Microalgae and their associated microorganisms (PRJCA037712)

The phycosphere is considered a localized microenvironment surrounding microalgal cells, playing a critical role in nutrient cycling, microbial interaction, and pollutant transformation. However, existing studies have primarily focused on its microscopic-scale effects and overlooked temporal dynamics, leaving its broader impact on the environmental behavior of metal(loid)s in mining drainage poorly understood. This study employed a centimeter-scale diffusion chamber system to investigate the role of phycosphere fluctuations in microbial recruitment and multi-metal(loid) immobilization. Results revealed that microalgae modified nutrient availability and physicochemical properties over a range of at least 30 cm, leading to a spatial gradient in metal(loid) concentrations and achieving up to 99% removal of As and 93% removal of Cd. Phycosphere fluctuations across microalgal growth stages modulated metal(loid) concentrations and species. Variance partitioning analysis indicated that the phycosphere explained over 95% of the metal(loid) removal, with structural equation modeling demonstrating its regulation of the microbial community as a critical factor. Specifically, phycospheres with distinct properties sequentially recruited aerobic Fe-oxidizing bacteria during early microalgal growth and anaerobic sulfate-reducing bacteria during later growth, contributing to the removal of As and Cd, respectively. Overall, our study highlights the importance of microbial transition driven by macroscopic phycosphere fluctuations in achieving multi-metal(loid) immobilization, providing valuable insights and a theoretical basis for advancing phycoremediation strategies in mine drainage.