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

Abstract

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.