Coccolithophores from the central Arabian Sea: Sediment trap results

Sediment trap samples collected from a depth of 1018 m in the Central Arabian Sea Trap (CAST) at 14°28.2′N, 64°35.8′E were analyzed for temporal variation of coccolithophore fluxes from October 1993 to August 1994. Out of the twenty species of coccolithophores encountered,Gephyrocapsa oceanica, Emiliania huxleyi, Umbilicosphaera sibogae andUmbellosphaera irregularis were the most abundant. The total coccolithophore fluxes ranged from 28.5 × 106m-2d-1 to 50.3 × 106m-2d-1 showing seasonality with higher fluxes during the northeast (NE) monsoon and lower fluxes during the spring intermonsoon. The higher fluxes were attributed to the enhancement of primary production in the central Arabian Sea due to southward extent of nutrients from the northeast Arabian Sea by the prevailing surface currents. Similarly, the occurrences of relatively lower coccolithophore fluxes during the spring intermonsoon and southwest (SW) monsoon were attributed to the low nutrients in the warm, shallow surface mixed layer and downwelling to the south of Findlater Jet respectively in the central Arabian Sea. Some of the coccolithophore species such asE. huxleyi, G. oceanica, Calcidiscus leptoporus andUmbellosphaera tenuis showed signs of dissolution.