Origin-specific molecular signatures of dissolved organic matter in the Lena Delta.

• Published in: Biogeochemistry
• Main Authors: Dubinenkov, I.V., Flerus, R., Schmitt-Kopplin, P., Kattner, G.G., Koch, B.P.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Springer 2015
• Subjects: Arctic; Dom; Ft-icr Ms; Lena Delta; Molecular Markers; Permafrost; Arctic Ocean; Buor-Khaya; Khaya; Laptev Sea; Ice; laptev; lena delta; lena river; permafrost
• Online Access: https://push-zb.helmholtz-muenchen.de/frontdoor.php?source_opus=42926; https://doi.org/10.1007/s10533-014-0049-0

Large Arctic rivers discharge significant amounts of dissolved organic matter (DOM) into the Arctic Ocean. We sampled natural waters of the Lena River, the Buor-Khaya Bay (Laptev Sea), permafrost melt water creeks, ice complex melt water creeks and a lake. The goal of this study was to characterize the molecular DOM composition with respect to different water bodies within the Lena Delta. We aimed at an identification of source-specific DOM molecular markers and their relative contribution to DOM of different origin. The molecular characterization was performed for solid-phase extracted DOM by Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS). Average dissolved organic carbon concentrations in the original samples were 490 ± 75 µmol C L−1 for riverine and bay samples and 399 ± 115 µmol C L−1 for permafrost melt water creeks. Average TDN concentrations were elevated in the permafrost melt waters (19.7 ± 7.1 µmol N L−1) in comparison to the river and the bay (both 13.2 ± 2.6 µmol N L−1). FT-ICR MS and statistical tools demonstrated that the origin of DOM in the Lena Delta was systematically reflected in its molecular composition. Magnitude weighted parameters calculated from MS data (O/Cwa, H/Cwa, C/Nwa) highlighted preliminary sample discrimination. The highest H/Cwa of 1.315 was found for DOM in melt water creeks in comparison to 1.281 for river and 1.230 for the bay samples. In the bay samples we observed a higher fraction of oxygen-rich components which was reflected in an O/Cwa ratio of 0.445 in comparison to 0.425 and 0.427 in the river and creeks, respectively. From the southernmost location to the bay a relative depletion of nitrogenous molecular markers and an enrichment of oxidized DOM components occurred. The highest contribution of nitrogenous components was indicative for creeks reflected in a C/Nwa of 104 in comparison to 143 and 176 in the river and bay, respectively. These observations were studied on a molecular formula level using principal component and indicator value ...