Bioturbation by Chinese mitten crabs (Eriocheir sinensis H. Milne Edwards) mitigates the global warming potential of integrated rice-crab farming systems in saline-alkaline soils

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• Eriocheir sinensis bioturbation reduces CH₄ emissions but enhances N 2 O emissions in saline-alkaline paddy fields. • Greenhouse gas emissions exhibit significant dynamic variations under different bioturbation intensities. • The rice-crab co-culture system achieves synergistic benefits in saline-alkaline soil amelioration and greenhouse gas mitigation. As global demand for sustainable agricultural development continues to grow, rice-aquaculture coculture systems in saline-alkaline lands have garnered widespread attention due to their dual ecological and economic benefits. However, the impact of aquatic animals on greenhouse gas emissions in rice-aquaculture coculture systems in saline-alkaline lands remains unclear, which limits a comprehensive assessment of the ecological and environmental benefits of this model. In this study, we established three experimental treatments: a crab-free control (CK), a low-density group (D1, 75 kg/ha), and a high-density group (D2, 112.5 kg/ha) of Chinese mitten crab ( Eriocheir sinensis ). Through field experiments, we systematically investigated the effects of bioturbation on methane (CH₄) and nitrous oxide (N₂O) emissions in a saline-alkaline rice-crab co-culture system. The results demonstrated that the bioturbation effect of E. sinensis significantly suppressed CH₄ emissions, with the total emissions in the high-density (D2) group decreasing by 15.7% compared to the control (CK) group without crabs. This reduction was attributed to enhanced sediment redox potential (Eh increased by 13.4%) and elevated expression of the methane oxidation functional gene pmoA (84.0% increase in the D2 group).In contrast, the bioturbation effect of E. sinensis significantly promoted N₂O emissions, with total emissions in the low-density (D1) and high-density (D2) groups increasing by 73.2%–119.6% compared to the CK group. This increase was associated with reduced soil salinity and higher expression of nitrification ( amoA-B , 54.3%–78.7%) and denitrification ( nirS , 50%–82.2%; nirK , 17.1%–32.2%) genes in sediments. Notably, ditches contributed 43.1% and 46.8% of the N₂O emissions, respectively. Under both bioturbation intensities, the global warming potential of the rice-crab coculture system decreased by 6.1%–15.7%, with CH₄ reduction accounting for 99% of the net climate effect. The findings suggest that rice-crab co-culture offers a promising low-carbon and sustainable farming strategy for saline-alkaline lands. Graphical abstract illustrating the effects of crab bioturbation on greenhouse gas emissions in saline–alkaline rice–crab co-culture systems. Crab activities reduce soil salinity, improve redox conditions, and regulate microbial functional genes, thereby suppressing CH₄ emissions while enhancing N₂O release. Overall, the dominant CH₄ reduction effect decreases the 100-year global warming potential (GWP) of the system by 6.1%–15.7%.