Colonization of artificial substrates by exotic ascidians (Tunicata, Ascidiacea) at patagonian harbors

TATIAN M; LAGGER C; SCHWINDT E

MAR DEL PLATA

Congreso; 2nd World Conference on Biological Invasions and Ecosystem Functioning; 2011

Grieta

Ascidians are important members of the benthic marine communities throughout the oceans. They are one of the taxonomic groups in focus for marine invasion, as records are currently accumulated worldwide for this group. While the transport by anthropogenic vectors (ballast water and hull fouling), is considered the main dispersion route by non-indigenous ascidians, the harbor areas offer conditions for primary colonization. Invasive ascidians may displace native species and affect community structure of their newly invaded habitats. In spite of the poorly studied biodiversity of the Southwestern Atlantic, several exotic ascidian species have already been reported. Here we detail the distribution of species, previously considered as highly invasives, and review its historical records to define their status at the SW Atlantic. For this purpose, we examined ascidians from museum collections dated as from 1914 and inspected randomly sampled natural biota collections as well as colonization on plates deployed in situ for two years throughout six major harbors along Patagonia Argentina coast. Museum collections revealed a sudden presence of several species, as the case of Ascidiella aspersa early in the 1960’s. The species is actually distributed over 10 latitudinal degrees in harbors and subtidal areas along the SW Atlantic. Results obtained from the plates suggest that other two recent findings, the species Diplosoma listerianum and Lissoclinum fragile, exotics for the SW Atlantic, are able to colonizing new areas. A study to assess the ascidian invasion processes and its impact on biodiversity is actually in course in one Patagonian harbor.