Shifts in organic matter character and microbial community dynamics from glacier headwaters to downstream rivers in the Canadian Rocky Mountains

• Author / Creator

  Drapeau, Hayley

• Climate change is causing mountain glacial systems to warm rapidly, leading to increased water fluxes from these catchments and concomitant export of glacially-derived sediment and organic matter (OM). Glacial OM represents an aged, but potentially bioavailable carbon pool that is compositionally distinct from OM found in non-glacially sourced waters. Despite this, the composition of riverine OM from glacial headwaters to downstream reaches and its role in structuring microbial communities has yet to be characterized in the Canadian Rockies. Over three summers (2019-2021) samples were collected from four glacially-fed rivers within Banff and Jasper National Parks. Samples were collected before, during and after glacial icemelt along a transect ranging 0 – 100 km downstream of glacial termini. Organic carbon (OC) isotopes (Δ14C-OC, δ13C-OC) were used to assess OM age and source, dissolved OM absorbance and fluorescence were used to assess OM character. Microbial community composition was assessed utilizing 16S rRNA gene sequencing. From headwater to rivers OM transitioned from being aged and protein-like with an apparent microbial source to being relatively younger, humic-like and sourced from plants and benthic algae. This transition was likely driven by changing catchment characteristics with movement downstream, and the presence of more developed soils. Total nitrogen, deuterium excess (correlated with glacial ice contribution), water temperature and protein-like DOM were significant in explaining microbial community structure, although only to a small extent (14%). This finding paired with the identification of a core community that made up large fraction of relative abundance at each site, indicating mass effects as driving a fraction of microbial community composition within these streams. Research into key taxa at sites near glaciers identified taxa that likely harbour adaptations to cold temperatures, nutrient poor conditions and chemolithoautotrophic metabolisms. This could indicate that glacially exported microbes can seed proglacial stream communities. Together these findings suggest that both OC cycling and microbial community structure in glacier-fed streams in the Rockies will be impacted by glacial retreat, with unknown ecosystem impacts.

• Subjects / Keywords

  • Organic Matter
  • Microbial Communities
  • Biogeochemsitry
  • Glacier

• Graduation date

  Spring 2023

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-6exy-8864

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.