Stream Habitat Assessment
Habitat, as it relates to stream biosurveys, is simply the space occupied by living organisms. In a stream, habitat for macroinvertebrates includes the rocks and sediments of the stream bottom, the plants in and around the stream, leaf litter and other decomposing organic material that falls into the stream, and submerged logs, sticks, and woody debris. Macroinvertebrates need the shelter and food these habitats provide and tend to congregate in areas that provide the best shelter, the most food, and the most dissolved oxygen. A habitat survey examines these aspects and rates the stream according to their quality.
In western North Carolina streams there is a net flow of energy and materials from the terrestrial landscape to the stream. Most of the energy available for organisms living in the streams comes in the form of leaves and woody debris. Streams that drain forested areas are generally habitat for many organisms that utilize forest materials for food; leaves and debris from the riparian zones provide the energy for the benthic macroinvertebrate community. Interruptions to this flow of energy and material will impact the abundance and diversity of the community. Common adverse stream impacts include: removal of woody vegetation from the riparian zone, accelerated erosion of upland areas and streambanks that cause excessive sedimentation in the stream, removal of tree canopy and shade that keeps streams cool and oxygen content high, point discharges of heated water or chemical pollutants, and in-stream disturbances.