from marine locations and lindane which had concentrations in mussels from the Great Lakes less than one-tenth of those from marine mussels.