The main objective of the thesis is to study the disribution and seasonal variation of the nutrients in association with the productivity cycles.The variations observed are related with the physical forcings.N:P ratios shows variations in coastal and open oceanic environments.The value of 16:1 is observed in open ocean.But in coastal areas it shows fluctuations due to the proximity of land which distubs the normal pattern of ratio.Analysis of plankton collected from costal areas shows a ratio of about 15:1,which shows similarity in the ratio from other parts of Indian ocean.No active sites of denitrification was observed in the sudy area irrespective of seasons.Even though the area receives a large volume of fresh water which is rich in nutrients it cannot be brout back to surface waters due to the presence of narrow shelf.This together with heavy cloud coverage makes the area less productive when compared to Arabian sea.Analysis of a few trace metals are done to study the biogeochemical process involving it.They show surface depletion and bottom enrichment showing there involvement in the bio-geochemical cycling.The particulate and dissolved trace metals concentrations are correlated to understand the possible transfer of metals in between them.Trace metal distribution in zooplankton from different depths are studied to find which metal is being accumulated by them.Analysis of total phosphorus shows that even at 1000m depth organic phoshorus is there with slight decomposition.The surface layers show higher amount of organic phosphorus than middle layers.