Journal cover Journal topic
Biogeosciences An interactive open-access journal of the European Geosciences Union
Journal topic
Preprints
https://doi.org/10.5194/bg-2020-227
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.
https://doi.org/10.5194/bg-2020-227
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

  03 Jul 2020

03 Jul 2020

Review status
This preprint is currently under review for the journal BG.

Photodegradation and biodegradation of dissolved organic matter on the surface of the Greenland Ice Sheet

Miranda J. Nicholes1, Christopher Williamson1, Martyn Tranter1, Alexandra Holland1, Marian Yallop2, and Alexandre Anesio3 Miranda J. Nicholes et al.
  • 1Bristol Glaciology Centre, School of Geographical Sciences, University of Bristol, Bristol, BS8 1SS, UK
  • 2School of Biological Sciences, University of Bristol, Bristol, BS8 1TQ, UK
  • 3Department of Environmental Science, Aarhus University, Roskilde, 4000, Denmark

Abstract. The surface (supraglacial) environment of the Greenland Ice Sheet (GrIS) is an active site for the storage, transformation and transport of carbon, which is driven by extremely high levels of solar radiation throughout the ablation season. Within the south west of the GrIS, blooms of Streptophyte micro-algae (hereafter glacier algae) at abundances of ~ 105 cell mL−1 dominate primary production in the surface ice and provide dissolved organic matter (DOM) to the heterotrophic bacterial community. Glacier algae contain photoprotective secondary phenolic pigment that comprises a large proportion of the cell (~ 4 % of the dry weight) and could represent a substantial, additional carbon source for the heterotrophic community. The transformation and degradation of DOM by solar radiation (photodegradation) and heterotrophic communities (biodegradation) represent two crucial controls on DOM composition and quantity; however, the influence of these processes within the surface ice is yet to be constrained. This study therefore assessed responses in the composition and quantity of two carbon sources (glacier algae secondary pigment and surface ice DOM) following exposure to UV, PAR, UV+PAR (photodegradation) and subsequent incubation with bacterial communities isolated from the ambient environment (biodegradation). Our results indicate that exposure to predominantly UV radiation altered the composition of glacier algal pigment and surface ice DOM; however, the quantity of DOM remained constant. Biodegradation caused the greatest changes to both DOM composition and quantity, particularly in surface ice DOM. Secondary pigment extracted from glacier algae was not a highly bioavailable source of carbon and did not support significant growth of surface ice heterotrophic bacterial communities. Conversely, low molecular weight compounds in surface ice DOM were rapidly utilised by heterotrophic bacteria supporting between a 3 and 9-fold increase in bacterial abundance over a 30-day incubation. We found that photodegradation of glacier algal pigment and surface ice DOM did not influence heterotrophic consumption. Photodegradation and biodegradation of DOM in the surface ice habitat are likely intimately linked and act as fundamental controls on the composition and quantity of DOM exported to downstream environments.

Miranda J. Nicholes et al.

Interactive discussion

Status: open (until 28 Aug 2020)
Status: open (until 28 Aug 2020)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment
[Subscribe to comment alert] Printer-friendly Version - Printer-friendly version Supplement - Supplement

Miranda J. Nicholes et al.

Miranda J. Nicholes et al.

Viewed

Total article views: 135 (including HTML, PDF, and XML)
HTML PDF XML Total BibTeX EndNote
86 43 6 135 2 5
  • HTML: 86
  • PDF: 43
  • XML: 6
  • Total: 135
  • BibTeX: 2
  • EndNote: 5
Views and downloads (calculated since 03 Jul 2020)
Cumulative views and downloads (calculated since 03 Jul 2020)

Viewed (geographical distribution)

Total article views: 119 (including HTML, PDF, and XML) Thereof 119 with geography defined and 0 with unknown origin.
Country # Views %
  • 1
1
 
 
 
 

Cited

Saved

No saved metrics found.

Discussed

No discussed metrics found.
Latest update: 05 Aug 2020
Publications Copernicus
Download
Short summary
This incubation experiment assessed the role of solar radiation and heterotrophic bacteria in the degradation of organic carbon in surface ice of the Greenland Ice Sheet. Although ultraviolet radiation was found to alter carbon composition, heterotrophic degradation caused the greatest changes to both carbon composition and quantity. Both processes are likely interlinked within the surface ice and are fundamental to controlling the composition of carbon exported to downstream environments.
This incubation experiment assessed the role of solar radiation and heterotrophic bacteria in...
Citation