Master of Science (MSc)
Faculty of Science
Giant Mine is an inactive gold mine located nine kilometers north of Yellowknife, Northwest Territories. Giant Mine has been the source of arsenic trioxide for the Baker Creek watershed since it opened over 60 years ago. Although arsenic levels in the creek are above the limits considered to be biologically relevant, there is no concrete evidence that plants and mycorrhizae have actually been affected. This study provides an initial assessment of the impacts mining activity at Giant Mine has had on plants and mycorrhizae in the Baker Creek watershed. Nine sites were sampled around Giant Mine: five sites downstream from Giant Mine along Baker Creek, one site upstream, two nearby wetlands and a distant reference site at Yellowknife River. Sites were distinguished by their level of exposure to the mine; downstream sites were considered the most impacted because they received mine water discharges, therefore having the highest arsenic levels. Two species of plants (Epilobium angustifolium and Phalaris arundinacea) were grown in these soils under laboratory conditions to compare growth responses and mycorrhizal colonization of plants in impacted versus non-impacted soils. A vegetation survey of Baker Creek was also conducted during soil collections in order to determine how patterns in plant species composition differ between sites. Plant roots were also collected to compare levels of colonization among sites to confirm that laboratory results were consistent with those obtained in natural conditions. This study tests the hypothesis that diminished growth and lower mycorrhizal colonization would be observed in plants growing in more impacted soils, and that these results would be reflected in the field through relatively different assemblages of plant species between impacted and non- impacted areas. Results from the growth room study were consistent with this hypothesis. Mean root length of P. arundinacea was 332.99 ± 15.52 cm and 299.75 ± 33.55 cm in soils collected from the upstream site and reference site, respectively, significantly greater than the next highest site downstream from the mine, where mean root length was 155.69 ± 18.01 cm. E. angustifolium only grew larger in references soils where mean root length was 44.41 ± 8.74 cm, compared to the next largest, 11.66 ± 2.68 centimeters, from a site downstream from Giant Mine. Mean mycorrhizal colonization was less than 7% in all samples except in plants from reference soils and from those from a reconstructed channel of the creek; mean colonization at these two sites was 13.44 ± 8.94 % and 18.08 ± 3.35 %, respectively, in P. arundinacea and 29.0 ± 8.79 % and 16.27 ± 10.54 % in E. angustifolium. These two sites were also distinguished from other sites based on different assemblages of plants species, however, opposed to the hypothesis, these were not mycorrhizal plant species that had been excluded from impacted sites. Certain habitat variables exclusive to Reach 4 and Yellowknife River may have favoured the establishment of these plant species, rather than the presence of mycorrhizal fungi. In conclusion, this study has demonstrated disturbed growing conditions along Baker Creek and a reduction in mycorrhizal infectivity; however, it could not relate these trends to patterns in plant species distribution. This study will be the first on the plant and mycorrhizal status of a mine-impacted watershed in Northern Canada, and as such, will contribute to a growing body of work on mine remediation specifically for this region.
MacColl, Kevin, "An Assessment of How Plant and Mycorrhizal Communities Have Been Affected Along a Mine-Impacted Watershed In The Northwest Territories" (2017). Theses and Dissertations (Comprehensive). 1948.