MACROINVERTEBRATE BIODIVERSITY AND WATER CHEMISTRY ACROSS LAND USE IN SUB WATERSHEDS OF THE RAPPAHANNOCK RIVER

Maintaining the water quality of smaller sub watersheds in urbanizing areas is important to the health of larger water bodies. Other studies have demonstrated that land use within a watershed can influence water chemistry, by altering nutrients, specific conductance, and turbidity, as well as stream biota. In this study we compared the water chemistry and macroinvertebrate biodiversity of six sub watersheds of the Rappahannock River in northeastern Virginia representing 3 differnt land uses (forested, agriculture and urban). ArcGIS 9.0 and Digital Orthophoto Quadrangles (DOQs) were used to determine land use for each watershed. At each sub watershed macroinvertebrates were sampled at 3 pools and 3 riffle/runs, with 3 surber samples taken at each habitat unit. We also collected environmental data at each sub watershed including shade, nitrates, phosphates dissolved oxygen, current speed, pH, substrate size, temperature and conductivity. Several biological metrics were calculated to characterize the invertebrate community including diversity, richness, evenness, density, and %EPT (ephemeroptera, plecoptera, trichoptera). We found that in general, forested sites had the highest biodiversity, agricultural sites had the second highest biodiversity, and urban sites had the lowest biodiversity. In addition to lower diversity urban streams were dominated by pollution tolerant taxa (primarily Chironomidae).