作者：Peng, Y., Zhou, M., Peng, Y., Xie, W., Zhang, Z., Zhou, C., Kinouchi, T., Doi, H. & Xu, X.

Lake carbon emissions have increased markedly under climate warming and eutrophication, yet the underlying mechanisms remain poorly understood. Here, we reveal a clear spatiotemporal expansion of cyanobacterial blooms in Lake Taihu from 2000 to 2023 based on the floating algae index (FAI) analysis, indicating a year-onyear increase in bloom frequency and intensity. Furthermore, this study examined how cyanobacterial-derived organic matter inputs influence carbon emissions and sediment carbon pool structures across three representative zones: a cyanobacterial-dominated region, a macrophyte-dominated region, and the lake center. Field observations showed that CH4 and CO2 fluxes in the cyanobacterial-dominated region were significantly higher than in the other regions, reaching 133.9 and 2361.2 mu g/m2 & sdot;min, respectively. The total organic carbon (TOC) content in the surface sediment was highest at 58.5 g/kg, while microbial biomass carbon (MBC) reached 554.1 mg/kg; both declined sharply with depth. In contrast, the macrophyte-dominated region displayed the highest TOC in bottom sediment (49.5 g/kg), indicating strong carbon burial. Microcosm experiments confirmed that cyanobacterial-derived organic carbon input induced co-metabolic processes in sediments, and significantly increased CH4 and CO2 fluxes-especially in regions with high recalcitrant organic carbon (ROC) content. The relative increase in sediment carbon emissions was positively correlated with ROC and negatively with labile organic carbon (LOC). Moreover, the proportion of ROC in sediments significantly decreased before and after incubation, indicating that co-metabolism promotes ROC degradation and enhances the role of lakes as carbon sources. However, based on microcosm experiments, where cyanobacterial input enhanced carbon emissions from sediments while TOC concentration still increased, lakes remain net carbon sinks overall. These findings improve our understanding of the role of co-metabolism in regulating lake carbon source-sink dynamics and provide critical insights for regional and global carbon assessments.

在气候变暖和富营养化的影响下，湖泊碳排放已显著增加，但其内在机制仍不清楚。本研究基于漂浮藻类指数（FAI）分析，揭示了2000至2023年间太湖蓝藻水华在时空上的明显扩张，表明水华发生频率和强度呈逐年上升趋势。在此基础上，我们进一步考察了蓝藻源有机质输入如何影响三个代表性区域（蓝藻主导区、大型水生植物主导区和湖心区）的碳排放与沉积物碳库结构。野外实测表明，蓝藻主导区的CH₄和CO₂通量显著高于其他区域，分别达到133.9和2361.2 μg/m²·min。该区表层沉积物总有机碳（TOC）含量最高，为58.5 g/kg，微生物生物量碳（MBC）达554.1 mg/kg，两者均随深度增加而急剧下降。相比之下，大型水生植物主导区底部沉积物的TOC最高（49.5 g/kg），显示出强烈的碳埋藏作用。微宇宙实验证实，蓝藻源有机碳输入会诱导沉积物中的共代谢过程，并显著提高CH₄和CO₂通量——尤其在惰性有机碳（ROC）含量较高的区域更为明显。沉积物碳排放的相对增幅与ROC含量呈正相关，而与活性有机碳（LOC）含量呈负相关。此外，培养前后沉积物中ROC的占比显著降低，表明共代谢促进了ROC的降解，从而强化了湖泊的碳源功能。但微宇宙实验结果也显示，尽管蓝藻输入增强了沉积物的碳排放，TOC浓度仍然增加，说明湖泊整体上仍为净碳汇。上述发现深化了我们对共代谢在调节湖泊碳源–汇动态中作用的认识，并为区域和全球碳评估提供了关键依据。

（来源：Water Research 2026  DOI: 10.1016/j.watres.2025.125277）