Organotins in zebra mussels (Dreissena polymorpha) from the Saint LawrenceRiver

Tox-ic antifouling compounds such as organotins have been released ir; the aquatic ecosystems throughout the world and can be bioaccumulating in biota . The purpose of this study was to assess the use of zebra mussels (Dreisse na polymorpha) as a biomonitor for investigating the geographical variation s of organotin bioavailability along the St. Lawrence River. The presence o f organotins (tributyltins (TBT) and triphenyltins (TPT)) and their degrada tion products were measured in the soft tissues of zebra mussels collected from II sites along the St. Lawrence River (between Cornwall and Ile d'Orle ans) in June 1996. TBT and TPT were generally low (< 0.001 to 0.030 mu g/g wet weight) and were similar to those reported in Kingston Harbour, Ontario in Canada and Nieuwkoop and Brielse meer in the Netherlands. The highest c oncentration of TBT (1.44 mu g/g wet weight) was found in mussels from Bass in Louise, a marina in Quebec City. This-suggests that zebra mussels are ef five biomonitors of organotin compounds and that residual levels in the sed iment, or illegal rise of antifouling paints still remain problematic in lo calized sectors of the river. A move detailed study on the availability of TBT in marinas and harbors along the freshwater part of the St. Lawrence Ri ver is recommended.