Relationships between total mercury in sediments and methyl mercury in thefreshwater gastropod prosobranch Bithynia tentaculata in the St. Lawrence River, Quebec

Total Hg concentrations in sediment and methyl mercury (MeHg) levels in the gastropod species Bithynia tentaculata were evaluated at 21 stations in th e fluvial corridor of the St. Lawrence River (Quebec, Canada). In the sedim ents (n = 21), total Hg concentrations ranged from 34 to 2790 ng.g dry weig ht(-1). In the gastropods, MeHg concentrations varied from 15 to 290 ng.g d ry weight(-1) in undepurated gastropods (n = 20) and from 41 to 420 ng.g dr y weight(-1) in depurated gastropods (n = 13; without gut contents). The so uthern sector of Lake St. Louis, located near the Iles-de-la-Paix, had sign ificantly higher Hg concentrations than any other sectors under study, both for total Hg in the sediments and MeHg in the gastropods. We established l inear models to describe the relationships between ng contamination in sedi ments and molluscs for the fluvial corridor of the St. Lawrence River and f or the Lake St. Louis sector. Total Hg in sediments and MeHg in gastropods were highly correlated for all pooled stations (r = 0.83), and the relation ship was even stronger for the Lake St. Louis stations (r = 0.92). Our stud y suggests that the gastropod B. tentaculata is a promising biomonitor spec ies for assessing Hg contamination in the fluvial corridor and lakes of the St. Lawrence River.