VTechWorks staff will be away for the winter holidays starting Tuesday, December 24, 2024, through Wednesday, January 1, 2025, and will not be replying to requests during this time. Thank you for your patience, and happy holidays!

Browsing by Author "Evans, Shane Kent"

Now showing 1 - 1 of 1
  • Thumbnail Image
    Studies of Benthic Macroinvertebrates in Western Virginia Streams as Related to the Implementation of Rapid Bioassessment Techniques
    Evans, Shane Kent (Virginia Tech, 1997-05-16)
    This study tested two key assumptions in developing regional biocriteria: (1) the accuracy of the ecoregion classification framework and (2) the accuracy of standardized qualitative sampling. Except for the Central Appalachians ecoregion, there was little or no correspondence of benthic macroinvertebrate distribution with the ecoregions or subregions of western Virginia. I found that it was more accurate to rearrange the subregions into three larger regions called bioregions: the forested hills and mountains (subregion 69a), valleys and plateaus (subregions 66c, 67a, and 67b), and the mountains (subregions 66a, 66b, 67c, and 67d). As an alternative to the ecoregion classification scheme, I classified my reference sites in biotic groups and then assessed the effect of several environmental variables on discriminating between the groups. There was a 69.8% correct classification rate using 14 environmental variables. Stepwise multiple discriminant analysis and graphical analysis showed that sampling date, slope, pH, habitat assessment score and distance to source were the best predictors of community structure. These environmental variables correctly classified 52.8% of the reference sites. These classification rates are comparable to rates published in similar studies. My study demonstrated that aggregations of subregions into bioregions and a biotic approach are more accurate classification schemes than ecoregions or subregions for biocriteria based on benthic macroinvertebrates. A second study evaluated the accuracy of a standardized qualitative sampling approach, commonly used in rapid bioassessments, in assessing the biological condition of lotic systems. I compared a typical standardized qualitative sampling method with subsampling with a typical quantitative sampling method on a stream with varying degrees of impairment. Although some metrics did respond to differences in sample abundance, overall the two methods made similar estimates of community composition. The two sampling methods made the same assessment an average 89% of the time using multimetric index developed for the Mid-Atlantic Region. I found no pattern showing one method was more accurate in making assessments of biological condition than the other. Given the greater time and costs associated with quantitative sampling methods, I conclude that standardized qualitative methods, are preferable for rapid bioassessment approaches to environmental assessment.