Análise da influência da atividade de carcinicultura sobre aspectos hidro-morfológicos e de qualidade da água de corpos d’água costeiros : um estudo de caso no sistema lagunar de Guaraíras, RN

Abstract

In coastal regions occupied by large clusters of aquaculture farms operating with excavated ponds, the combination of water management strategies individually performed in each cultivation unit may generate cumulative effects on estuarine water bodies, which analysis and prediction become of difficult interpretation. In this study, Delft3D model was used to evaluate hydro-morphodynamic processes alterations in a hypothetical coastal lagoon. Further, modeling scenarios were implemented to investigate impacts in the Guaraíras Lagoon System case (RN, Brazil), including water quality modeling analysis. A stochastic generator of shrimp farming effluent discharges was developed, and coupled to a DO-BOD model, in order to represent the regional dynamics of pollutant loads produced during the shrimp harvesting in each pond. Among the results achieved in this work the following finds are highlighted: i) strategies to standardize pond size at different proportions do not expressively change the risk of Dissolved Oxygen depletion in the system; ii) reductions in the periodicity of culture cycles degrade lagoons water quality; iii) in the long term, estuarine water intake operations performed by shrimp farming activity increase sediment importation to the system, but the impact on sedimentological processes is reduced as the lagoon’s morphology approaches an equilibrium state; iv) water exchange operations performed by aquaculture farms may change the expected natural morphological equilibrium state of an estuarine system, especially if carried out synchronously to the local tidal oscillation.