SEASONAL AND VERTICAL VARIATIONS OF SINKING PARTICLE FLUXES IN THE WEST CAROLINE BASIN

A sediment trap experiment was carried out in the West Caroline Basin, located in the equatorial western Pacific between influences of the A sian monsoon and the open ocean. Annual mass flux at the shallow trap at Site 1 was 57.10 g m(-2)yr(-1). Generally, the higher flux of organ ic matter was associated with higher activities of biogenic opal-produ cing and carbonate-producing plankton communities. In addition, as the organic matter content increases, the organic carbon/carbonate carbon ratio shows a tendency to increase. Carbonate-producing plankton was predominant during periods 1 and 3 (May to July and November to the be ginning of December), which could be due to limited silica supply to t he euphotic zone. On the other hand, surface sea water was more nutrie nt-rich during periods 2 and 4 (August to October and the end of Decem ber to April) at Site 1. These high total mass fluxes could be stimula ted by wind. The amount of biogenic components collected in the sedime nt traps and the accumulation in surface sediments at Site 1 could be compared with primary productivity values. Carbonate and biogenic opal fluxes were 99 % and 90 % less, respectively, in the surface sediment s compared to those in the shallow sediment trap. This could be due to the reaction of sinking particles with undersaturated deep sea water just above the sea floor, rather than with the water column during sin king. About 20 % of the organic matter was decomposed between the shal low and deep sediment traps and more than 98 % between the deep sedime nt trap and final burial in the surface sediments. The relative amount of organic carbon preserved in surface sediments was about 0.10 % of annual primary productivity. (C) Elsevier, Paris.