Paropkari, A.L., Hilda João, D.V. Borole, V. Ramaswamy, S.R. Shetye, P.G. Mislankar, V. Fernando, S. Afzulpurkar, G.E. Nampoothiri, P. Marathe, V.D. Khedekar and N. Volvoikar

National Institute of Oceanography, Dona Paula, Goa – 403 004, Tel: 91 0832 2456700, Fax: 91 0832 2456702, E-mail: parop@darya.nio.org

Particle fluxes along the monsoon dominated Western Margin of India

To understand the influence of monsoon on particle and organic carbon fluxes, two sediment traps were deployed for the last two years on the continental slope, off the central west coast of India, at depths of about 200m (shallow trap) and about 1150m (deep trap) coinciding approximately with the upper and lower boundaries of the oxygen minimum zone (OMZ) in the Arabian Sea.

Sediment trap samples collected between December 2000 and February 2002 have been analyzed for total particulate matter, calcium carbonate, organic carbon, biogenic silica and lithogenic matter. Average annual particle fluxes in this slope region are found to be 3-5 times higher as compared to the open ocean. Biogenic matter constitutes 70 to 80% of the total flux. The data shows that enhanced particle fluxes are not only restricted to monsoonal periods but are also observed during inter-monsoon periods. Significant inter-annual fluctuations were also observed in the fluxes of above components. Large seasonal variations in smectite and illite compositions were also observed. These results have bearing on understanding the biogeochemical cycle of carbon.