Using Biological Responses to Monitor Freshwater Post-Spill Conditions over 3years in Blacktail Creek, North Dakota, USA.

Abstract

A pipeline carrying unconventional oil and gas (OG) wastewater spilled approximately 11 million liters of wastewater into Blacktail Creek, North Dakota, USA. Flow of the mix of stream water and wastewater down the channel resulted in storage of contaminants in the hyporheic zone and along the banks, providing a long-term source of wastewater constituents to the stream. A multi-levelinvestigation was used toassessthe potential effectsofoilandbrine spillson aquatic life. In this study, we used a combination of experiments using a native fishspecies, Fathead Minnow (Pimephalespromelas), field sampling of the microbial community structure, and measures of estrogenicity. The fish investigation included in situ experiments and experiments with collected site water. Estrogenicity was measured in collected site water samples, and microbial community analyses were conducted on collected sediments. Duringthe initial post-spill investigation, February 2015, performingin situ fish bioassays was impossible because of ice conditions. However, microbial community(e.g., the presence ofmembers of theHalomonadaceae, a family that is indicativeofelevated salinity) andestrogenicitydifferences were compared to reference sitesand point toearlybiological effects of the spill. We noted water column effects on in situ fish survival 6months post-spill during June 2015. At that time, total dissolved ammonium (sum of ammonium and ammonia, TAN) was 4.41mgNH4/L with an associated NH3of 1.09mg/L, a concentration greater than the water quality criteria established to protect aquatic life. Biological measurements in the sediment defined early and long-lasting effects ofthe spill on aquatic resources. The microbial community structure wasaffected during all sampling events. Therefore, sediment may act as a sink for constituents spilled and as such provide an indication of continuedand cumulativeeffects post-spill. However, lack of later water column effects may reflect pulse hyporheic flow of ammonia from shallow ground water. Combining fish toxicological, microbial community structureandestrogenicity informationprovides a completeecologicalinvestigation that defines potential influencesof contaminantsatorganismal, population, and community levels. In general, in situ bioassays have implications for the individualsurvivalandchanges at thepopulation level, microbial community structure defines potential changes at the community level, andestrogenicitymeasurements define changes at theindividual andmolecularlevel. By understanding effects at these various levels of biological organization, natural resource managers can interpret how a course of action, especially for remediation/restoration, might affect a larger group of organisms in the system. The current work also reviews potential effects of additional constituents defined during chemistry investigations on aquatic resources.