Assessing the impact of dredging on phytoplankton association of Aratu harbor, in Todos os Santos Bay, Bahia State

Abstract

In the area of influence of dredging to deepen the Aratu harbor, in All Saints Bay, the pattern of the structure of phytoplankton association (composition, richness, relative abundance, frequency and density), oceanographic structure (temperature and salinity), nutrient (phosphorus and nitrogen) and quality water quality (pH and dissolved oxygen) and trace-elements were used aiming at a comparative interpretation of the effects of dredging, which would be used to assess the environmental recovery of the pelagic ecosystem. There were two campaigns in February (late dry season) and September (end of rainy season), in ebb and flood. We identified 50 species, before the dredging process and 40 species during dredging, the Bacillariophyta were the representatives with the highest relative abundance and richness compared to other groups of microalgae. This study indicated a decrease of species richness and density increase during the dredging. The composition of phytoplankton association reflected the observed temporal variability in oceanographic characteristics of the water caused by the gradient of rainfall and water quality probably due to the dredging activity and a clear separation between the phase of dredging (dry season) and phase Pre-dredging (rainy season).