Historic, current, and future oil and natural gas development can affect water quality in streams flowing through developed areas. We compared small stream drainages in a semiarid landscape with varying amounts of disturbance from oil and natural gas development to examine potential effects of this development on surface water quality. We used physical, chemical, and biological approaches to assess water quality and found several potential avenues of degradation. Surface disturbance likely contributed to elevated suspended sediment concentrations and spill history likely led to elevated stream polycyclic aromatic hydrocarbon concentrations. In combination, these environmental stressors could explain the loss of aquatic macroinvertebrate taxon at sites highly affected by oil and natural gas development. Our results provide insight into advantages and disadvantages of approaches for assessing surface water quality in areas affected by oil and natural gas development. Integr Environ Assess Manag 2019;00:000–000. © 2019 SETAC

Oil and natural gas (ONG) development can affect aquatic ecosystems through water contamination, water withdrawals and disturbance of soil and vegetation (surface disturbance) from infrastructure development. Research on how these potential sources of watershed and aquatic ecosystem impairment can affect fish assemblages is limited. Fish–habitat relationships were evaluated across stream sites experiencing differing levels of ONG development. Colorado River cutthroat trout, Oncorhynchus clarkii pleuriticus (Cope), and mottled sculpin, Cottus bairdii Girard, presence and abundance were associated with habitat conditions predominantly found in the less disturbed streams, such as higher proportion of shrub cover, greater stream depths and gravel substrate. Mountain sucker, Catostomus platyrhynchus (Cope), appeared to be a habitat generalist and was able to persist in a wide range of conditions, including degraded sites. Natural resource managers can use habitat preferences of these fish species to establish the development plans that mitigate negative effects of ONG development by protecting the aquatic habitats they rely upon.

1. As ecosystems experience simultaneous disturbances, it is critical to understand how multiple stressors interact to affect ecological change. Land-use change and extreme flow events are two important stressors that could interact to affect fish populations.2. We evaluated the individual and interactive effects of discharge and land-use change associated with oil and natural gas development on populations of two stream fishes over a 7-year period. We used repeated-state (i.e. abundance trends) and rate (i.e. colonization and persistence) responses to advance our understanding of flow-ecology relationships in a multiple-stressor framework.3. Overall, fish abundance, colonization and persistence declined as discharge decreased. The effect of land-use change associated with oil and natural gas development differed between species, with the abundance of Mottled Sculpin declining and Mountain Sucker increasing as land-use change increased. We found both synergistic and antagonistic interactions between discharge and land-use change.Land-use change intensified the effect of low flows for Mottled Sculpin and lead to greater variability in responses to flow for Mountain Sucker. These differences between species' responses are likely due to differences in their physiological tolerances and behavioural adaptations to disturbance. Synthesis and applications.Our research provides empirical evidence for the complex interactions that can arise between discharge and anthropogenic land-use change. Management efforts to reduce inputs of sediments and chemical contaminants associated with land-use change (e.g. silt fences, vegetative buffers) and promote quality refuge habitats (i.e. in-stream habitat restoration) could help mitigate the negative effects of low-flow extremes on stream fishes. Further development of flow-ecology relationships in a multiple-stressor framework will help guide management of stream fishes, and provide a better understanding of the mechanisms underlying responses of different species. K E Y W O R D S colonization, multiple stressors, natural flow regime, oil and natural gas development, persistence, rate responses, repeated-state responses, stream fishes 150 | Journal of Applied Ecology WALKER Et AL. L a n d -u s e c h a n g e (% ) La nd -u se ch an ge (% ) Land-use change (%) Land-use change (%) Land-use change (%) Land-use change (%) Land-use change (%) Land-use change (%)

For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment-visit http://www.usgs.gov or call 1-888-ASK-USGS.For an overview of USGS information products, including maps, imagery, and publications, visit http://store.usgs.gov.Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner. AcknowledgmentsThe authors gratefully acknowledge the generous assistance of landowners, State and local agencies, and business owners who provided the data used in the report. Their efforts provide the foundation for the analyses of the area. Assistance with data collection and analysis was provided by Dan Leemon, Friends of Fish Creek.The authors also acknowledge assistance with analyses, report reviews, and report preparation from U.S. Teton County, Wyoming, 2011 Altitude, as used in this report, refers to distance above the vertical datum. Supplemental InformationConcentrations of chemical constituents in water are given in milligrams per liter (mg/L).Concentrations of effluent or input are given in pounds per gallon (lb/gal), pounds per year (lb/yr), or pounds per 10-acre cell (lb/10-acre cell). AbstractNutrients, such as nitrogen and phosphorus, are essential for plant and animal growth and nourishment, but the overabundance of bioavailable nitrogen and phosphorus in water can cause adverse health and ecological effects.