EGU2020-17679
https://doi.org/10.5194/egusphere-egu2020-17679
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

When mobilized organic matter and glacial suspended sediment meet: effects of adsorption, photo- and biodegradation

Marloes Groeneveld1, Elizabeth Jakobsson1, Jeffrey Hawkes2, Jörg Tittel3, Dolly Kothawala1, and Lars Tranvik1
Marloes Groeneveld et al.
  • 1Department of Ecology and Genetics - Limnology, Uppsala University, Uppsala, Sweden
  • 2Department of Chemistry - Analytical Chemistry, Uppsala University, Uppsala, Sweden
  • 3Department of Lake Research, Helmholtz Centre for Environmental Research - UFZ, Magdeburg, Germany

The thawing of permafrost is leading to increased export of organic matter into aquatic ecosystems that was previously stored within frozen peatland soils. This organic matter has been found to be reactive to microbial and photochemical processes, so that permafrost thaw is expected to lead to an increased production of greenhouse gases. Being able to predict the fate of these increased loads of terrestrial organic carbon in aquatic systems is therefore important from a climate change perspective. In a previous study we suggest that terrestrial organic compounds susceptible to photodegradation are also prone to adsorb to mineral particles. Whereas photodegradation stimulates CO2 production, adsorption has the potential to remove organic matter from the water column and store it in the sediment. Warming at high latitudes involves both permafrost thaw and glacial melt. Glacial runoff streams often contain high loads of suspended sediment. As these minerogenic particles are transported downstream the aquatic continuum, they can eventually mix with water containing high concentrations of freshly released organic matter, and act as an adsorbent.

In order to predict CO2 production from mobilized permafrost organic matter, we need to study the bioavailability of this material before and after alteration by physical and chemical processes such as photodegradation and adsorption to mineral particles. In this study, we compared the effect of adsorption to glacial suspended sediment to that of photodegradation on the dissolved organic matter composition of surface water collected from a thawing peat plateau in northern Sweden. We used optical measurements and mass spectrometry to evaluate changes in the composition of the organic matter and employed a three-month incubation to determine its bioavailability. Initial results from optical measurements indicate that while chromophoric compounds in general were removed by both photodegradation and adsorption, humic-like fluorescent compounds were more susceptible to photodegradation than adsorption. UV-irradiation increased bioavailability of the organic matter, whereas pre-treatment by adsorption to mineral particles slightly decreased bioavailability compared to the control. Results from this study will help advance our understanding of interactive effects between physico-chemical processes and microbial degradation at an increasingly relevant interface where melting permafrost meets glacial meltwaters.

How to cite: Groeneveld, M., Jakobsson, E., Hawkes, J., Tittel, J., Kothawala, D., and Tranvik, L.: When mobilized organic matter and glacial suspended sediment meet: effects of adsorption, photo- and biodegradation , EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-17679, https://doi.org/10.5194/egusphere-egu2020-17679, 2020

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