Toxicological characterization of sediments from Baie des Anglais on the St. Lawrence Estuary

The sediments of Bale des Anglais on the St. Lawrence Estuary have a histor y of environmental contamination, but no information exists relating to the ir toxicity. The purpose of the present study was to characterize three sit es in and near Bale des Anglais, in terms of sediment toxicity and contamin ants, Sites 1 and 2 within the Bale des Anglais are relatively close to loc al industry and municipal sewage discharge points, while Site 3 is outside the bay. Three microscale bioassays, Microtox(R), echinoderm fertilization and Toxi-ChromoPad(R), showed that sediments from Site 1 were the most toxi c, followed by Site 2. Site 3 was non-toxic. While the solid phase Microtox (R) test did indicate that Site 1 was most toxic, the absolute response was weak. Liver cytochrome P450 1A1 mRNA in American plaice (Hippoglossoides p latessoides), captured at Site 1 in the bay was significantly induced compa red to the P450 system of plaice captured at Sites 2 and 3. Hepatic metallo thionein mRNA levels were not significantly different between plaice captur ed at all three sites. Sediment chemical analyses revealed a gradient in po lycyclic aromatic hydrocarbons, polychlorinated biphenyls and dibenzofurans (PCDF) with the highest levels recorded at Site 1, about 10-fold less at S ite 2 and 100-fold less at Site 3. Amongst the organochlorines the PCDF gro up were deemed the most important due to their prevalence and known toxicit y. Heavy metal concentrations were low and representative of background lev els for the St. Lawrence Estuary. (C) 1999 Elsevier Science Ltd. All rights reserved.