Metal concentrations in littoral sediments and aquatic macroinvertebrates in the St. Lawrence River, near Cornwall, Ontario.

Abstract

Concentrations of Cd, Cr, Cu, Fe, Hg, Ni, Pb, and Zn were measured in surficial sediments and in five aquatic macroinvertebrate taxa from shallow littoral areas of the St. Lawrence River, near Cornwall, Ontario. The principal objectives were to assess metal levels in littoral sediments and littoral macroinvertebrates, and to determine the influence of local point sources relative to upstream inputs. Hg concentrations were, however, greatly enriched at a site 1 km downstream of two historical point sources of Hg (Domtar Fine Papers/ICI Forest Products). Littoral sediments had lower metal levels than contaminated areas of the Great Lakes and deeper sites in the Cornwall area. Results of these comparisons, however, suggested a problem of Hg contamination in the Cornwall area. Metal levels in littoral macroinvertebrates were assessed for the amphipod Gammarus fasciatus, the decapod Orconectes sp., the gastropod Bythinia tentaculata, the Chironomidae (midges) and the Oligochaeta (worms). Metal concentrations in macroinvertebrates were found to differ among taxonomic groups, and these differences were metal-specific. When compared to concentrations in sediments, invertebrates had lower levels of Cd (except for B. tentaculata), Cr, Fe, Ni and Pb, and higher concentrations of Cu and Zn. Concentrations of Hg were similar to levels in the sediments, except for slightly higher concentrations in B. tentaculata. Concentrations of Cr, Fe, Ni and Zn in chironomids and oligochaetes were similar or higher than levels reported for contaminated areas of the Great Lakes and deeper sites in the Cornwall area, and this despite the relatively much lower concentrations in littoral sediments. (Abstract shortened by UMI.)