Macroinvertebrate Assemblages in Shale-Draining Streams of North- Central Arkansas, USA

摘要

Natural and anthropogenic release of metals into surface waters and sediments may alter benthic communitystructure. To better understand macroinvertebrate communities in metal-impacted shale-draining streams in north-centralArkansas, sediment and macroinvertebrate samples were collected from sites on black shale-draining (BLS) and limestone-draining streams (LMS; used as a reference stream). The samples were collected during three sampling occasionstargeting periods of stable flows between October 2003 and July 2005. Analyses of metals in water and sediment sampleswere done according to US EPA 200.8 and 6020 methodologies, respectively. Habitat surveys and macroinvertebratecommunity sampling, processing and taxonomy were done following US EPA’s rapid bioassessment protocols as well asmethods outlined in Ohio Environmental Protection Agency. Concentrations of cadmium, copper, and nickel in BLSsediments were significantly (p < 0.05) higher than those of LMS samples. The concentrations of cadmium (range: 0.5 -5.3 ppm), copper (2.2–64), and nickel (6.2–18) in the BLS sediments exceeded the Effect Range-Low values of NOAA’ssediment quality guidelines. Except for Chironomidae genera, all macroinvertebrate abundance and richness metrics weresignificantly lower in BLS than LMS sites (p < 0.05). The percent Ephemeroptera-Plecoptera-Trichoptera (EPT) was betweentwo and seven times higher in LMS than BLS sites. The abundance and richness of metal-sensitive taxa (e.g. Heptageniidaeand Chloroperlidae) were significantly lower in BLS samples than those of LMS. Negative correlations betweensediment metal concentrations and macroinvertebrate richness metrics were also observed. The observed low macroinvertebrateabundance and taxa richness at BLS sites were attributed in part to elevated metal concentrations in sedimentsand water. Knowledge of the impacts of shale-derived metals on the spatial and temporal distribution of macroinvertebrateis vital in the management of watersheds underlain by black shales. Such information forms the basis uponwhich sound state and federal government land and water management and conservation policies are made.