Methanotroph community structure and processes in an inland river affected by natural gas macro-seeps

Abstract

Methane availability in freshwaters is usually associated with spatial-temporal variation in methanogenesis. Unusually, however, natural gas macro-seeps occur along the Condamine River in eastern Australia which elevate ambient water-column methane concentrations more than 3,000 times. We quantified the spatial-temporal variation in methane oxidation rates and the total microbial and methanotroph community composition (through the amplification and sequencing of 16S rRNA and particulate methane monooxygenase (pmoA) genes), and the factors mediating this variation, in reaches with and without macro-seeps. Sediment methane oxidation rates were, on average, 29 times greater, and the abundance of methanotrophs significantly higher, in the vicinity of methane macro-seeps compared to non-seep sites. Methylocystis was the most abundant methanotroph group at all sites, but type Ib methanotrophs showed the steepest increase in abundance at seep sites. pmoA gene analysis identified these as clade 501, while 16S rRNA gene analysis identified these as the closely related genus Methylocaldum. Sediment methane oxidation rates and the relative abundance and composition of benthic microbial communities were primarily influenced by methane availability which was in turn related to variation in river discharge. Methane-derived carbon may be an important energy source for the aquatic food webs in reaches affected by natural gas macro-seeps.

Aerobic methane synthesis and dynamics in a river water environment

“…4a ). Methanotrophs are components of a river microbiome ( Erwin et al 2005 ; Burrows et al 2021 ; Bussmann et al 2021 ) and thus it could perhaps be argued that their activity could increase with temperature, potentially exceeding synthesis, regardless of its source. However, this putative methanotroph activity occurred during peak irradiance ( Fig.…”

Methanotrophic potential of Dutch canal wall biofilms is driven by Methylomonadaceae

“…In lakes and rivers, MOB thrive at the sediment–water interface or in the water column. Several studies have determined the methanotrophic potential of the water column in lakes ( e.g ., Carini et al 2005 , Guérin and Abril 2007 , Thottathil et al 2019 , Reis et al 2020 ), but for flowing waters, this has been performed only for the rivers Saar and Elbe, Germany (Zaiss et al 1982 , Matoušů et al 2017 ), the Yellow River, China (Hao et al 2020 ), and the Condamine River, Australia (Burrows et al 2021 ).…”