Large branchiopod assemblages common to Mexico and the United States

Cu, Cd, Zn and Pb concentrations in both dissolved andparticulate phase were assessed during 1995. DataQuality Assurance was an integral part of this studyand involved all major steps of the analysis proceduresuch as sampling, sample handling, preconcentrationand determination. Desorption and redox processes clearly control thedissolved Cu and Cd profiles. Mobilisation ofdissolved Zn is small and essentially restricted tothe low salinity area and the late spring survey.Dissolved Pb shows the clearest dilution pattern. Theparameters representative of these processes(dissolved oxygen and salinity) also correlate verywell with the particulate metal profiles. In addition, the plankton activity (expressed by thechlorophyll-a levels) may influence the dissolved andparticulate metal profiles. In combination withdesorption and redox processes, seasonal variationswere induced. This revised version was published online in July 2006 with corrections to the Cover Date.