Avaliação do estado trófico da água da Lagoa de Extremoz, RN, Brasil.

Abstract

Eutrophication can be characterized as the process of water enrichment by nutrients, especially phosphorus and nitrogen, resulting in increased primary productivity. This process is a progressive degradation of water quality that, in addition to reducing the supply of adequate water for different uses, increases the costs of treating this resource for public supply. Classifications of trophic status are important for study and maintenance of water bodies, as we know that eutrophication is very harmful to water quality and monitoring of trophic level allows an essential diagnosis to promote the efficient management of water resources. Extremoz Lake is a natural system, used for water supply of the northern zone of the municipality of Natal, RN. The aim of this work was to evaluate the trophic state of this source according to the limnological variables. The sampling period was from October 2017 to June 2018. Considering two methods of classifying trophic status categories, the total phosphorus variable of the study period (2017-2018) classified the lake as a mesotrophic system, whereas chlorophyll- to a eutrophic system. Comparing with previous studies it was possible to verify that the Extremoz Lake is undergoing a gradual process of eutrophication. Although total phosphorus concentrations do not classify the reservoir as eutrophic, water already presents high rates of chlorophyll-a, indicating high algal biomass for this parameter that is more representative for the consequence of eutrophication.