Aquatic Ecology

The southern Appalachians are a center of endemism-- a region where enormous concentrations of life forms occur, reflecting special local conditions. In contrast, most of the world is inhabited by widely distributed and very adaptive species.

The uniqueness of the aquatic systems in the southern Appalachians can be attributed primarily to the geologic history and climatic conditions that have influenced the evolution of species and development of biological communities. Since their rise in the late Paleozoic Era (around 250 million years ago), the southern Appalachian mountains have been above sea level. Precipitation falling on these highlands has drained into thousands of kilometers of freshwater streams and rivers. During the Pleistocene Epoch (1.8 million to 11,000 years ago), glaciers advanced over North America but did not reach southern Appalachia. Consequently, evolution proceeded in this region without the catastrophic disruption that occurred further north during that time. The great time scales over which the flora and fauna developed, a relatively mild climate, and the great heterogeneity of landscapes and habitats all combined to produce unique ecological conditions within a temperate aquatic setting. The region forms a global center of biological diversity for many groups of organisms, including fishes, mussels, crayfishes, and aquatic insects.

Aquatic systems integrate the landscape through hydrologic processes. Aquatic ecosystems, therefore, are influenced by terrestrial characteristics of watersheds as well as submersed, in-channel features. Our description of aquatic ecology discusses: 

• Drainages and the Hydrologic Cycle-- Primary organization of aquatic ecosystems. The broad scale interactions of climate and geology that determine drainage systems.
• Ecology of Running Water-- Structure and function of streams and rivers (lotic).
• Ecology of Lakes and Reservoirs-- Structure and function of standing water (lentic).