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Abstract Despite substantial contributions of ecosystem services, mutualistic plant-microbe associations in wetlands are severely threatened by human activities. Therefore, promoting positive plant-microbe associations underpins coastal wetland restoration, where human stressors and climate change challenge successful outcomes. This study examined how salinity stressors influence plant-microbe relationships, where we hypothesized that the presence of marsh microbes would provide a rescue effect by buffering abiotic stressors and yielding higher plant biomass. We used a whole sediment inocula approach and exposed marsh cordgrass (Sporobolus alterniflorus) plugs to a factorial experiment with three levels of microbiome addition (microbial inocula, autoclaved microbial inocula, no microbe control) and two levels of salinity (< 0.5 psu, 20 psu), replicated ten times. We added marsh-site microbial inocula with autoclaved peat-based greenhouse soil and exposed half the plugs to saltwater (20 psu) and half to freshwater (< 0.5 psu). Results revealed that marsh microbial inocula additions during early plant development may ameliorate salinity stressors. Plants treated with microbial inocula and salinity stress exhibited greater aboveground biomass (P < 0.09) than those under freshwater conditions. With live microbial inocula, the median of aboveground biomass and change in plant height were higher in saltwater compared to freshwater conditions. Change in plant height, belowground biomass, root-to-shoot ratio, soil bacterial diversity H’, and evenness J’ were similar across microbial and salinity treatments. However, salinity (P < 0.001) and microbial treatments (P < 0.001) significantly influenced the bacterial community composition, with distinct assemblages under salinity conditions. This work underscores the need for continued research to develop robust protocols for microbiome stewardship that enhance plant resilience and improve the success of future wetland restoration efforts. 

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. 

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. 

Agriculture is a major contributor to nutrient pollution that drives eutrophication in aquatic ecosystems. This study integrates hydrological modeling with farmer behavioral analysis to assess the effectiveness of two agricultural conservation practices—cover crops and reduced nitrogen fertilizer application—in reducing nitrate loss from fields in the Tar-Pamlico River Basin of North Carolina. Survey responses from 279 farmers revealed widespread reluctance to adopt conservation practices, particularly strict fertilizer reductions. A hydrological model showed that applying each practice to 25 percent of agricultural land could substantially reduce nitrate export, with cover crops showing greater effectiveness than reduced fertilizer use. However, an integrated socio-hydrological model, which incorporated behavioral responses from farmers, predicted much smaller reductions in nitrate loss due to limited voluntary adoption. Specifically, nitrate reductions were overestimated by a factor of 8 for cover crops and by a factor of 25 for reduced fertilizer application when behavioral responses were excluded. This result highlights a critical limitation of traditional modeling approaches and underscores the importance of integrating human decision-making into environmental policy analysis. By linking policy incentives with both biophysical and social responses, this study offers a more realistic framework for designing cost-effective and impactful agricultural conservation strategies. 

ABSTRACT Temperature significantly impacts microbial communities’ composition and function, which plays a vital role in the global carbon cycle that determines climate change. Nutrient influxes often accompany rising temperatures due to human activity. While ecological interactions between different microorganisms could shape their response to environmental change, we do not understand how predation may influence these responses in a warmer and increasingly nutrient-rich world. Here, we assess whether predation by a ciliate community of bacterial consumers influences changes in the diversity, biomass, and function of a freshwater prokaryotic community under different temperature and nutrient conditions. We found that predator presence mediates the effects of temperature and nutrients on the total prokaryotic community biomass and composition through various mechanisms, including direct and indirect effects. However, the total community function was resilient. Our study supports previous findings that temperature and nutrients are essential drivers of microbial community composition and function but also demonstrates how predation can mediate these effects, indicating that the biotic context is as important as the abiotic context to understanding microbial responses to novel climates.IMPORTANCEWhile the importance of the abiotic environment in microbial communities has long been acknowledged, how prevalent ecological interactions like predation may influence these microbial community responses to shifting abiotic conditions is largely unknown. Our study addresses the complex interplay between temperature, nutrients, predation, and their joint effects on microbial community diversity and function. Our findings suggest that while temperature and nutrients are fundamental drivers of microbial community dynamics, the presence of predators significantly alters these responses. Our study underscores the impact of abiotic factors on microbial communities and the importance of accounting for the biotic context in which these occur to understand, let alone predict, these responses properly. 

Although the gut and the brain vastly differ in physiological function, they have been interlinked in a variety of different neurological and behavioral disorders. The bacteria that comprise the gut microbiome communicate and influence the function of various physiological processes within the body, including nervous system function. However, the effects of social experience in the context of dominance and social stress on gut microbiome remain poorly understood. Here, we examined whether social experience impacts the host zebrafish (Danio rerio) gut microbiome. We studied how social dominance during the first 2 weeks of social interactions changed the composition of zebrafish gut microbiome by comparing gut bacterial composition, diversity, and relative abundance between socially dominant, submissive, social isolates and control group–housed communal fish. Using amplicon sequencing of the 16S rRNA gene, we report that social dominance significantly affects host gut bacterial community composition but not bacterial diversity. At the genus level, Aeromonas and unclassified Enterobacteriaceae relative abundance decreased in dominant individuals while commensal bacteria (e.g., Exiguobacterium and Cetobacterium) increased in relative abundance. Conversely, the relative abundance of Psychrobacter and Acinetobacter was increased in subordinates, isolates, and communal fish compared to dominant fish. The shift in commensal and pathogenic bacteria highlights the impact of social experience and the accompanying stress on gut microbiome, with potentially similar effects in other social organisms.