Hydrography and plankton as indicators of marine resources

Available data on the standing crop of phytoplankton and zooplankton are presented for the Indian region and hydrographical factors such as upwelling, divergence, convergence, currents, nutrients responsible for production of plankton, and distribution of plankton in time and space are dealt with. Role of southwest monsoon and the magnitude of the intense bloom of phytoplankton during this period are pointed out. The significance of the distribution of plankton to other organisms in the food chain including fish is indicated. Attempt is made to correlate the fisheries of the region with the above several factors and point out the potential resources and their location. The possibilities of using some of the factors as indicators of fishery resources are examined. Certain similarities in the hydrological features, production of plankton, its distribution and fisheries occurring here and elsewhere are reviewed. It is also suggested that the high production of plankton which is also rich in oil—a product of the photosynthesis of the diatoms which form the bulk of the synthesizers of the organic matter-is responsible for the rather extensive oil deposits in the past geological ages in the northern Arabian Sea region which we are exploiting now; this is a continuing process. It is also pointed out that the general pattern of circulation of water during the period of heavy bloom of plankton, viz., south-west monsoon in the Arabian Sea, is clockwise which is likely to lead to anticyclonic eddies on a large scale, particularly around Saurashtra coast which would have the effect of taking plankton to the bottom leading to gradual deposition of matter