Enhancing marine coastal biodiversity in Normandy: towards a new species signalling network using Artificial Structures

Abstract

Non-Indigenous Species (NIS) are a threat to native biodiversity and ecosystem services. The European seas are known to be the recipient of several hundreds of NIS due two main origins: shipping and aquaculture. They are the focus of Descriptor 2 of good environmental status in the Marine Strategy Framework Directive. 153 NNS had been recorded along the Normandy coast in 2018. Marinas are priority sites for monitoring, being ‘hotspots’ for the NIS occurrence. The aim of the ENBIMANOR project was to study and compare the composition and the hard-bottom macrofauna including the NIS prevalence in marinas along the Normandy coast (from Granville to Dieppe-Le Tréport) focusing primarily on mobile and benthic invertebrates. A total of 19 marinas were surveyed during two years (2018-2020). At each harbour, nine settlements panels (acting as artificial reef) were immerged at a depth of 1.50 m. Every quarter, at each site, a settlement panel was replaced and the species colonising the panel were identified. The analysis revealed higher taxonomic richness in marinas open to the sea or with high salinity than in closed marinas or with low salinity. Results highlighted that each marina has its own species composition. This survey identified more than one hundred taxa, including known NIS species such as the amphipod Monocorophium acherusicum and M. sextonae, the ascidians Perophora japonica and Stylea clava, and detect four new NIS for the Normandy waters (Aoroides longimerus, A. curvipes, Paranthura japonica and Ianiropsis serricaudis). Our study shows the need to continue the census of NIS and to evaluate their impacts on the artificial hard-bottom structures in marine coastal ecosystem on two major zones: the intertidal zone and the marina/harbours waters.