Interactive effects of multiple stressors and restoration priorities in a mined Appalachian watershed

Abstract

We surveyed benthic macroinvertebrate communities, water chemistry, and thermal regime in the Cheat River, WV, USA in an attempt to quantify the interactive effects of multiple stressors on ecological condition and identify priorities for restoration in this mined Appalachian watershed. We used a novel approach, which combined use of the West Virginia Stream Condition Index (WVSCI) to quantify ecological losses and community similarity analysis to assign specific levels of ecological loss to AMD, thermal effluent, and their interaction. Finally, we developed an ecological currency to quantify the relative benefits of a restoration program that focused either on AMD remediation or heat reduction and to identify spatially explicit restoration priorities. Variation in ecological condition was strongly correlated to variation in water quality when AMD and heat stress occurred in isolation. Acute inputs of AMD or heat caused predictable reductions in condition followed by rapid recovery downstream. However, benthic communities failed to recover from combined inputs of heat and AMD even when these stressors occurred at relatively low levels. Over the course of an entire year, AMD alone was over two times more responsible than heat alone for ecological loss. Consequently, AMD is the dominant factor limiting ecological condition and should be the primary target for restoration. Nevertheless, an AMD · heat interaction also was responsible for extensive ecological loss in lower reaches of the river. Consequently, full restoration of the lower Cheat River mainstem will require an approach that integrates AMD remediation with effective management of thermal effluent. Our results provide some of the first field evidence of the interactive effects of multiple stressors on biological communities in a mined watershed. This approach may be valuable for quantifying impacts from multiple interacting stressors and for prioritizing restoration efforts in other mined watersheds.

Identifying Cost-Effective Restoration Strategies in Mining Impacted West Virginia Watersheds

“…Ecological condition typically is determined as a function of an index of biotic integrity (Freund and Petty, 2007;Merovich and Petty, 2007). Restoration potential is a function of underlying habitat quality and the likelihood of restoration success (Merovich et al, 2007).…”

“…The highest quality stream segments for brook trout reproduction tend to be small and possess moderate gradient, moderate substrate size, and exceptionally clean water (Petty et al, 2005). In contrast, we developed diversity and a warmwater fishery EUs for application in the lower Cheat River where brook trout fisheries are less common and warmwater fisheries represent the most valuable ecological functions of stream segments (Merovich and Petty, 2007).…”

“…Furthermore, it will require that localized restoration projects be integrated into holistic, watershed-scale, restoration plans (Petty and Thorne, 2005;Merovich and Petty, 2007;Poplar-Jeffers et al, in press). Through strategic planning of AMD remediation, it may be possible to achieve significant improvements to ecological conditions and fisheries at the watershed scale while targeting only a small percentage of the problem sources.…”

Thermal tolerance of juvenile freshwater mussels (Unionidae) under the added stress of copper

“…Organisms in their natural environment are probably most commonly impacted by multiple stressors [16,17], and because Cu is ubiquitous in the aquatic environment, it is reasonable to suspect that some populations of freshwater mussels will be exposed to the combined stress of both Cu and increased water temperature through heated effluent, land use change, or climate change. In ectotherms, because temperature controls physiological processes, any toxicant that acts on the same processes can be expected to have an interactive effect [18].…”

“…However, interactive effects among multiple stressors do not always have an obvious and/or positive relationship [16,17,31]. Some stressors, when combined, have no apparent interactive effects [32], but others can interact in a synergistic manner [33,34].…”