Factors Affecting Macroinvertebrates in the Tuolumne River Watershed

A river is a continuously evolving environment that acts on many different time scales. These changes may be attributed to fluctuations in water temperature, dissolved oxygen concentration, anthropogenic flow regulation, and fine sediment composition. Macroinvertebrates living in these dynamic environments are affected by slight differences in stream composition and water quality (Vannote, 1980). As such, they have evolved their life histories, feeding habits, and physiology to best utilize their local resources. The Tuolumne River provides a large subset of dynamic habitats in which aquatic macroinvertebrates live and adapt. These varying habitat types result in differences in macroinvertebrate biodiversity, species composition, and percentage of sensitive EPT taxa. In this paper I discuss the effects that elevation, sediment size, and regulated flows may have had on aquatic macroinvertebrate communities sampled from various reaches along the Tuolumne.