Diagnóstico geoambiental da Lagoa de Maricá (RJ) como subsídio as formas de uso e ocupação do litoral

Abstract

The present study aimed to contribute to the understanding of the anthropic impacts in the Lagoa de Maricá, as a subsidy to the forms of use and occupation of the coast. For this purpose, the objective is to identify the main environmental problems caused by the various activities around the lagoon. Anthropogenic impacts on coastal lagoons can cause eutrophication and contamination of this environment through the discharge of untreated sewage, in addition to generating public health problems. Damage to ecosystems in the lagoon system tends to jeopardize the fishing activity, which has been handmade by local fishermen for more than a century. The establishment of measures aimed at coastal management necessarily implies the knowledge of the characteristics of an impacted area, its specificities and the sources directly responsible for the degradation. It is in this sense that it is important to identify the main problems related to the forms of use and occupation of this coast and the impacts on the lagoon systems, especially inMaricá Lagoon, from the analysis of the physicochemical parameters and nutrients of water and chlorophyll a . The results allowed to characterize the parameters temperature, pH, dissolved oxygen, salinity, turbidity, electrical conductivity, Eh at different points in the Maricá Lagoon, in the dry and rainy seasons. The concentrations of nutrients were analyzed for nitrite, nitrate, ammonia, total nitrogen and phosphate. The levels of chlorophyll a and feopigments were also verified in this study. The integration of the results allowed to identify in the lagoon two sectors with physico-chemical characteristics and nutrient concentrations above that established by CONAMA 357 (2005) for this environment type. The northwest sector of the lagoon, near the mouth of the São Bento channel, is the most worrisome. In this area, higher values were observed for the majority of the analyzed parameters and the lower values of dissolved oxygen. This place is visibly degraded, with plenty of solid materials in the water, which presents dark color and strong smell of decomposition. The highest concentrations of nutrients were observed in the same sector of the lagoon, probably due to the higher nutrient load from untreated sewage in this area. The northern portion of the Maricá Lagoon, with emphasis on the area near the mouth of the Mumbuca River, also presented high concentrations of nutrients when compared to the other areas. In the north margin is great concentration of houses and condominiums. The values of the analyzed parameters and nutrient concentrations gradually decrease towards the south and southeast of the Maricá Lagoon, where the Maricá APA and the Zacarias Fishermen's Community, respectively, are located.