Roches de Penmarc'h

Mapis based on the interpretation of various types of data from a number of surveys carried out between 2011-2012 both in the intertidal and subtidal zones. Additionally the seabed ┬½ Carte G ┬╗ from the French hydrographic survey (SHOM) was used in the interpretation process. In the tidal zone the identification was made by interpreting coastal ortho-photographs from BD Ortho (2005 et 2009) and digitising them on scale 1 : 2000├¿me with further qualification of the polygons based on ground truth data. For the subtidal zone, several data sources from 2011 were available: bathymetric lidar (with sounding density about 1pt*3m-2), side scan sonar (resolution of about 0.2m), underwater video, sediment and fauna samples collected with grabs and trawls. Addtionnally a single beam sounder was running at all times during the transects, which contributing to improve the depth DTM. In the outer rocky circalittoral zone, side scan sonar corridors were surveyed with a coverage of 30-50% depending on places. In the offshore deep circalittoral zone (known as La Grande vasi├¿re) where soft sediment is predominant, side scan sonar coverage was reduced to about 5-10%. In these latter two circalittoral zones, interpolation between sonar corridors was supported by SHOM ┬½ Carte G ┬╗ (approx. scale 1:100000) along with a 100m resolution depth DTM. On rocky seabed, exposure at the seabed was described using kinetic energy from a combination of wave and current hydrodynamic models according to the methods described in: http://doi.org/10.13155/49975. Rocky substrate in intertidal and infralittoral zones was derived from the combined interpretation of both the topographic and bathymetric Lidar DTMs and aerial photographs, where permitted by water transparency. Various representations of the DTMs (slope, hillshade) helped delineate rocky outcrops with good reliability. Biological qualification of the substrate polygons was made through taxonomic analysis of benthos samples collected by MNHN in the framework of the project"Ecological assessment of Natura 2000 site - Roches de PenmarcÔÇÖh".The final habitat classification was a synthesis of the main habitat classifications, namely: Generic habitats from the Habitat Directive (EUR 27), Elementary habitats from the French Cahiers dÔÇÖhabitats, The Rebent classificationand EUNIS level 4 as much as possible.