Recovery of a mining-damaged stream ecosystem

Abstract

This paper presents a 30+ year record of changes in benthic macroinvertebrate communities and fish populations associated with improving water quality in mining-influenced streams. Panther Creek, a tributary to the Salmon River in central Idaho, USA suffered intensive damage from mining and milling operations at the Blackbird Mine that released copper (Cu), arsenic (As), and cobalt (Co) into tributaries. From the 1960s through the 1980s, no fish and few aquatic invertebrates could be found in 40 km of mine-affected reaches of Panther Creek downstream of the metals contaminated tributaries, Blackbird and Big Deer Creeks.Efforts to restore water quality began in 1995, and by 2002 Cu levels had been reduced by about 90%, with incremental declines since. Rainbow Trout (Oncorhynchus mykiss) were early colonizers, quickly expanding their range as areas became habitable when Cu concentrations dropped below about 3X the U.S. Environmental Protection Agency's biotic ligand model (BLM) based chronic aquatic life criterion. Anadromous Chinook Salmon (O. tshawytscha) and steelhead (O. mykiss) have also reoccupied Panther Creek. Full recovery of salmonid populations occurred within about 12-years after the onset of restoration efforts and about 4-years after the Cu chronic criteria had mostly been met, with recovery interpreted as similarity in densities, biomass, year class strength, and condition factors between reference sites and mining-influenced sites. Shorthead Sculpin (Cottus confusus) were slower than salmonids to disperse and colonize. While benthic macroinvertebrate biomass has increased, species richness has plateaued at about 70 to 90% of reference despite the Cu criterion having been met for several years. Different invertebrate taxa had distinctly different recovery trajectories. Among the slowest taxa to recover were Ephemerella, Cinygmula and Rhithrogena mayflies, Enchytraeidae oligochaetes, and Heterlimnius aquatic beetles. Potential reasons for the failure of some invertebrate taxa to recover include competition, and high sensitivity to Co and Cu.

Caddisflies Hydropsyche spp. as biomonitors of trace metal bioavailability thresholds causing disturbance in freshwater stream benthic communities

“…The response of the mayflies in this study were generally similar to the results obtained in other field studies from the USA (Balistrieri et al, 2015;Besser et al, 2001;Kiffney and Clements, 1993;Luoma et al, 2010;Mebane et al, 2015), SW England (Rainbow et al, 2012), NW England (De Jonge et al, 2013) and the Philippines (David, 2003). The sensitivity of mayflies to elevated levels of metals varied significantly between mayfly families, ephemerellid and heptageniid mayflies being the most sensitive indicators of metal ecotoxicity in these rivers.…”

Larval aquatic insect responses to cadmium and zinc in experimental streams

“…Although the 2-site BLM yielded the overall best fit, it had the drawback of greater complexity and more adustable parameters. Whole-body tissue residues have in turn been shown to be good predictors of other community-level effects such as loss of sensitive species [22,34,35]. For our circumneutral scenarios with variable metals, we would not expect H þ to be directly toxic.…”

“…In contrast, aquatic insects are not usually acutely sensitive to metals, which results in large and uncertain acute-tochronic ratios [16][17][18]. As a result, completely contradictory viewpoints have emerged between laboratory-oriented and fieldoriented investigators as to whether aquatic insects should be considered among the most or least sensitive taxonomic group to elevated metal concentrations in freshwaters [6,17,[19][20][21][22].…”

“…Mayflies (Ephemeroptera) as a group are generally sensitive to metal contamination relative to other major taxonomic groups such as stoneflies (Plecoptera), caddisflies (Tricoptera), and Diptera (true flies) [22,37,38]. Our hope was that aggregated metrics would be less sensitive to variability and patchiness than individual taxa responses across the experimental stream experiments.…”

“…Our hope was that aggregated metrics would be less sensitive to variability and patchiness than individual taxa responses across the experimental stream experiments. Baetis mayflies in particular appear able to persist in locations with elevated metals, where other mayfly taxa may be completely extirpated [22,28,37]. Taxa richness is the number of unique taxa present in a sample and functions as a simple index of relative diversity.…”