Speciation and bioavailability of dissolved copper in different freshwaters: comparison of modelling, biological and chemical responses in aquatic mosses and gammarids.

Biological and chemical measurements were performed in mesocosms to investigate the bioavailability of copper, with a greater emphasis on the effects of competing ions and copper speciation. Measurements were achieved in three different natural waters for two aquatic species (Gammarus pulex and Fontinalis antipyretica) along a copper gradient concentration: natural concentration, spiked at 5 and 15 μg L(-1). Aquatic mosses exhibited high enrichment rates that were above the background levels compared to gammarids. The accumulation of copper in F. antipyretica is better correlated to the weakly complexed copper concentrations measured using differential pulse anodic stripping voltammetry (DPASV) and diffusive gradient in thin film (DGT) than to the free copper concentration measured using an ion selective electrode (ISE). In unspiked natural waters, the presence of dissolved organic ligands strongly controls the metal speciation and consequently largely minimised the impact of competing cations on the accumulation of Cu in mosses. Furthermore, the BioMet Biotic Ligand Model (BLM) successfully describes the site-specific copper bioaccumulation for the freshwater mosses studied. However, the comparison of the results with a previous study appears to indicate that the adsorption/desorption of Cu in mosses is impacted by seasons. This highlights a limit of the BioMet model in which the physiological state of aquatic organisms is not considered. No toxic effect of Cu exposure on lipid peroxidation was observed in the mosses and gammarids regardless of the site and the concentration considered. However, the oxidative stress measured in the mosses via their guaiacol peroxidase (GPX) activity increased in the case where internalised Cu reached maximal values, which suggests a threshold effect on the GPX activity.
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