The eutrophication process in the lagoon systems of eastern Rio de janeiro investigated through the analysis of sedimentary phosphorus and historic of basin occupation

Abstract

Lagoons along the eastern coast of Rio de Janeiro serve as vital corridors for the preservation of marine and coastal biodiversity. However, these ecosystems are facing substantial threats stemming from environmental degradation and cultural eutrophication. This study aims to investigate the process of eutrophication by analyzing sedimentary environments in coastal lagoons located in the municipalities of (Itaipu) Niterói, (Fora) Saquarema, and Araruama (São Pedro da Aldeia). The investigation involves the analysis of sedimentary records collected at various times in each lagoon, with particular focus on phosphorus content and grain size distribution, emphasizing silt, clay and sand fractions. These analyses are correlated with the historical population growth in the drainage basins. Our working hypothesis posits that the impacts of urbanization on the degradation of lagoon systems are archived within the sedimentary records. It is anticipated that the extent and magnitude of these impacts are correlated with population density. The notable increase in demographic density can be attributed to the inauguration of the Rio-Niteroi Bridge, resulting in a significant influx of residents and tourists into the coastal region in question. This hypothesis is supported by census data, which reveal substantial population growth in coastal areas. In addition, this study utilizes ordination analysis, specifically Principal Component Analysis (PCA), to classify sedimentary layers based on their depositional characteristics. The PCA allows for the categorization of sedimentary data, unveiling changes in erosion and sedimentarion patterns. Remarkably, our research stablishes a significant correlation between the escalating total phosphorus fluxes and population growth, thereby providing valuable insights into the historical progression of cultural eutrophication within the coastal lagoon systems of eastern Rio de Janeiro. Overall, our findings contribute to an enhanced understanding of how urbanization and population dynamics have influenced the eutrophication process within there vital coastal ecosystems over the past five decades.