Cadmium concentrations in the Bahia Blanca Estuary (Argentina). Potential effects of dissolved cadmium on the diatom Thalassiosira curviseriata

Concentrations of dissolved and particulate cadmium were measured in the water of the Bah´ıa Blanca Estuary, one of the most highly industrialised regions in Argentina. Simultaneously, Cd contents were also determined in samples of phytoplankton. Thus, the estuary was characterised from the viewpoint of Cd occurrence. Additionally, a microscale environment was selected within the estuary in order to carry out an ecotoxicological study. Thus, environmental parameters (i.e. temperature, salinity, nutrients, chlorophyll a) were measured weekly at Puerto Cuatreros (in the inner estuary) during winter, when the phytoplankton bloom occurs; during the other seasons sampling was done twice a week. In addition, cells of the diatom Thalassiosira curviseriata – the dominant species in the phytoplankton bloom – were isolated and cultivated in the laboratory. The monoclonal cultures obtained were exposed to increasing concentrations of Cd under controlled environmental conditions and the growth rate inhibition was measured. As a preliminary conclusion it was found that Cd levels in the Bah´ıa Blanca Estuary are significantly lower than the EC50 value for T. curviseriata.