Heavy Metal Concentrations Found in Seston and Microplankton from an Impacted Temperate Shallow Estuary along the Southwestern Atlantic Ocean

Heavy metal concentrations (Cd, Cu, Cr, Fe, Mn, Ni, Pb, and Zn) were studied in the Bahia Blanca Estuary (BBE), one of the most anthropogenically disturbed estuaries in the SW Atlantic Ocean. This study evaluated metal concentrations in the microplankton and seston for the first time, as well as their role in the transport of contaminants in a disturbed coastal environment of the SW Atlantic. Spatial patterns of metals in suspended particulate matter (SPM; seston > 0.45 mu m) and microplankton (20-200 mu m) were analyzed at sampling sites located at sewage or industrial discharges and, also far from this area, during warm months in 2012 and 2013. Dissolved inorganic nutrients, particulate organic matter (POM), and chlorophyll alpha (Chl-alpha) were also analyzed. The POM and Chl-alpha concentrations were higher near to the sewage discharges; however, metals showed different concentrations between sampling site stations. Those located far from human disturbances showed similar levels to the sites at the sewage or industrial discharges in some cases. In general, the SPM had higher concentrations of metals than the microplankton. In particular, Cr presented important levels in this fraction, which was potentially associated with industrial discharges. On the other hand, a contrasting partition was found for Pb, Zn, and Cu that exhibited higher levels in the microplankton-net material. The high levels of Pb in the microplankton of the BBE may indicate a high availability of this metal in the environment and high uptake rates, with potential health risks to humans and marine life attributable to its toxic effects.