Natural and anthropogenic impacts on a macrotidal sandy beach of the Brazilian Amazon (Ajuruteua, Pará): guidelines for coastal management

The Amazon coast presents a diversified landscape, varying from established urban areas with high rates of population growth to vast, well-preserved natural systems with low population density. In the Brazilian state of Pará, both human activities and natural impacts affect coastal resources and the local economy, which is based on tourism and fishing. The aim of the present study was to evaluate the influence of these two processes on the characteristics of a macrotidal beach (Ajuruteua) in northeastern Pará and provide local authorities with guidelines for the implementation of effective coastal management programs. Social and natural variables were assessed between April 2008, and September 2009. The Ajuruteua waterfront is characterized by the presence of precarious wooden structures built on mangroves, dunes and the intertidal zone, with limited infrastructure. Unregulated urban expansion, associated with natural conditions, is the main factor responsible for the erosive processes observed in the northwestern sector of the beach. River discharge and circulation processes are the main factors responsible for the high levels of water turbidity and dissolved nutrients observed in the study. Bacterial contamination is caused by the discharge of untreated domestic sewage, although the rapid turnover of the water in this high-energy environment dissipates the pollution rapidly. Priorities for local environment planning should include: (i) the prohibition of new buildings in risk areas; (ii) the improvement of recreational facilities and the provision of adequate services (public sanitation system and water supply); and (iii) the establishment of a permanent and appropriate water quality monitoring program.