The Use of Field and Mesocosm Experiments to Quantify Effects of Physical and Chemical Stressors in Mining-Contaminated Streams

Abstract

Identifying causal relationships between acid mine drainage (AMD) and ecological responses in the field is challenging. In addition to the direct toxicological effects of elevated metals and reduced pH, mining activities influence aquatic organisms indirectly through physical alterations of habitat. The primary goal of this research was to quantify the relative importance of physical (metal-oxide deposition) and chemical (elevated metal concentrations) stressors on benthic macroinvertebrate communities. Mesocosm experiments conducted with natural assemblages of benthic macroinvertebrates established concentration–response relationships between metals and community structure. Field experiments quantified effects of metal-oxide contaminated substrate and showed significant differences in sensitivity among taxa. To predict the recovery of dominant taxa in the field, we integrated our measures of metal tolerance and substrate tolerance with estimates of drift propensity obtained from the literature. Our estimates of recovery were consistent with patterns observed at downstream recovery sites in the NFCC, which were dominated by caddisflies and baetid mayflies. We conclude that mesocosm and small-scale field experiments, particularly those conducted with natural communities, provide an ecologically realistic complement to laboratory toxicity tests. These experiments also control for the confounding variables associated with field-based approaches, thereby supporting causal relationships between AMD stressors and responses.

Structural and functional responses of periphyton and macroinvertebrate communities to ferric Fe, Cu, and Zn in stream mesocosms

“…In agreement with previous investigations (Guasch et al ), adverse effects of metals on photosynthetic performance were observed after 2 d of exposure, followed by biomass reduction after 4 d. Sublethal responses such as growth rate, photosynthetic activity, protein content, or community metabolism may be more meaningful measures of Fe effects than alterations in periphyton community structure. We expected to see greater effects of metals in the low metals and Fe–low metals treatments on periphyton community composition because the measured Cu concentration exceeded the toxicity threshold for periphyton (0.009 mg/L) observed in previous studies (Cadmus et al ). We have previously reported that the presence of Zn can reduce the toxicity of Cu to macroinvertebrate communities (Clements et al ), and it is possible that a similar protective effect of Zn occurred in the present study.…”

“…Experiments investigating effects of metal mixtures on stream benthic communities are surprisingly limited in the literature (Clements et al ; Cadmus et al ; Mebane et al ), despite the fact that aquatic insects often dominate stream ecosystems and most mining polluted streams are impacted by multiple metals. Our study demonstrated additional risk to aquatic insects and periphyton in metal mixtures that included ferric Fe.…”

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

“…The use of biomonitoring as an indicator of ecological toxicity and mining‐related pollution impacts and improvements has been substantiated through studies that show close correlation of bioassessment metrics with the standard bioassays using specific test organisms, and with dissolved metal contaminant concentrations (Schmidt et al ; Griffith et al ). Studies combining controlled exposure of natural assemblages to metals and field manipulations of metal oxides on substrates have been used to detail recovery potential of different taxonomic groups (Cadmus et al ). The well‐documented trends of benthic macroinvertebrate community responses to improving water quality on the Arkansas River offer a strikingly similar example to Leviathan Creek of seasonal and flow‐related effects, as well as downstream spatial variation in restoration success (Clements et al ).…”

Influence of Metal Contamination and Sediment Deposition on Benthic Invertebrate Colonization at the North Fork Clear Creek Superfund Site, Colorado, USA

“…Previous investigators have measured effects of contaminated substrate on colonization dynamics and recovery potential of benthic macroinvertebrates. 22,38 For example, recovery potential based on tolerance to aqueous metals, avoidance of metal-contaminated coarse substrate and natural drift propensity of benthic invertebrates have been previously estimated. 38 Although natural drift propensity may determine the movement of macroinvertebrates to downstream habitat patches, the present study suggests that recovery of some macroinvertebrates is also influenced by avoidance of fine sediments.…”

“…35 Therefore, a mesocosm experiment was conducted to test the hypothesis that contaminated habitats influence downstream colonization, and the likelihood of benthic invertebrate movement beyond patches of contaminated sediment. Since previous research has shown that feeding strategies and mobility traits may influence sensitivity or exposure to metals, 20,38 we also examined whether trait responses influenced downstream colonization in our mesocosm experiment. These research objectives were designed to help predict recovery at the NFCC following improvements in water quality, but also to answer broader ecological questions about the effects of multiple stressors on the distribution and recruitment of macroinvertebrates in restored streams.…”