Rissanen Antti J, Jilbert Tom, Simojoki Asko, Mangayil Rahul, Aalto Sanni L, Khanongnuch Ramita, Peura Sari, Jäntti Helena
Faculty of Engineering and Natural Sciences, Tampere University , Tampere, Finland.
Natural Resources Institute Finland (Luke) , Helsinki, Finland.
Microbiol Spectr. 2023 Sep 12;11(5):e0195523. doi: 10.1128/spectrum.01955-23.
Eutrophication increases the input of labile, algae-derived, organic matter (OM) into lake sediments. This potentially increases methane (CH) emissions from sediment to water through increased methane production rates and decreased methane oxidation efficiency in sediments. However, the effect of OM lability on the structure of methane oxidizing (methanotrophic) and methane producing (methanogenic) microbial communities in lake sediments is still understudied. We studied the vertical profiles of the sediment and porewater geochemistry and the microbial communities (16S rRNA gene amplicon sequencing) at five profundal stations of an oligo-mesotrophic, boreal lake (Lake Pääjärvi, Finland), varying in surface sediment OM sources (assessed via sediment C:N ratio). Porewater profiles of methane, dissolved inorganic carbon (DIC), acetate, iron, and sulfur suggested that sites with more autochthonous OM showed higher overall OM lability, which increased remineralization rates, leading to increased electron acceptor (EA) consumption and methane emissions from sediment to water. When OM lability increased, the abundance of anaerobic nitrite-reducing methanotrophs ( Methylomirabilis) relative to aerobic methanotrophs () in the methane oxidation layer of sediment surface decreased, suggesting that were more competitive than . Methylomirabilis under decreasing redox conditions and increasing methane availability due to their more diverse metabolism (fermentation and anaerobic respiration) and lower affinity for methane. Furthermore, when OM lability increased, the abundance of methanotrophic community in the sediment surface layer, especially . Methylomirabilis, relative to the methanogenic community decreased. We conclude that increasing input of labile OM, subsequently affecting the redox zonation of sediments, significantly modifies the methane producing and consuming microbial community of lake sediments. IMPORTANCE Lakes are important natural emitters of the greenhouse gas methane (CH). It has been shown that eutrophication, via increasing the input of labile organic matter (OM) into lake sediments and subsequently affecting the redox conditions, increases methane emissions from lake sediments through increased sediment methane production rates and decreased methane oxidation efficiency. However, the effect of organic matter lability on the structure of the methane-related microbial communities of lake sediments is not known. In this study, we show that, besides the activity, also the structure of lake sediment methane producing and consuming microbial community is significantly affected by changes in the sediment organic matter lability.
富营养化增加了不稳定的、源自藻类的有机物质（OM）向湖泊沉积物的输入。这可能通过提高沉积物中甲烷的产生速率和降低甲烷氧化效率，增加从沉积物到水体的甲烷（CH）排放。然而，OM的不稳定性对湖泊沉积物中甲烷氧化（甲烷营养型）和甲烷产生（产甲烷型）微生物群落结构的影响仍未得到充分研究。我们研究了芬兰一个贫中营养的北方湖泊（派亚尔维湖）五个深水区站点的沉积物和孔隙水地球化学垂直剖面以及微生物群落（16S rRNA基因扩增子测序），这些站点的表层沉积物OM来源不同（通过沉积物碳氮比评估）。甲烷、溶解无机碳（DIC）、乙酸盐、铁和硫的孔隙水剖面表明，具有更多自源OM的站点总体OM不稳定性更高，这提高了再矿化速率，导致电子受体（EA）消耗增加以及从沉积物到水体的甲烷排放增加。当OM不稳定性增加时，沉积物表面甲烷氧化层中厌氧亚硝酸盐还原型甲烷营养菌（嗜甲基菌属）相对于好氧甲烷营养菌的丰度降低，这表明嗜甲基菌属在氧化还原条件降低和甲烷可用性增加的情况下更具竞争力，因为它们具有更多样化的代谢（发酵和厌氧呼吸）且对甲烷的亲和力较低。此外，当OM不稳定性增加时，沉积物表层甲烷营养菌群落，尤其是嗜甲基菌属，相对于产甲烷菌群落的丰度降低。我们得出结论，不稳定OM输入的增加，随后影响沉积物的氧化还原分区，显著改变了湖泊沉积物中产生和消耗甲烷的微生物群落。重要性湖泊是温室气体甲烷（CH）的重要天然排放源。研究表明，富营养化通过增加不稳定有机物质（OM）向湖泊沉积物的输入并随后影响氧化还原条件，通过提高沉积物甲烷产生速率和降低甲烷氧化效率来增加湖泊沉积物的甲烷排放。然而，有机物质不稳定性对湖泊沉积物中与甲烷相关的微生物群落结构的影响尚不清楚。在本研究中，我们表明，除了活性外，湖泊沉积物中产生和消耗甲烷的微生物群落结构也受到沉积物有机物质不稳定性变化的显著影响。
