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Brest, France

Breton M.,Safege Actimar | Le Gac S.,Safege Actimar | Perenne N.,Safege Actimar | Raillard O.,Safege Actimar | And 5 more authors.
Techniques - Sciences - Methodes | Year: 2013

Shellfish within the Benoît estuary register, under certain conditions, phases of contamination by faecal germs. The origin of the phenomenon and the conditions of its realization raise a number of questions. The study realized by Safege (for CCAC) has attempted to provide answers. A significant effort has been devoted to the evaluation of agricultural and domestic effluents is which reject into the estuary and its tributaries. On this basis, different scenarios have been defined that characterize emissions depending on the season and rainfall intensity. A mathematical model was constructed and implemented to calculate (simulate) currents, dispersion of faecal bacteria discharge and shellfish contamination in the Benoît estuary, under the combined action of the tide, wind and of freshwater inflows. The model also takes into account the processes of concentration and retention of Escherichia coli in bivalves. Using this model, the understanding has been improved of hydrodynamic behavior of the aber and health vulnerability of shellfish to discharges. The contribution of different emissions to water contamination and livestock shellfish have been specified, as well as the role played by the meteorological and sea conditions and season. The study also highlighted the ability of the estuary to evacuate peaks of faecal germs pollution caused by discharges during rainfall events, considering the role of hydrodynamics and the mechanisms of shellfish contamination/decontamination. These results provide an essential basis to stimulate debate between the users (farmers, shellfish farmers), local and state services and to define actions in order to restore water and shellfish quality of the estuary.

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