Syracuse

Impact of the construction of the MRE platform in the semi-enclosed Bay bordering the English Channel ("Rade de Cherbourg") on benthic habitat and geomorphology. Impact de la construction de nouveaux terre-pleins portuaires EMR sur les habitats benthiques et la géomorphologie de la rade de Cherbourg

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Baux, Noémie | Gregoire, Gwendoline | Gallon, Régis | Murat, Anne | Méar, Yann | Poizot, Emmanuel

Edité par CCSD -

International audience. The Cherbourg roadstead has been radically altered by the installation of industrial infrastructures (major dredging and reclamation works in 2015 and 2016 to allow the passage of deeper-draught ships and the creation of a new quay: 39 ha). A research program was carried out before and after the transformation of the port platforms to improve knowledge of the roadstead and assess its impact. Three complementary environmental approaches were used: (1) morphological changes based on a comparison of bathymetric data; (2) changes in sediment cover based on granulometric data; and (3) the impact on macrofauna benthic communities. It appears that the new construction is the cause of a morphological change in the seabed, leading to the creation of multi-metric "hollows" and "humps", responsible for a general change in hydrodynamics and widespread silting of the Grand Rade (+14% silt). To the east, more than 10% of the well-sorted, unimodal sandy seabed has silted up after the extension. This siltation reduced the exceptional diversity of benthic habitats and has led to a drastic reduction in fragile species (amphipods) and an increase in opportunistic species, probably altering the entire structure of the food web.

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