LIVING FORAMINIFERA IN THE SHALLOW WATERS OF ADMIRALTY BAY: DISTRIBUTIONS AND ENVIRONMENTAL FACTORS

摘要

The living foraminiferal fauna and associated environmental factors were examined using shallow-water sediment and bottom-water samples collected in the Admiralty Bay (King George Island, Antarctica) during the austral summer of 2004-05. Admiralty Bay has similar environmental characteristics to other Antarctic coastal areas, with bottom water rich in inorganic nutrients and heterogeneous bottom sediments with high concentrations of mud and sand. We found 45 foraminiferal species, including 28 agglutinated and 17 calcareous species. The dominant species were the calcareous Bolivina pseudopunctata and the agglutinated Pseudobolivina antarctica and Portatrochammina antarctica. Only the agglutinated Spiroplectammina biformis was found in all samples. Admiralty Bay contained a typical Antarctic foraminiferal fauna, mainly distinguishable by the type of bottom sediment. We detected two distinct assemblages: (a) from the entrance of the bay area with a main channel, we found an assemblage with relatively high species richness, abundance and diversity, and with abundant Bolivina pseudopunctata and Fursenkoina fusiformis; and (b) in the inner parts of the three inlets of the bay (Ezcurra, MacKellar, and Martel inlets), mud- and sulfur-rich sediments contained relatively few foraminifers dominated by a few species, mainly of Globocassidulina and Cassidulinoides.