Soft Bottom Macrobenthic Communities in Sandy Enclaves from the North Cotentin Peninsula (Central English Channel)

The North Cotentin Peninsula (Normandy, France) presents a mosaic of substrates (from gravel to fine sand) favorable to the development of diversified marine benthic communities, so far, never described outside the Rade of Cherbourg. A total of 28 stations was sampled in winter 2017 and 2018, along a North Cotentin coasts, to complete the 30 stations already studied into the Rade de Cherbourg from 2012 to 2015 for a total number of 61 stations. Hierarchical Ascendant Classification and Multidimensional Scaling ordination on the 61 stations allows the identification of eight benthic assemblages corresponding to six EUNIS habitats: 1) Amphipholis squamata and Apseudopsis latreillii in mixed sediment; 2) Spio decorata with or without Apseudopsis latreillii in fine sand; 3) Melinna palmata in muddy sand; 4) Ampelisca spp., Photis longicaudata and other amphipods and tubicolous polychaetes in muddy sand; 5) Crepidula fornicata in coarse mixed sediment, and 6) Mediomastus fragilis, Lumbrineris spp. and venerid bivalves in circalittoral coarse sand or gravel. The area shows a high taxonomic diversity and remarkable benthic habitats with high natural heritage value, including the new Spio decorata fine sand habitat not previously identified in the EUNIS classification. Moreover, very high abundances of the tanaidacean crustacean Apseudopsis latreillii (>1,000 ind. 0.1 m²) are recorded in mixed sediment, whereas the species is absent in sand.