Colonization of Patagonian harbours (SW Atlantic) by an invasive sea squirt

Abstract

Despite the poorly studied biodiversity of the Southwestern Atlantic, several exotic species have already been detected. Here we detail the distribution and abundance of the invasive ascidian Ascidiella aspersa (Müller, 1776) in the SW Atlantic and review its historical records. For this purpose, we determined ascidians collected since 1914 from museum collections and inspected randomly sampled natural biota collections as well as colonization on plates deployed in situ for two years throughout six major harbours along the Patagonian Argentine coast. Museum collections revealed a sudden presence of A. aspersa early in the 1960’s. The species is actually distributed over 10 latitudinal degrees in harbours and subtidal areas along the SW Atlantic. Altogether, results suggest that this species, an exotic for the SW Atlantic, is able to colonize new areas. Further studies are needed to assess A. aspersa invasion impacts on biodiversity in the study area.