Data from: Spartina alterniflora invasion drastically increases methane production potential by shifting methanogenesis from hydrogenotrophic to methylotrophic pathway in a coastal marsh

1. Plant invasion can strongly influence carbon (C) cycling processes,
thus it may affect climate change by altering C sequestration and
greenhouse gas emissions in the invaded ecosystem. Since 1979, the exotic
Spartina alterniflora has rapidly expanded in China’s coastal areas, where
significant increase in methane (CH4) emissions has been documented from
post-invaded sites. However, a mechanistic understanding of the structural
and functional changes of associated methanogens accompanying this
invasion remains elusive. 2. Here we conducted integrated biogeochemical
investigations on methanogenic substrates, activity, and diversity to
identify implications of S. alterniflora invasion for methanogenesis in
coastal wetlands. To do this, we collected and analyzed 0–50 cm soil
profiles from an uncolonized tidal flat (TF) and salt marshes that S.
alterniflora has invaded for 1 year (SA-1) and 12 years (SA-12) in
Jiangsu, China. Methanogenic community composition was characterized by
massive parallel sequencing. The rates and pathways of methanogenesis were
determined by adding trace concentrations of 13C-labeled substrates to
anaerobic incubated samples. 3. Our results revealed that 12-year invasion
of S. alterniflora drastically increased CH4 production potential by one
order of magnitude over that of TF. This substantial increase was
primarily attributed to methanogenesis from trimethylamine; its rates
increased by two orders of magnitude over TF whereas those from acetate
and H2/CO2 increased far less. Hydrogenotrophic methanogenesis was the
dominant pathway operating in the TF, but methanotrophic pathway
contributed most to CH4 production in the surface layer of SA-1 and
upper-most 40-cm layers of SA-12. Consistent with these observations, the
dominant methanogens shifted from obligate hydrogenotrophic
Methanococcales in TF to potential methylamine-utilizing
Methanosarcinaceae in SA-12. Our Mantel analysis indicated that
‘non-competitive’ trimethylamine, derived from cytoplasmic osmolytes of S.
alterniflora, was the major driver of this change in methanogenic
community composition. 4. Synthesis. Our results suggest that invasive S.
alterniflora plants gradually facilitated the local dominance of
methylotrophic Methanosarcinaceae by changing the key type of methanogenic
substrate in coastal marshes. Shifts in methanogen communities and
enhanced availability of trimethylamine elevated the rates and importance
of methylotrophic methanogenesis, thereby markedly increasing CH4
production potential and emission rates in this type of ecosystem.