Experimental Determination of Benthic Macroinvertebrate Metric Sensitivity to Fine Sediment in Appalachian Streams

Many fisheries management agencies incorporate benthic macroinvertebrate metrics in stream assessment, yet concern exists over regional variability in metric sensitivity and the reproducibility of results over time. Two field experiments were conducted in Mullenax Run, Pocahontas County, West Virginia during summers 1999 and 2000 to investigate the sensitivity of benthic macroinvertebrate metrics to fine sediment and annual variation. Substrate composition of fine sediment (< 2mm) was manipulated from 0%-40% in 10% increments in 0.3-m2 circular trays arrayed in 2 sections of the study stream. The trays were allowed to colonize for 5 weeks in each year. In 1999, Ephemeroptera, Plecoptera, and Trichoptera, (EPT) taxa richness (R2=0.144, P=0.0031) was negatively related to increasing fine sediment while % Climber (R2=0.217, P=0.0019) was positively related to increasing fine sediment. In 2000, annual flow differences may have clouded relationships between fine sediment and benthic macroinvertebrate metrics in the experiment suggesting that low flow may mask the sensitivity of metrics used in stream bioassessment.

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