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Sediment trap samples collected from the Western Arabian Sea yielded a rich assemblage of intact and non-living (opaque white) pteropod tests from a water depth of 919 m during January to September 1993. Nine species of pteropods were recorded, all (except one) displaying distinct seasonality in abundance, suggesting their response to changing hydrographical conditions influenced by the summer/winter monsoon cycle. Pteropod fluxes increased during the April--May peak of the summer monsoon, and reached maximum levels in the late phase of the southwest summer monsoon, probably due to the shallowing of the mixed layer depth. This shallowing of MLD coupled with enhanced nutrient availability provides ideal conditions for pteropod growth which is also reflected in corresponding fluctuations in the flux of the foraminifer Globigerina bulloides.Pteropod/planktic foraminifer ratios displayed marked seasonal variations, the values increasing during the warmer months of April and May when planktic foraminiferal fluxes declined. The variation in fluxes of calcium carbonate, organic carbon and biogenic opal show positive correlations with fluxes of pteropods and planktic foraminifera. Calcium carbonate followed by biogenic opal was the main contributor to the total particulate flux especially during the SW monsoon. In the study area pteropod flux variations follow the other flux patterns indicating that they too could be used as a potential tool for palaeoclimatic reconstruction of the immediate past.

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 and Umbellosphaera irregularis were the most abundant. The total coccolithophore fluxes ranged from 28.5 × 10 6 m −2 d −1 to 50.3 × 10 6 m −2 d −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 as E. huxleyi, G. oceanica, Calcidiscus leptoporus and Umbellosphaera tenuis showed signs of dissolution.

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