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

Abstract

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.

Redox Zone and Trophic State as Drivers of Methane-Oxidizing Bacterial Abundance and Community Structure in Lake Sediments

“…The community composition of MOB in lake sediments has so far mainly been studied by microbial enrichment and isolation methods (e.g., Auman et al, 2000;He et al, 2012;Danilova et al, 2016), and by cultivation-independent methods involving fluorescence-in-situ-hybridization (FISH; Rahalkar et al, 2009), sequencing of 16S rRNA genes (Fiskal et al, 2021;Pierangeli et al, 2021), and sequencing of catabolic functional genes (for reviews see (McDonald et al, 2008;Knief, 2015). Hereby pmoA, a functional gene that encodes the catalytic subunit of particulate methane monooxygenase (pMMO), an enzyme which performs the initial conversion of methane to methanol, has been widely targeted.…”

Lake Sediments From Littoral and Profundal Zones are Heterogeneous but Equivalent Sources of Methane Produced by Distinct Methanogenic Communities—A Case Study From Lake Remoray

“…When assessing the methane cycle microbial actors, recent studies observed the absence of relationships between the abundances of methanogens and/or methanotrophs and the recorded activity rates of fluxes (Emerson et al., 2021; Pierangeli et al., 2021), making these descriptors weak predictors of the methane cycle activity rates. Opposite, bacterial community composition was shown to significantly influence methanogenic community activity, particularly through the strong relationships occurring between fermentative bacteria and methanogenic archaea (Bertolet et al., 2019; Emerson et al., 2021; Lavergne et al., 2021; Pierangeli et al., 2021), with fermentative bacteria supplying substrates to methanogenic archaea, thus supporting trophic cooperation. At horizontal scales, methanogenic communities are generally different between low and high water depth areas, with site‐related changes in the relative abundances of the major genera (Berberich et al., 2020).…”

Variations in the archaeal community and associated methanogenesis in peat profiles of three typical peatland types in China

“…Some recent studies have highlighted similar methanogenesis pathways of Bathyarchaeota species to those of some methanogens (e.g., Methanomassiliicoccales ) [ 33 , 86 , 96 ]. In addition, these species are capable of performing anaerobic mineralization of proteins and anaerobic CH 4 oxidation [ 97 , 98 ]. The RDA and correlation analysis revealed negative relationships between pH and MBG–D/DHVEG–1 and positive relationships between DOC and MBG–D/DHVEG–1 (Fig.…”