Preprints
https://doi.org/10.5194/egusphere-2022-908
https://doi.org/10.5194/egusphere-2022-908
 
05 Oct 2022
05 Oct 2022

Abrasion of sedimentary rocks as a source of hydrogen peroxide and nutrients to subglacial ecosystems

Beatriz Gill-Olivas1, Jon Telling2, Mark Skidmore3, and Martyn Tranter1 Beatriz Gill-Olivas et al.
  • 1Department of Environmental Science, Aarhus University, Roskilde, Denmark
  • 2School of Natural and Environmental Sciences, Newcastle University, Newcastle, UK
  • 3Department of Earth Sciences, Montana State University, Bozeman, United States

Abstract. Glaciers and ice-sheets are renowned for their abrasive power, yet little is known of the mechanochemical reactions which are initiated by abrasion in these environments and their effect on subglacial biogeochemistry. Here, we use sedimentary rocks representative of different subglacial environments and from a previously glaciated terrain to investigate the potential for subglacial erosion to generate H2O2 and release bio-utilisable organic carbon and nutrients (N, Fe). Samples were crushed using a ball mill, water added to rock powders within gastight vials, and samples incubated in the dark at 4 °C. Headspace and water samples were taken immediately after the addition of water and then again after 5 and 25 h. Samples generated up to 1.5 µmol H2O2 g-1. The total sulphur content, a proxy for the sulphide content, did not correlate with H2O2 generation, suggesting that the pyrite content was not the sole determinant of net H2O2 production. Other factors, including the presence of carbonates, Fe-driven Fenton reactions and the pH of the solution were also likely to be important in controlling both the initial rate of production and subsequent rates of destruction of H2O2. Further, we found erosion can provide previously unaccounted sources of bio-utilisable energy substrates and nutrients, including up to 880 nmol CH4 g-1, 680 nmol H2 g-1, volatile fatty acids (up to 1.7 µmol acetate g-1) and 8.2 µmol NH4+ g-1 to subglacial ecosystems. These results highlight the potentially important role that abrasion plays in providing nutrient and energy sources to subglacial microbial ecosystems underlain by sedimentary rocks.

Beatriz Gill-Olivas et al.

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2022-908', Anonymous Referee #1, 17 Nov 2022
  • RC2: 'Comment on egusphere-2022-908', Simon Bottrell, 22 Nov 2022

Beatriz Gill-Olivas et al.

Beatriz Gill-Olivas et al.

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Short summary
Microbial ecosystems have been found in all subglacial environments sampled to date. Yet, little is known of the sources of energy and nutrients that sustain these microbial populations. This study shows that crushing of sedimentary rocks, which contain organic carbon, carbonate and sulphide minerals, along with previously weathered silicate minerals, produces a range of compounds and nutrients which can be utilised by the diverse suite of microbes that inhabit glacier beds.