Light-mediated synergistic phosphorus uptake by biofilms on ZnAlLa-LDHs coatings: A novel strategy for lake phosphorus control

Layered double hydroxides (LDHs) and natural biofilms are both effective in controlling endogenous phosphorus (P) release in lakes, yet their synergistic mechanisms remain underexplored. In this study, ternary ZnAlLa-LDHs were synthesized via co-precipitation and applied as P-adsorbent coatings to access their interaction with natural biofilms under different light intensities (0, 2000 and 6000 lx). The presence of biofilms markedly reduced P release from P-loaded LDHs (63 mg/g), with reduction rates increasing from 52.6 % at 0 lx to 82.3 % at 6000 lx, highlighting the coupled influence of biofilm activity and illumination in suppressing P re-release. Biofilm physiological parameters, including chlorophyll a , dehydrogenase, and alkaline phosphatase activities, varied significantly with light intensity but were not adversely affected by LDH coatings, confirming their biocompatibility. Confocal laser scanning microscopy (CLSM) revealed that P-loaded LDH coatings promoted algal-derived EPS secretion by ∼60 % and enhanced structural stability, despite reducing direct bacterial–algal syntrophy under low-light conditions. Microbial community analysis further showed a stable consortium dominated by Ca. Competibacter, Thiobacillus, Desmodesmus and EPS-producing diatoms ( Aulacoseira, Navicula, Nitzschia ), indicating that controlled P release from LDHs fostered community balance and suppressed opportunistic taxa. P uptake followed a negative exponential model ( R 2 > 0.7) across initial P concentrations (0.04–0.25 mg/L), with P uptake rate coefficients ( K ) increasing significantly under stronger illumination. These results demonstrate, for the first time, the light-mediated synergistic biofilm–LDH interaction in regulating P dynamics, providing new insights for eco-friendly functional materials in sustainable eutrophic lake remediation.