Diatom distribution in Southern Ocean surface sediments (Atlantic sector): Implications for paleoenvironmental reconstructions

A study of 230 surface sediment samples collected in the Atlantic sector of the Southern Ocean between the southernmost Weddell Sea and the Subtropical Zone documents the modern distribution of diatoms revealing patterns of paleoenvironmental significance. Estimations of diatom valves per gram dry sediment display numbers of (50–200) × 106 in the zone of high opal burial located between the mean position of the winter sea ice edge and the Polar Front and maximum values of greater than 200 × 106 in the near-shore sedimentary basins off the Antarctic Peninsula. Lowest diatom concentrations and assemblages strongly affected by dissolution were encountered in the Weddell Basin. Despite alteration of the diatom assemblages prior to their incorporation into the sediment record, the biogeographic distribution and the abundance pattern of most of the 35 studied diatom species shows a close relationship with the surface hydrography (water temperature). These relationships can be used to estimate past surface water temperatures based on statistical treatments of the assemblages or on simple relations of species occurrences in the geological record. Another close link occurs between the distribution of sea ice and sea ice related diatoms.