Geochemical distribution of forms of phosphorus in marine sediment of Bay of Bengal, southeast coast of India

Sediment samples were collected from three transects in the continental shelf region (up to 30km offshore) between Chennai to Marakkanam. Sedimentary parameters such as sand, silt, clay and organic carbon percentage were analyzed in order to find out their relation with various phosphorus fractions. Sediment was found to be predominantly sandy in nature with low silt and clay content. Among all the fractions (loosely bound- Lo-P, calcium bound- Ca-P, iron bound-Fe-P, aluminum bound- Al-P and organically bound- OP), Ca-P fraction constituted the largest portion (71.38%) followed by OP (16.16%). Bioavailable fractions of phosphorus ranged from 9.3 to 36.2% (avg. 20.9%) of the total phosphorus (TP) during the present study. Total phosphorus content in the offshore sediments ranged between 469.35 and 1219.34 mg/kg with an average of 824.66 mg/kg. The abundance of the major forms of P in the surface sediments of Kalpakkam coast followed the order: Ca-P > OP > Al-P > Lo-P > Fe-P. Cluster analysis clearly showed that all the three transects were different from each other as they formed three different clusters.