Effects of Marcellus shale gas drilling on fishes, salamanders and crayfish in streams in north-central Pennsylvania

Background/Question/Methods

The recent increase in hydro-fracturing to extract Marcellus shale gas has raised concerns about environmental impacts resulting from water withdrawals, contamination, and infrastructure development. Pathways for impacts on aquatic systems include: contamination of surface and shallow ground water by spills or leaks of flowback water from well pads, storage lagoons, or waste-transport trucks; contamination of shallow groundwater via poorly sealed well casings; and land cover-related effects from construction and maintenance of well pads, pipelines, and access roads. These concerns have been particularly acute in parts of north-central Pennsylvania, where shale gas extraction is occurring in many of the highest quality drainages in the region.  In 2011, we sampled 27 streams in the Susquehanna Drainage. Study watersheds had >90% forest cover and a range of well pad densities, including reference.  We did not consider spill or violation history at well pads in selecting sites. The study watersheds are mainly on public lands which have regulations on well pad placement, and the range of well pad densities was lower than the regional range. Depletion reach sampling of fish and crayfish was done by electrofishing, with additional salamander surveys. Complementary studies were done on water chemistry, attached algae, and macroinvertebrates.

Results/Conclusions

Virtually all sites had similar assemblages of native, salamanders, crayfish and cold water fish. We found no statistically significant relationships between response variables (species or life stage densities, species richness) and well pad densities. We are analyzing the causes of differences at a few sites, which may have resulted from differences in habitat or non-drilling related land uses.  These results suggest that construction and operation of well pads can be done with minimal effects on the aquatic macrofauna, where well pad placement and densities are regulated to minimize impacts. In this study, we investigated effects of construction, drilling, and maintenance on aquatic communities, but did not measure longer term effects, effects of additional construction (e.g., new wells), or terrestrial impacts. In 2012, we re-sampled some of the 2011 sites and sampled sites in more developed watersheds with a greater range of well pad densities.