Biodiversity, distribution and community structure of benthic hydroids from Point Géologie Archipelago (Dumont d’Urville Sea, Adélie Land, Antarctica)

Abstract

Hydrozoans are one of the main and most characteristic zoological groups of Antarctic benthic communities, yet there are Antarctic areas where the hydrozoan fauna is completely unknown (e.g. the Admunsen Sea, West Antarctica) or scarcely known (e.g. Adelie Land, East Antarctica). Hitherto, only one study, published in 1972, has been devoted to hydroids inhabiting marine bottoms off Adelie Land. The present study contributes to a better knowledge of the benthic hydroid fauna of this region by studying material from the Antarctic Specially Protected Area of Pointe Geologie Archipelago (ASPA 120), area of considerable biological value and great importance for scientific research. 35 species of benthic hydroids were found, belonging to 14 families and 18 genera. 15 species represent new records for the area, bringing the number of species reported in the zone to 45. Leptothecata is dominant, with 30 species, while Anthoathecata is represented by just five species. Symplectoscyphidae is the most speciose family, with 11 species (31%), whereas Kirchenpaueriidae has the highest biomass due to Oswaldella terranovae, the species with the highest abundance and biomass and that could be considered a true habitat builder and biodiversity hotspot. The study of the hydroid assemblages has revealed the overwhelming dominance in the area of a community characterised mainly by O. terranovae; three other assemblages are present, albeit much less represented. The hydroid fauna is clearly dominated by eurybathic species (65%) and most of the species studied (88%) are restricted to Antarctic or Antarctic/sub-Antarctic waters, with 65% endemic to the Antarctic region.