Limnology of reservoirs in the Southeastern part of São Paulo State, Brazil. IV. Nutrients and chlorophyl a.

Abstract

This research was based on quarterly determinations made at one station in each one of 17 reservoirs. It was studied the relation among ammonia, nitrite, nitrate, dissolved inorganic and organic phosphate, free CO₂, bicarbonate and chlorophyll a concentration. All variables presented variation among the sampling time showing higher values in the warm and raining season. It was also observed an alternation among the nutrients which limited the phytoplankton development in each different time or reservoir. Billings Complex Reservoirs (Pedreira, Riacho Grande and Rio das Pedras) showed very high values of nutrients and chlorophyll a concentration and a relationship between those two parameters was not valuable. Although Itapeva showed low values of ions, it was the reservoir in which (after the Billings Complex) the chlorophyll a concentration was higher. This value possibly was related to the interaction between N and P than to the availability of the other elements. Guarapiranga, Itupararanga and Alecrim reservoirs showed low values of chlorophyll a, total CO₂, and phosphate concentration but without evident relation among these concentrations. In Itupararanga, Águas Claras, Juqueri, Batista and São José, the nitrogen compounds seemed to be more limitative than the phosphate to the phytoplankton development.