Response of greenhouse gas production to aquaculture activities and the underlying microbial mechanisms in mangrove wetlands

Tidal wetland reclamation could profoundly alter ecological function and ecosystem service provision, but its impacts on sediment microbial communities and functions remain poorly understood. We investigated spatial and seasonal patterns of greenhouse gas (GHG) production response to aquaculture activities in mangrove wetlands and unraveled the underlying mechanisms by integrating environmental parameters and microbial communities. Microbial community richness and diversity substantially reduced, and the composition was reshaped. Converting mangrove to chronically flooded aquaculture pond increased sediment CH₄ production rates, but reduced N₂O and CO₂ production rates. Although increasing anthropogenic disturbance in aquaculture pond have reduced microbial community richness and diversity compared to native mangrove wetland, they have increased complexity of species associations resulting in a more complex and stable network. Microbial community richness and network complexity and stability were strongly related to CH₄ and N₂O production rates, but not significantly associated with CO₂ production rates, suggesting microbial community richness, network complexity and stability are better predictors of the specialized soil/sediment functions CH₄and N₂O production). Therefore, preserving microbial “interaction” could be important to mitigate the negative effects of microbial community richness and diversity loss caused by human activities. Furthermore, as the residual bait accumulation is a severe issue in aquaculture activities, we especially focused on the influence of bait input at time scale through a 90-day incubation experiment, aiming to observe temporal variations of physicochemical properties, sediment microbial community, and GHG production in response to different amounts of bait input. The results showed that dissolved oxygen of overlying water was profoundly decreased owing to bait input, while dissolved organic carbon of overlying water and several sediment properties (e.g., organic matter, sulfide, and ammonium) varied in reverse patterns. Meanwhile, bait input strongly altered microbial compositions from aerobic, slow-growing, and oligotrophic to anaerobic, fast-growing, and copiotrophic. Moreover, both GHG production and global warming potential were enhanced by bait input, implying that aquaculture ecosystem is an important hotspot for global GHG emission. Overall, bait input triggered quick responses of physicochemical properties, sediment microbial community, and GHG production, followed by long-term resilience of the ecosystem. Future research should comprehensively consider microbial diversity, species composition and interaction strength, functions, and environmental conditions to accurately predict soil/sediment functioning and emphasize the necessity of sustainable assessment and effective management.