V. Ramaswamy*, M.M.Sarin and R. Rengarajan

*National Insititute of Oceanography, Dona Paula, Goa-403004, India

Physical Research Laboratory, Ahmedabad 380 009

The export of carbon from the upper mixed layer to the deep sea is an important link in the global carbon cycle, direct measurement of which is carried out using drifting sediment traps. In the present study export fluxes of carbon were measured in the Arabian Sea using drifting sediment traps during the inter-monsoon (April-May)and winter monsoon(Feb-March)periods. Export fluxes of carbon ranged between 14 to 424 mg^-2 day^-1. It was found that export fluxes measured by sediment trap were not consistent with measurement of primary productivity at the same location. The main problem of using drifting sediment traps in the tropical regions is that was swimmers which consumed particles in the sediment traps of died in the sediment trap thereby adding to the measured flux. To overcome this problem dissolved and particulate ²³⁴Th were measured in the water column. Using the ²³⁴Th deficiency in the water column, and Corg/²³⁴Th ratios in the trap material, export fluxes were recalculated. It is possible to get reliable results of export fluxes if the swimmers are separated cleanly from the settling particles. Using a Corg/²³⁴Th ratio in trap material as 0.12 mg/dpm export fluxes pf carbon ranged between 185 to 276 mg m^-2 day^-1. 

34, IGCP 396-3AC,NIO,Goa,India/KAR/26-31 Oct, 1998