Observations on physico-chemical variability of seawater along Tamil Nadu coast, India onboard CRV Sagar Purvi

Abstract

Parameters that define the environmental variables, such as, phytoplankton biomass, chl-<em>a</em>, and nutrient concentration have been studied and analyzed during July 2017. During this study, vertical distribution of physico-chemical and water quality parameters has also been analyzed. Decrease in water temperature and dissolved oxygen from the surface to deep water up to the thermocline and oxycline were observed, which would be in relation to oxygen minimum zone. At the depth of 100 m, the concentration of chl-<em>a</em> is found high as compared to the surface water. The estimation of deep chlorophyll maximum has been chosen as a major investigation in this study. Moderate and high chl-<em>a</em> concentration (0.5-2.8 mg m^-3) regardless of less NO₃ flux (0.01-0.6 µM) have been recorded through <em>in-situ</em> and satellite observations. The concentration of SiO₄ (5-35 µM) is likely enhanced in the vertical and surface water productivity. Principal component analysis and multiple linear regressions were carried out in order to determine the difference of the variables between the surface and deep water.