An eDNA-based assessment of the impact of 55,000-gallon gas spill on the local hellbender populations

Environmental DNA (eDNA) analysis has become widely available as a conservation tool to survey and monitor wildlife populations. Despite its versatile applicability and effectiveness, eDNA analysis has rarely been used to assess the impact of natural or anthropogenic disturbance in aquatic environments. Eastern hellbenders (Cryptobranchus allegheniensis allegheniensis) are fully aquatic giant salamanders inhabiting fast-flowing mountain streams in the Eastern US including the tributaries of the West Branch Susquehanna River. The hellbender populations have declined throughout its distribution range and it is listed as a species of special concern in Pennsylvania. One of the threats to hellbenders is pollution. In addition to chronic pollution from agricultural practices and other human activities, sporadic gas and oil spills from gas stations and fracking sites likely cause serious damages to stream ecosystems. By analyzing hellbender eDNA concentrations in water samples, we conducted a comparative assessment of the population status of hellbenders in Loyalsock Creek before and after the gas pipeline rupture which caused 55,000 gallons of gas spills into the creek in October 2016 at a site approximately 16 km upstream from the mouth. Given hellbender’s sensitivity to water quality, we predicted a significant decline in eDNA concentration in 2017 compared with the data collected before the 2016 gas spill. Contrary to the prediction, the comparison in eDNA concentration revealed no significant change before and after the gas spill. We will discuss possible reasons for the result