Stratigraphic evidence of organic carbon depletion in an intensely trawled muddy seabed

Abstract Understanding the long-term effects of bottom trawling on sedimentary organic carbon (OC) is crucial for assessing its role in carbon cycling and climate regulation. Most studies analyse effects on surface sediments (≤10 cm), leaving impacts on deeper sediments poorly resolved. This study investigates how bottom trawling influences sediment OC density (SCD) and OC content within 0–50 cm of the Western Irish Sea Mud Belt, representing sediments deposited from 1860 to 2022. SCD and OC content were lower in intensely trawled areas, declining by 0.031 × 10 −2 gC cm −3 and 0.05 wt% per additional swept area ratio (+1 yr −1 ). OC decreased by 0.007×1 0 −2 gC cm −3 and 0.01 wt% for every centimetre into the sediment. Mud content had a significant effect on OC content, but not SCD, whereas Nephrops burrowing did not significantly affect either. These findings support evidence of trawlings potentially long-term negative impact on OC in muddy sediments.