| 湖泊底泥土著微生物对盐度变化响应的差异性：以白洋淀和青海湖为例 |
| 摘要点击 537 全文点击 50 投稿时间：2024-03-29 修订日期：2024-06-04 |
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| 中文关键词 反硝化厌氧甲烷氧化（DAMO） 咸水湖 淡水湖 甲烷（CH4） 二氧化碳（CO2） |
| 英文关键词 denitrifying anaerobic methane oxidation （DAMO） saline lake freshwater lake methane（CH4） carbon dioxide（CO2） |
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| 中文摘要 |
| 有研究发现,湖水中的盐度胁迫影响底泥中甲烷氧化微生物的群落结构和功能,并且能够影响湖泊甲烷的排放量. 反硝化厌氧甲烷氧化（DAMO）是湖泊底泥中重要的甲烷氧化过程,由已知的DAMO特征菌及相关碳氮转化功能菌合作完成. 但目前对不同的盐度环境下湖泊底泥DAMO菌群差异以及相应的温室气体产生量的差异还缺乏足够的认知. 选取典型咸水湖（青海湖）和淡水湖（白洋淀）,以探究不同盐度湖泊底泥土著菌群的差异性. α多样性结果显示白洋淀底泥Shannon和Observed-Richness丰富度指数均大于青海湖底泥相应丰富度指数,Inv-Simpson指数则小于青海湖底泥. 两湖底泥微生物在门水平上优势种群基本一致,但共有微生物种群的丰度占比存在显著差异. 湖水盐度与沉积物中微生物多样性和甲烷氧化微生物的多样性呈显著负相关. 进一步探究了盐度变化对两湖泊底泥中DAMO过程的影响,设置0 、11 和110 g·L-1这3个盐度梯度对两湖沉积物样品进行以CH4和KNO3为底物的厌氧微宇宙培养. 青海湖底泥系统中各组亚硝酸盐生成速率和硝酸盐消耗速率较白洋淀底泥低. 白洋淀底泥中的CO2产生量随培养盐度的升高而下降,高盐度组比低盐度组甲烷氧化量更低,氧化亚氮生成量更高. 青海湖底泥中的甲烷氧化在原始样品盐度（11 g·L-1）下最为活跃,甲烷氧化量最高达481.67 μmol·L-1,且该组氧化亚氮的生成量最低,约为1.69 μmol·L-1. 青海湖底泥在其原始盐度下培养时其甲烷氧化能力优于其他盐度组,氧化亚氮的产量也更低. 说明高盐度湖泊中的DAMO菌群经过长期的筛选和驯化后能够适应其生境盐度. 因此,咸水湖和淡水湖湖泊底泥中土著微生物的显著差异会导致其对盐度环境变化的响应差异,进一步对湖泊中DAMO过程产生影响. 两种DAMO特征菌基因定量结果显示,ANME-2d M. nitroreducens和NC10 M. oxyfera均在青海湖、白洋淀原始样品盐度处理组丰度最高. 在白洋淀底泥处理组中,随盐度的升高 DAMO菌活性和DAMO过程均被抑制,而在青海湖底泥处理组中,原始样品盐度（11 g·L-1）下具有最高的DAMO菌丰度和DAMO速率. 因此,在原始样品盐度基础上提高或降低盐度都会抑制湖泊底泥中的DAMO过程,导致甲烷消耗量的减少和氧化亚氮生成量的增加. 研究结果可为气候变暖背景下湖泊温室气体排放预测提供参考. |
| 英文摘要 |
| The impact of salinity stress on methane-oxidizing microorganisms in lake sediments has been recognized as influential in altering both the community structure and function, thereby affecting methane emissions in lake water. Denitrifying anaerobic methane oxidation （DAMO） is a crucial process within the lake sediment, involving a consortium of known DAMO characteristic microorganisms and associated carbon and nitrogen-transforming functional bacteria. However, the variations in DAMO flora in lake sediments under diverse salinity conditions and their implications on greenhouse gas production remain inadequately explored. To address this gap, a comparative study was conducted on the indigenous flora in sediments from two lakes with contrasting salinities, namely the saline Qinghai Lake and the freshwater Baiyangdian Lake. The α-diversity analysis revealed higher Shannon and Observed-Richness indices in the Baiyangdian Lake sediment compared to the Qinghai Lake sediment, while the Inv-Simpson index showed the opposite trend. While the dominant microbial populations were similar at the phylum level, significant differences were observed in the abundance and proportion of common microbial populations. Notably, the salinity of lake water exhibited a negative correlation with microbial diversity and methane-oxidizing microbial diversity in sediments. Further investigation on the indigenous DAMO microflora in the lake sediments under different salinity conditions revealed distinct patterns. Specifically, anaerobic microcultures were carried out at different salinity gradients （0, 11, and 110 g·L-1）, with CH4 and KNO3 as substrates. The rates of nitrite formation and nitrate consumption were lower in the Qinghai Lake sediment compared to those in the Baiyangdian sediment with respect to individual salinity. CO2 production in the Baiyangdian sediment decreased with increasing salinity. Additionally, for the Baiyangdian sediment, methane oxidation and nitrous oxide production were lower in the high salinity group than those in the low salinity group. In the Qinghai Lake sediment, the most active methane oxidation was observed at the original sample's salinity （11 g·L-1）, with the highest methane oxidation reaching 481.67 μmol·L-1 and the lowest nitrous oxide production around 1.69 μmol·L-1. The methane oxidation capacity of the Qinghai Lake sediment cultured at its original salinity was better than that of other salinity groups, and the yield of nitrous oxide was also lower. These results indicated that DAMO flora in high salinity lakes could adapt to the salinity of their habitats after long-term screening and domestication. Therefore, the significant difference in indigenous microorganisms in the sediments of saltwater and freshwater lakes lead to the differences in their response to changes in the salinity environment and further affect the DAMO process in lakes. Quantitative analysis of DAMO characteristic bacterial genes revealed varying abundances of ANME-2d Methanoperedens nitroreducens and NC10 Methylomirabilis oxyfera in the sediments of the Qinghai Lake and Baiyangdian Lake, influenced by salinity treatments. The DAMO bacteria activity and process were inhibited with increasing salinity in the Baiyangdian Lake sediment, whereas in the Qinghai Lake sediment, the highest DAMO microbe abundance and rate were observed at the salinity of the original sample （11 g·L-1）. Manipulating the salinity of the original sample resulted in the inhibition of the DAMO process in the lake sediment, leading to lower DAMO microbe abundance, reduced methane oxidation, and increased nitrous oxide production. These findings underscore the marked impact of lake salinity on indigenous microorganisms in lake sediments, with implications for their responses to changes in the salinity environment and subsequent effects on the DAMO process in lakes. This provides insights for predicting lake greenhouse gas emissions in the context of climate warming. |
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