Investigation and prediction of the biotoxicity of Cu2+ to Chlorella vulgaris: modification of the biotic ligand model.

Abstract

The increased copper ion (Cu2+) concentrations in aquatic ecosystem significantly influence the environmental quality and ecosystem safety, while information on the Cu2+ biotoxicity to aquatic microorganisms and the models for biotoxicity prediction are still unclear. In this study, the toxicities of Cu2+ to Chlorella vulgaris under different environmental conditions (e.g., Na+, K+, Ca2+, Mg2+, pH, and dissolved organic matter) were explored, with the experimental results in comparison with those predicted by the biotic ligand model (BLM). Results showed that increased Cu2+ concentration caused obvious toxicities to C. vulgaris, whereas the commonly occurring cations and dissolved organic matters can protect the metabolism system of C. vulgaris. The presence of extracellular polymeric substances (EPS) matrix can alleviate the biotoxicity via increasing the surface biosorption but decreasing cell internalization of Cu2+ in C. vulgaris. Due to the presence of EPS matrix, the experimental biotoxicity results under each condition were significantly lower than those predicted by the BLM model, which was thus modified via taking the EPS matrix as the supplement of allochthonous organic matters. After that, the modified BLM was characterized with a higher degree of precision and can be used in natural waters for biotoxicity prediction. Results obtained can enhance our insights into the ecological effects and biotoxicity prediction of heavy metals in natural aquatic ecosystems.