Ostras (Crassostrea gasar) como biomonitores de contaminação costeira no estuário do rio Paciência, na margem equatorial amazônica

Abstract

The present study evaluated the distribution of metals (Al, Cd, Cr, Cu, Fe, Mn, Pb and Zn) in oysters (Crassostrea gasar) along physical and chemical gradients under different conditions of drought and rainfall in the river estuary. Patience (ERP). The determination of the physical and chemical parameters of surface and bottom water samples, such as salinity, temperature and dissolved oxygen (DO) were recorded in situ. For pH determination, surface and bottom water samples were stored and preserved on ice for laboratory determination. Metal concentrations in oysters were determined by Plasma Optical Emission Spectrometry (ICP-OES). The results showed that the physical and chemical characteristics of ERP waters varied seasonally and spatially. Behavior clearly driven by rainfall, where together with the estuarine hydrodynamics, regulated by semidiurnal macro tides, altered the analyzed parameters. The metal bioaccumulation results showed that the elements Al, Fe and Zn presented the highest bioaccumulation concentrations in oysters and a decreasing concentration gradient with increasing salinity and pH. The elements Cd, Cu and Pb had a different behavior, where the accumulation may be occurring via MPS or diffuse sources. Cr and Mn showed no direct influence of ERP geochemical patterns. The comparative analysis with estuaries considered contaminated in the world showed similarities regarding the accumulated metal levels and showed that the ERP oysters may be susceptible to reproductive implications when compared to the world literature. In addition, the accumulated Cr and Zn levels in the oysters were above the maximum limit allowed by ANVISA in almost all sampled points and periods, revealing possible implications for public health. Thus, it is evident the need to monitor the levels of metals in oysters, studies that identify the clearance time for them to be consumed by the population and studies that identify the population effects of the accumulation of these metals in oysters ERP.