Wide coverage but few quantitative data: Coarse sediments in the English Channel
Résumé
Offshore Wind Farms (OWFs) in the English Channel and along the coast of Normandy (France) will be installed on coarse sediments, which cover about 80% of the seabed of the English Channel. A BACI (Before After Control Impact) approach has been recommended by the French State for each of these OWFs. This provides the opportunity to acquire macrofauna data and assess the Ecological Quality Status in areas that are poorly sampled. In the case of the Dieppe-Le Tréport (DLT) OWF, for that, a sampling strategy was developed in 2014–2016 to establish a ‘Before’ state for the sediment and macrofauna. Results highlight that the DLT OWF project site includes three different sediment type: sandy Gravel (sG), gravelly Sand (gS) and medium Sand (mS). Taxonomic Richness and abundances are dominated by Annelids in all three habitats, followed by Arthropods and Molluscs. In terms of biomass, Molluscs (bivalves) are predominant in sG and gS, while Echinoderms and Polychaetes along with bivalves represent a high fraction of the biomass in mS. Surface Deposit Feeders are the most important group in terms of abundance, while Filter feeders largely dominate the biomass. The benthic indices based on abundances reveal a high Ecological Quality Status for the three sediment types. However, due to the predominant contribution of the bivalve Glycymeris glycymeris to the biomass, the habitat quality appears to vary from moderate to bad. In comparison with other similar habitats, the Taxonomic Richness and Abundances of coarse sediments and medium sand are in the same order of magnitude as other sites. However, the biomasses are among the highest so far recorded, reflecting the importance of this area as a hotspot of biomass in the English Channel.
Origine : Publication financée par une institution
