Variação espaço-temporal dos nutrientes nas águas do Furo do Muriá (Curuçá - Brasil)

Abstract

During the last decades, the development of urban-industrial activities has contributed to the increase in the supply of polluting loads to aquatic ecosystems, especially estuarine ones, providing an excessive load of nutrients in the environment. In this way, the development of studies aimed at identifying and quantifying the main nutrient inputs, has contributed positively, providing subsidies for the management of the quality of water resources. The present study was carried out in a tropical Amazon estuary (furo of Muriá ) located in the Northeast of Pará and the micro region of Salgado with the objective of knowing the dynamics of dissolved nutrients (Nitrogen, Phosphorus and Silicate) at the water-air interface and the interaction mechanisms of these nutrients with the abiotic and biotic parameters (chlorophyll a). This system is influenced by seasonality that involves aspects under tidal regimes. For this, the spatial and temporal variability of dissolved inorganic nutrients was evaluated: N-ammoniacal, Nitrite, Nitrate, Phosphate and Silicate together with the physical-chemical parameters through mixture diagrams, stoichiometric ratios and Principal Component Analysis. The N-ammoniacal was the most representative form of NID in both seasons with maximum values (~ 199 μM) subsidizing primary productivity, with a maximum chlorophyll a (122 μg.m-3). The high level of N-ammoniacal was also associated with the release of domestic effluents, fish farming and degradation of organic matter that occur in the mangrove areas along the furo of Muriá. Phosphate among the dissolved nutrients was the one that suffered the most “neutralizing action”, with low concentrations so as not to offer signs of eutrophication. The anthropic influence influenced the silicate concentrations downstream of the system. In general, the results obtained allowed an excessive intake of nutrients to be observed along the furo of Muriá, with fluctuations in their concentrations influenced by seasonality, tides and anthropic activities indicating a dynamic environment, which influences the primary productivity of the region.