Numerical Simulation of Plankton Dynamics and its Sensitivity to Seasonal Variations in Freshwater Forcing

A coupled physical-biogeochemical model is developed for Bay of Bengal (BoB) to simulate the plankton dynamics and examine its sensitivity to seasonal variations in freshwater forcing. Satellite-derived chlorophyll-concentration data is assimilated numerically using OA-method and SOR-algorithm for the model input. Intensification of bloom is marked on the western coast of BoB during August-September due to increased nutrients supply from runoff and wind-driven upwelling whereas in eastern coast two peaks of plankton biomass are observed in March followed by September. Apart from the coast, bloom intensification in open and southern part of BoB are linked with upwelling, entrainment-detrainment events and advection processes. Sensitivity experiments are performed based on Exp1, by doubling the freshwater discharge in Exp 1- FD D, increases the bloom by 60-65 percent; halved in Exp1-FDH reduces the bloom by 25-15 percent signifies that the freshwater plays a dominant role along the coast but nonlinearly related to plankton dynamics.