Date of Graduation

Spring 2019

Degree

Master of Science in Biology

Department

Biology

Committee Chair

Debra Finn

Abstract

The hyporheic zone, a key component of stream vertical connectivity, supports stream function (e.g., nutrient regeneration) and provides habitat for aquatic biota. The Ozark Highlands ecoregion contains gravel-bed streams that have extensive hyporheic zones and that are subject to recurrent flash floods. I sampled Leuctra tenuis(Pictet) nymphs from the hyporheic habitat (30-45 cm below the streambed) in a gravel-bed reach and an intermittent tributary of an Ozark stream from early instar to adult emergence. Concurrently, I sampled benthic insects in two reaches of the same stream that differed primarily in amount of hyporheic habitat (bedrock vs. gravel) and monitored the hyporheic insect community in the gravel reach for an entire year (October 2017 to September 2018). I calculated secondary production and development of hyporheic L. tenuis. I also monitored the response of benthic and hyporheic insect communities after two floods and documented reductions in richness and densities of benthic insects, especially in the bedrock reach. Pre- and post-flood communities were significantly different between bedrock and gravel benthic habitats. However, differences in community composition were not significant across the entire year, indicating that floods mixed the communities. Insect richness in the hyporheic zone increased post-flood, which may have facilitated quicker recovery in the gravel reach. It is imperative that we understand the role of vertical connectivity to stream secondary production and how the hyporheic zone can contribute to supporting diverse and resilient aquatic communities in order to better protect stream ecosystems.

Keywords

interstitial, flow, gravel-bed, diversity, resilience, hyporheos, life-history, ephemeral

Subject Categories

Biodiversity | Entomology | Population Biology | Terrestrial and Aquatic Ecology

Copyright

© Nathan C. Dorff

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