Structural and functional characteristics of natural and constructed channels draining a reclaimed mountaintop removal and valley fill coal mine Ken M. Fritz 1,6 , Stephanie Fulton 2,7 , Brent R. Johnson 1,8 , Chris D. Barton 3,9 , Jeff D. Jack 4,10 , David A. Word 4,11 , AND Roger A. Burke 5,12 1 Office of Research and Development, National Exposure Research Laboratory, US Environmental Protection Agency, Cincinnati, Ohio 45268 USA 2 Region 4, Watershed Protection Division, US Environmental Protection Agency, Atlanta, Georgia 30303 USA 3 Department of Forestry, University of Kentucky, Lexington, Kentucky 40546 USA 4 Department of Biology, University of Louisville, Louisville, Kentucky 40292 USA 5 Office of Research and Development, National Exposure Research Laboratory, US Environmental Protection Agency, Athens, Georgia 30605 USA Abstract. Mountaintop removal and valley fill (MTR/VF) coal mining has altered the landscape of the Central Appalachian region in the USA. Among the changes are large-scale topographic recontouring, burial of headwater streams, and degradation of downstream water quality. The goals of our study were to: 1) compare the structure and function of natural and constructed stream channels in forested and MTR/ VF catchments across ephemeral, intermittent, and perennial flow regimes and 2) assess the relationship between leaf litter breakdown and structural measures, such as the habitat assessments currently used by regulatory agencies. Specific conductance of stream water was, on average, 36 to 573 higher at perennial reaches below valley fills than at perennial reaches in forested catchments, whereas pH was circumneutral in both catchment types. Channel habitat and invertebrate assemblages in litter bags differed between forested streams and constructed channels in VF catchments. Invertebrate density, diversity, and biomass were typically higher in litter bags from forested catchments than from VF catchments. No differences in fungal biomass, estimated as ergosterol concentration, were detected between litter bags from forested and VF catchments. Breakdown of oak (Quercus alba) leaves was slower at perennial and intermittent reaches in VF catchments than at perennial and intermittent reaches in forested catchments. However, breakdown rates did not differ between ephemeral reaches on VFs and in forested catchments. Breakdown rates of oak leaves were significantly correlated to conductivity at perennial and intermittent reaches and to shredder diversity across all reaches, but were not correlated with habitat assessment scores currently being used to determine compensatory mitigation. Landuse changes associated with MTR/VF have detrimental consequences to headwater stream function that are not adequately evaluated using the prevalent habitat assessment. Key words: mountaintop removal, valley fill, coal mining, litter breakdown, organic matter processing, hydrologic permanence, reclaimed mine, rapid functional methods, stream assessment, mitigation. Worldwide coal production has increased over the last 30 y from 4.2 billion to 7 billion tons/y to meet increasing global energy demands (USDOE-EIA 2008c). In the USA, where coal-fired power plants supply half of the electricity, coal consumption for electricity is expected to increase 42% from 2008 to 2030 (USDOE-EIA 2008b) despite changing energy 6 E-mail addresses: fritz.ken@epa.gov 7 fulton.stephanie@epa.gov 8 johnson.brent@epa.gov 9 barton@uky.edu 10 Deceased 11 daword@gmail.com 12 burke.roger@epa.gov J. N. Am. Benthol. Soc., 2010, 29(2):673–689 ’ 2010 by The North American Benthological Society DOI: 10.1899/09-060.1 Published online: 6 April 2010 673