Lake Powell Food Web Structure: Predicting Effects of Quagga Mussel Food webs in aquatic ecosystems can be dramatically altered by invasive species. Quagga mussels are prevalent invaders that compete with existing species and disrupt nutrient cycling. In 2012, the Quagga Mussel (Dreissena rostriformus bugensis) was introduced into Lake Powell and is expected to move throughout the reservoir in the near future. Stable isotope analysis is a powerful tool for characterizing food webs and trophic

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... teractions. To predict the long-term effects of Quagga Mussels, we used stable isotope analysis of primary producers, primary consumers, prey fish species, and predator fish species in Lake Powell to determine food web structure. Quagga Mussel are positioned to disrupt the pelagic arm of the food web by interfering with the link between phytoplankton and herbivorous zooplankton. This will likely have negative impacts on pelagic fish such as striped bass (Morone saxatilis) and threadfin shad (Dorosoma petenense). Quagga Mussel may also boost benthic productivity in the littoral zone by diverting nutrients from the water column to the benthos. This may have positive impacts on littoral fishes such as largemouth bass (Micropterus salmoides), smallmouth bass (Micropterus dolomieu), bluegill (Lepomis macrochirus), and green sunfish (Lepomis cyanellus).