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Coastal wetlands can store carbon by sequestering more carbon through primary production than they release though biogenic greenhouse gas production. The joint effects of saltwater intrusion and sea level rise (SWISLR) and changing precipitation patterns alter sulfate and oxygen availability, challenging estimates of biogenic greenhouse gas emissions. Iron-rich soils have been shown to buffer soil sulfidization by sequestering sulfide into iron-sulfide. But as SWISLR increases soil sulfate concentrations, sulfide produced via sulfate reduction will likely exceed the buffering capacity of soil iron, allowing toxic sulfide levels to accumulate. We used a soil mesocosm approach to examine the influence of hydrology (wet, dry, interim) and plant presence (with or without plants) on wetland soils sourced from different hydrologic histories at a restored coastal wetland. We hypothesized that reducing conditions (i.e., flooded, no plants) impact anaerobic metabolisms similarly, whereas oxidizing conditions (i.e., dry, plant presence) disrupt coupled sulfate reduction and iron reduction. Over eight weeks of hydrologic manipulation, 16S rRNA amplicon sequencing and shotgun metagenomic sequencing were used to characterize microbial communities, while greenhouse gas fluxes, soil redox potential, and physicochemical properties were measured. Results showed that contemporary hydrologic treatment affected assimilatory sulfate reduction gene composition, and hydrologic history influenced dissimilatory sulfate reduction and iron reduction gene composition. Sulfate and iron reduction genes were correlated, and dissimilatory sulfate reduction genes explained variance in methane fluxes. These findings highlight the role of historical hydrology, potential saltwater exposure, and soil iron in shaping microbial responses to future changes in soil moisture and salinity.
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Wetland soil history shapes microbial community composition, while hydrologic disturbance alters greenhouse gas fluxes
Abstract While wetlands represent a small fraction (~5%–10%) of the world's land surface, it is estimated that one‐third of wetlands have been lost due to human activities. Wetland habitat loss decreases ecosystem benefits, including improved water quality and climate change mitigation. These microbially mediated functions are dependent on redox conditions, which are altered by soil hydrology and the presence of plants. We tested the overarching hypothesis that while microbial community composition would be resistant to change due to long‐term hydrologic history, key functions like greenhouse gas production would remain plastic and responsive to short‐term environmental shifts. Using a mesocosm design, we manipulated the duration of hydrologic conditions (i.e., stable dry, stable flooding, and alternating wet/dry) and the presence of plants to induce soil redox changes in wetland soils. We measured soil redox status, used targeted amplicon and shotgun metagenomic sequencing to characterize microbial communities, and measured greenhouse gas production to assess microbial function. The 8‐week hydrologic treatment shifted community composition but did not override the stronger effects of long‐term hydrologic history. Methane and carbon dioxide fluxes were altered by short‐term hydrologic treatment, with methane production favored in the wet treatment and carbon dioxide production favored in the dry treatment. Plant presence versus absence manipulation had little impact on soil microbiome composition or soil greenhouse gas production. The results highlight the resistance of microbial community structure shaped by historical hydrologic regimes, and emphasize that hydrologic conditions exert a stronger influence than plant presence on microbial composition and function. Predicting the outcomes of wetland disturbance and restoration requires an enhanced understanding of community stability and functional plasticity. Our results suggest that wetland hydrologic restoration can establish a stable microbial community that is resistant to environmental shifts, but microbial functions such as greenhouse gas emissions remain responsive to hydrologic disturbances, including flooding and drought.
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- PAR ID:
- 10673426
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Ecosphere
- Volume:
- 17
- Issue:
- 3
- ISSN:
- 2150-8925
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript
- Journal Article:
- https://doi.org/10.1002/ecs2.70571
