Li Huimin, Si Duanmiao, Wang Haoyan, Jiang Haixia, Li Peng, He Yiliang
School of Environmental Science and Engineering, Shanghai Jiao Tong University, Shanghai, PR China.
School of Life Sciences and Technology, Tongji University, Shanghai 200092, PR China.
Water Res. 2025 Sep 1;283:123752. doi: 10.1016/j.watres.2025.123752. Epub 2025 May 1.
Estuaries serve as vital interfaces in the global carbon cycle by mediating land-ocean exchange and regulating dissolved organic matter (DOM) dynamics. However, the role of microbial communities in regulating autochthonous DOM under phosphorus-limited estuarine conditions remains insufficiently understood. This study explored the biogeochemical parameters, inorganic carbon dynamics, DOM optical properties, and algal-bacterial community composition in a picocyanobacteria-dominated estuarine reservoir subject to seasonal salinity and nutrient fluctuations. Samples were classified into three groups based on DOM compositional features: pristine autochthonous group (PG), high allochthonous group (HG), and balanced group (BG). In BG, picocyanobacteria, particularly Cyanobium PCC-6307, promoted the accumulation of labile tryptophan-like DOM (component C4), which was associated with the lowest autochthonous DOM stability ratios (AuSR). In HG, terrestrial runoff led to a decline in C4 and an increase in DOM stability, reflecting rapid microbial degradation and partial transformation. In BG, colder temperatures and elevated microbial α-diversity facilitated the conversion of DOM into more humified forms, as indicated by higher proportions of humic-like components and AuSR. Key microbial taxa showed substrate-specific metabolic traits related to amino acid, polysaccharide, and one-carbon compound processing. By integrating DOM-defined groupings, fluorescence-derived stability metrics, and microbial marker analysis, this study reveals a sequential cascade of microbial regulation in DOM production, transformation, and stabilization. These findings offer the first detailed evidence of such processes in a phosphorus-limited estuarine system and provide a new framework for linking DOM properties with microbial ecological functions in dynamic aquatic environments.
河口通过介导陆地-海洋交换和调节溶解有机物（DOM）动态，在全球碳循环中发挥着至关重要的作用。然而，在磷限制的河口条件下，微生物群落调节本地DOM的作用仍未得到充分了解。本研究探讨了一个以聚球藻为主的河口水库中的生物地球化学参数、无机碳动态、DOM光学性质以及藻菌群落组成，该水库受季节性盐度和养分波动影响。根据DOM组成特征，样本分为三组：原始本地组（PG）、高异地组（HG）和平衡组（BG）。在BG组中，聚球藻，特别是蓝细菌PCC-6307，促进了不稳定的类色氨酸DOM（组分C4）的积累，这与最低的本地DOM稳定性比率（AuSR）相关。在HG组中，陆地径流导致C4下降和DOM稳定性增加，反映了微生物的快速降解和部分转化。在BG组中，较低的温度和微生物α多样性的增加促进了DOM向更腐殖化形式的转化，腐殖类组分和AuSR的比例更高表明了这一点。关键微生物类群表现出与氨基酸、多糖和一碳化合物加工相关的底物特异性代谢特征。通过整合DOM定义的分组、荧光衍生的稳定性指标和微生物标记分析，本研究揭示了DOM产生、转化和稳定过程中微生物调节的连续级联。这些发现首次详细证明了磷限制河口系统中的此类过程，并为在动态水生环境中将DOM性质与微生物生态功能联系起来提供了一个新框架。
