Abstract

Composition, abundance and richness of the intertidal and shallow subtidal (<30 metres) benthic polychaetes are presented. Several coastal fieldworks in fjords, channels and islands were undertaken between 2001 and 2003 in relationship with Biodiversity Aysen Project. 1.364 individuals and a total number of 76 taxa belonging to 30 families were recorded. The higher species richness was observed by Spionidae and Nereididae with nine and eight species respectively, with Platynereis australis (Schmarda, 1861) showing the highest dominance across overall sampling fieldworks. Specimens of Chrysopetalidae, Saccocirridae and Arenicolidae families are recorded for first time in the region, while another species increase their distribution range. The high species richness of some places (e.g. Kent Island) and some special oceanographic, environmental and geographic conditions suppose that diversity 'hotspots' have place at the Aisen region. A hypothesis is presented in terms of, some polychaetes species with high abundance and frequency in comparison to other invertebrates and specific environmental conditions where they live would allow developing a 'subiotope' in the studied coastal environmental. The 'subiotope' would be mainly defined by dominance of these polychaete species.