Spatio-temporal variation of metal concentrations in estuarine zones of the todos OS Santos Bay, Bahia, Brazil

The knowledge of metal behavior in the aquatic environment is important for understanding its effects in estuarine zones and mangrove areas. These important and precious ecosystems are affected by many different factors that may vary temporally and spatially. The present study investigated the spatial and temporal variation of physicochemical parameters (pH, dissolved oxygen, temperature, salinity, etc.) and metal concentrations (Zn, Fe, Ni, Cu) at three different locations along the Todos os Santos Bay, North East Brazil, by analyzing surface water, sediment and mangrove oysters (Cassostrea rhizophorae (Guildin, 1828)). Metal concentrations in surface waters and sediments differed between the three sampling times (March and August 2014; January 2015) and locations and were affected by fluctuating physicochemical parameters, which in this way also affected the metal bioconcentration in the oysters. The pH of the surface waters, for example, increased from the 1^st to the 3^rd sampling time while the concentrations of Zn and Fe decreased during the same period. The sediment concentrations of Zn and Fe were strongly correlated with organic matter content. These results suggests that seasonality as well as the different water and sediment properties along the bay directly affect metal concentration and bioavailability in the environment.