Functional traits and taxonomy of benthic macroinvertebrates as alternative tools for ecological risk assessment: The case of the St. Lawrence River

The St. Lawrence River is one of the most world's largest watercourses. This river, an essential waterway for North America, is exposed to many anthropogenic stresses, as 97% of the Quebec population is living in its watershed. This study is a part of a large research project aiming at developing an ERA tiered framework for sediment management, in the context of integrated management of contaminated sediment, site restoration and sustainable navigation. The purpose of this study is to assess sediment quality by exploring the relationships between chemical contamination and benthic community structure using classical taxonomy and functional traits approaches. During falls 2004-2005, macroinvertebrates were collected in 59 sites in the St. Lawrence River, especially in its three fluvial lakes and in the harbour zone of Montreal. Organic (PCBs, PAHs, petroleum hydrocarbons), inorganic (As, Cd, Cu, Cr, Hg, Ni, Pb and Zn) contaminants and sediments characteristics (e.g. grain size, metal-binding phases, nutrients) were measured in whole sediment. Different descriptors (taxonomy and functional traits) of benthic macroinvertebrates in the St. Lawrence levels are used to assess the relative impact of chemical contamination and sediment characteristics on macroinvertebrate community, using multivariate analysis and variance partitioning. We compared the potential of taxonomy and functional traits approaches for assessing sediment contamination and toxicity. We also established sediment classification with different methods such as benthic community (taxonomy or traits), bioassay and chemical concentrations based on St. Lawrence River sediment quality guidelines. Implication for the development of an ERA tiered framework will be discussed. This research is being carried out within the context of a cooperation program involving the Groupe de Recherche Interuniversitaire en Limnologie et en Environnement Aquatique (GRIL) at the Université de Montréal, Environment Canada, the Ministère du Développement Durable, de l'Environnement et des Parcs du Québec, and Cemagref groupement de Lyon.