The influence of human impacts on stream ecosystem function and plant growth
Natural gas extraction represents a significant resource and provides a considerably large portion of energy to the U.S-- enough to fuel the US for 90-100 years. However the effects of fracking and flow back fluid used in these operations on adjacent ecosystems and water quality is largely unknown. This research explores the effects of stream ecosystem function below fracking sites and examines the effects of fracking mud on plant growth, chlorophyll a concentration and biomass. Our sites are located below and above a Marcellus Shale fracking operation in Central Pennsylvania. We measured conductivity, nitrate, phosphorous, temperature and dissolved oxygen at each site in the fall and winter. Dissolved oxygen and light meters were deployed for 6 weeks and collected data every 5mins. We calculated differences in gross primary production and community respiration at these locations. A mesocosm study was used to monitor the growth of plants in soils contaminated with fracking fluid. We amended soil with frack material at different concentrations and monitored growth over 8 weeks in a greenhouse. We predicted ecosystem function and plant growth would be reduced after exposure to fracking compounds.
Conductivity and total dissolved solids were much higher at the downstream location compared to upstream of the fracking pad. We found higher concentrations of DO at the downstream site, although leaf cover also varied significantly between the two locations which may have contributed to variability. Gross primary production and community respiration were not significantly different between the locations. Conductivity and total dissolved solids were higher at the impacted location compared to the non-impacted site. Although we measured only minor differences between the two sites, the impacted stream was located below the confluence of tributaries, which may have diluted potential consequences from the upstream impacted locations. In the greenhouse study, we found germination rates to not differ between treatments, but growth differed throughout the experiment and was significantly lower at week 8 in treated soils. We hypothesize that the high concentration of phosphorus (7g/L) in the fracking material initially stimulated plant growth, but such high levels eventually hinder growth and caused mortality. This research shows that ecosystems can potentially remain in a natural state below frack sites if precautions are used by the industry and there is enough adjacent water flow or soils to dilute inputs of novel contaminants, however further research is warranted.