Shifts in the source and composition of dissolved organic matter in Southwest Greenland lakes along a regional hydro-climatic gradient

Christopher L. Osburn*, Nicholas J. Anderson, Colin A. Stedmon, Madeline E. Giles, Erika J. Whiteford, Terry J. Mcgenity, Alex J. Dumbrell, Graham J.C. Underwood

*Corresponding author for this work

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Abstract

Dissolved organic matter (DOM) concentration and quality were examined from Arctic lakes located in three clusters across south-west (SW) Greenland, covering the regional climatic gradient: cool, wet coastal zone; dry inland interior; and cool, dry ice-marginal areas. We hypothesized that differences in mean annual precipitation between sites would result in a reduced hydrological connectivity between lakes and their catchments and that this concentrates degraded DOM. The DOM in the inland lake group was characterized by a lower aromaticity and molecular weight, a low soil-like fluorescence, and carbon stable isotope (δ13C-DOC) values enriched by ~2‰ relative to the coastal group. DOC-specific absorbance (SUVA254) and DOC-specific soil-like fluorescence (SUVFC1) revealed seasonal and climatic gradients across which DOM exhibited a dynamic we term "pulse-process": Pulses of DOM exported from soils to lakes during snow and ice melt were followed by pulses of autochthonous DOM inputs (possibly from macrophytes), and their subsequent photochemical and microbial processing. These effects regulated the dynamics of DOM in the inland lakes and suggested that if circumpolar lakes currently situated in cool wetter climatic regimes with strong hydrological connectivity have reduced connectivity under a drier future climate, they may evolve toward an end-point of large stocks of highly degraded DOC, equivalent to the inland lakes in the present study. The regional climatic gradient across SW Greenland and its influence on DOM properties in these lakes provide a model of possible future changes to lake C cycling in high-latitude systems where climatic changes are most pronounced.

Original languageEnglish
JournalJournal of Geophysical Research: Biogeosciences
Volume122
Issue number12
Pages (from-to)3431-3445
ISSN2169-8953
DOIs
Publication statusPublished - 2018

Bibliographical note

©2017. The Authors. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

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