Effects of bottom-trawling induced organic matter resuspension on carbon cycling in the North Sea

Understanding how human activities influence ocean–atmosphere CO₂ exchanges require quantifying both natural variability and anthropogenic drivers of the marine carbon cycle. The climate implications of trawling-induced organic matter resuspension remain contentious, and biogeochemical feedback unassessed. Using a 3-dimensional coupled physics–biogeochemistry model, we provide basin-scale estimate of how sediment resuspension from bottom trawling affects the North Sea carbon system. The direction and intensity of trawling impacts show spatial variabilities, with amplified heterotrophic respiration and CO₂ outgassing in shallow, well-mixed areas whereas enhanced CO₂ uptake occurs in deep, stratified areas. We find that trawling-induced resuspension results in a slight net increase in oceanic CO₂ uptake of ~1.02%. This net effect arises from shifts in biological carbon pathways rather than from direct physical disruption alone. Resuspension stimulates primary production and strengthens biological control on surface pCO₂. Annual average total benthic remineralization decreased by 0.066 (12.14 %) Tmol C yr⁻¹ and annual average total pelagic remineralization increased by 0.078 (1.49 %)Tmol C yr⁻¹, enhancing the vertical gradient of net community production. Increased nutrient remineralization leads to more carbon uptake within the North Sea, while much of the additional POC and DIC in the water column are laterally transported to the Atlantic before winter. By disentangling the role of sediment resuspension, this study complements previous assessments and fills an important gap in quantifying bottom-trawling impacts on carbon cycles. Our results emphasize that the climate impact of bottom trawling cannot be generalized globally and must be evaluated in a region-specific biogeochemical context.