Diatom recovery from core MD88-779: Raw counts

Core MD88-779 was taken during the 1988 French ASPARA IV cruise in the South East Indian Ocean aboard the Marion Dufresne. The core is situated on the South Tasman Rise (47º50.690S, 146º32.750E) at a depth of 2260m. Although the core recovered was 6.7m long, only the top 2.6m were studied as preliminary investigations had indicated that this section covered the last two glacial cycles.

A total of 37 diatom species and taxa were observed in the core samples, comprising predominantly warm-water fauna. The majority of samples were poorly preserved and showed high levels of dissolution making identification to species level often difficult. Species with greatest abundances were those more heavily silicified (e.g. Fragilariopsis kerguelansis), and to a lesser extent the warm-water forms (e.g. Fragilariopsis doliolu).

The complete loss of a diatom record at 170cm and 210/220cm in the core is extremely unusual. The diatom signal is interpreted as having been removed by increased water mass velocity, extreme post-depositional silica dissolution or decreased productivity. There is no sedimentological evidence from the core which provides further interpretation.

The diatom recovery from this core is considerably low when compared to samples from the Southern Ocean.