COMPARING WATER QUALITY AND BIOLOGIC COMMUNITIES ACROSS CARBONATE AND NON-CARBONATE GEOLOGY IN TWO AGRICULTURALLY INFLUENCED STREAMS IN THE CUMBERLAND VALLEY OF PENNSYLVANIA

Agricultural activity is considered the largest single source of nutrients to the Chesapeake Bay by the US Environmental Protection Agency. To effectively manage these pollutants and restore water quality in the Chesapeake Bay, it is critical to understand the source and transport of nutrients to the stream system. Three sites in two small, agriculturally dominated watersheds in Cumberland County, Pennsylvania were investigated to compare how the hydrologic pathways offered by their respective geologic settings influenced water quality and the biologic communities that reflect it. The Three Square Hollow Run watershed (32.8km²) is dominated by resistant shale, the upper Burd Run watershed (37.2km²) contains resistant bedrock in its headwaters and quarzitic colluvium in its lower reaches, and the lower Burd Run watershed (48.8km²) is dominated by carbonate bedrock. The carbonate bedrock and karst features provide efficient sub-surface pathways for water and pollutants to travel and are expected to result in significant water quality differences at the lower Burd Run site. From January 2019 to December 2019 each site was sampled biweekly for dissolved nutrients (nitrate and orthophosphate) and continuously for basic water quality parameters (temperature, specific conductance, pH, and dissolved oxygen) to serve as indicators of geologic influence and characterize local water quality. Three macroinvertebrate and one fish survey were performed at each site to measure biologic response to water quality. Preliminary results suggest that the lower Burd Run site, being influenced by carbonate geology, experiences substantially higher concentrations of nitrate and less diverse biologic communities than the sites influenced by colluvium and shale. The results of this study will help evaluate the influence of carbonate geology on nutrient transport and inform future management efforts across the region.