Physico-chemical parameters of the SW and post NE monsoon (2009) seawater along the continental slope, Tamil Nadu, east coast of India, Bay of Bengal

Variations in sea water temperature, salinity, light intensity and availability of nutrients strongly influence the phytoplankton distribution that forms an important part of the coastal food chain. In this paper, we present the results of the physico-chemical parameters and nutrient concentrations in seawaters sampled during the 2009 South West (SW) and post North East (NE) monsoon periods along the continental shelf from Chennai to Nagapattinam, east coast, Tamil Nadu. This study was conducted to assess the status of the coastal biogeochemical environment and for this purpose, seawater samples were collected from the sea surface and also at varying depths (surface to 150 m depth) at six different locations. The nutrient analyses and the CTD data reveal a distinct variation with water depth along the continental slope and also the physico-chemical properties of seawater are not homogenous. The observed values of nutrients for the post NE monsoon period are low compared to the SW monsoon period. Contour plots indicate seasonal and spatial variations in physico-chemical parameters along the continental shelf of the east coast of India. The data suggests that during the 2009 SW monsoon period, a significant increase of freshwater input into the Bay of Bengal could have elevated nutrient concentration compared to that observed during the post 2009 NE monsoon.