Distribution of nutrients in the coastal and estuarine waters of Goa

Abstract

Concentrations of nitrate and phosphate in the coastal waters of Goa varied from 0 to 2.4 mu g at 1-1 and from 0.1 to 2.4 mu g at 1-1 respectively, during post and premonsoon periods. In the estuarine region the nutrients like nitrate and ammonia remained higher than those in the coastal waters. The relation between salinity and nutrients suggest that the fresh water is the main source for the addition of nitrate to the estuary. Seasonal fluctuation in the primary productivity and chlorophyll a values were noticed in the Mandovi estuary and the adjoining coastal waters. The NO3 -: PO4 -3 concentration ratio remained low during post and premonsoon periods when the primary productivity was high. The ratio of change for nitrate and phosphate (Delta N : Delta P) showed a low value of 11 (by atoms). The No3 - : PO4 -3 concentration ratio and the assimilation ratio clearly showed that the nitrate is deficient in these waters during post and premonsoon periods. But the high levels of ammonia (ranging between 0.23 to 7.8 mu g at 1-1 available in these waters could suggests that this nutrient compensates to some extent the observed deficiencies of nitrate