Significant contribution of petrogenic organic carbon to suspended particulate organic carbon in the Beaufort Sea

초록

Remobilized terrestrial organic carbon from permafrost-affected landscapes is increasingly recognized as a key component of Arctic carbon cycling. In this study, we investigated the sources of particulate organic carbon in the surface mixed layers across the Mackenzie Trough by combining dual-isotope analyses (Δ14Corg, δ13Corg) with molecular biomarkers (lignin phenols). Building on previous sediment-based source apportionment approaches, we assessed their applicability to suspended particulate matter collected along a shelf-to-slope transect in the Canadian Beaufort Sea. To address uncertainties in end-member composition, we implemented a Monte Carlo-based mixing model that integrates multiple geochemical tracers, including Δ14Corg, δ13Corg, 3,5-dihydroxybenzoic acid to vanillyl phenols (3,5-Bd/V) ratio, and lignin phenol concentrations. Our results showed that petrogenic organic carbon contributed substantially, ranging from 11% to 53%, to particulate organic carbon in both the upper and lower polar mixed layers. These findings provide direct evidence for the presence of petrogenic organic carbon in Arctic surface waters and highlight its active role in shelf carbon dynamics. The persistence of this ancient, refractory carbon pool in suspension emphasizes the need to include petrogenic organic carbon in assessments of terrestrial carbon mobilization, transformation, and burial in a rapidly warming Arctic. © 2026 Association for the Sciences of Limnology and Oceanography.

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