AUTHOR=Pierangeli Gabrielle Maria Fonseca , Domingues Mercia Regina , Jesus Tatiane Araujo de , Coelho Lúcia Helena Gomes , Hanisch Werner Siegfried , Pompêo Marcelo Luiz Martins , Saia Flávia Talarico , Gregoracci Gustavo Bueno , Benassi Roseli Frederigi 

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

JOURNAL=Frontiers in Microbiology

VOLUME=12

YEAR=2021

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2021.647921

DOI=10.3389/fmicb.2021.647921

ISSN=1664-302X

ABSTRACT=<p>Freshwater reservoirs emit greenhouse gases (GHGs) such as methane (CH<sub>4</sub>) and carbon dioxide (CO<sub>2</sub>), 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 CH<sub>4</sub> and CO<sub>2</sub> flows, also correlating them to limnological variables. Our results showed that deeper water columns promote high methanogen abundance, with predominance of acetoclastic <italic>Methanosaeta</italic> spp. and hydrogenotrophs <italic>Methanoregula</italic> spp. and <italic>Methanolinea</italic> spp. The aerobic methanotrophic community was affected by dissolved total carbon (DTC) and was dominated by <italic>Crenothrix</italic> spp. However, both relative abundance of the total methanogenic and aerobic methanotrophic communities in sediments were uncoupled to CH<sub>4</sub> and CO<sub>2</sub> flows. Network based approach showed that fermentative microbiota, including <italic>Leptolinea</italic> spp. and <italic>Longilinea</italic> spp., which produces substrates for methanogenesis, influence CH<sub>4</sub> flows and was favored by anthropogenic pollution, such as untreated sewage loads. Additionally, less polluted conditions favored probable anaerobic methanotrophs such as <italic>Candidatus</italic> Bathyarchaeota, <italic>Sva0485</italic>, <italic>NC10</italic>, and <italic>MBG-D/DHVEG-1</italic>, 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.</p>