Investigation the Effects of Humic Acid on Growth Rate and Active Oxygen Radicals (ROS) Production in Chlorella Vulgaris Algae

Natural organic matter, which is considered the main pollutant of drinking water, is recently increasing. Therefore, assessing the biological effects of these compounds is very important. Algae with a short growth cycle, separate cultivation and high sensitivity to pesticides are among the most important species in assessing the biological effects of pesticides in the environment. The aim of this study was to determine the effects of different concentration of humic acid (4-132 mg/L) on the cell growth rate and Reactive Oxygen Species (ROS) production in Chlorella Vulgaris. Algae cells of chlorella species were added to the culture medium with relative density of 1×105 cells/ml and different concentrations of humic acid. The number of algae was counted daily and the amount of intracellular active oxygen species was assessed by fluorometric test. Humic acid at low concentrations (4 mg/l) causes a significant increase in algae growth in 48 hours (p<0.05), but higher concentrations (8 ≤ mg/l) and duration time (≥72h), show a toxic effect on algae. However, higher concentrations (≥8 mg/l) and duration time (≥72h) showed toxicity effect on alge. In addition, in the presence of humic acid, the intracellular ROS level significantly increased compared to the control group (p<0.05). Oxidative stress seems to have oxidative stress effects on chlorella algae. These effects are decreasing the relative growth rate and the constant growth rate of algae and increasing intracellular ROS formation.