Biogenic reefs affect multiple components of intertidal soft-bottom benthic assemblages: the Lanice conchilega case study
Résumé
Biogenic reefs composed of the tube-building polychaete Lanice conchilega are important from a conservationpoint of view because they noticeably increase the biodiversity in otherwise species poorenvironments. However, up to now, little or no attention has been paid to the intertidal epi- andhyperbenthic communities associated with the reefs. Therefore, this is the first study which focuses onthe effect of L. conchilega reefs on the entire bentho-pelagic community at two different locations.Environmental variables were measured and macro-, epi- and hyperbenthic communities were sampledwithin a L. conchilega reef and a control area at two locations in France: the bay of the Mont Saint-Michel(BMSM) and Boulogne-sur-Mer (Boulogne). The effect of the reef presence on the benthic communitywas studied with a 3-factor (Reef, Location and Period) Permanova. In addition, the relationship betweenthe benthic community and the environmental variables was investigated using Distance-based linearmodels (DistLM). Most collected organisms were sampled in the reef area (macrobenthos: 91%, epibenthos:81% and hyperbenthos: 78.5%) indicating that, independent of the location, the L. conchilegareefs positively affect all three associated benthic communities. However, the extent of the effect seemsto be most pronounced for the macrobenthos and less distinct in case of the hyperbenthos. The macro-,and epibenthos are mainly structured by biotic variables (L. conchilega density and macrobenthic foodavailability respectively), while the hyperbenthos is rather structured by environmental variables. Ingeneral, L. conchilega reefs do not only affect abundances and diversity but they substantially steer thestructure of the intertidal benthic sandy beach ecosystem.