Accumulation of recalcitrant dissolved organic matter in aerobic aquatic systems

  • James B Cotner (Creator)
  • N. J. Anderson (Creator)
  • Christopher Osburn (Creator)



An oxygenated atmosphere led to many changes to life on Earth but it also provided a negative feedback to organic matter accumulation over billions of years by increasing decomposition rates. Nonetheless, dissolved organic carbon (DOC) is a huge carbon pool (>750 Pg) and it can accumulate to high concentrations (20-100 mg C L-1) in some freshwater aquatic systems, yet it is not clear why. Here, we examine DOC in several arctic lakes with varying concentrations and identify processes that alter its composition to make it recalcitrant to further degradation processes. Aging of DOC (from radiocarbon Δ14C ratios) corresponded with changes in its concentration, degradation rates, δ13C-DOC isotope ratios and optical quality, all suggesting that photochemical and microbial degradation processes contributed to decreased DOC reactivity over time. The degradation of young DOC was strongly stimulated by inorganic phosphorus, but older DOC was not, suggesting an important role for nutrients in regulating organic carbon degradation rates and pool sizes. Photochemical processing coupled with decreased habitat and microbial diversity in hydrologically isolated systems may enable recalcitrant DOC to accumulate with important implications for the Earth's carbon and oxygen cycles.

Data includes 2 parameter and 3 parameter degradation parameter estimates from several SW Greenland lakes from experiments in 2006; catchment data for all of the lakes, along with 13C-DOC and 14C-DOC natural abundance isotope data along with optical data that are included in Figures 1 and 2 of the paper. Lastly, we include measurements of and estimates of conductivity measurements for the lakes.

Funding information
Sponsorship: NSF; NSERC

Referenced by
submitted to PNAS
Date made availableFeb 5 2021
PublisherData Repository for the University of Minnesota
Date of data productionAug 2006 - Jul 2018

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