Radiolarian assemblages and their distribution characteristics in surface sediments of Prydz Bay

Radiolarian faunas from 16 surface sediment samples of Prydz Bay are studied by the authors. A total of 2 orders, 66 genera and 107 species are identified, which consists of 71 Nasseillaria species (40 genera) and 36 Spumellaria species (26 genera), of which the former is obviously higher in genus-species diversity and quantity of individuals. Radiolarians in the surface sediments of Prydz Bay are low in diversity but high in abundance, which may reach 3.36×10⁴ind/g (dry sample)on average. The distribution of abundance is in a descending order from the shelf zone, to the mouth of bay and to the front of ice shelf in general, and higher in the west but lower in the east, affected by such environmental factors as surface biological productivity, circulation pattern, sediment type and distribution of cold water mass. The Antarctissa group, mainly composed of Antarctissa strelkovi and Antarctissa denticulata, is the dominating assemblage in Prydz Bay, which may be as high as 42.43% on average depending upon water temperature.Therefore, the high percentage of this assemblage could be used as an indicator of cold water mass. The abundance of the assemblage is also affected by water circulation and subsurface topography. The typical assemblage, which is composed of Phormacantha hystrix, Plectacantha oikiskos and Rhizoplegma boreale, occupies 12.54% in samples. Its distribution pattern of abundance is an indicator to the mixing degree of water mass of concerned circulating currents, but not water depth or the distance to the coast in the bay.