Skip to main content

Effects on Aquatic Macroinvertebrate Community from Mitigating Impacts of Legacy Mining near Telluride, CO

Colorado has undergone extensive hard-rock mining activities for over 100 years. Many of these mines were abandoned with little-to-no environmental remediation plans. Hard-rock mining can negatively impact the land, streams, flora, and fauna in the area and downstream. A partnership with Trout Unlimited and the Telluride Valley Floor (TVF) was created with the goal of removing a tailings pile near the San Miguel River in Telluride and restoring the stream habitat and water quality. However, their project did not include monitoring the aquatic insect community. Benthic macroinvertebrates (aquatic insects) are prominent in freshwater ecosystems and can exhibit large-scale impacts within a scaled-down environment. Studying their individual size distributions (ISDs) within this restoration site can illustrate the effects of mining on the freshwater biological community, as well as provide reference data for future analyses. This project aimed to collect aquatic macroinvertebrates from four stations at the project site with two primary goals: 1) assess the current conditions of the biotic community above and below the tailings pile and 2) collect pre-restoration data for a planned before-after-control-impact study to be conducted once the restoration efforts have been completed.

Methodology

Samples were collected on August 13th, 2024 by Dr. Pomeranz and Nia Taubr. We concentrated collecting randomized samples from riffle habitats at 1 station above the tailings pile (reference site/Site 1) as well as at 3 random stations below the tailings pile (impacted sites/Sites 2-4). At each station, we collected five replicate quantitative macroinvertebrate samples using a Hess sampler from each station. The samples were placed in containers with 70-80% ethanol and returned to the lab for processing where we separated each macroinvertebrate, identified to the lowest taxonomic unit (family for most groups), measured their length, and photographed them with a dissecting microscope. Their measurements were converted to dry mass (grams) based on referenced equations. Individual biomass calculations from all samples at a station were then combined and used to estimate parameters describing ISDs. Standard biomonitoring metrics including species diversity and evenness were calculated as well. All analyses were conducted in the R programming language.
Results

Results from above and below the tailings pile were compared to assess the impacts of legacy mining. Time constraints limited identifying all the macroinvertebrates at two of the stations below the tailings pile, but Site 1 (reference site) and Site 3 (one of the impacted sites) were entirely identified, measured, and calculated. Macroinvertebrate diversity and abundance decreased below the mine tailings pile at Site 3. The size distribution of the macroinvertebrates was also smaller downstream compared to above the tailings pile. This indicated that the aquatic insect community at Site 3 was less efficient at transferring energy and supported fewer large individuals than Site 1.

Conclusions

Overall, the mine tailings pile had a negative impact on the macroinvertebrate community at Site 3 versus the reference site, limiting their abundance and diversity, but further research is recommended to compare the other two sites. It is important to study aquatic habitats and utilize the stream's natural health indicators: macroinvertebrates. Their abundance could inform management and conservation efforts in aquatic habitats. The data collected for this project will also assist future research on how ISD relationships respond to restoration activities. This project provided an opportunity to monitor long term restoration, and a snapshot of the water quality at a tailings pile. Overall, freshwater systems unite all walks of life and determining how to preserve it is vital.

Our 2024-2025 Researchers

Antonia (Nia) Taubr
Student Researcher
Justin Pomeranz
Assistant Professor of Environmental Sciences & Technology