Table_3_Higher Abundance of Sediment Methanogens and Methanotrophs Do Not Predict the Atmospheric Methane and Carbon Dioxide Flows in Eutrophic Tropical Freshwater Reservoirs.XLSX

Freshwater reservoirs emit greenhouse gases (GHGs) such as methane (CH4) and carbon dioxide (CO2), contributing to global warming, mainly when impacted by untreated sewage and other anthropogenic sources. These gases can be produced by microbial organic carbon decomposition, but little is known about the microbiota and its participation in GHG production and consumption in these environments. In this paper we analyzed the sediment microbiota of three eutrophic tropical urban freshwater reservoirs, in different seasons and evaluated the correlations between microorganisms and the atmospheric CH4 and CO2 flows, also correlating them to limnological variables. Our results showed that deeper water columns promote high methanogen abundance, with predominance of acetoclastic Methanosaeta spp. and hydrogenotrophs Methanoregula spp. and Methanolinea spp. The aerobic methanotrophic community was affected by dissolved total carbon (DTC) and was dominated by Crenothrix spp. However, both relative abundance of the total methanogenic and aerobic methanotrophic communities in sediments were uncoupled to CH4 and CO2 flows. Network based approach showed that fermentative microbiota, including Leptolinea spp. and Longilinea spp., which produces substrates for methanogenesis, influence CH4 flows and was favored by anthropogenic pollution, such as untreated sewage loads. Additionally, less polluted conditions favored probable anaerobic methanotrophs such as Candidatus Bathyarchaeota, Sva0485, NC10, and MBG-D/DHVEG-1, which promoted lower gaseous flows, confirming the importance of sanitation improvement to reduce these flows in tropical urban freshwater reservoirs and their local and global warming impact.

淡水水库会排放甲烷（methane, CH4）、二氧化碳（carbon dioxide, CO2）等温室气体（greenhouse gases, GHGs），在受到未经处理的污水及其他人为来源影响时，会加剧全球变暖。这类温室气体可通过微生物对有机碳的分解作用产生，但目前学界对这类环境中的微生物群落（microbiota）及其在温室气体产生与消耗过程中的参与机制仍知之甚少。本研究对三个富营养化热带城市淡水水库的沉积物微生物群落开展了跨季节分析，评估了微生物与大气甲烷、二氧化碳通量之间的相关性，并将其与湖沼学变量（limnological variables）进行关联。研究结果显示，较深的水柱会提升产甲烷古菌（methanogen）的丰度，优势类群为产乙酸型的Methanosaeta spp.以及氢营养型的Methanoregula spp.和Methanolinea spp.。好氧甲烷氧化菌群落受总溶解碳（dissolved total carbon, DTC）的调控，其优势类群为Crenothrix spp.。不过，沉积物中产甲烷菌总群落与好氧甲烷氧化菌群落的相对丰度，均与甲烷和二氧化碳通量未呈现耦合关系。基于网络的分析方法表明，包括Leptolinea spp.和Longilinea spp.在内的发酵型微生物群落可为产甲烷作用提供底物，它们会对甲烷通量产生影响，且会因未经处理的污水负荷等人为污染而得到富集。此外，污染程度较低的环境更利于潜在厌氧甲烷氧化菌的生长，如候选类群Candidatus Bathyarchaeota、Sva0485、NC10以及MBG-D/DHVEG-1，这类菌群可降低气体通量，这证实了改善卫生设施对于减少热带城市淡水水库的温室气体通量及其局地与全球变暖影响的重要性。