The fertility of the coastal and estuarine waters is of great concern because of its influence on the
productivity of these waters. Seasonal variations in the distribution of organic carbon, total nitrogen and
total phosphorus in the sediments of Kuttanad Waters, a part of the tropical Cochin Estuary on the south
west coast of India, are examined to identify the contribution of sediments to the fertility of the
aquatic systems. The adjoining region has considerable agricultural activity. The fresh water zones had
higher quantities of silt and clay whereas the estuarine zone was more sandy. Organic carbon, total
phosphorus and total nitrogen were higher in the fresh water zones and lower in the estuarine zones.
Total phosphorus and organic carbon showed the lowest values during monsoon periods. No significant
trends were observed in the seasonal distributions of total nitrogen.
Ratios of C/N, C/P and N/P, and the phosphorus and nitrogen content indicate significant modification
in the character of the organic matter. Substantial amounts of the organic matter can contribute to
reducing conditions and modify diagenetic processes