A multitrophic approach to monitoring the effects of metal mining in otherwise pristine and ecologically sensitive rivers in Northern Canada

Abstract

It is not known if current chemical and biological monitoring methods are appropriate for assessing the impacts of growing industrial development on ecologically sensitive northern waters. We used a multitrophic level approach to evaluate current monitoring methods and to determine whether metal-mining activities had affected 2 otherwise pristine rivers that flow into the South Nahanni River, Northwest Territories, a World Heritage Site. We compared upstream reference conditions in the rivers to sites downstream and further downstream of mines. The endpoints we evaluated included concentrations of metals in river water, sediments, and liver and flesh of slimy sculpin (Cottus cognatus); benthic algal and macroinvertebrate abundance, richness, diversity, and community composition; and various slimy sculpin measures, our sentinel forage fish species. Elevated concentrations of copper and iron in liver tissue of sculpin from the Flat River were associated with high concentrations of mine-derived iron in river water and copper in sediments that were above national guidelines. In addition, sites downstream of the mine on the Flat River had increased algal abundances and altered benthic macroinvertebrate communities, whereas the sites downstream of the mine on Prairie Creek had increased benthic macroinvertebrate taxa richness and improved sculpin condition. Biological differences in both rivers were consistent with mild enrichment of the rivers downstream of current and historical mining activity. We recommend that monitoring in these northern rivers focus on indicators in epilithon and benthic macroinvertebrate communities due to their responsiveness and as alternatives to lethal fish sampling in habitats with low fish abundance. We also recommend monitoring of metal burdens in periphyton and benthic invertebrates for assessment of exposure to mine effluent and causal association. Although the effects of mining activities on riverine biota currently are limited, our results show that there is potential for effects to occur with proposed growth in mining activities.

Development and application of benthic algal reference condition models to assess stream condition in the South Nahanni Watershed

“…Their results indicated that metal and nutrient concentrations along Prairie Creek either remained at upstream reference levels or were elevated at the near‐field site and then back within upstream reference concentrations at the far‐field site. Along Flat River, Spencer et al () found that concentrations of metals and nutrients at the near‐field and far‐field sites were either both consistently elevated above upstream reference concentrations or concentrations continued to increase at the far‐field site. Bowman et al () compared near‐field and far‐field sites to regional reference sites and generally found a decreasing trend in metal and nutrient concentration from near‐field to far‐field sites along Prairie Creek.…”

“…Here, we develop reference condition models for the South Nahanni River Watershed using 3 descriptors of benthic algal communities (algal taxonomy, diatom taxonomy, and algal pigments) from a total of 62 undisturbed regional reference river sites, apply them at river sites adjacent to and downstream of 2 metals mines, and compare results of the assessments to longitudinal patterns in water chemistry which include use of water physicochemistry data to determine potential zones of impairment downstream of each mine. We predicted that RCA models would identify impairment at some sites downstream of each mine, given marked increases in concentrations of some metals and nutrients adjacent to and immediately downstream of mine discharges (Scrimgeour et al ; Thomas et al ) and strong relations between variance in algal community structure and water physicochemistry (Spencer et al ; Thomas et al ). We also anticipated differences in site assessments when algal communities were defined using the 3 community descriptors, because they reflect different components of the overall benthic algal community (i.e., taxonomy of all algal species vs solely diatoms) and differ in the ways that they are described (i.e., taxon percent abundance vs concentrations of pigments).…”

“…Given the uncertainty that diatom and nondiatom assessments are comparable, and the high site‐access costs using helicopters, we chose to collect and make these comparisons. Also, diatoms comprise a large portion of the algal community, especially along Prairie Creek (Spencer et al ). We specifically included algal pigments as a descriptor of algal communities because our previous work has shown that they represent a highly cost‐effective way to describe algal communities (Thomas et al ).…”

Changes in the epipelic diatom assemblage in nutrient rich streams due to the variations of simultaneous stressors

“…Decreases in the diversity of the assemblage when under stress have been reported (such as Patrick & Reimer, 1966;Sabater, 2000;Gold et al, 2003;Spencer et al, 2008), although it has to be considered that the diversity indices for the benthic diatom assemblages are very variable, and no authors have described a direct cause-effect relationship between chemical pollution and diversity (Ricciardi et al, 2009). …”

Ecological and Human Health Risk Assessment

“…The survey and analysis of ecological risk assessment in decision making shows that such assessments have been most effective when clear management goals were included in the problem formulation; translated into information needs; and, developed in collaboration with decision makers, assessors, scientists, and stakeholders. Spencer et al (2008) used a multitrophic level approach to evaluate current monitoring methods and to determine whether metal-mining activities had affected two otherwise pristine rivers that flow into the South Nahanni River, Northwest Territories, a World Heritage Site. Their results showed that although the effects of mining activities on riverine biota currently are limited, there is potential for effects to occur with proposed growth in mining activities.…”