Influences of Vegetative Best Management Practices on Macroinvertebrate Populations in Agricultural Streams of Montgomery County, Maryland

Abstract

Best management practices are critical for mitigating the pernicious effects of urbanization on water quality within the Chesapeake Bay Watershed. This study examined the influences of vegetative best management practices on stream benthic macroinvertebrate populations within Montgomery County, Maryland. Databases from the Department of Environmental Protection and Maryland Department of Agricultural were analyzed and cross-referenced to evaluate vegetative practices and the condition of macroinvertebrate populations. Using ESRI ArcMap Geographic Information Systems, impervious surface area and agricultural land use were determined within six watersheds. Average BIBI health condition ranged from scores of 20 to 34 (within the fair to good range) while annual cover crop sizes ranged from 0 to 4,387 acres. Best management practices and stream benthic macroinvertebrate populations exhibited no discernable trends. In contrast, an inverse relationship between watershed imperviousness and macroinvertebrate populations was observed. Watersheds with the lowest percent imperviousness (3%) had a “good” health condition score (31 and 34) while the watershed with the highest imperviousness (24%) had a “fair” health condition score (20). Although no direct relationship was observed with cover crop acres, it is possible that vegetative practices have an indirect influence on benthic macroinvertebrate populations through conservation of natural ground cover and reduction in impervious surface.