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SFS Annual Meeting

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Aquatic-Terrestrial Linkages Downstream of Glen Canyon Dam

From the early days of ecology, researchers have recognized the permeability of ecosystem boundaries to the movement of energy, nutrients, and organisms. Emergent insects represent one example of this exchange, maturing in the aquatic system and emerging into the terrestrial system once adults, where they become a food source for riparian predators. The concept of emergent insects as subsidies has been applied to a variety of environs. However, despite its demonstrated significance, this dynamic remains unexamined for large, altered river systems, including the Colorado River. To accomplish this, tissue samples were obtained from riparian consumers between Glen Canyon and Hoover dams and analyzed for 13C and 15N composition. Comparing consumer isotope ratios to those of aquatic insects demonstrated the trophic linkages between these groups. Isotope ratios of predators also allowed for comparisons of food chain length along the river. This is of special interest, as hydropeaking waves, a daily tide caused by dam operations, affect the structure of aquatic and terrestrial communities alike. Though this study was restricted to a stretch of the Colorado, its findings are relevant for managing rivers affected by hydropeaking worldwide.

Christina Lupoli (Primary Presenter/Author), Arizona State University,;