Contaminant exposure and ecotoxicological impacts in estuaries

Abstract

Estuaries are highly dynamic geohydrological systems that form a transition zone between continental rivers and marine environments. They are subjected to many influences such as tides, waves, and influx/efflux of saline water and freshwater. The dynamic mixing of these types of waters provides nutrients in surface waters and sediments making estuaries among the most productive habitats of coastlines. Organisms dwelling in these environments are thus subjected to many combined stresses (salinities, tides and temperature fluctuations) and are particularly at risks to the influence of anthropogenic activity leading to pollution, climate changes and habitats perturbations. Hence, estuaries are area of choice to study the cumulative impacts of pollution in transition zones. A “sustainable partnership” was set up by a France– Quebec initiative in 2003 with the goal to promote and disseminate studies on the wide range of biological responses from organisms exposed to pollution gradients in estuaries of the Atlantic Ocean. This network combines stakeholders involved in both research, teaching, conservation, and protection activities pertaining to science of estuarine ecotoxicology. The success of this endeavor resided on the comparative examination of the impacts of pollution in estuaries from both the Canadian and European coastlines using similar species some cases and focusing on common objectives on either side of the Atlantic in France and Canada (Quebec). The EXECO International Consortium (contaminant exposure and ecotoxicological effects along continental–coastal continuums: http://wwz.ifremer.fr/pollution/Collaborations/GDR-IEXECO ) launched in 2009 has consolidated this important undertaking by combining the actions of two strategic networks: the Canadian (Quebec) CIRE network (Inter-Institutional Ecotoxicology Research Center: http://www.ecotox.uquebec.ca/programmes/htm) and French IMOPHYS network (Integration of Molecular and Physiological Responses to Chemical Contaminants in the Coastal Environment). This special edition on the impacts of pollution in estuarine organisms features a series of articles on work conducted on either side of the Atlantic in the common purpose to gain a better understanding on ecotoxicological effects of anthropogenic activities along the estuarine continuum. These studies featured a blend of both laboratory and field studies at different levels of biological organization and trophic levels. The studies on regulation and adaptation mechanisms were conducted on a molecular basis, e.g., DNA and immune defense alterations, the alteration of physiological functions such as reproduction, and the epidemiological study of chemical contaminant-related tumors. Many papers are based on fish (Platichthys flesus, Microgadus tomcod, Scophtalmus maximus, Limanda limanda, Alosa alosa, Liza ramada), which possess a strong metabolic capacity but the reader will also find papers on bivalve mollusks: the Mytilus edulis mussel and soft shell clam Mya arenaria. Responsible editor: Philippe Garrigues