Avaliação do gradiente ambiental em um rio da planície costeira neotropical sujeito a múltiplos estressores

Abstract

Coastal aquatic ecosystems are subject to various changes resulting from human activities, particularly the removal of riparian vegetation, pollution, urbanization, and biological invasions. This study aimed to assess environmental conditions and identify a gradient of anthropogenic disturbance in the Guaraguaçu River, located on the coastal plain of southern Brazil. To this end, data on land use and land cover were collected, water and sediment characteristics were analyzed, and a rapid physical habitat assessment protocol was applied. Sampling was conducted quarterly throughout 2024 at 22 sites along the main channel of the Guaraguaçu River and two of its tributaries, the Pery and Pombas rivers. Environmental variables were summarized using Principal Coordinates Analysis (PcoA), and axis scores were used to determine the environmental gradient. The results revealed a clear gradient in environmental conditions, likely driven by anthropogenic pressures throughout the watershed. Conductivity, salinity, ammoniacal nitrogen, and orthophosphate were the variables that contributed most to the determination of the environmental gradient. The highest values of these parameters were recorded in the Pery River tributary and downstream of its confluence with the Guaraguaçu River, indicating a decline in the environmental quality of this tributary and, consequently, of the downstream region in the Guaraguaçu River basin.