Hydrogen Peroxide Can Be a Plausible Biomarker in Cyanobacterial Bloom Treatment

The effect of combined stresses, photoinhibition and nutrient depletion, on the oxidative stress of cyanobacteria was measured in laboratory experiments, to develop the biomass prediction model. Phormidium ambiguum was exposed to various photosynthetically active radiation (PAR) intensities and phosphorous concentrations with fixed nitrogen concentration. The samples were subjected to stress assays by detecting hydrogen peroxide (H 2 O 2 ) concentration and antioxidant activities of catalase (CAT) and superoxide dismutase (SOD). H 2 O 2 concentration decreased to 30 µmolm -2 s -1 of PAR, then increased further with higher PAR intensity. Regarding phosphorus concentration, H 2 O 2 concentration generally decreased with increasing phosphorus concentration. SOD and CAT activities were proportionate to the H 2 O 2 protein -1 . No H 2 O 2 concentration detected outside of cells indicated the biological production of H 2 O 2 , and the accumulated H 2 O 2 concentration inside cells was parameterized with H 2 O 2 concentration protein -1 . Over 30 µmolm -2 s -1 of PAR, H 2 O 2 concentration protein -1 had a similar increasing trend with PAR intensity, independently of phosphorous concentration. Meanwhile, with increasing phosphorous concentration, H 2 O 2 protein -1 decreased in a similar pattern regardless of PAR intensity. Protein content decreased with increasing H 2 O 2 gradually up to 4nmol H 2 O 2 mg -1 protein, which provides a threshold to restrict the growth of cyanobacteria. With these results. an empirical formula was developed to obtain the cyanobacteria biomass.