Particulate organic carbon fluxes: compilation of results from the 1995 USJGOFS Arabian Sea Process Study

Organic carbon fluxes in the Arabian Sea were measured as a function of dep th, season and distance from the coast of Oman. We present here a compilati on of measurements of primary production, water-column export flux and sedi ment accumulation of organic carbon over a full annual monsoon cycle on a 1 500-km transect from the coast of Oman toward the central Arabian Sea. This represents an integration of measurements spanning one day (primary produc tion) to 1000 yr (sediments) and gives a broad overview of organic carbon r emoval and remineralization in the highly productive, seasonally varying re gion of the northern Indian Ocean. Organic carbon fluxes decreased from the surface to the sediments by a factor of 500-10,000, with the largest rates of change in the upper ocean and at the sediment-seawater interface. Organ ic carbon fluxes generally decreased with distance offshore, with the large st gradient between surface and seafloor being at the offshore station. Sed iment accumulation rates of organic carbon differed by a factor of 40 betwe en nearshore and offshore, while primary productivity varied only by a fact or of 2. The decrease in carbon flux with depth that occurs between the dee pest traps and the sediment becomes a greater proportion of the total loss with increasing distance from shore. Thus, the influence of processes at th e sediment-water interface on the proportion of primary productivity preser ved in the sediment increases offshore relative to upper water column proce sses. Carbon fluxes changed greatly with season, with highest fluxes during the Southwest Monsoon. Export fluxes varied more with season than primary productivity or mid-water fluxes. (C) 1998 Elsevier Science Ltd. All rights reserved.