Effects of Fintrol (antimycin A) application on benthic macroinvertebrate communities in the Lynn Camp Prong watershed, Great Smoky Mountains National Park

Fintrol® (active ingredient - antimycin A), an aquatic pesticide, was applied to 12.8 km of Lynn Camp Prong and to 4.8 km of its tributaries in the Great Smoky Mountains National Park (GRSM) during September 2008 to remove non-native rainbow trout Onchorhynchus mykiss and to restore a viable population of native "Southern Appalachian" brook trout Salvelinus fontinalis. Chemical applications have become widely utilized as fish removal and restoration tools and although Fintrol is designed to minimize effects on non-target species, benthic macroinvertebrate assessments are recommended, pre-and post-treatment, by National Park Service protocols to determine short- and long-term effects to aquatic macroinvertebrate communities.;Macroinvertebrate samples were collected before, during, and after treatment. Indicators, metrics, biological index scores, and community compositional values were analyzed using analysis of variance (ANOVA) and repeated measures analysis of variance (RMANOVA) to determine differences between control, treatment, and neutralization sites over time. SIMPER procedures were used to analyze taxa contributions to differences among sites.;Overall, negative effects to the macroinvertebrate community due to Fintrol application were minimal and short-term (i.e., recovery within two months post-treatment). However, most results indicated positive effects (i.e., greater abundance and richness) after treatment among the major stream-dwelling benthic macroinvertebrate orders. Negative effects were greatest in KMnO 4 neutralization sites with several community structure attributes recovering after six months post-application. A large-scale downstream shift in the macroinvertebrate community was observed in larger stream sections; however, no taxa were eradicated as a result of Fintrol or KMnO4 exposure.;Taxa that were most affected and displaced during this study share several behavioral and morphological characteristics. Regardless of subadult type (i.e., larvae or nymphs), affected taxa tended to be the least robust (i.e., slender or diminutive) of all taxa collected. The larger surface area to volume body ratio could allow for greater exposure and cutaneous absorption of Fintrol or KMnO4. Several affected taxa also possess highly exposed plate-like or filamentous gills allowing for greater potential for exposure. Behaviorally, most affected taxa are very active and mobile and typically reside in the upper interstitial zone or on the surface of the substrate, which resulted in greater risk of exposure. Increased activity and metabolic rates coincide with increased gill surface area and/or large body surface area to volume ratios in highly oxygenated, turbulent water to meet internal oxygen demands. All of these factors contribute to increased risk of exposure to aqueous toxicants such as Fintrol or KMnO4.;Brook trout restoration efforts that have utilized Fintrol within GRSM and throughout the southeast have collectively demonstrated minimal effects to the macroinvertebrate community, and recovery occurred within a short time period. In most instances, increased drift and benthic macroinvertebrate abundances after treatment indicated a thriving macroinvertebrate community in the absence of predation. This phenomenon suggests high rates of food availability for insectivorous fishes immediately after treatment and may allow the opportunity to stock brook trout shortly after treatment during future restoration projects. If Fintrol application and brook trout stocking transpired before fall spawning, an additional year-class of brook trout would be established expediting restoration efforts.