From victims to protectors: Microalgae's unexpected capacity for diuron elimination

Diuron is a widespread PSII-inhibiting herbicide that persists in aquatic ecosystems and threatens environmental health. However, cost-effective removal solutions remain elusive. This study revealed that microalgae have the ability to remove diuron efficiently under mixotrophic conditions, e.g., Parachlorella kessleri could completely remove 60 μg·L^-1 of diuron within 60 hours. The primary process of this removal is bioabsorption, which relies more on new biomass generation than on total biomass. Additionally, diuron significantly enhances the mixotrophic growth of P. kessleri by maintaining a stable pH environment, stabilizing between 7.0 and 7.5 without the need for buffers or adjustments. This pH stabilization is attributed to diuron's reduction of the alkalizing effect of microalgal photosynthetic carbon assimilation. Other microalgae species, including Chlorella vulgaris, Chlorella ellipsoidea and Scenedesmus quadricauda, also show high diuron removal efficiencies and growth promotion under mixotrophic conditions. These findings collectively suggest that the use of mixotrophic microalgae could represent a new potential method for diuron removal.