"Potential Impacts of Human Physical Disturbance on Benthic Communities in Tributaries of the Niobrara National Scenic River" Kim Lang, MS Student, University of Nebraska-Lincoln; Advisor Kyle Hoagland. The Niobrara National Scenic River is a 76-mile segment with over 200 waterfalls in the western stretch of the river. Visitors are attracted to the Niobrara River to enjoy the waterfalls, canoeing, kayaking, tubing, swimming, and fishing. This study investigated the impacts of visitors, walking in the streams to visit the waterfalls, on the benthic community. Disturbances can result in a variety of changes such as increased turbidity, increased drift among aquatic invertebrates, and the elimination of sensitive species. Ten tributaries, located along the south bank of the Niobrara River were sampled monthly from May through September. The tributaries were divided into five streams that were potentially impacted from visitors, located upstream, and five streams that were known to have no visitors. A mini-surber sampler was used to collect benthic invertebrates from upstream sections of the tributary (above the waterfalls with no visitors) and from downstream, below the waterfall. Current velocity, depth, width, and distance from the edge of the tributary were recorded at each location. Water temperature, pH and conductivity were measured and a water sample taken to measure total nitrogen, total phosphorus and turbidity. In June, July and August visitor information was collected by volunteers at each potentially impacted tributary. Volunteers counted the number of times each tributary was disturbed. These data, along with daily visitor use collected by Fort Niobrara, U.S. Fish and Wildlife Service, will be used to estimate the degree of disturbance at each location and its impact on benthic species composition and abundance.