The influence of dissolved organic matter composition on microbial degradation and carbon dioxide production in pristine subarctic rivers
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Saarela, Taija. Zhu, Xudan. Jäntti, Helena. Ohashi, Mizue. Ide, Jun'ichiro. Siljanen Henri. Pesonen, Aake. Aaltonen, Heidi. Ojala, Anne. Nishimura, Hiroshi. Kekäläinen, Timo. Jänis, Janne. Berninger, Frank. Pumpanen, Jukka. (2024). The influence of dissolved organic matter composition on microbial degradation and carbon dioxide production in pristine subarctic rivers.29, 131-148.Rights
Abstract
Dissolved organic matter (DOM) degradation in freshwaters plays an important role in
the global carbon cycle, yet there is limited understanding of how the origin and composi-
tion of DOM regulate the production of riverine greenhouse gases. We investigated the
molecular composition of DOM using Fourier transform ion cyclotron resonance mass
spectrometry (FT-ICR MS) and measured the potential carbon dioxide (CO2) production in
pristine subarctic rivers of Finnish Lapland. During 21-day incubations, dissolved organic
carbon (DOC) was effectively mineralized into CO2 in the clearwater river associated with
mineral soils. The high degradability of mineral soil-derived DOM was supported by a
high presence of aliphatic and peptide-like compounds. Significantly lower CO2 produc-
tion per DOC was observed in the brown-water river, likely due to a large number of less
biodegradable, vascular plant-derived compounds from surrounding peatlands. These find-
ings highlight the significance of biolabile molecular compounds in the DOM degradation
dynamics of subarctic catchments.