Understanding the role of species as drivers of ecosystem processes is imperative to preserve, utilize, and sustain ecosystems globally. Addition of species through invasion and loss of species through extirpation or extinction can have profound effects on ecosystem structure and function (Zavaleta et al. 2009). This is especially true for freshwater ecosystems in which a preponderance of native species are threatened with extinction and where nonnative species are frequently introduced (Dudgeon and Smith 2006). Commonly, anthropogenic activities result in the loss of biodiversity and enhance the ability of exotic species to invade and persist in novel habitats (Dudgeon and Smith 2006). Because these activities are expected to increase through time, advances in understanding the consequences of species loss and addition on ecosystem function are needed to guide appropriate management and conservation decisions. The loss and addition of organisms may render habitats functionally impaired (Covich et al. 2004); therefore, understanding the consequences of such change is imperative to manage, mitigate, and restore freshwater ecosystems.