Date of Graduation

Summer 2022


Master of Science in Biology



Committee Chair

Debra Finn


The hyporheic zone (HZ), an ecotone between surface water and groundwater in streams, provides extensive but underappreciated habitat for invertebrates in alluvial systems like the gravel-bed streams common in the Ozark highlands. Relative to its importance as a habitat, little is known about spatial distribution and response to disturbance by invertebrates in the HZ. In riffle-pool systems, surface water typically enters the HZ at the head of riffles (downwelling) and returns to the surface at the tail of riffles (upwelling). Previous research has found differences in invertebrate communities and environmental variables between upwelling and downwelling zones, but results have been inconsistent. I sampled the hyporheic zone at three depths in upwelling and downwelling zones for four months (Oct-Jan) in high flow and three months (June-Aug) in low flow seasons, as well as opportunistically in response to floods. Abundance and richness were significantly greater in downwelling zones than upwelling zones, and greater at shallower depths. Dissolved oxygen and particulate organic matter, two important resources for invertebrates, showed no spatial patterns and no correlation with abundance and richness. Invertebrate communities showed no differences in abundance or richness between pre and post flood samples, suggesting that the HZ was not used as a refuge in response to disturbance. While invertebrates were not observed using the HZ as a refuge, sampling difficulties likely impacted these results and further research is needed on this topic. My research highlights the importance of the HZ as habitat for a high diversity and biomass of invertebrates and emphasizes the need for further research on this understudied part of stream ecosystems.


stream ecosystems, invertebrates, connectivity, hyporheic, flow, diversity, resilience, streambed sediments

Subject Categories

Terrestrial and Aquatic Ecology


© David Fleshman

Open Access