Increasing dominance of terrigenous organic matter in circumpolar freshwaters due to permafrost thaw

• Published in: Limnology and oceanography letters Vol. 3; no. 3; pp. 186 - 198
• Main Authors: Wauthy, Maxime, Rautio, Milla, Christoffersen, Kirsten S., Forsström, Laura, Laurion, Isabelle, Mariash, Heather L., Peura, Sari, Vincent, Warwick F.
• Format: Journal Article
• Language: English
• Published: Hoboken John Wiley & Sons, Inc 01.06.2018; Wiley
• Subjects: Aquatic ecosystems; Carbon; Cellulose acetate; Climate change; Dissolved organic matter; Freshwater ecosystems; Freshwater ice; Frozen ground; Greenhouse gases; Metabolism; Oceanografi, hydrologi, vattenresurser; Oceanography, Hydrology, Water Resources; open climate campaign; Optical analysis; Organic carbon; Permafrost; Permafrost thaws; Research centers; Stable isotopes; Taiga & tundra; Terrestrial environments; Thawing; Tundra; Vegetation; Canada; Arctic region
• ISSN: 2378-2242; 2378-2242
• DOI: 10.1002/lol2.10063

Climate change and permafrost thaw are unlocking the vast storage of organic carbon held in northern frozen soils. Here, we evaluated the effects of thawing ice‐rich permafrost on dissolved organic matter (DOM) in freshwaters by optical analysis of 253 ponds across the circumpolar North. For a subset of waters in subarctic Quebec, we also quantified the contribution of terrestrial sources to the DOM pool by stable isotopes. The optical measurements showed a higher proportion of terrestrial carbon and a lower algal contribution to DOM in waters affected by thawing permafrost. DOM composition was largely dominated (mean of 93%) by terrestrial substances at sites influenced by thawing permafrost, while the terrestrial influence was much less in waterbodies located on bedrock (36%) or with tundra soils unaffected by thermokarst processes (42%) in the catchment. Our results demonstrate a strong terrestrial imprint on freshwater ecosystems in degrading ice‐rich permafrost catchments, and the likely shift toward increasing dominance of land‐derived organic carbon in waters with ongoing permafrost thaw.