Date of Award

11-2023

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Biology

First Advisor

Dr. David Manning

Abstract

The Niobrara River is a 914 km tributary of the Missouri River. The Niobrara has a 122 km section near Valentine, Nebraska, USA that was designated a National Scenic River in 1991. Despite its protected status, this section of the river still has many human influences including livestock grazing, row-crop agriculture, upriver impoundments, and, most directly, recreational activities like kayaking, canoeing, and tubing. The goal of my thesis was to document macroinvertebrate communities within the Niobrara National Scenic River and evaluate how community assemblages and diversity responded to recreational activities. I also used macroinvertebrate assemblages as indicators for the water quality of the river. The river was separated into fifteen sites with three sets of five sites located within three river sections with varying recreation levels: none, low levels, and high levels. I sampled macroinvertebrates using a D-frame net at each of the fifteen sites for three months, June, July, and August, in 2020. I subsampled and identified 4,971 macroinvertebrates from 50 different families. I found, for family richness and Shannon Index, there were no significant differences across recreation levels or month sampled and there was no interaction between those two variables. For percent EPT, there was no significant difference across recreation levels, but there was a significant difference in month sampled and an interaction between recreation level and month sampled. The most abundant families I found were mayflies of the families Baetidae, Isonychiidae, and Caenidae; true flies of the family Chironomidae; and beetle larvae and adults of the family Elmidae. These results suggest recreational activity is not strongly impacting water quality within the protected section of the river; however, an overall assessment of the macroinvertebrate community suggests there is still some organic pollution present within all recreation levels. The Shannon Index suggests the river has low to medium levels of macroinvertebrate family diversity, and the Hilsenhoff Biotic Index suggests that the river has good quality with possible slight organic pollution. This study can serve as a baseline for future work on macroinvertebrate community structure in the Niobrara and other grassland rivers.

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