MA1 Large-Scale Investigations of Contaminated Sediments
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() Assessment of ecological effects of contaminated sediments in the Laurentian Great Lakes.

Grapentine, L1, Milani, D1, Reynoldson, T2, 1 Environment Canada, Burlington, Ontario, Canada2 Acadia University, Wolfville, Nova Scotia, Canada

ABSTRACT- As part of a 5-year program to assess ecological effects of contaminated sediments in Canadian regions of the Laurentian Great Lakes, physicochemical and biological evaluations of the benthic environment in 15 Areas of Concern are underway. A multiple-lines-of-evidence approach is used, involving the collection of data on surficial sediment chemistry and grain size, sediment toxicity, benthic invertebrate community structure and, where warranted, bioaccumulation of contaminants in invertebrates. Detection of ecological effects is based on comparisons of conditions in test sites to those in appropriate reference sites, drawn from a database of corresponding sediment conditions for over 170 locations throughout Canadian and Lake Michigan nearshore regions. Procedures for evaluating the information from multiple descriptors of sediment conditions involve (1) integrating the data within each category of variables using multivariate statistical methods, and (2) combining outcomes from within-category effects assessments using a rule-based, weight-of-evidence interpretation table to determine the overall status of each test site. A supplemental assessment of sediment stability can also be performed to evaluate the hazard of off-site transfer of contaminants. Under our assessment framework, a recommendation for management action requires evidence of adverse effects on either the biota resident in the sediment, or on biota affected by contaminants originating from the sediment. Assessments completed to date indicate that (a) exceedences of Canadian sediment quality guidelines for contaminant concentrations are often not associated with sediment toxicity or altered benthic community structure, and (b) bioaccumulation of contaminants liable to biomagnify is an important determinant of the overall risk characterization of contaminated sediments.

Key words: toxicity, sediment, macroinvertebrates, bioaccumulation

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