Is the Muddy Creek food web affected by coalbed natural gas inputs ?

The Muddy Creek watershed is a unique ecosystem because the stream contains a distinctive fish assemblage, is physically degraded, and will soon be influenced by oil and gas development. Separating the effects of multiple stressors can be challenging; however, having prior data can be very useful in determining the influence of different stressors. In our study, we attempted to separate the effects of physical degradation, and oil and gas development by sampling prior to most energy development. To extract oil and gas, groundwater must be pumped to the surface; groundwater associated with oil and gas resources can contain detectable concentrations of trace elements. The produced groundwater is often discharged into streams or ponds. Trace elements in produced water can be taken up into food resources (e.g., algae) and transferred to higher trophic levels in the food web through predation. We collected animals from each trophic level in the Muddy Creek food web above and below the current coalbed natural gas (CBNG) input, and measured their tissue for trace element concentrations and δ 15 N (trophic position). As a result, we regressed trophic position (δ 15 N) against trace element concentration for each organism (e.g., μg Se/g tissue) to measure how trace elements moved through the food web. Al and Zn concentrations in Muddy Creek exceeded chronic standards for aquatic life. We found that only Se and Hg bioaccumulated in the Muddy Creek food web, but other trace elements biodiminished, peaked at intermediate trophic levels, or concentrations remained similar in the food web (Be, B, Mg, Al, v, Cr, Mn, Fe, Ni, Cu, Zn, As, Sr, Mo, Cd, Ba, and Pb). By understanding the Muddy Creek ecosystem now, land managers and developers can make informed decisions about management needs and potential mitigation efforts. This study will record baseline (pre-CBNG) influences on the Muddy Creek food web. We plan to repeat this study in 3-5 years after CBNG development has occurred to determine if trace metals are accumulating differently in the food web. Objectives 1. Are trace elements detectable in water and biota before most energy development in Muddy Creek? We collected and analyzed water, aquatic food sources, invertebrates, birds, frogs, and fish for trace element concentrations (Be, B, Mg, Al, v, Cr, Mn, Fe, Ni, Cu, Zn, As, Se, Sr, Mo, Cd, Ba, Hg, and Pb) at 2 sites along Muddy Creek (above and below the current coalbed natural gas well). 2. What does the food web at Muddy Creek look like? We collected aquatic food sources, aquatic invertebrates, spiders, birds, frogs, and fish at 2 sites along Muddy Creek and analyzed these samples for δ 15 N and δ 13 C. δ 15 N describes trophic position of each group, because 15 N accumulates in biota at higher trophic levels. δ 13 C describes carbon sources. 3. Do trace elements bioaccumulate in the Muddy Creek food web? To estimate how each trace element behaves in the food web, we regressed trace element concentration (e.g., μg Se/g tissue) against δ 15 N (trophic position). Study Sites Muddy Creek is located south of Rawlins, Wyoming in the Colorado River Basin. Muddy Creek originates by the continental divide near the Atlantic Rim and Bridger Pass at ~2500 m elevation (Figure 1). The stream flows across high desert prairie dominated by sagebrush (Artemisia sp.) and greasewood (Sarcobatus sp.). Several tributaries empty into Muddy Creek within the watershed, including Wild Cow Creek and Dry Cow Creek. Finally, Muddy Creek joins the Little Snake River by the Colorado boarder near Baggs, Wyoming.