Ecological Effects of Higher Water Temperature in Experimental Montane Streams

• Author / Creator

  Mercer, Benjamin DJ

• Montane rivers are some of the most pristine water sources on earth, providing a wide variety of ecosystem services to downstream regions. However, these cold-water ecosystems are at risk due to climatic warming and other anthropogenic impacts. Importantly, they are potentially being impacted by disproportionately higher rates of warming when compared to those at lower elevations. Thus, I experimentally tested for the effects of elevated water temperatures on benthic communities by constructing and heating mountain-fed stream mesocosms. The experimental design consisted of 12 three-meter-long high density polyethylene troughs, which were each modified to simulate flowing headwaters. Attached algal biofilms and macroinvertebrate communities were each sampled three times during the 28-day experiment. High performance liquid chromatography of concentrated algal pigment collections from the experiment was used to quantify the effects of heating on primary producers. My results revealed no significant effects of warming on chlorophyll-inferred algal biomass. However, there was some evidence that algal community composition in the heated mesocosms had diverged from controls by the end of the experiment. Macroinvertebrate samples were taxonomical analysed using the morphological species concept and light microscopy. The effects of environmental warming on the abundance, taxonomic richness and community composition of benthic macroinvertebrates were all non-significant. My findings support other evidence of species composition rather than more robust functional aggregate properties (e.g. primary and secondary production) of aquatic algal communities being among the most sensitive and earliest responders to ecosystem stress. This cost-effective experimental stream facility provides an opportunity for testing future hypotheses regarding the direct and interactive effects of warming and other stressor (e.g., exotic sportfish introductions) on mountain stream ecosystems.

• Subjects / Keywords

  • Warming
  • Mesocosm
  • Stream
  • Montane
  • Water Temperature

• Graduation date

  Fall 2023

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-ee95-5r24

• 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.