Hydrogen Peroxide Can Be a Plausible Biomarker in Cyanobacterial Bloom Treatment
Abstract 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 (H2O2) concentration and antioxidant activities of catalase (CAT) and superoxide dismutase (SOD). H2O2 concentration decreased to 30 µmolm-2s-1 of PAR, then increased further with higher PAR intensity. Regarding phosphorus concentration, H2O2 concentration generally decreased with increasing phosphorus concentration. SOD and CAT activities were proportionate to the H2O2 protein-1. No H2O2 concentration detected outside of cells indicated the biological production of H2O2, and the accumulated H2O2 concentration inside cells was parameterized with H2O2 concentration protein-1. Over 30 µmolm-2s-1 of PAR, H2O2 concentration protein-1 had a similar increasing trend with PAR intensity, independently of phosphorous concentration. Meanwhile, with increasing phosphorous concentration, H2O2 protein-1 decreased in a similar pattern regardless of PAR intensity. Protein content decreased with increasing H2O2 gradually up to 4nmol H2O2 mg-1protein, which provides a threshold to restrict the growth of cyanobacteria. With these results. an empirical formula was developed to obtain the cyanobacteria biomass.