In order to determine the distribution of various parameters like temperature, dissolved oxygen, pH, nutrients, pigments also salinity, in relation to different seasons of the year, monthly samples were made from the surface waters of the Manzanares river, Cumaná, Venezuela during a period of 9 months (November 1988-July 1989). The distribution and change in dissolved oxygen and pH indicated the existence of high concentration of organic matter in the estuarine zone, which has its origin from several external sources to the ecosystem. Nitrates in the river waters were found in relatively high concentrations, while ammonia and orthophosphate concentrations showed during the study period, a sure supply in the inner area of the system. The silicates showed high concentrations at the freshwater level, its distribution being conservative, exepting May, when a decrease in the concentrationswas observed throughout the estuary. High turbidity and reduced permanence of the waters are 2 factors which limit phytoplankton production and consequently the consumption of nutritive elements in the high and intermediate zone of the ecosystem.