Rapid assessment of stream ecosystem function across an agricultural impact gradient in central Pennsylvania

Elaine Langone Center, Forum

The capacity to reliably assess the functional integrity of stream ecosystems is at the heart of stream assessment and restoration. However, direct measures of ecosystem function are often cumbersome, expensive and have not been used widely enough to develop predictive models relating functional indicator responses to the myriad of potential stressors. The goal of this project was to utilize a suite of “rapid” ecosystem assessment protocols to examine the response of 19 stream ecosystems spanning a gradient of agricultural impact in central Pennsylvania. We measured ecosystem metabolism (diel oxygen data coupled with inverse modeling), nitrogen and phosphorus uptake in portable mesocosms, photosynthetic capacity (pulse amplitude modulated fluorometery) and extracellular enzymes (β-glucosidase, β-xylosidase, alkaline phosphatase, leucine-aminopeptidase, β-Nacetylglucosaminidase and phenol oxidase). Our preliminary results indicate that, although stream size and underlying geology are potentially important covariates, these “rapid” protocols for characterizing ecosystem function responded well to variations in nutrient concentrations, canopy cover and sedimentation observed across this agricultural gradient.