Human impacts on marine sedimentary carbon sequestration

The seafloor functions as a substantial long-term (>100 yr) carbon sink and reservoir in the form of sedimentary organic particles. Human activities can modify the seafloor's natural carbon sequestration capacity by disturbing the upper sediment layers and thereby altering biogeochemical processes and releasing previously trapped carbon. Yet, the overall magnitudes of the changes in sedimentary carbon pools induced by these processes are not well known and could not be adequately considered in environmental impact assessments so far.

In this study, we quantify anthropogenic disturbances of sedimentary carbon sequestration in the North Sea using a combination of measurement data and numerical modeling. In particular, we examine the effects of bottom-contacting fisheries, sediment extraction, and material dumping. By resolving spatial and temporal patterns of both natural and anthropogenic drivers, we identify areas particularly vulnerable to degradation, representing the most detailed large-scale estimates of human impacts on North Sea sediments to date. Our results indicate that while the impacts of human activities on sedimentary carbon sequestration are comparable in magnitude to natural sedimentation processes, the resulting carbon benefits are considerably lower than previously estimated.

Although remaining uncertainties need to be further confined and missing processes such as ecosystem feedbacks considered, our findings can serve as a useful basis for the consideration of sedimentary carbon disturbance in the context of marine spatial management plans.