Accumulation rates of sediments and particulate organic carbon (POC) will be studied in the Heligoland mud area and in the Skagerrak since these areas serve as major sediment depo-centers in the North Sea. WP1 will take sediment cores and reconstruct changes in mass and POC accumulation rates in these key areas over the last centuries using a range of different dating methods. The resulting time series will be employed to reconstruct how sediment and POC dynamics have changed over time and how the observed changes are related to natural variability and anthropogenic impacts on sediment/POC turnover in the North Sea. These data will serve as an important basis for the modeling work in APOC and will help to quantify how POC and CO₂ cycling in the North Sea has been affected by bottom-touching fisheries, dredging and other human interventions.