The development of new extraction technologies has driven a development of shale oil and shale gas. While this development has led to a rapid increase in domestically produced oil and gas, relatively little is known about the potential for environmental risks associated with the exploration and exploitation of these resources. Oil and gas extraction from unconventional reservoirs, including the Bakken formation, is accompanied by the production of wastewater brines (UOG WW) that are typically characterized by high total dissolved solids, naturally occurring radioactive materials, and hydrocarbons. Millions of liters of UOG WW have been accidentally released to the environment since the beginning of the shale oil and gas boom, a portion of which has reached surface waters.
A pipeline rupture adjacent to Blacktail Creek north of Williston, ND, in January 2015 released an estimated 3 million gallons of UOG WW. Blacktail Creek joins the Little Muddy River 7.1 km downstream from the spill, which joins the Missouri River at Williston, ND. In response, USGS sampled stream water and bed sediment in February and June 2015 from Blacktail Creek (upstream, adjacent to, and downstream from the rupture), and from the Little Muddy River, above and below the confluence with Blacktail Creek. Surface soil samples were taken from the floodplain near the pipeline rupture. Several weeks following reporting of the spill, water samples collected downstream from the spill had elevated concentrations of B, Br, Cl and Li relative to samples collected upstream, suggesting that the downstream sites were impacted by Bakken UOG WW. We investigated the potential for a spill to impact microbial communities responsible for hydrocarbon biodegradation and inorganic transformations via Illumina sequencing of the 16S rRNA gene. Streambed microbial communities downstream from the spill were found to most closely resemble those in surface soils at the spill site, rather than those of streambed sediments upstream from the spill. Alterations to community structure included the loss of anaerobic Desulfobacterales and Anaerolineales from surface soils impacted by the spill, whereas these same samples were found to have a greater prevalence of organisms associated with UOG WW, including Halanerobiales, relative to those outside the spill area. Together, these findings show the potential for a UOG WW spill to surface water to lead to alterations in soil and streambed microbial community structure. Analysis of samples from June 2015 is ongoing, and will help to determine if these changes to community structure are persistent.