Impact of Graphene Oxide on Algal Organic Matter of Microcystis aeruginosa

Abstract

Graphene oxide (GO) as a novel and promising material has a huge market and multiple applications. The release of GO into the aquatic system during their life cycle would lead to potential risks for the environment and aquatic organisms. This study evaluated the impacts of GO on algal growth and algal organic matter (AOM) of Microcystis aeruginosa. GO exhibited moderate effects on algal growth and the photosynthetic system. There was no evident influence on cell density and chlorophyll-a content at GO concentrations below 10 mg/L. Variation and characteristics of AOM after the interaction between GO and algae were analyzed. The characteristics of intracellular organic matter on algae’s exposure to GO showed no significant difference compared with the control group. Conversely, GO had greater impacts on extracellular organic matter after the interaction with algae. The dissolved organic carbon and microcystin-LR showed a significant decline with the increasing GO concentration. The overall molecular weight decreased as well, typically for low molecules. Moreover, the three-dimensional fluorescence spectrum showed that the humic acid- or fulvic acid-like organics decreased obviously. These conclusions reflect that GO has a strong adsorption capacity for removing extracellular organic matter, whereas it did not inflict damage to the algal cells, so that little change could be found in intracellular organic matter. The current study is expected to be beneficial in interpreting the potential risks of GO on algal growth and the variation of AOM.