FLUX AND STABLE-ISOTOPE COMPOSITION OF NEOGLOBOQUADRINA-PACHYDERMA AND OTHER PLANKTONIC FORAMINIFERS IN THE SOUTHERN-OCEAN (ATLANTIC SECTOR)

Planktonic foraminifers were collected with time-series sediment-traps in Bransfield Strait, Northern Weddell Sea, and near Maud Rise. Seasonal flux patterns of planktonic foraminifers are similar to total flux patterns. The dominant species was the left-coiling Neogloboquadrina pachyderma. At the Maud Rise, in an open-ocean polynya, Turborotalita quinqueloba, Globigerinita glutinata and Globigerinoides ruber (white) also were abundant. delta(18)O values of N. pachyderma ranged from 3 to 3.6 parts per thousand, corresponding to an apparent temperature range of about 3 degrees C. The smaller size classes showed the lower delta(18)O values. Oxygen isotope variability between size classes and during the year are explained by seasonal changes in temperature and vital effect. delta(13)C values of the foraminifer shells ranged from 0.1 to 1.1 parts per thousand. The largest sizes had the highest and the smallest sizes the lowest values. Changes in the deviation from thermodynamic equilibrium during bio-mineralization seem to be involved in this pattern of C-13/C-12 ratios.