Bragança's socioeconomic situation is highly dependent on estuarine and marine biological resources that are influenced by tidal cycles and climatology. Field measurements (hydrological, hydrodynamic and microbiological variables) were taken in the most urbanized zone from Caeté estuary to characterise the quality of the local environment. During the dry period, the estuary was more eutrophic and presented the highest temperature (30.5 • C in Oct./06), salinity (17 psu in Feb./07), pH (8.24 in Feb./07) and fecal coliform (>1000 MPN/100 ml in Dec./06 and Feb./07) values. The phytoplankton Cyclotella meneghiniana, Coscinodiscus centralis and other r-strategist species were observed. The lack of basic hydric canalization was responsible for the local contamination, especially during the dry period when more concentrated wastewater from the city was emitted into the estuary, showing the human influence on the reduction of local estuarine water quality. In Bragança, the fishery is considered one of the main economic activities so, this contamination is worrisome because a large part of the local economy depends on biological resources and, thus, the contamination could negatively affect the environmental health of this Amazon ecosystem.

Estuarine waters are usually eutrophic due to nutrients input derived from natural and anthropogenic sources. In the Caete Estuary, nutrients and thermotolerant coliforms input is intensified by the absence of a public sanitation system and by mangrove outwelling. This input is more accentuated in the upper sector of the estuary where 90% of the local population is concentrated and a high incidence of commercial activities (public markets, ice factories and boat repairing among others) is located. As a consequence, eutrophic waters with high concentrations of thermotolerant coliforms (up to 1100 MPN/100 ml) were observed during the dry season when dilution and/or advection are less effective. Eutrophication, though less pronounced, also occurred in the other sectors (middle and lower), but these results seem to indicate that this could be a natural condition of an Amazon region which is naturally enriched with a high amount of nutrients. On the other hand, nutrient concentration values in the upper sector are similar to those found in other highly populated and industrialized Brazilian estuaries. Taking into account that the population increases by about 20% per decade in the region, this growth may lead to a significant increase in human pressure and impacts on the area, mainly during periods when the estuary is more susceptible to retaining nutrients (e.g., during the dry season). In order to improve water quality, the DPSIR framework was used as a guide for proposing potential measures to be implemented in the Caete Estuary based on (i) urban planning to control sewage discharges, (ii) construction of water treatment infrastructures to reduce untreated effluents inputs and (iii) water use regulations as a function of the current water quality.Peer ReviewedPostprint (author's final draft

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Este trabalho foi realizado na praia de Ajuruteua, localizada a 36km da cidade de Bragança, e teve como objetivo caracterizar a influência dos processos costeiros de origem natural e antrópica, sobre as variações morfológicas nesta praia. Desta forma, dois perfis de praia foram monitorados e um levantamento completo sobre as formas de ocupação territorial foi realizado. A praia de Ajuruteua está dividida em dois setores, o setor SE (acrescivo) e o setor NW (erosivo). A ocupação territorial ocorre sobre dunas e de forma desordenada, principalmente no setor NW, fato que vem acelerando os processos erosivos próximos à linha de preamar máxima e, como consequência, novas ocupações estão sendo realizadas em áreas de manguezal e marisma. A falta de planejamento na ocupação territorial, de associações comunitárias e de políticas públicas voltadas para o desenvolvimento social e para o turismo na região vêm gerando sérios problemas ambientais e sociais que repercutem na qualidade de vida da população usuária e na degradação do meio ambiente. A elaboração de planos/programas costeiros são necessários para racionalizar a ocupação territorial e impedir/minimizar os processos erosivos em Ajuruteua. Palavras-Chave: dinâmica praial, ocupação territorial e praia Amazônica brasileira.

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