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Gentes S.,Equipe Environnement et Microbiologie | Monperrus M.,University of Pau and Pays de lAdour | Legeay A.,CNRS Laboratory of Oceanic Environments and Paleo-environments (EPOC) | Maury-Brachet R.,CNRS Laboratory of Oceanic Environments and Paleo-environments (EPOC) | And 3 more authors.
Environmental Pollution | Year: 2013

Several studies demonstrated high mercury (Hg) methylation and demethylation in the periphyton associated with floating roots in tropical ecosystems. The importance of aquatic plants on methylmercury production in three temperate ecosystems from south-western France was evaluated through Hg species concentrations, and Hg methylation/demethylation activities by using stable isotopic tracers (199Hg(II), Me201Hg). Hg accumulation and high methylation and demethylation yields were detected in plant roots and periphyton, whereas results for sediment and water were low to insignificant. The presence of sulfate reducing prokaryotes was detected in all compartments (T-RFLP based on dsrAB amplified through nested PCR) and their main role in Hg methylation could be demonstrated. In turn, sulfate reduction inhibition did not affect demethylation activities. The estimation of net MeHg budgets in these ecosystems suggested that aquatic rhizosphere is the principal location for methylmercury production and may represent an important source for the contamination of the aquatic food chain. © 2012 Published by Elsevier Ltd. Source

Gentes S.,University of Pau and Pays de lAdour | Maury-Brachet R.,CNRS Laboratory of Oceanic Environments and Paleo-environments (EPOC) | Guyoneaud R.,University of Pau and Pays de lAdour | Monperrus M.,University of Pau and Pays de lAdour | And 3 more authors.
Ecotoxicology and Environmental Safety | Year: 2013

Mercury (Hg) is considered as an important pollutant for aquatic systems as its organic form, methylmercury (MeHg), is easily bioaccumulated and bioamplified along food webs. In various ecosystems, aquatic periphyton associated with macrophyte was identified as an important place for Hg storage and methylation by microorganisms. Our study concerns temperate aquatic ecosystems (South Western France) colonized by invasive macrophytes and characterized by high mercury methylation potentials. This work establishes original data concerning Hg bioaccumulation in organisms (plants, crustaceans, molluscs and fish) from five contrasting ecosystems. For low trophic level species, total Hg (THg) concentrations were low (from 27±2ngTHgg-1dw in asiatic clam Corbicula fluminea to 418±114ngTHgg-1dw in crayfish Procambarus clarkii). THg concentrations in some carnivorous fish (high trophic level) were close to or exceeded the International Marketing Level (IML) with values ranging from 1049±220ngTHgg-1dw in pike perch muscle (Sander lucioperca) to 3910±1307ngTHgg-1dw in eel muscle (Anguilla Anguilla). Trophic levels for the individuals were also evaluated through stable isotope analysis, and linked to Hg concentrations of organisms. A significant Hg biomagnification (r2= 0.9) was observed in the Aureilhan lake, despite the absence of top predator fish. For this site, Ludwigia sp. periphyton, as an entry point of Hg into food webs, is a serious hypothesis which remains to be confirmed. This study provides a first investigation of Hg transfer in the ecosystems of south western France and allows the assessment of the risk associated with the presence of Hg in aquatic food webs. © 2013 Elsevier Inc. Source

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