Fonseca, A. L., Newton, A., Cabral, A.
Natural and anthropogenic pressures drive coastal eutrophication worldwide, depending on the system's physical and biogeochemical dynamics in multiple spatial and temporal scales. Understanding the complexity of this process is essential to support management efforts and sustainability. Nutrients load to the Bay of Santa Catarina Island (BSCI), an important area for mollusc aquaculture, fisheries and tourism in Brazil, were assessed to identify the pressures of the eutrophication process. An updated Driver-Pressure-State-Impact-Response framework was used to facilitate the understanding of the relationship between human activities and impacts on human welfare. Pressures from runoff and effluents from combined sources resulted in inputs of 1998 t N.year−1 and 155 t P.year−1 to the system. The watersheds were characterized as meso-active to eury-active for both N and P yields. In addition to the local anthropogenic pressures, meso-scale events, such as the seasonal influence of the Plata Plume River, act as an external source of nutrients, sometimes associated with harmful algae bloom events. The results show that eutrophication and its symptoms could impact 85% of the ecosystem services of the region. Management of eutrophication at BSCI requires integrated actions between the nine municipalities of the watershed, but there are obstacles in environmental legislation and political interest to promote it. This study provides the scientific basis for stakeholders and decision-makers to establish priorities and actions in coastal municipalities to minimize eutrophication.