The general aspects of the distribution of Antarctic foraminifera

Abstract

Benthic foraminifers collected in different regions of the high Antarctic (Weddell Sea, Mawson Sea, Davis Sea and some other locations in East Antarctic) on the shelf and upper part of the bathyal zone (2–2315m) were analyzed to determine regularities in their distribution. Most samples contained living organisms. The composition of the foraminiferal assemblages is influenced by many factors of water characteristics such as temperature, salinity, nutrient composition, availability of carbonate and variations in CCD, presence of near-bottom flows. The changes of water masses at different depths or mixing of the different water masses are clearly seen in the changes of the foraminiferal species composition. In some cases the local variations of water characteristics, seasonality and ice melting are also responsible for the foraminiferal distribution. Two faunas were identified: those of the shelf associated with the cold-water masses (−1° to 1.9°) and the upper slope with warmer water (−0.5°), the majority of the characteristic forms being circumantarctic. Species abundance displays two maximums at depths of 180-300m and 1500-2300m. At depths to 500, and even to 700m, both arenaceous and calcareous forms, especially miliolids, are abundant. Below this boundary some living calcareous forms were also found, though arenaceous ones were dominant. The presence of calcareous foraminifers at the majority of the stations in our material may be explained by the higher resistance of living calcareous forms to carbonate dissolution comparing the empty tests, dissolving more rapidly. The overall pattern of these our data and of data from previous studies allows to draw some general conclusions with regard to the Antarctic foraminiferal fauna: a high degree of endemism which, for the shelf depths of 2-50m, sometimes reaches 80%; the gigantism of many species; a wide range of vertical distribution of many species; introduction of deep water species of other oceans onto the shelf and the upper part of the bathyal zone; often high species diversity and high quantity abundance of many species in the community; abundance of circumantarctic species, often with a great number of species belonging to a single genus; the abundance (often predominance) of agglutinated forms compared to calcareous ones. Some taxonomic notes and morphological observations are given, as well as comparisons of some closely related Arctic and Antarctic forms.