Environmental risk assessment methodology for urban tropical lagoons based on feasible lines of evidence under limited resources conditions: Jacarepaguá Lagoon/Brazil.

Determining environmental risk levels posed to different urban lagoon can provide an important overview regarding the relative severity of the environmental degradation of these ecosystems, increasing the risks visibility, which can be used as an important decision-making tool to prioritize investments. Jacarepaguá Lagoon (JPAL) is part of a coastal lagoon system comprising four interconnected lagoons in Rio de Janeiro city, Southeastern Brazil. Real estate speculation and insufficient sanitation infrastructure resulted in untreated sewage discharge into this ecologically sensitive lagoon system. An Environmental Risk Assessment for Jacarepaguá lagoon was carried out integrating three Lines of Evidence (LoE): (i) Water Quality LoE; (ii) Ecotoxicological LoE; (iii) Ecological LoE to estimate an Environmental Risk Index (EnvRI) for this area. Surface water samples were collected during four bimonthly campaigns at five JPAL sampling points as well as an upstream reference area. The Water Quality LoE based on physicochemical parameters was used to estimate the Water Quality Risk Index (WQRI); the Ecotoxicological LoE based on two chronic ecotoxicity bioassays was used to estimate the Ecotoxicological Risk Index (EcotoxRI); and the Ecological LoE based on the richness and the abundance of phytoplankton taxa was used to estimate the Ecological Risk Index (EcoRI). The final EnvRI was then estimated by integrating these three Risk Indices. The WQRI (0.79 ± 0.07), as well as the EcotoxRI (0.80 ± 0.21), and the EcoRI (0.78 ± 0.13), were all in the range classified as very high. The EnvRI for JPAL was consequently also very high (0.81 ± 0.12), which indicates urgent intervention. EnvRI combined with high concentrations of organic compounds directly affected the diversity of phytoplankton species; however, it was observed that the high content of phytoplankton biomass also represents a part of the organic matter in question. The final goal was achieved: a feasible risk assessment tool available for comparison of different aquatic ecosystems, to facilitate decision making establishing priorities of investments under a limited resources scenario.