CS₂ increasing CH₄-derived carbon emissions and active microbial diversity in lake sediments.

Area of Science:

• Environmental microbiology
• Biogeochemistry
• Limnology

Background:

• Eutrophic lakes are significant methane (CH₄) sources.
• Volatile sulfur compounds (VSCs) are co-emitted with CH₄, potentially affecting its fate.
• Methane oxidation is crucial for mitigating lake CH₄ emissions.

Purpose of the Study:

• To investigate the impact of carbon disulfide (CS₂), a typical VSC, on CH₄-derived carbon cycling.
• To characterize active microbial communities in lake sediments under CS₂ exposure.
• To understand the interplay between CH₄ and VSCs in eutrophic lake ecosystems.

Main Methods:

• Stable isotope probing (SIP) microcosm incubations.
• Measurement of CH₄ and VSC fluxes.
• Analysis of microbial community structure and abundance (e.g., methanotrophs, methylotrophs).
• Quantification of sulfur oxidation products.

Main Results:

• CS₂ reduced CH₄-derived carbon incorporation into sediment organic matter (21.1% with CS₂ vs. 27.3% without).
• Aerobic CS₂ oxidation primarily yielded sulfate (SO₄^2--S, 59.3-62.7%).
• CS₂ decreased methanotroph and methylotroph abundance while stimulating extracellular polymeric substances (EPS) production.
• γ-proteobacteria methanotrophs were more dominant than α-proteobacteria.
• CS₂ shifted CH₄-derived carbon flow towards non-methylotrophs, including sulfur-metabolizing bacteria.

Conclusions:

• VSCs, exemplified by CS₂, significantly influence microbial processes and carbon cycling in lake sediments.
• CS₂ and its metabolites are key drivers of microbial community structure.
• Understanding these interactions is vital for predicting carbon fluxes from eutrophic lakes.