Contrasting composition of terrigenous organic matter in the dissolved, particulate and sedimentary organic carbon pools on the outer East Siberian Arctic Shelf

• Published in: Biogeosciences
• Main Authors: J. A. Salvadó, T. Tesi, M. Sundbom, E. Karlsson, M. Kruså, I. P. Semiletov, E. Panova, Ö. Gustafsson
• Format: Article in Journal/Newspaper
• Language: English
• Published: Copernicus Publications 2016
• Subjects: Ecology; QH540-549.5; Life; QH501-531; Geology; QE1-996.5; Arctic; Laptev Sea; Kara Sea; Pacific; East Siberian Sea; Ice; laptev; lena river; permafrost; Sea ice; SWERUS-C3
• Online Access: https://doi.org/10.5194/bg-13-6121-2016; https://doaj.org/article/e76f4daf0e1f4cc1aa5cb52b937e56bc

Fluvial discharge and coastal erosion of the permafrost-dominated East Siberian Arctic delivers large quantities of terrigenous organic carbon (Terr-OC) to marine waters. The composition and fate of the remobilized Terr-OC needs to be better constrained as it impacts the potential for a climate–carbon feedback. In the present study, the bulk isotope ( δ 13 C and Δ 14 C) and macromolecular (lignin-derived phenols) composition of the cross-shelf exported organic carbon (OC) in different marine pools is evaluated. For this purpose, as part of the SWERUS-C3 expedition (July–September 2014), sediment organic carbon (SOC) as well as water column (from surface and near-bottom seawater) dissolved organic carbon (DOC) and particulate organic carbon (POC) samples were collected along the outer shelves of the Kara Sea, Laptev Sea and East Siberian Sea. The results show that the Lena River and the DOC may have a preferential role in the transport of Terr-OC to the outer shelf. DOC concentrations (740–3600 µg L −1 ) were 1 order of magnitude higher than POC (20–360 µg L −1 ), with higher concentrations towards the Lena River plume. The δ 13 C signatures in the three carbon pools varied from −23.9 ± 1.9 ‰ in the SOC, −26.1 ± 1.2 ‰ in the DOC and −27.1 ± 1.9 ‰ in the POC. The Δ 14 C values ranged between −395 ± 83 (SOC), −226 ± 92 (DOC) and −113 ± 122 ‰ (POC). These stable and radiocarbon isotopes were also different between the Laptev Sea and the East Siberian Sea. Both DOC and POC showed a depleted and younger trend off the Lena River plume. Further, the Pacific inflow and the sea-ice coverage, which works as a barrier preventing the input of “young” DOC and POC, seem to have a strong influence in these carbon pools, presenting older and more enriched δ 13 C signatures under the sea-ice extent. Lignin phenols exhibited higher OC-normalized concentrations in the SOC (0.10–2.34 mg g −1 OC) and DOC (0.08–2.40 mg g −1 OC) than in the POC (0.03–1.14 mg g −1 OC). The good relationship between lignin and Δ 14 C signatures in the ...