Sierra Nevada Aquatic Research Laboratory, University of California, Mammoth Lakes, California, USA.
Region 9, US Environmental Protection Agency, San Francisco, California, USA.
Environ Toxicol Chem. 2018 Oct;37(10):2575-2592. doi: 10.1002/etc.4217. Epub 2018 Sep 5.
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.
对接收酸性金属污染水的溪流中的底栖无脊椎动物进行了 18 年的监测，结果表明，在下游的一系列位置，溪流的状况既出现了恶化，也出现了恢复。与参考溪流相比，在加利福尼亚州内华达山脉中部一座废弃露天硫矿下游的清理修复工作过程中，随着水质的改善，一些地点的底栖生物群落也得到了恢复。在酸性矿山排水不完全捕获且金属负荷随径流增加的情况下，多年的高流量导致了生物状况恶化。在夏季处理季后的秋季，恢复的季节性模式明显，但在下一个冬季过后，当源头未被捕获时，这种模式又恢复了。随着金属负荷的降低，群落结构、功能和相似性的阶段性恢复逐渐接近参考组合的分类组成。从受影响的群落中，相对耐受的摇蚊占主导地位，重新组装涉及密度增加、长寿类群的回归、敏感与耐受形态的比例增加、整体多样性和群落组成的增加，最终大型捕食者和食草动物与蜉蝣、石蝇和石蛾的丰富度一起再次出现。使用几种分析方法定义的阈值效应水平表明，生物指标的响应范围与美国环境保护署（USEPA）利用金属毒性累积标准单位（CCU）预测效应的指南相对应（即 CCU∼1）。随着时间的推移，所有站点的某些或所有营养级群体的密度增加，功能都有所改善。尽管恢复正在进行，但可能需要全年处理才能完全恢复最靠近矿山的溪流的生物完整性。环境毒理化学 2018;37:2575-2592. © 2018 SETAC。
