Aggravation of nitrous oxide emissions driven by burrowing crab activities in intertidal marsh soils: Mechanisms and environmental implications.

Coastal wetlands are hotspots for nitrogen (N) cycling and a significant natural source of the potent greenhouse gas nitrous oxide (N 2 O). Burrowing benthos are known to transform N in intertidal marsh soils, but their contribution to N 2 O emissions and the underlying molecular mechanisms remain unclear. Here, the effects of crab bioturbation on N 2 O emissions in coastal marshes, where Chiromantes dehaani and Helice tridens tientsinensis were the dominant crab species, were investigated in field and indoor experiments. The N 2 O emissions increased significantly in the presence of crabs, being positively correlated with the intensity of crab bioturbation but differing among crab species. Natural-abundance isotope analyses indicated that crab bioturbation greatly promoted the contribution of hydroxylamine oxidation to N 2 O production; nevertheless, bacterial denitrification (including heterotrophic denitrification and nitrifier denitrification) remained the dominant pathway. Molecular analyses suggested that the increased N 2 O emissions in crab-disturbed habitats might be driven by underlying changes to microbial communities, especially by the disproportionate stimulation of nitric oxide reductase-carrying microbes over nitrous oxide reductase-carrying microbes. This study highlights the importance of considering the burrowing activity, density, and species of benthos when evaluating the N cycle in coastal wetlands. [Display omitted] • Crab bioturbation greatly accelerates N 2 O emission in intertidal marsh soils. • Increase of N 2 O emission is closely related to reshaped microbial community by crab. • Different species of crabs exhibit different promoting effects on N 2 O emission. • Crab bioturbation affects N 2 O production pathways based on N 2 O isotopic signatures. • Activity and species of crabs should be considered when restoring coastal wetlands. [ABSTRACT FROM AUTHOR]