Stocks (abundance and biomass) of the slipper limpet Crepidula fornicata Linnaeus, 1758 in the Pertuis Charentais shallows were estimated in 2011 and mapped (Sauriau et al., 2011). The influence of the estimate includes the Pertuis Breton, the eastern part Pertuis Antioch Fouras peninsula and the Bay of Marennes-Oléron where the latter earlier estimates are available. Contours and surface areas of the crepidula were previously determined by acoustic imaging performed aboard the VO/Haliotis in 2008 and 2009, interpreted and validated by spot sampling in 2009 (Curti, 2009). Sampling stocks of 2011 is based on a stratified random sample of 40 banks with a proportional distribution of sampling of 200 stations between banks. The listing for each crepidula bank stocks (abundance in millions, biomass in tonnes) both living and dead, these shells may provide support to potential new colonization.

The shapefile corresponds to areas where predicted bioregions were extrapolated for lack of benthic in-situ observations.

These rasters correspond to the environmental predictors used in the production of Mediterranean bioregions of megabenthic communities

The rasters correspond to the prediction uncertainties associted with the production of Mediterranean bioregions of megabenthic communities

The raster corresponds to the predicted Mediterranean bioregions of megabenthic communities.

Sediment average grain size in the Mediterranean was generated from sediment categories. This rough granulometry estimate may be used for habitat models at meso- and large scale.

An inventory of mäerl ( unfixed red marine algae Corallinaceae with calcified arbuscular thalli) is taken in the Pertuis Charentais using the compilation of historical data and new observations over the period 2006-2012. The geographic extent of the inventory includes Pertuis Breton, Antioch and Maumusson, extends from the Lay estuary in the north to the Bay of Marennes-Oléron in the south and includes the edges of the islands of Ré, Oléron and Aix. Contributing to this inventory are, surveys DCE 2006 DCE, control monitoring DCE 2007 to 2012 under the aegis of Ifremer and Agences de l’Eau Loire-Bretagne and Adour-Garonne, surveys conducted for the Port Atlantique La Rochelle on the site of dredge spoil deposits in Lavardin from 2007 to 2012, surveys in 2007 FONSOLE by Ifremer and the surveys by Ifremer and laboratory LIENSs to map the crepidula stocks in the Pertuis Charentais Sea. Adding specific surveys conducted in 2011 by the ship Estran by dredge on subtidal bottom sediments of Pertuis Breton and intertidal quadrat in 2012 on the periphery of the islands of Ré, Oléron and along the cliffs of Aytré. The positioning of ground truthing stations were identified by GPS or dGPS. Initially identified by samples of the dredged material in October 2009 during the validation of sonar surveys to individualize stocks of crepidula, a live maerl bed is mapped in July 2011 in the harbor of Saint-Martin in Pertuis Breton. Its area is estimated at more than 2 km². Surveys of pedibus jambi conducted at the point of Grouin and Saint-Martin de Ré has confirmed the presence of live maerl scattered on the lower foreshore. This suggests a scattering of live maerl thalli of several tens of km² around the main bed of Saint-Martin. It is also confirmed by the single algological extraction of Phymatolithon calcareum done at the beginning of the twentieth century in Saint-Martin de Ré by Dollfus, probably already on the lower foreshore as observed in 2012 near the Couronneau beacon. Numerous dead maerl thalli in the procress of diagenesis have also been observed in the East and Southeast of Pertuis Breton and Antioch suggesting passive transport by contributions from live beds farther to the West, including Pertuis in Antioch. The presence of live maerl on the lower foreshore is seen very occasionally in the western islands of Oléron (Pointe Chassiron) and Ré (Phare des Baleines) via recent algologiques and fauna surveys. In biogeographic terms, the maerl bed of Pertuis Breton is the easternmost and southernmost of those known in the Bay of Biscay. The nearest mäerl beds known are respectively located in Noirmoutier (Bourgneuf Bay) and Galicia (Spain). These observations complement the atlas mapping of maerl populations in Europe published under the auspices of the OSPAR Convention. They provide a knowledge base for future conservation actions defined locally in the context of Natura 2000 Sea Marine Natural Park of the Gironde estuary and the Pertuis Charentais.

The geographical distribution of the main Sabellaria Hermelles alveolata beds (Linné, 1767) from the coast of the Pertuis Charentais was compiled from 2010 to 2012. The inventory focuses on the tidal beds (+ 6-0 m marine coast) and compiles two cartographic sources from the project CARTHAM Natura 2000 at sea of the Agency of Marine Protected Areas: 1) Hermelles inventories made on 2011 by the Association IODDE on the west of Oleron Island and 2) mapping inventory of intertidal marine habitats by LIENSs (in cooperation with CREOCEAN, Ré Nature Environnement, GEO-Transfert et la LPO Moëze-Oléron). Methodologies used by IODDE on Oléron combine ground truths with reports with Geographic Information System (GIS). The methodologies used by LIENSs to estimate the extension of the intertidal habitats throughout the Pertuis Charentais combine aerial image analysis, remote sensing, field validations by differential GPS and thematic analysis using GIS (Cajeri et al., 2012). It is during these ground truths that the presence of tackles or small Hermelles reefs was noted. The IODDE results have allowed an almost exhaustive inventory of Hermelles reefs west of Oleron. Those of LIENSs have clarified the distribution of Hermelles on most of the Pertuis Charentais foreshores.

Process-driven seafloor habitat sensitivity (PDS) has been defined from the method developed by Kostylev and Hannah (2007), which takes into account physical disturbances and food availability as structuring factors for benthic communities. It is a conceptual model, relating species’ life history traits to environmental properties. Physical environment maps have been converted into a map of benthic habitat types, each supporting species communities with specific sensitivity to human pressures. It is based on two axes of selected environmental forces. The "Disturbance" (Dist) axis reflects the magnitude of change (destruction) of habitats (i.e. the stability through time of habitats), only due to natural processes influencing the seabed and which are responsible for the selection of life history traits. The "Scope for Growth" (SfG) axis takes into account environmental stresses inducing a physiological cost to organisms and limiting their growth and reproduction potential. This axis estimates the remaining energy available for growth and reproduction of a species (the energy spent on adapting itself to the environment being already taken into account). It can be related to the metabolic theory of the ecology. The process-driven sensitivity (PDS) can be seen as a risk map that combines the two previous axes and reflects the main ecological characteristics of the benthic habitats regarding natural processes. Areas with low disturbance are areas with a naturally low reworking of the sediment, allowing the establishment of a rich sessile epifauna community, with K-strategy species. Areas with low SfG means that the environmental factors, even though there are not limiting, are in lower values, i.e. that it imposes a cost for species to live. In areas combining low disturbance and low SfG, big suspension-feeder species with long life and slow growth can often be found: these species are more vulnerable in case of added disturbance.