Lagoas costeiras urbanas sujeitas a impactos antrópicos via aporte de efluentes: aspectos gerais e a concentração de metano na Lagoa Imboassica, Macaé, RJ

Coastal lagoons occupy 13% of the planet’s coast. In Brazil, they occur along the entire coast, with emphasis on the states of Rio de Janeiro and Rio Grande do Sul. Due to their geographic location, coastal lagoons are subject to several anthropic impacts. Multidisciplinary actions to mitigate these impacts are essential for changing the current conditions of coastal lagoons on the Brazilian coast. For this, it is necessary to have a better knowledge of the impacts caused and their consequences for the functioning of these ecosystems. Sewage input is one of the environmental impacts and is directly related to the increase in ecosystem productivity. In turn, the higher the aquatic productivity in lentic water, the greater the emission of methane into the atmosphere. In an effort to better understand the influence of eutrophication on the methane cycle, we analyzed the concentration of methane in the sediment in four regions of the Imboassica lagoon that have different environmental characteristics. In each region, 10 cm sediment cores were collected, which were subdivided into five 2 cm profiles. We analyzed the methane concentration in the sediment’s interstitial water in each profile. We observed that the lagoon regions influenced by the sewage supply had the highest concentrations of methane in the sediment. We conclude that sewage treatment is essential to mitigate eutrophication and, consequently, methane production in the ecosystem.