Photolysis triggers multiple microbial responses: New insights of phosphorus compensation for algal blooms

Photolysis and microbial degradation enabling the rapid mineralization of organic phosphorus constitute the crucial mechanism for phosphorus compensation during algal bloom outbreaks in shallow lakes. This study explored the key pathways of microbial degradation of algae-derived organic phosphorus (ADOP) exacerbated by photolysis through molecular biology techniques. The results showed that photolysis could exacerbate microbial degradation, and the effects on microbial degradation were multifaceted. The photolysis process changes the composition of dissolved organic matter (DOM) in the environment and generates DOM components required for microbial activity, among which the saturated compounds significantly promote the increase of microbial biomass. Differential analysis showed that the photolysis process mainly affected the distribution of bacteria and fungi. The saturated compounds and highly aromatic compounds accompanying the photolysis process stimulated the increase of the abundance of phosphorus-cycling functional bacteria and related functional genes. Simultaneously, photolysis also promoted the growth of extracellular reactive oxygen species (ROS)-producing bacteria, and enhanced biological metabolism by stimulating the significant upregulation and differentiation of multiple enzyme protein subunits in cells. In summary, various changes in microorganisms caused by photolysis enhanced their mineralization of ADOP. These results bring new insights into the mechanism of the persistence of algal blooms.