Adverse effects and potential accumulation of the herbicide atrazine in the cyanobacterium Microcystis aeruginosa

Abstract

Pest control in agricultural activities leads to herbicide contamination in the environment. The presence of herbicide, such as atrazine, in water systems can negatively impact aquatic organisms, especially vulnerable species, thereby disrupting ecosystem functioning. Phytoplankton, including microalgae and cyanobacteria, are primary producers in the aquatic food chain. Therefore, they hold a central position and serve as key drivers of material and energy flows in aquatic ecosystems. In this study, we tested the influence of atrazine at four different levels (0, 6, 53, 511 μg/L) on the development of Microcystis aeruginosa at two initial abundance (1.1 × 10 4 cells/mL, and 11.9 × 10 4 cells/mL) over 16 days under laboratory conditions. We also determined the total protein in dry mass and the amount of atrazine removed by M. aeruginosa at the end of the experiment. The results showed that the lowest atrazine level (6 μg/L) slightly influenced the development of M. aeruginosa, but significant growth inhibition was clearly observed from the 4 th day to the end of the experimental period at higher atrazine concentrations (53 and 511 μg/L). Total protein content in cells at the low Microcystis abundance was similar between the control and atrazine exposures. At the higher Microcystis abundance, total protein increased by 32% at 53 μg atrazine/L, but decreased by 12% at 511 μg atrazine/L, compared to the control. Atrazine removal by M. aeruginosa ranged from 22% to 43%, with higher atrazine concentrations resulting in greater removal. Our study provides foundational information on the growth and total protein content of M. aeruginosa under laboratory conditions. Besides, it enhances understanding of the toxicity of atrazine to phytoplankton and the potential risks to phytoplankton grazers due to atrazine accumulation.