Organic matter content of sediments in continental shelf area of southeast coast of India.

Total organic matter (TOM) content of sediment samples collected from various depths of continental shelf region of the southeast coast of India varied from 0.19% to 7.73%. Higher TOM content and lower median particle diameter could be attributed to the influence of higher riverine flow. Higher values were observed at 100 m depth and above (average 5.29%) and lower values in shallower depths below 100 m (average 3.07%). In the Principal Coordinate Analysis (PCO), the first two axes explained about 83.1% of the total variability. The direction of the vector representing total organic matter was towards 150 m depth. In the Canonical Analysis of Principal Coordinates (CAP) done to confirm the above pattern, the canonical correlation value obtained for the first axis was high (0.9999). The same for the second axis was 0.9995. The direction of the axis representing TOM in this analysis was towards the 100 m depth truly reflecting higher TOM level recorded here (average TOM at 100 m depth-5.81% and at 150 m depth-5.33%). The percentage of samples allocated to the correct group in CAP was 91.67% (33 out of the 36 samples). As the allocation success of samples is substantially greater around 92%, the CAP is explaining greater percentage of variability of TOM than PCO and was found to be quite useful for studies of this nature.