Etude de la flore introduite dans le Bassin d'Arcachon

An inventory of the marine macrophytes introduced into the Arcachon Basin has been carried out through an exhaustive bibliographical analysis complemented by several sampling campaign made in November 2005, July 2006, February and December 2007. As a result, 22 introduced species have been listed. Nine of them are new to the region, and Herposiphonia parca and Pterosiphonia tanakae, are recorded for the first time from the Atlantic Ocean. Of this exotic flora, 17 species have also been introduced into the Thau Lagoon (France, Mediterranean). Except for some old introductions for which the most probable vector is the shipping, an introduction along with shellfish transfers, directly from Japan or via other aquaculture sites is highly probable. The great similarity between the exotic floras of the Arcachon Basin and Thau Lagoon highlights the high risks of introduction and dissemination of marine macrophytes through the oyster importations and the shellfish transfers between aquaculture sites. Several species introduced to Arcachon are invasive or potentially invasive: Codium fragile, Colpomenia peregrina, Dasya sessilis, Feldmannophycus okamurae, Gracilaria vermiculophylla, Heterosiphonia japonica, Sargassum muticum, Ulva cf. fasciata, Ulva pertusa et Ulvaria obscura.