CMI Annual Report 2021

more methanogenic (Figure 6.1a, Wilmoth et al., 2021). The
researchers have pieced together fragments of genetic
information from peat microbiomes to recreate microbial
genomes. This has allowed the researchers to show that
transient oxygenation selects for different keystone
microorganisms at multiple steps of the microbial food chain
underlying peat carbon conversion into methane (Figure 6.1b,
Reji et al., submitted).
Figure 6.1a-b.
(a) Transient oxygen
exposure triggers a shift
in microbial community
succession during
microbial degradation of
complex aromatic peat
carbon that promotes
methane formation.
(b) Genome
reconstructions indicate
functionally distinct
microbial organisms
with varying metabolic
adaptations that are
enriched under anoxic
versus oxygen-oscillated
conditions (Reji et al.,
submitted).
To better constrain the effects of hydrologically driven oxygen
variability on methane emissions from a greater diversity of
wetlands, current work examines wetlands along a fresh to
saltwater continuum, including organic-rich peat, mineral-soil
marsh, and saltmarsh sediments. Preliminary results indicate
that oxygen-rich to poor transitions accelerate methane
emissions from peat and marsh soils, but not from saltmarsh
sediments. Geochemical variables such as pH, mineral
composition, and organic carbon content are significantly
different between the peat and marsh soils. This suggests
that distinct microbial mechanisms underlie the observed
methane emission patterns. Researchers are in the process of
disentangling these biological and geochemical mechanisms.
They have also started to examine the efficacy of chemical
amendments like biochar in reducing wetland methane
emissions.
The CMI Wetland Project has identified the influence of
environmental conditions (e.g., O 2
, soil saturation, water table,
salinity) and soil molecular form on microbial biodiversity
as keys to better constrain and mitigate wetland methane
emissions. The researchers urge the adoption of strategies to
limit greenhouse gas emissions from natural and constructed
Carbon Mitigation Initiative Twenty-first Year Report 2021
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