Long‐term effects and recovery of streams from acid mine drainage and evaluation of toxic metal threshold ranges for macroinvertebrate community reassembly

Abstract

Monitoring of benthic invertebrates in streams receiving acidic metal-contaminated water over an 18-yr period revealed both degraded conditions and recovery along a network of downstream locations. Compared with reference streams, and over the course of clean-up remediation efforts below an abandoned open-pit sulfur mine in the central Sierra Nevada of California, improving water quality was accompanied by recovery of benthic communities at some sites. Years of high flow resulted in degraded biological status when acid mine drainage capture was incomplete and metal loading had increased with runoff. Seasonal patterns of recovery evident in the fall after the summer treatment season reverted in the next spring after overwinter periods when sources were not captured. As the metal load has been reduced, phased recovery of community structure, function, and similarity progressed toward that of reference assemblage taxonomic composition. From impacted communities dominated by relatively tolerant midges, reassembly involved an increase in density, return of long-lived taxa, an increased ratio of sensitive-to-tolerant forms, then overall diversity and community composition, and eventually large predators and grazers reappearing along with mayfly, stonefly, and caddisfly richness. Threshold effect levels defined using several analysis methods showed that the response range of biological indicators corresponds to US Environmental Protection Agency guidelines of predicted effects utilizing cumulative criterion units (CCUs) of metal toxicity (i.e., CCU ∼ 1). All sites have shown improved function with increased density of some or all trophic groups over time. Although recovery is progressing, year-around treatment may be necessary to fully restore biological integrity in streams nearest the mine. Environ Toxicol Chem 2018;37:2575-2592. © 2018 SETAC.

Resilience and regime shifts: Do novel communities impede ecological recovery in a historically metal‐contaminated stream?

“…In contrast, downstream communities remain dominated by metal‐tolerant species and show little evidence of recovery 15 years after restoration. This lack of recovery is surprising given that other investigators have reported rapid improvements in benthic communities following less dramatic reductions in metal concentrations (Herbst et al, ; Hornberger, Luoma, Johnson, & Holyoak, ). In addition, the proximity of a diverse and highly productive upstream source of colonists, a critical requirement for recovery from mining pollution in streams (Kitto et al, ; Swan & Brown, ), should have expedited recovery of this system.…”

“…These differences in metal tolerance between communities persisted throughout the study, despite significant improvements in water quality over the past 15 years. Although several macroinvertebrate taxa from the upstream site were more sensitive to metals, the greatest difference between sites was observed for grazing mayflies, organisms known to be especially sensitive to mining discharges (Clements et al, ; Herbst, Medhurst, & Black, ; Mebane, Eakins, Fraser, & Adams, ).…”

Stream Mesocosm Experiments Show Significant Differences in Sensitivity of Larval and Emerging Adults to Metals

“…Additionally, R. robusta develop to a much larger overall body size compared to Baetidae, potentially increasing its relative tolerance to metals . Metal exposure in the field is spatiotemporally variable, ,, and because aquatic insects exhibit complex life histories, our ability to characterize full-life cycle sensitivity with mesocosms is limited by the exposure duration and the phenology of the community. Moreover, our mesocosms are closed systems that do not allow for natural colonization.…”

Evaluation of the Impacts of Abandoned Mining Areas: A Case Study with Benthic Macroinvertebrate Assemblages

“…To date, when evaluating the changes in stream environments near abandoned mining areas, only the water quality variables or the coarse level of benthic macroinvertebrate data (i.e., family level) have been used (but also see [ 34 , 35 ]), and descriptive or multivariate analyses have been applied to interpret the results. Network analysis [ 36 ], which has now been increasingly used to understand the interactions and stability of complex ecological communities, can provide undetectable insights compared with traditional analytical methods that analyze the species separately [ 37 , 38 ].…”