Organic matter compounds as a tool for trophic state characterization in a hypersaline environment: Araruama Lagoon, Brazil

Araruama Lagoon, located in Rio de Janeiro (SE, Brazil), is considered the largest hypersaline lagoon in the world. Over the last decades, this environment has been influenced by urban growth around its margins, which has consequently led to the discharge of untreated sewage, particularly during the summer season (December-March). Excessive nutrient discharges may lead to the rapid enrichment of organic and inorganic nutrients and consequently, eutrophication. Within this context, organic matter quality and amount evaluations become an essential tool to assess the trophic state of coastal environments. Therefore, the present study aims to characterize the trophic state and define the depositional dynamics based on biopolymer content (carbohydrates, lipids and proteins), total organic carbon, total sulfur and sediment granulometry at the Araruama Lagoon region affected by urban activities (Itajuru Channel and adjacencies). The integration of physio-chemical water and sediment data allowed for the identification of four regions presenting different trophic condition, namely the Itajuru Channel - sandy with high hydrodynamics and undergoing marine influence; a region influenced by salt-production activity; the innermost region, presenting high protein concentrations originating from microbiological activity and the most eutrophic area, located in a marina activity region, marked by high anthropogenic organic matter levels.