Changes in the burial efficiency and composition of terrestrial organic carbon along the Mackenzie Trough in the Beaufort Sea

In this study, we investigated surface sediments collected along a Mackenzie Trough transect during the R/V Araon expeditions (ARA04C, ARA05C, and ARA08C) in the Beaufort Sea in 2013, 2014, and 2017. We applied various inorganic and organic geochemical tools (major elements, carbon and nitrogen contents, stable carbon and radiocarbon isotope compositions, and molecular biomarkers) in combination with sedimentological mea-surements (mineral surface area (SA) and grain size) to assess the source and burial characteristics of organic carbon (OC). In general, the sediment mean grain size decreased with water depth whereas the SA increased, resulting in a decrease in the OC loading and the burial efficiency of terrestrial OC. The sedimentary OC was further influenced by the loss of terrestrial OC and replacement with marine OC with increasing water depth. Accordingly, our results suggest that hydrodynamic sorting and degradation of terrestrial OC co-occurred together with the enrichment of marine OC with distance offshore. Such processes controlled the burial and reactivity of terrestrial OC along the Mackenzie Trough transect.

Automated summary

In this study, surface sediments collected during expeditions in the Beaufort Sea were analyzed using various geochemical tools to assess the source and burial characteristics of organic carbon. The results showed complex interactions between water depth and the burial of organic carbon in the sediments, with a decrease in burial efficiency of terrestrial organic carbon with increasing water depth. The study also highlighted the role of hydrodynamic sorting and degradation in controlling the burial and reactivity of terrestrial organic carbon along the Mackenzie Trough transect.