Relation Between Deep Chlorophyll Maximum and Vertical Thermal Structure in the Andaman Sea

Abstract

This study investigates the deep chlorophyll maximum and physico-chemical properties of the water column to delineate the underlying relation between vertical thermal structure and chlorophyll maxima. The biophysical variability in the Andaman Sea can be characterized as (i) enhanced Chl due to mixing and sediment resuspension in Northeastern Andaman Sea (ii) depressed Chl (0 < Chl < 0.5 mg/m3) in the offshore surface waters; (iii) deep Chl maxima (DCM; 0.5 < Chl < 3.3 mg/m3) observed below the surface mixed layer in the depth range 40–80 m; and (iv) well defined oxygen minima (DO < 3 mL/L) below the DCM. The empirical relation between subsurface temperature and Chl suggests a significant correlation (R2 = 0.78–0.96) indicating optimum light and nutrient conditions for deep accumulation of phytoplankton which linearly decreases down the water column. Future work has to be carried out to understand the underlying relationship between temperature and chlorophyll in coastal and shelf waters.