Intense and persistent bottom trawling impairs long-term carbon storage in shelf sea sediments

Abstract Bottom trawling represents the most widespread anthropogenic physical disturbance to shelf sea sediments 1-3 . While trawling-induced changes in benthic communities are widely recognized, current evidence of its impact on long-term organic carbon (OC) storage in seabed sediments remains controversial 2,4-6 . To address this, we first combined independent datasets of sediment and bottom trawling intensity for the global shelf seas and for a heavily trawled region, the North Sea, respectively, to explore the relationship between OC storage and trawling. A pattern emerges when comparing the surface sediment OC-to-mud ratio (OC/mud) and the trawling intensity represented by the annual swept area ratio (SAR). OC/mud is relatively scattered where SAR < 1, but becomes increasingly confined to a narrower and lower range as SAR increases. The constraint of bottom trawling on OC/mud can be described by a power function, namely OC/mud ≤ 0.25×SAR -0.25 . We then applied three-dimensional physical–biogeochemical modeling to investigate the underlying driving mechanisms. Results suggest that intense and persistent trawling (SAR > 1) results in a net reduction of sedimentary carbon in the long term. The identified dependence of OC/mud on trawling, and the associated process-based understanding could assist both national and international marine spatial planning for climate change mitigation.