Depositional behaviour of C-org, N, P and K in the surface sediments of two shallow water bodies in a tropical coast, India.

The present paper deals with the distribution of sediment and sediment-bound nutrients in two important coastal lagoons of southern Kerala such as the Ashtamudi Estuarine Lagoon in the Kollam district and the Kadinamkulam Lagoon in the Thiruvananthapuram district. Among the two lagoons, the former is coast perpendicular, and the latter is coast parallel. An analysis of the textural characteristics reveals that, in both lagoons, the estuarine mouth and areas close to it are dominated by sand and sand-rich sediment species, indicating a high-energy depositional regime prevailing the region. On the other hand, the silt and clay dominant arms are almost sheltered and enjoy a low-energy depositional environment. The nutrient and organic carbon contents in the sheltered areas are significantly higher than the most dynamic high-energy estuarine mouth regions. This peculiar behaviour of these coastal water bodies has to be given adequate importance while laying down strategies for the conservation and management of these fragile aquatic systems in the south-western coast of India in particular and tropical coasts of the world in general.