Date of Report EPA Agreement Number Center Name and Institution of Center Director Identifier used by Center for Project Title of Project:

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1 Date of Report: March 31, 23 EPA Agreement Number: R Center Name and Institution of Center Director: Rocky Mountain regional Hazardous Substance Research Center, Colorado State University Identifier used by Center for Project: Project No. 4 Title of Project: Evaluating Recovery of Stream Ecosystems from Mining Pollution: Integrating Biochemical, Population, Community and Ecosystem Indicators Investigator(s) and Institution(s): William H. Clements, Dept. of Fishery & Wildlife Biology, Colorado State University, Fort Collins, CO and James Ranville, Dept. of Chemistry and Geochemistry, Colorado School of Mines, Golden, CO Type of Research: Applied Project Period: 11/1/21-1/31/23 (2 years) Goals of Research The goals of our research are to 1) identify sensitive indicators of heavy metal pollution in Rocky Mountain streams; 2) estimate concentrations of heavy metals that are protective of aquatic communities in mining-polluted streams 3) examine the influence of physicochemical factors (e.g., dissolved organic carbon) and other stressors on metal bioavailability and toxicity; and 4) assess interactions between heavy metals and other anthropogenic stressors. Statement of Work Results of an ongoing, long-term (14 year) monitoring project in the Arkansas River have identified a suite of indicators across several levels of biological organization that are sensitive to heavy metal contamination. Experiments conducted in the field and in stream microcosms quantified concentration-response relationships between heavy metals and these biological indicators (Clements, in review). These experiments estimated concentrations of metals that must be achieved during remediation to protect aquatic organisms in the Arkansas River. To expand the scale of our studies, we conducted a spatially extensive survey of 16 watersheds in the Upper Arkansas River basin. Results showed that landscape characteristics (e.g., amount of vegetation in a watershed) determined dissolved organic carbon (DOC) concentrations and ultimately regulated metal bioavailability to aquatic organisms (Prusha and Clements, in review). The specific objectives of this research were to: 1. Improve the mechanistic understanding of ecological responses to heavy metals across levels of biological organization (biochemical, population, community, ecosystem); 2. Evaluate biological indicators of recovery in a metal polluted stream (the Arkansas River) following remediation and improvements in water quality; 3. Estimate concentrations of metals necessary to protect aquatic organisms; 4. Assess the influence of dissolved organic carbon on metal bioavailability and toxicity; 5. Investigate potential interactions between heavy metals and other anthropogenic stressors. Relevance of Research to the Overall Goals of the Center Because of the spatial extent of mining pollution in Colorado and other western states, reasonable clean-up goals must be established so that the limited resources available for remediation can be used effectively. Remediation activities in the Arkansas River have been underway for about 1 years, and are designed to reduce instream metal levels and restore healthy aquatic communities. Results of our research will be used to validate clean-up goals for this system and to evaluate the success of remediation. Because of naturally elevated metal levels 1

2 in the watershed and significant discharge from California Gulch, it is unlikely that the current U.S. EPA water quality criteria for metals in the Arkansas River (e.g., approx. 55 µg Zn/L) can be achieved. Our research is testing the hypothesis that water quality criteria for metals in the Arkansas River can be relaxed, with no deleterious effects on aquatic organisms. Biological monitoring of mining-polluted streams is conducted with the explicit intent of demonstrating that metals cause changes in aquatic communities. However, demonstrating causation is complicated because numerous factors, in addition to metals, influence aquatic communities. Demonstrating causation is especially important in Natural Resource Damage Assessments (NRDA) and other programs where compensation for damages may be determined by litigation. By integrating long-term biological monitoring with field and microcosm experiments we demonstrated that changes observed in the Arkansas River are caused by metal contamination. This combined monitoring and experimental approach can be applied in other mining-polluted watersheds in the Rocky Mountain region to demonstrate causation. Progress 1. Improved mechanistic understanding across levels of biological organization Progress to date- We completed field experiments that measured effects of heavy metals at several levels of biological organization (biochemical, population, community, and ecosystem). We identified a suite of indicators that are highly sensitive to metal exposure in Rocky Mountain streams. (8% complete) Unexpected results- The most unexpected result of these experiments was the extreme sensitivity of small, early instar organisms to heavy metals (Fig. 1). These results indicate that risk assessment of metal-contaminated streams must account for intraspecific differences in size of aquatic organisms. Future activities- Analyses of these results will be completed in approximately 4 weeks. A second set of experiments will be conducted during spring runoff (May, 23) when metal concentrations in the Arkansas River are expected to be significantly higher. 2. Evaluate biological indicators of recovery following improvements in water quality Progress to date- We completed all chemical analyses and most of the taxonomic work since the start of this project. (75% complete) Unexpected results- We observed rapid recovery downstream from Leadville Mine drainage Tunnel as a result of reduced metals (Fig. 2). In contrast, we observed only partial recovery downstream from California Gulch, where metal levels remain elevated. Future activities- We will continue to sample heavy metals, physicochemical characteristics, and macroinvertebrate communities in spring and fall, 23 as part of this long-term monitoring program. 3. Estimate safe concentrations of metals necessary to protect aquatic organisms Progress to date- We completed one set of microcosm experiments and results from a second set of experiments are being analyzed. Results of the first experiment have been submitted for publication. (75% complete) Unexpected results- Results of these experiments showed that community respiration was highly sensitive to heavy metals (Fig. 3). These results were not expected because previous studies have shown that functional measures were generally insensitive to anthropogenic stressors. 2

3 Future activities- We will conduct a second set of stream microcosm experiments in spring 23 to investigate sublethal effects of heavy metals on aquatic communities. 4. The influence of dissolved organic carbon (DOC) on metal bioavailability Progress to date- We completed our analyses of landscape influences on DOC and metal bioavailability in the upper Arkansas River watershed (Fig. 4). Results of this research have been submitted for publication. (1% complete) Unexpected results- We observed highly significant differences in metal uptake between two species of aquatic macroinvertebrates. These differences were attributed to speciesspecific feeding habits (Table 1). Future activities- We will expand the spatial scale of our analyses beyond the upper Arkansas River watershed and include streams across a broader geographic region. 5. Interactions between heavy metals and other anthropogenic stressors Progress to date- Microcosm experiments showing the interaction between heavy metals and UV-B radiation were completed in fall, 22. We are currently analyzing results of these experiments. (% complete) Unexpected results- None at this point in the analyses. Future activities- We have one additional experiment planned for summer 23 to investigate interactions between heavy metals and UV-B radiation. Summary of Relevant Data To demonstrate a causal relationship between heavy metals and biological responses, we have designed a unique experimental approach using natural communities of benthic macroinvertebrates. Communities obtained from a reference station (AR1) were placed in exposure chambers and transferred to sites upstream (EF5) and downstream (AR3, AR5) from California Gulch (CG). Results show that mayfly abundance is significantly reduced below CG, but recovers 5 km downstream (Fig. 1). These results also show that small, early instars of mayflies are highly sensitive to metals. Comparison of size frequency distributions of mayflies indicates that most mortality observed at station AR3 occurs in the smaller size classes. 3

4 Number of Heptageniidae per Chamber EF5 AR1 AR3 AR5 Station Number per Size Class < Size Class AR1 AR >1.19 Figure 1. Results of field experiments showing abundance (left panel) and size distribution (right panel) of metal-sensitive mayflies (Heptageniidae) in exposure chambers placed at stations upstream (EF5, AR1) and downstream (AR3, AR5) from California Gulch. We have monitored benthic macroinvertebrate communities and assessed water quality in the Arkansas River biannually (spring and fall) since 1989 as part of a long-term monitoring program. Samples were collected upstream and downstream from the two primary sources of heavy metals: Leadville Mine Drainage Tunnel (LMDT) and California Gulch (CG). Metal levels downstream from LMDT (station EF5) decreased significantly, resulting in a dramatic improvement in benthic macroinvertebrate communities (Fig. 2). Although metal levels at station AR3 remain elevated, we observed partial recovery in benthic communities. Zn Concentration (ug/l) 8 EF5 AR Date Number of Heptageniidae per.1 m Date Figure 2. Results of long term monitoring of Zn concentrations (left panel) and number of metalsensitive mayflies (right panel) in the Arkansas River, Microcosm experiments have established concentration-response relationships between metal levels and several biological indicators (Fig. 3). These results will be used in combination with field experiments to estimate safe metal concentrations for aquatic organisms in the Arkansas 4

5 River. Results also indicate that mixtures of metals (Cd+Cu+Zn) were generally more toxic to aquatic organisms than Zn alone. 2 Number of Heptagenidae Zn Zn+Cd Zn+Cd+Cu Community Respiration ( mg/l O 2 ) CCU Figure 3. Examples of concentration-response relationships derived from stream microcosm experiments showing effects of heavy metals on metal-sensitive organisms (left panel) and community respiration (right panel). CCU = cumulative criterion unit for metal mixtures. Analysis of the relationship between landscape attributes (geology, soils, vegetation, topography) and physicochemical characteristics in streams showed that dissolved organic carbon (DOC) concentrations increased with the percent forested area in a watershed (Fig. 4). Our research also showed that uptake of Zn by the caddisfly Arctopsyche grandis was inversely related to DOC concentration (Table 1). Although it is well established that high levels of DOC reduce metal bioavailability in the laboratory, this is the first research to demonstrate the influence of DOC on metal uptake in the field. More importantly, our research is the first to link metal uptake in aquatic organisms to a watershed-level attribute (e.g., % forested area). These intriguing results indicate that differences in metal bioavailability and toxicity among watersheds may be partially explained by landscape characteristics. CCU 6 Mean DOC (mg/l) Figure 4. Relationship between percent forested area and DOC in 16 watersheds of the Upper Arkansas Basin, CO Percent Forested Area 5

6 Table 1. Results of multiple linear regression showing the relationship between metal concentrations in two species of macroinvertebrates (the caddisfly Arctopsyche grandis and the mayfly Drunella doddsi) and physicochemical characteristics from 16 watersheds in the Upper Arkansas River Basin, Colorado. Species Variables in model Partial R 2 p-value Overall Model R 2 Arctopsyche grandis (+) Zn (-) DOC (+) Temperature Drunella doddsi (+) Zn Schedule and Scope Based on the original proposed schedule and the work completed to date, we expect that the timetable for completion of this research is valid. In summer 23 we anticipate expanding the spatial scale of our research beyond the Arkansas River watershed to include other mining polluted streams in Colorado. 6

7 Appendix I Publications and Presentations Peer reviewed Journal Articles Clements, W.H. (in review) Small-scale experiments support causal relationships between metal contamination and macroinvertebrate community responses. Submitted to Ecological Applications, January, 23. Prusha, B.A. and W.H. Clements (in review) Landscape attributes, dissolved organic carbon, and metal accumulation in aquatic macroinvertebrates (Arkansas River Basin, Colorado). Submitted to the Journal of the North American Benthological Society, February, 23. Published Abstracts Clements, W.H. 22. The utility of small-scale experiments for supporting causal relationships between stressors and community-level responses. Program Abstracts, North American Benthological Society th Annual Meeting, Pittsburgh, PA. pp 23. Prusha, B.A. and W.H. Clements 22. Relationships between landscape attributes, dissolved organic carbon, and metal accumulation in Arctopsyche grandis: an investigation of the upper Arkansas River basin (Leadville, CO). Program Abstracts, North American Benthological Society th Annual Meeting, Pittsburgh, PA. pp 214. Walski, K., S.B. Shaffer, W.H. Clements, and J.F. Ranville. 22. Effect of particle size on metal bioavailability and toxicity in the midge, Chironomus tentans. Society of Environmental Toxicology and Chemistry, 23th Annual Meeting Abstracts, pp. 12 Project Personnel Dr. Donna Kashian, Postdoctoral Fellow Mr. Blair Prusha, Research Associate Mr. Richard Thorp, Research Associate Mr. Jeff Clark, M.S. Student Ms. Katy Mitchell, Hughes Undergraduate Research Scholar Ms. Jennifer Woodward, Undergraduate Laboratory Assistant Mr. Joe Nicholson, Undergraduate Laboratory Assistant 7