ORGANIC-CARBON AND HUMIC-ACID IN SEDIMENTS OF THE ARABIAN SEA AND FACTORS GOVERNING THEIR DISTRIBUTION

Organic carbon and humic acids in the sediments of the Arabian Sea sho w distinct regional variations to the south and north of 15-degrees-N latitude. Significant variations are also observed from the shelf of t he slope regions. Organic carbon and humic acids are enriched on the s lope compared to the inner and outer shelf. While upwelling, primary p roductivity and redox conditions at the bottom are known to influence organic matter accumulation in sediments, bacterial population and sed iment texture also contribute to the preservation of organic matter an d humic acids. A positive correlation (r = 0.716) between total organi c carbon and humic acid content in the sediments indicates fairly favo urable conditions for the humification of organic matter. The C/N rati o indicates more terrigenous matter on the shelf, whereas organic matt er of planktonic origin seems to dominate the slope region.