Browsing by Author "Cotner, James"

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    Accumulation of recalcitrant dissolved organic matter in aerobic aquatic systems
    (2021-02-09) Cotner, James; Anderson, NJ; Osburn, Christopher; cotne002@umn.edu; Cotner, James; Cotner Lab
    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.
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    Accumulation of recalcitrant dissolved organic matter in aerobic aquatic systems - Version 2
    (2021-10-04) Cotner, James; Anderson, N.J.; Osburn, Christopher; cotne002@umn.edu; Cotner, James
    Dataset from a paper submitted to Limnology and Oceanography Letters titled 'Accumulation of recalcitrant dissolved organic matter in aerobic aquatic systems'. Data include both experimental and observational data from a set of lakes just west of Kangerlussuaq, SW Greenland (67° N, 51° W). Experimental data were from incubations of lake water from several lakes that differ in salinity with microbes to examine the degradation of dissolved organic matter (DOM). The loss of DOM was followed for nearly a year and the results were fit to an exponential decline model. The observational data come from some of the same lakes but includes others in the region. These data include measurements of dissolved organic carbon (DOC), carbon stable and unstable isotopes (13C, 14C), optical properties (absorbance, SUVA, spectral slope) and specific conductivity. Other data include catchment characteristics for lakes in the region (lake and catchment area, altitude, maximum depth). Other data include profiles of dissolved oxygen and temperature for several of the lakes and the 14C dates.