Coccolithophore fluxes from sediment traps in the northeastern Arabian Seaoff Pakistan

We investigated coccolithophore fluxes from four sediment traps located in the northeastern Arabian Sea at the continental slope of Pakistan. Two moor ings, WPT and EPT (Western/Eastern PAKOMIN Trap), consisting of one and two sediment traps were deployed at water depths of about 500 m and 1500 m. Th ey collected settling particles from October 1993 to February 1994 and from May 1995 to February 1996 at intervals of 22 and 24 days, respectively. A longer sampling was prevented probably due to high sedimentation events whi ch occluded the trap cones. Both areas were characterised by a strong seaso nality in coccolith fluxes. High fluxes were recorded with up to 2000 x 10( 6) coccoliths m(-2) d(-1) in the early SW (summer) monsoon and up to 5400 x 10(6) coccoliths m(-2) d(-1) in the early NE (winter) monsoon. Generally, coccosphere fluxes exhibited a similar trend but were some orders of magnit ude lower than coccolith fluxes, Twenty-seven taxa were identified in this study, all well to moderately well preserved and with a small range of dive rsity. The species composition was dominated by Gephyrocapsa oceanica, Flor isphaera profunda, and Emiliania huxleyi making up about 70% of the assembl ages. During the SW (summer) monsoon high productivity in the surface water s of the eastern Arabian Sea may be linked to the upwelling system off Oman . Apparently nutrient-rich surface water derived from the southwestern upwe lling areas off Oman with high standing stocks were carried into this area by northeast flowing currents. In contrast, during the NE (winter) monsoon the locally observed high coccolithophore production is hypothesised to res pond to local injections of nutrient-rich deep water into the surface water due to sea-surface cooling leading to convection. Consequently, fluxes dur ing the winter monsoon were in the same range as during the summer monsoon. (C) 2000 Elsevier Science B.V. All rights reserved.