The dominance of large, symbiont-bearing Rotaliida on the Vietnam Shelf reflects a nutrient-deficient and high energy environment. On the Vietnam Shelf, winnowing processes are prevalent, and there may be reduced deposition of organic matter to the sea-floor due to stronger bottom currents. Shallow water (< 200 m) assemblages from the Vietnam and Sunda Shelves exhibit significantly different species composition and distinct distribution patterns correlated to current activity, the depth of light penetration, substrate properties and the levels of organic matter reaching the benthos. The standing stock values are between 20 and 330 indiv./10 cm2. Diversity indices (H(S) and Fisher’s Alpha) are high in both areas studied, while the species dominance is low. The remaining species exhibit a depth related distribution. The material revealed more than 800 taxa, 90 of which occur through the entire studied water depth range (50-2000 m). The investigation is based on the analyses of Rose Bengal stained benthic foraminifera from 75 sites (R/V SONNE 115 cruise, Stattegger et al., 1997).
Species composition and spatial distribution patterns of modern shallow-water and bathyal benthic foraminifera were studied on the Vietnam Shelf and Sunda Shelf of the south-western South China Sea. Our inference of a decrease in sea ice meltwater stratification influence in the central Bering Sea after the MBT is consistent with records showing that the Arctic and Pacific Ocean warmed during glacials and suggests that high-latitude productivity and sea ice changes were an important feature of this climate event. weddellensis occur, which we suggest reflect a time of more sea-ice-related seasonal stratification and ice edge blooms. Before the MBT, more numerous intervals of the very high-productivity Assemblage 1 and A. laevigata, indicative of seasonal phytoplankton blooms. Other assemblages contain the phytodetritivore species A. delicata, Bolivina spissa, and Brizalina, which occur sporadically within intervals of laminated, biogenic-rich sediment, mostly during glacials and also some deglacials, and are interpreted as indicating very high productivity. Correspondence analysis shows that the most significant Assemblage 1 comprises B. 2, Cassidulina laevigata, Islandiella norcrossi, and Uvigerina bifurcata, consistent with broadly high net primary production throughout the last 600 kyr. The most abundant species are Bulimina exilis, Takayanagia delicata, Alabaminella weddellensis, Gyroidina sp. Foraminiferal preservation is markedly higher during glacials, indicating the presence of less corrosive GNPIW.
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We identified and imaged 71 taxa and provide a full taxonomy. To understand palaeoceanographic change in the region, we analysed benthic foraminiferal faunas from Bowers Ridge (Site U1342, 800 m of water depth) over the past 600 kyr, as they are uniquely well preserved and sensitive to changes in deep and surface ocean conditions. The Bering Sea is the link between the Arctic and Pacific Ocean and is an area of high productivity and CO 2 ventilation it hosts a pronounced oxygen minimum zone (OMZ) and is thought to be the location of Glacial North Pacific Intermediate Water (GNPIW) formation in the Pleistocene. The Arctic Ocean is thought to have warmed and exhibited reduced sea ice, but little is known of sea ice marginal locations such as the Bering Sea. The Mid-Brunhes Transition (MBT) saw an increase in the amplitude of glacial cycles expressed in ice core and deep ocean records from about 400 ka, but its influence on high-latitude climates is not fully understood.
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