An integrative assessment of a watershed impacted by abandoned mined land discharges

The Fly Creek watershed in Lee County, VA, USA, contains an abundance of ab andoned mined land areas with acid mine drainage (AMD) that contaminate the majority of the creek and its confluence into Stone Creek. Acidic pH measu rements ranged from 2.73 to 5.2 at several stations throughout the watershe d. Sediments had high concentrations of iron (similar to 10,000 mg kg(-1)), aluminum (similar to1,500 mg kg(-1)), magnesium (similar to 400 mg kg(-1)) and manganese (-150 mg kg(-1)), and habitat was partially to non-sup porti ng at half of the stations due to sedimentation. Benthic macroinvertebrate surveys at six of 20 stations sampled in the watershed yielded no macroinve rtebrates, while eight others had total abundances of only one to nine orga nisms. Four reference stations contained greater than or equal to 100 organ isms and at least 13 different taxa. Asian clam in situ toxicity testing su pported field survey results. Laboratory, 10-day survival/impairment sedime nts tests with Daphnia magna and Chironomus tentans and 48-h water column b ioassays with Ceriodaphnia dubia indicated environmental stress to a lesser degree. Ten parameters that were directly influenced by AMD through physic al, chemical, ecological and toxicological endpoints were assimilated into an ecotoxicological rating (ETR) to form a score of 0-100 points for the 20 sampling stations, and the lower the score the greater the AMD stress. Twe lve of the 15 sampling stations influenced by AMD received an ETR score of 13.75-57.5, which were categorized as severely stressed (i.e. comprised the < 60 percentile category) and worthy of the highest priority for future ec ological restoration activities in the watershed. (C) 2000 Elsevier Science Ltd. All rights reserved.