UNRAVELLING THE PRODUCTIVITY FLUCTUATIONS IN THE COASTAL ENVIRONMENT – CAUSES AND EFFECTS

An attempt has been made to develop a holistic understanding of factors determining the variability in primary productivity along the coastal waters of west coast of India. Analysis revealed that, marked asymmetry in temperature and phytoplankton biomass was observed between the south-west and north-west coast of India. Inter-annually there are some uncertainties observed in the seasonal rise and fall of sea surface temperature (SST) and productivity pattern along the west coast of India. This changes in productivity pattern and temperature probably will have an impact on carrying capacity of coastal waters of eastern Arabian Sea.

A slab physics model "EMPOWER" with utility of seasonal oscillation of mixed layer and temperature are used in this study for the understanding of primary productivity along the west coast of India. Results of analyses of euphotic zone depth, mixed layer depth, temperature and nutrients revealed that nitrates acts as the limiting factor for determining the productivity along the eastern Arabian Sea. Along the south-west coast of India, even though the mixed layer was limited to the vicinity of euphotic zone during both the summer and winter monsoon, the coast manifested enhanced productivity only during the summer monsoon. This was due to the entrainment of nitrates into the mixed mixed layer due to the upwelling during the summer monsoon (Figure1&2). During the winter monsoon the coast was chracterised by downwelling and nitrates were detrained from the mixed layer. The productivity information of coastal waters can be an indicator of the carrying capacity of the aquatic environment available for mariculture operations.