1 ICES CM 2007/I:09 Not to be cited without prior reference to the authors A COMPREHENSIVE METHODOLOGY FOR THE ASSESSMENT OF THE HEALTH STATUS OF ESTUARINE ECOSYSTEMS Claude Amiard-Triquet 1 , Cyril Durou 1,2 , Jean-Claude Amiard 1 , Thierry Berthe 3 , Gabriel Billon 4 , Hélène Budzinski 5 , Anne Créach 4 , Michèle Roméo 6 , Jean-Pierre Debenay 7 , Julien Deloffre 3 , Françoise Denis 8 , Lionel Denis 4 , Tim Ferrero 9 , Patrick Gillet 2 , Herman Hummel 10 , Catherine Mouneyrac 1,2 , Bagdad Ouddane 4 , Fabienne Petit 3 , Laurence Poirier 1 , Laurent Quillet 3 , Brian Smith 9 , Florence Sylvestre 11 1 Université de Nantes, Nantes Atlantique Universités, SMAB, EA2160, Faculté de pharmacie, 1 rue G. Veil – BP 53508, Nantes F-44000, France, tel : (33) 251 12 56 76, fax : (33) 251 12 56 79, Claude.Amiard-Triquet@univ- nantes.fr 2 Univ. Catholique de l’Ouest, Angers, Fr. ; 3 Univ. Rouen, Fr. ; 4 Univ. Lille & Marine Station Wimereux, Fr.; 5 Univ. Bordeaux I, Fr.; 6 Univ. Nice, Fr.; 7 Univ. Angers, Fr. ; 8 Université du Maine & MNHM, Concarneau, Fr. ; 9 Natural History Museum, London, UK ; 10 Center for Estuarine and Coastal Ecology, The Neth. ; 11 CEREGE, Aix-en-Provence, Fr. Abstract—In the framework of the French National Program of Ecotoxicology, environmental quality was assessed in the multi-polluted Seine estuary and the comparatively clean Authie estuary, France (2002-2004, quarterly sampling) by determining contaminant levels in water, sediments and the infaunal worm Nereis diversicolor. Contamination effects were examined in different constituents of the biota. A higher abundance of cadmium and mercury resistant bacteria was shown in Seine mudflats. The physiological status, abundance and population structure of N. diversicolor were degraded in the Seine estuary despite its tolerance likely due to genetic adaptation to contamination. Chemical stress might act directly, or through lower food availability in the Seine (diatoms, foraminiferans, nematofauna). In return, the influence of biota on the fate of contaminants was focussed on metals and interactions with the sulphur cycle. Biogeochemical transformations in the upper layers of sediments were examined considering inorganic forms of sulphur, fatty acids and dsrAB gene (which codes for an enzyme responsible for the production of H 2 S) used as markers of microbial activity. Early diagenesis modelling has shown the influence of bioturbation due to N. diversicolor on the profiles of dissolved compounds (oxygen, sulphates, H 2 S). The main achievements for coastal zone management and society include: i) the development of analytical tools for the determination of speciation and bioavailability of metals in interstitial water; ii) the validation of biochemical and physiological markers in an estuarine species representative of the sedimentary compartment; iii) a proposal for a comprehensive methodology to assess the health status of estuarine ecosystems. Key-words—Estuaries, sediments, chemicals, biomonitoring, biogeochemical cycle INTRODUCTION Biomonitoring programs including chemical analyses or biomarker determinations are mainly based on organisms living in the water column, particularly filter-feeders such as different mussel and oyster species. Endobenthic species are not so widely used despite they are living in close contact with the sediment which is the main sink for most of organic and inorganic contaminants in the aquatic environment (Gagnon and Fisher, 1997; Bernes, 2000). Thus in the present work, based on the comparison of a multi-polluted estuary (Seine estuary, Fr.) and a relatively unimpacted site (Authie estuary, Fr.) (Claisse et al., 2006), the quality of the environment was characterized by analyzing micropollutants in water, sediments and in the endobenthic polychaete annelid Nereis diversicolor. This program designed for a period of three years (2002-2004) with quarterly sampling, was an excellent opportunity to correlate these