Distinct Microenvironments Driven by Crab Bioturbation Enhance Aerobic and Anaerobic Methane Oxidation in Intertidal...

Coastal wetlands act as significant natural sources of the potent greenhouse gas, methane (CH₄). While burrowing benthos such as crabs are recognized as important regulators of biogeochemical processes in these ecosystems, their specific impacts on CH₄ oxidation and the underlying mechanisms remain poorly understood. Here, we demonstrate that crab bioturbation substantially enhances potential aerobic and anaerobic CH₄ oxidation within burrow systems. This stimulatory effect exhibits distinct spatial heterogeneity, diminishing with an increase in the distance from the burrow walls. We found that this heterogeneity is driven by the three-dimensional burrow architecture, which establishes steep gradients in physicochemical conditions, electron-acceptor availability, and the abundance of CH₄-oxidizing microorganisms. Furthermore, total organic carbon, salinity, the Fe²⁺/Fe³⁺ ratio, and nutrient contents were identified as key environmental predictors of the CH₄ oxidation dynamics. These findings advance the mechanistic understanding of CH₄ sinks in complex coastal habitats and provide a critical scientific basis for accurately assessing wetland carbon budgets in the context of global climate change.