Epilithic Algal Community Responses to Rapid Glacier Loss in the Canadian Rocky Mountains

• Author / Creator

  Sudlow, Karson Ian

• Global melting of mountain glaciers is altering downstream ecosystems. As glaciers disappear, downstream water temperatures are rising while turbidity and nutrient concentrations decline. Here, knowledge gaps exist concerning how these abiotic changes will affect primary producers in glacial meltwater streams. I quantified abiotic variables and rock-attached algal communities termed epilithon in 10 stream sites along an environmental gradient of glacial influence in the Canadian Rockies. I hypothesized that physical factors would be the strongest predictors of community composition due to the damage incurred by biofilms from frequent scouring and abrasion events. Turbidity best explained an observed unimodal response of epilithic algal biomass accrual to glacial influence. However, abiotic variables poorly explained variation in community composition.

  To further explore the impacts of glacial meltwater turbidity on epilithon, I designed a mesocosm experiment to test the effects of glacial flour, the primary determinant of turbidity in glacial streams, on algal community structure. Artificial stream channels were inoculated with algae and meltwater collected from a low turbidity glacial stream. Epilithic algal communities were then exposed to one of five turbidity levels by mixing varying amounts of glacial flour into meltwater. Moderate levels of turbidity significantly stimulated epilithic algal biomass accrual relative to the effects of low and extreme turbidity treatment levels, appearing to favor growth by chlorophytes over that of diatoms and other chromophytes. Potential explanations of low biomass accrual by epilithon to low and extreme turbidity involved nutrient limitation and physical disturbance, respectively.

  My findings suggest that the turbidity of glacial streams has a strong influence on the growth and diversity of algal biofilms. I expect that further glacier loss will suppress epilithic algal growth in glacial meltwater streams due to declining nutrient availability and heightened exposure to damaging levels of ultraviolet radiation. Since algal growth supports the productivity of glacial meltwater ecosystems in the absence of terrestrial subsidies from surrounding barren alpine landscapes, I anticipate that loss of glaciers could in certain cases impair the downstream productive capacity for harvestable coldwater fishes.

• Subjects / Keywords

  • Biology
  • Ecology
  • Algae
  • Glaciers

• Graduation date

  Fall 2023

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-vv7j-3h98

• 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.