Use of an integrated metabolomics platform for mechanistic investigations of three commonly used algaecides on cyanobacterium, Microcystis aeruginosa

Algal blooms are a global environmental and public health problem. Copper Sulfate (CuSO4), Hydrogen Peroxide (H2O2) and Sodium Carbonate Peroxide (SCP) are commonly used algaecides for algal bloom control. However, their efficacy and mechanisms of interaction with algae have not been well studied. This study aimed to compare their capability, and concurrently elucidate the metabolic responses of a common cyanobacterium, Microcystis aeruginosa. Algal responses were measured by cell density, chlorophyll a, toxin release and an integrated GC- and LC- Mass Spectrometry-Time of Flight metabolomics platform. CuSO4 was observed to kill the algae cells rapidly at relative low concentration, compared with the other two algaecides. However, it led to severe secondary contamination, with substantial release of various microcystins. Metabolomics data showed that a total of 32 metabolites were significantly changed compared with the controls. Most of the metabolites identified in CuSO4 treated algae were significantly reduced, whereas metabolites in algae treated with H2O2 and SCP were found to increase, and were of similar types. Although most of the metabolites identified for the three algaecides are associated to oxidative stress, the pathways affected appear to be different.