From Pleistocene Permafrost to Lena River Water – Organic Matter Characteristics using Biomarker Analysis and Isotope Hydrochemistry

• Main Author: Haugk, Charlotte
• Other Authors: Strauß, Jens, Grosse, Guido
• Format: Thesis
• Language: unknown
• Published: 2020
• Subjects: Arctic; lena delta; lena river; permafrost
• Online Access: https://epic.awi.de/id/eprint/57566/; https://epic.awi.de/id/eprint/57566/1/Masterthesis_CH_final.pdf; https://hdl.handle.net/10013/epic.f659891e-66b6-428f-8f81-12694ec06798; https://hdl.handle.net/

Organic matter stored in permafrost represents one of the largest global carbon pools that are especially vulnerable due to its susceptibility to thaw and mobilisation caused by climate warming across the Arctic. However, the amount and quality of the stored carbon (C) and nitrogen (N) as well as its composition during river transit is largely unknown. The purpose of this master’s thesis is to characterize and define the source and fate of riverine C and N from the delta interior to the nearshore zone and its possible effect on primary productivity in Arctic coastal waters using a multi-proxy approach. Organic matter quality and degradation state of a rapidly degrading yedoma cliff in the central Lena Delta (Sobo Sise Island) was analyzed using lipid biomarker analysis. To grasp the winter thaw impact, a transect of water samples from the cliff going seawards were primarily investigated for N species and stable isotope composition using a hydrochemical approach. Laboratory analyses showed an overall high organic matter quality and a low degradation state in yedoma deposits which suggests freeze-locking immediately after deposition. While the dominant winter water source was attributed mainly to subsurface permafrost flow, it was found that dissolved organic nitrogen (DON) rather than nitrate is the main N species to be released into the riverine environment and was susceptible to alteration by remineralization and denitrification. Describing organic matter associated with thawing permafrost at the terrestrial-marine interface in a season-explicit study leads to a better understanding of C and N dynamics and thus the effects of a warming climate in Arctic environments.