2024-2025 Student Research Findings | Colorado Mesa University

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

During the 2024 field season, aquatic macroinvertebrates were collected at four sites in Telluride, Colorado near the San Miguel River. Due to a history of extensive mining, Trout Unlimited and the Telluride Valley Floor (TVF) previously partnered to restore habitat and water quality at the site. However, their project did not monitor the aquatic insect community, and this population can illustrate the effects of mining on the freshwater biological community. This project assesses current environmental conditions above and below tailings piles through individual size distributions (ISDs).

This project looked at individual size distributions (ISD), a pattern where organisms with small bodies are more abundant than those with large bodies in an ecosystem, for benthic macroinvertebrates (or aquatic insects) at a project site near the San Miguel River in Telluride, Colorado. Due to extensive mining, the site originally had tailings piles left over, which often contain toxic chemicals. They were removed to restore habitat and water quality, but macroinvertebrate populations were not monitored during this process. We collected macroinvertebrate samples at four sites in August to assess the environmental conditions above and below the tailings. Comparing the data, we found that a site below the tailings had a smaller size distribution of macroinvertebrates. There were also less organisms at a site below compared to a site above, with mine tailings negatively impacting the diversity of macroinvertebrates. By studying these sites, we now have more information about how restoration efforts impact ISD relationships. However, further research is recommended to compare the other two sites. This information can help future management and conservation efforts in aquatic habitats.

Methodology

Sampling occurred on August 13th, 2024. Randomized samples were collected from riffle habitats at one station above the tailings pile and at three random stations below the tailings pile. At each station, five replicate quantitative macroinvertebrate samples were collected using a Hess sampler from each station. The samples were returned to the lab for processing where each macroinvertebrate was separated, identified to the lowest taxonomic unit, measured for length, and photographed with a dissecting microscope. Their measurements were converted to grams based on referenced equations. Individual biomass calculations from all samples at a station were then combined and used to estimate parameters describing ISDs.

Results

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

Conclusions

Overall, the mine tailings pile had a negative effect on impacted macroinvertebrate communities and limited their abundance and diversity. Macroinvertebrate presence can inform management and conservation efforts in aquatic habitats. The data collected for this project will assist future research on how ISD relationships respond to restoration activities. Further research is recommended to compare the remaining two sites.

Our 2024-2025 Researchers

Antonia (Nia) Taubr

Student Researcher

Justin Pomeranz

Assistant Professor of Environmental Sciences & Technology