Avaliação de risco ecológico da Lagoa de Jacarepaguá - RJ

Abstract

The Jacarepaguá Lagoon (LJPA) is part of the Baixada de Jacarepaguá lagoon complex occupying an area of 3.7 km2, which has suffered over the years with the constant release of untreatetd sewage due to the increasing population density without urban planning and increasing land speculation in the drainage basin. In this area there are ecosystems of restingas, marshelands and mangroves, which are exposed to the impacts resulting from the discharge of sewage. The Ecological Risk Assessment (ARE) is an important tool for the management of contaminated areas, since it includes the identification and assessment of the adverse effects of pollution, based on chemical, physical-chemical and biological analyzes. The objective of this study was to develop an Ecological Risk Assessment (ARE) for the Jacarepaguá Lagoon, at different levels of biological organization, through the water quality, ecotoxicological and ecological lines of evidence (LoE). Four campaigns to collect surface water samples were carried out throughout the year 2019, every two months, at six sampling points, one of which, being the reference area located in the Camorim reservoir and the other five points, located within the LJPA (four close to the margins and one in the central area). The Water Quality LoE was based on the physical-chemical parameters for calculating the Water Quality Index (AQI). The ecotoxicological LoE was based on the results of the chronic ecotoxicity tests carried out with the microalgae C. vulgaris and the microcrustacean C. dubia. The ecological LoE was based on the analysis of richness and abundance of algae species in the surface water samples. The environmental risk was calculated based on the integration of the risks obtained with all LoE. Regarding water quality risk, two points presented the highest values during the monitoring period. As for ecotoxicological risk, three points showed a very high risk in 75% of results, with the month of June having the lowest risk, even so, varying from moderate to high. The ecological risk was the highest at two sampling points with averages of 0.78 and 0.74, with 40% of the results in June indicating a very high ecological risk. With 55% of LJPA points presenting an integrated environmental risk classified as very high during the monitoring period, it was possible to conclude that LJPA was in advanced process of eutrophication and degradation, demanding urgent actions for the management and mitigation of ecological risks current and future in the region. The chosen ARE model proved to be an effective tool, enabling a more general and at the same timea detailed risk assessment of Lagoa de Jacarepaguá - RJ.