Responses of microbial communities and greenhouse gas production to land use change in mangrove wetland sediments

Tidal wetland reclamation is a worldwide issue that profoundly alters ecological functions and ecosystem service provisions; however, its impacts on sediment microbial communities and functions remain poorly understood. Here, we investigated the spatial and seasonal patterns of greenhouse gas (GHG) production in response to land use change in mangrove wetlands and elucidated the underlying mechanisms by integrating environmental parameters and microbial community characteristics. In the time period studied, land use change substantially reduced the sediment organic matter content, microbial community richness and diversity, and CO2 production rates. Converting mangroves to drier land cover types, namely orchard and vegetable field, significantly diminished reducing substrates (sulfide, Fe2+, and NH4+), microbial network complexity and stability, and CH4 production rates, while increasing N2O production rates. In contrast, these parameters showed the opposite trend following the conversion of mangroves to flooded aquaculture pond. Overall GHG production rate in mangrove wetlands was 399.8 mg CO2e kg−1 d−1, which respectively decreased by 68.83%, 69.86%, and 30.84% in orchard, vegetable field, and aquaculture pond. Microbial community richness and network complexity and stability were strongly related to the production rates of CH4 and N2O, rather than CO2, which can be better indicators of specialized functions (CH4 and 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 in aquatic environments. Future research should consider environmental conditions and microbial community diversity, composition, interactions, and activities to gain a comprehensive understanding of ecosystem functions.