An Assessment of the Effects of Light Intensities and Temperature Changes on Cyanobacteria’s Oxidative Stress via the Use of Hydrogen Peroxide as an Indicator

Abstract

Humans and other organisms are adversely affected by cyanobacterial blooming. This study aims to investigate the long-term effects of light intensities and different temperatures on Phormidium ambiguum and Pseudanabaena foetida. Enough P. ambiguum and P. foetida cells were acclimated for 24 days at 30 °C, 20 °C, and 10 °C in separate incubators. The starting day sample was collected after 24 days of acclimatization, and a second sample was collected seven days later at light intensities of 10, 30, 50, 200, and 600 µmol m−2 s−1 for each temperature. The optical density (OD730), hydrogen peroxide (H2O2) concentration, protein content, chlorophyll-a (Chl-a) concentration, and catalase (CAT) activity were measured. Light intensity changes soon after collection resulted in nearly identical starting day samples at each individual temperature. The H2O2 concentration and algal biomass increased until a light intensity of 200 µmol m−2 s−1 was reached and decreased afterward in each temperature for both species after seven days. In association with an increasing H2O2 concentration, the Chl-a concentration decreased after 50 µmol m−2s−1 of light intensity, affecting the protein content. The algal biomass was significantly lower at 10 °C compared to 30 °C. The CAT activity increased proportionately with the H2O2 concentration and algal biomass. Therefore, water bodies in the field can be illuminated with long-term high light intensities in different temperatures to reduce algal biomass.