This work was carried out within the framework of the HOOPLA WEAMEC project : “New methodological approaches for impact studies of offshore wind power farming structures on benthic habitats : case study of haploops fields”.
This project is a WEAMEC project with the funding from the Pays de la Loire Region.
Haploops spp. are bio-engineer amphipods who build dense tube mats in muddy environments. They play a bio-sedimentological key-role in ecosystems processes. Indeed, their constructions modify the local seafloor characteristics (densification and uplift), by catching the sediments particles and affecting the water flow. Their empty tubes rooted in the first centimeters of sediments potentially enhance down-sediment water circulation, thus influencing the early diagenesis processes. Haploops spp. occurrence in specific environments seems to be linked with the biogenic methane stored in in the sub-bottom sediments and the presence of active pockmarks. The coastal area between Le Croisic and the shoals of the plateau du Four (West Coast of France), is partially covered by a huge Haploop spp. field. This Haploops settlement is crossed by a trench (dug in 2012), where an electric cable has been buried to link offshore field test site for marine energy devices to the shore. The aims of our study are: 1) to describe the living benthic foraminiferal assemblages of the Haploops’ mats in comparison to the adjacent predominantly muddy area; 2) to identify indicative species to estimate the medium-term effects of the physical disturbance induced by anthropic activity, with or without Haploops. Two transects, close to far from the trench, were sampled in the “Haploops facies” area and the adjacent “mud facies” area and compared. Foraminiferal assemblages (>125 μm) of the two facies have a common species pool, but major differences in terms of absolute abundances and biodiversity. The “Haploops facies” show less dense and highly diverse faunas, while the assemblages in the “mud facies” are much more abundant and overwhelmed by the species Elphidium granosum. An effect of the physical disturbance is still visible on the faunas after 5 years from the trench’s excavation, especially in the Haploops facies.