A Comparison of Five Northern Virginia Watersheds in Contrasting Land Use Patterns
William R. Mangun
AbstractA study of the benthic macroinvertebrate community composition was conducted at five sites in Northern Virginia with contrasting land use patterns to determine the relative impact of the degree of urbanization on the biological condition of those watersheds. The biological diversity and productivity of the receiving streams was assessed through the collection and subsequent analysis of benthic invertebrates and periphyton in accordance with scientifically established procedures. Various physical and chemical parameters were also addressed in order to establish their relationship to the biological diversity and productivity of the streams. These parameters were water flow, pH, alkalinity, chlorophyll level, and suspended solids. The biological diversity of the benthic organisms and periphyton was found to be greater in those watersheds with a lower degree of urbanization. There were twenty or more taxa in the least developed areas and as few as eight in the most developed areas. The more urbanized area streams also had a substantially greater percentage of pollution-tolerant algal species and the chlorophyll-a values were greater as well. Furthermore, the quantity of suspended solids increased along with the degree of urbanization, in accordance with similar studies of this phenomenon, displaying increased erosion associated with reduced ground cover, especially during storm events.
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