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Lamand F.,ONEMA Office National de lEau et des Milieux Aquatiques | Beisel J.-N.,Ecole Nationale du Genie de lEau et de lEnvironnement de Strasbourg ENGEES | Beisel J.-N.,University of Strasbourg
Aquatic Ecology | Year: 2014

Numerous species of Unionidae are presently threatened by anthropogenic impacts on freshwater ecosystems. Field inventories, based on reliable presence/absence observations, are urgently needed to improve their protection. Such observations should be comparable between sites and collected with minimal surveying effort. Here, we demonstrate a strategy that minimises sampling effort while maximising inventory efficiency, formulated using hydromorphological data from 26 river sites sampled in north-eastern France between 2009 and 2010. Our findings indicate that a comprehensive visual survey of seven x river width with a bathyscope confirmed unionid presence in 96 % of cases, and presence of all unionid species in 88 % of cases. A further seven x width search increased this latter figure to 96 %, while a third (=21 × width) ensured that all species were registered in all rivers surveyed. Based on these results, we recommend that surveyors first undertake an initial seven x river width visual survey to confirm unionid presence. If no Unionidae are observed over this distance, sampling ceases and the site is marked negative. If at least one Unionidae is observed over this distance, an additional upstream stretch of the same length is surveyed with identical sampling effort. If at least one new species is observed within this second stretch, then a third and final stretch can be surveyed. This method is discussed in the light of representativeness of hydromorphological habitats (e.g. pool spacing and meander wavelength). © 2014 Springer Science+Business Media Dordrecht. Source


Arambourou H.,CEA DAM Ile-de-France | Beisel J.-N.,Ecole Nationale du Genie de lEau et de lEnvironnement de Strasbourg ENGEES | Beisel J.-N.,University of Strasbourg | Branchu P.,CEA DAM Ile-de-France | Debat V.,CNRS Systematics, Biodiversity and Evolution Institute
Science of the Total Environment | Year: 2014

Laboratory studies have sometimes failed to detect a relationship between toxic stress and morphological defects in invertebrates. Several hypotheses have been proposed to account for this lack of effect. (1) It was suggested that only a combination of stressful conditions - rather than a single one - would affect the phenotype. (2) Phenotypic defects should be detected on adult individuals, rather than on juveniles. (3) Phenotypic abnormalities might mostly affect the progeny of the exposed individuals, some contaminants exhibiting trans-generational effects. In the present study, we test those three hypotheses. We first examined the effects of a multiple exposure by using laboratory Chironomus riparius larvae cultured on two sediments sampled in contaminated rivers and those containing a mixture of mineral and organic compounds. On the larvae, we investigated mentum phenotypes: the frequency of phenodeviants, the shape fluctuating asymmetry and the mean shape. To test whether adult's morphology was more sensitive than the larval's, we also measured asymmetry and mean shape of the adult wings. Finally, to test for a trans-generational phenotypic effect, we measured mentum shape variations in the offspring derived from the measured adults. Overall, our results point out a very limited phenotypic response to contaminated sediments, suggesting that a multiple exposure is not necessarily sufficient to generate phenotypic defects. Adult traits were no more affected than larval traits, discarding the hypothesis that adult phenotypes would be more sensitive biomarkers. Finally, no effect was detected on the offspring generation, suggesting that no trans-generational effect occurs. This general lack of effect suggests that the use of phenotypic defects in C. riparius as an indicator of sediment contamination should be considered cautiously. © 2014 Elsevier B.V. Source


Lamand F.,ONEMA Office National de lEau et des Milieux Aquatiques | Beisel J.-N.,Ecole Nationale du Genie de lEau et de lEnvironnement de Strasbourg ENGEES | Beisel J.-N.,University of Strasbourg
Knowledge and Management of Aquatic Ecosystems | Year: 2014

In the context of a rapid decline in several protected unionid species, government agencies urgently require a reliable method to estimate population size for the most endangered species. We used a dataset collected from 16 river stations in north-eastern France to compare the efficiency of visual estimation (bathyscope) and a manual excavation to estimate numbers of the endangered bivalve Unio crassus. Our investigations indicated that, whereas a visual approach was sufficient to detect unionid presence, only 10% of all individuals were registered compared with manual excavation at the same site. In order to obtain an accurate density estimate (especially as regards the juvenile population), sediment excavation is necessary, despite it being time consuming and damaging to the mussel's habitat. © 2014 ONEMA. Source


Marescaux J.,University of Namur | Latli A.,University of Namur | Lorquet J.,University of Namur | Virgo J.,University of Namur | And 3 more authors.
Aquatic Ecology | Year: 2016

Dreissena (Bivalvia: Dreissenidae) species can act as ecosystem engineers, physically altering freshwater ecosystems and changing benthic macro-invertebrate assemblages. The mussel beds they form can provide shelter and food for detritivorous species, whereas fouling can directly impact native bivalves. In this study, we examined the effects of the zebra mussel (Dreissena polymorpha) and quagga mussel (Dreissena rostriformis) on the macro-invertebrate community in the Meuse River by characterizing the macro-invertebrate assemblage associated with Dreissena clumps on artificial substrates at four sampling sites and by quantifying the infestation of Dreissena on native mussels along six transects. We found that the study site with dense Dreissena clumps on artificial substrates hosted particular macro-invertebrate assemblages that were composed of amphipods, gastropods and some insect larvae. Oligochaeta and Ephemeroptera abundances were low at this site. Non-native Ponto-Caspian amphipods occurred in very high densities in mussel beds, and we report the first records of several new invasive amphipod species in the Meuse River. Our results also revealed that ca. 40 % of sampled Unionidae were infested by Dreissena, although infestation load was low (0.48–2.51 Dreissena per native bivalve). These results suggested that the interactions between Dreissena and other macro-invertebrates ranged between a probably low incapacitating relationship with Unio resulting from a long coexistence which allowed the two species to live in sympatry and a strong facilitation for exotic amphipods native from the same region as Dreissena. © 2015, Springer Science+Business Media Dordrecht. Source


Arambourou H.,CEREMA Dter Ile de France | Branchu P.,CEREMA Dter Ile de France | Beisel J.-N.,Ecole Nationale du Genie de lEau et de lEnvironnement de Strasbourg ENGEES | Beisel J.-N.,University of Strasbourg
Bulletin of Environmental Contamination and Toxicology | Year: 2015

In order to be a relevant indicator of exposure towards teratogenic stressors, morphological defects should not be passed on to the next generation. In this study, we compare morphological variations in Chironomids collected from a contaminated river stretch with those of their progeny, reared in uncontaminated sediment under laboratory conditions. We focused on mentum defects (deformities, fluctuating asymmetry and mean shape change), measured by geometric morphometrics. We observed no significant variation in deformity rate between the parental generation and its progeny. On the contrary, we observed a significant increase in fluctuating asymmetry and a significant decrease in mentum centroid size in the offspring. Our results suggest that shape defects are not caused by direct exposure to teratogenic stressors alone. We propose four hypotheses to explain this: (a) teratogenic contaminants are present in egg-clutches, (b) contaminants at the sampling site have mutagenic effects, (c) costs of tolerance, and (d) contamination-induced genetic impoverishment. © 2015 Springer Science+Business Media New York. Source

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