Assessing Effects of Habitat Manipulation on Invertebrates in an Arctic Barrenlands Stream

• Author / Creator

  Uherek, Christiane B

• As resource exploitation and development expands in northern Canada, threats to the ecological integrity of freshwater systems increase. In Canada, developments that could negatively affect aquatic ecosystems require offsetting or compensation measures. As a result of diamond mine development, a habitat compensation project was required to offset aquatic habitat losses at Diavik Diamond Mines Inc. (DDMI). The aim of the project was to convert West Island Stream (WIS), a stream that was generally inaccessible and impassable for fish, into a nature-like fishway that would improve ecological connectivity between Lac de Gras and a headwater lake, and thereby provide spawning and rearing habitat for fish, especially Arctic Grayling. Because reduced growth and production of young-of-year Arctic Grayling in a nearby constructed stream was attributed to lower densities and smaller sizes of benthic invertebrates, likely due to low amounts of autochthonous and allochthonous organic matter and homogeneous physical habitat, a Before-After-Control-Impact study was initiated to assess effects of DDMI’s offsetting project on key components of stream habitat structure and function and on invertebrates. I examined more than 40 physicochemical and biological parameters of stream habitat, as well as density, biomass, diversity, and taxonomic composition of aquatic invertebrates, before and after fishway construction. Data from three reference pristine streams were also collected to establish standards against which characteristics of the fishway could be compared, and to provide a better picture of aquatic invertebrate assemblages in Barrenlands streams. Based on biotic and abiotic data collected over six years (four years pre-impact and two years post-impact), WIS presented generally successful post- habitat manipulations recovery, for both habitat structure and function and invertebrate assemblages. Although a reduction in organic matter input, presence, and accumulation was observed, these changes were likely due to riparian vegetation removal from one of the stream banks during the manipulation, and I expect CPOM accumulation to increase as the riparian vegetation is reestablished. Conversion to the fishway also led to changes in substrate composition and flow, and best explains the observed shifts on invertebrate assemblages, especially in Simuliidae (which greatly increased in absolute and relative density and biomass) and Chironomidae (which decreased in absolute and relative density and biomass). For future studies I recommend limiting riparian vegetation removal to a single bank, and possibly leaving intermittent natural “green zones” that can mitigate possible effects of altered instream organic matter accumulation and invertebrate recolonization. I also recommend long-term monitoring to investigate trends in recovery of habitat variables and their effect on invertebrate assemblages and on fish populations.

• Subjects / Keywords

  • Habitat Compensation
  • Barrenlands
  • Arctic
  • Stream Ecosystems
  • Invertebrates
  • Habitat Offsetting
  • Habitat Manipulation

• Graduation date

  Fall 2016

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3B56D92X

• 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.