School of Environment, Nanjing Normal University, Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Jiangsu Key Laboratory of Environmental Change and Ecological Construction, Nanjing, 210023, China.
School of Environment, Nanjing Normal University, Jiangsu Center for Collaborative Innovation in Geographical Information Resource Development and Application, Jiangsu Key Laboratory of Environmental Change and Ecological Construction, Nanjing, 210023, China.
Environ Pollut. 2022 Jan 1;292(Pt B):118443. doi: 10.1016/j.envpol.2021.118443. Epub 2021 Oct 30.
Although cyanobacteria blooms lead to an increase in methane (CH) emissions in eutrophic lakes have been intensively studied, the methane production pathways and driving mechanisms of the associated CH emissions are still unclear. In this study, the hypereutrophic Lake Taihu, which has extreme cyanobacteria accumulation, was selected to test hypothesis of a potential methylotrophic CH production pathway. Field observation displayed that the CH emission flux from the area with cyanobacteria accumulation was 867.01 μg m·min, much higher than the flux of 3.44 μg m·min in the non-cyanobacteria accumulation area. The corresponding abundance of methane-producing archaea (MPA) in the cyanobacteria-concentrated area was 77.33% higher than that in the non-concentrated area via RT-qPCR technologies. Synchronously, sediments from these areas were incubated in anaerobic bottles, and results exhibited the high CH emission potential of the cyanobacteria concentrated area versus the non-concentrated area (1199.26 vs. 205.76 μmol/L) and more active biological processes (CO emission, 2072.8 vs. -714.62 μmol/L). We also found evidence for the methylotrophic methane producing pathway, which contributed to the high CH emission flux from the cyanobacteria accumulation area. Firstly, cyanobacteria decomposition provided the prerequisite of abundant methyl thioether substances, including DMS, DMDS, and DMTS. Results showed that the content of methyl thioethers increased with the biomass of cyanobacteria, and the released DMS, DMDS, and DMTS was up to 96.35, 3.22 and 13.61 μg/L, respectively, in the highly concentrated 25000 g/cm cyanobacteria treatment. Then, cyanobacteria decomposition created anaerobic microenvironments (DO 0.06 mg/L and Eh -304.8Mv) for methylotrophic methane production. Lastly, the relative abundance of Methanosarcinales was increased from 7.67% at the initial stage to 36.02% at the final stage within a sediment treatment with 10 mmol/L N(CH). Quantitatively, the proportion of the methylotrophic methane production pathway was as high as 32.58%. This finding is crucial for accurately evaluating the methane emission flux, and evaluating future management strategies of eutrophic lakes.
尽管富营养化湖泊中蓝藻水华导致甲烷（CH）排放增加已经得到了深入研究，但与相关 CH 排放相关的甲烷产生途径和驱动机制仍不清楚。在这项研究中，选择了太湖这个蓝藻大量积累的超富营养化湖泊，以检验潜在的甲基营养型 CH 产生途径的假设。野外观测显示，蓝藻积累区的 CH 排放通量为 867.01μg m·min，远高于非蓝藻积累区的 3.44μg m·min。通过 RT-qPCR 技术，蓝藻集中区产甲烷古菌（MPA）的丰度比非集中区高 77.33%。同时，从这些区域采集沉积物并在厌氧瓶中进行培养，结果表明，与非集中区相比，蓝藻集中区的 CH 排放潜力更高（1199.26 对 205.76μmol/L），生物过程更活跃（CO 排放，2072.8 对-714.62μmol/L）。我们还发现了甲基营养型甲烷产生途径的证据，这有助于解释蓝藻积累区高 CH 排放通量的原因。首先，蓝藻分解提供了丰富的甲基硫醚物质的前提，包括 DMS、DMDS 和 DMTS。结果表明，甲基硫醚的含量随蓝藻生物量的增加而增加，在高度集中的 25000g/cm 蓝藻处理中，释放的 DMS、DMDS 和 DMTS 分别达到 96.35、3.22 和 13.61μg/L。然后，蓝藻分解创造了适合甲基营养型甲烷产生的厌氧微环境（DO 0.06mg/L 和 Eh -304.8Mv）。最后，在沉积物处理中添加 10mmol/L N（CH）时，甲烷八叠球菌科的相对丰度从初始阶段的 7.67%增加到最终阶段的 36.02%。定量分析表明，甲基营养型甲烷产生途径的比例高达 32.58%。这一发现对于准确评估甲烷排放通量以及评价富营养化湖泊的未来管理策略至关重要。
