Zhongqing Huang, Chunmei Tian, Chen Wang, Jian Shen, Jimeng Feng, Xinze Wang
Plateau lakes are highly sensitive to algal blooms that increasingly threaten their ecological integrity. This study examined cyanobacterial bloom periods (Pseudanabaena sp.) and dinoflagellate bloom periods (Peridinium sp.) in Lake Erhai, integrating Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) with metagenomics to investigate dissolved organic matter (DOM) composition, microbial dynamics, and functional gene abundance. Pseudanabaena sp. bloom periods were associated with higher average molecular weight and elevated carboxyl-rich alicyclic molecules (CRAMs, 28.26%). Peridinium sp. bloom periods were associated with peptide-enriched DOM and elevated unsaturated aliphatic compounds (UACs, 24.15%). Putative CH2-related transformations dominated Pseudanabaena sp. peak bloom (32.93%), consistent with progressive functional group modifications toward operationally aromatic structures. Peridinium sp. showed elevated putative H2-related (30.35%) and O-related transformations (28.31%), coinciding with nitrogen-sulfur synergistic release patterns. Microbial Shannon diversity was higher during Peridinium sp. periods, with Actinomycetota more abundant during Pseudanabaena sp. peak bloom and Pseudomonadota more abundant during Peridinium sp. peak bloom. Enrichment of both Calvin-Benson-Bassham cycle and rTCA cycle genes during Pseudanabaena sp. peak bloom indicated enhanced autotrophic carbon fixation potential, whereas denitrification genes were abundant during Peridinium sp. peak bloom, indicating distinct functional potentials. DOM molecular traits emerged as statistically important predictors of microbial community composition and carbon-nitrogen-sulfur cycling gene abundance. These findings highlight the importance of integrating bloom type and seasonal dynamics when assessing DOM-mediated microbial processes in plateau lake ecosystems.