Date of Graduation

Fall 2014

Degree

Master of Science in Biology

Department

Biology

Committee Chair

John Havel

Abstract

Many planktonic organisms in both freshwater and marine environments show a daily pattern of vertical migration. Daphnia undergo daily movements, migrating deeper during the day and rising toward the surface at night. To confirm this movement, field surveys were conducted in Bull Shoals Lake (Missouri–Arkansas) during the summer of 2007. Surveys showed migration patterns differed for Daphnia living in two different areas of the reservoir. D. retrocurva showed a more pronounced diel vertical migration (DVM) at the downlake, lacustrine site (amplitude ≥8m) than the uplake, riverine site. D. pulicaria showed similar, though lower amplitude behavior. Daphnia diel migration may be controlled in part by exposure to fish predators. Daphnia should show greater amplitude DVM in the presence of predators. Daphnia behavioral responses to light and fish chemical cues were examined through experiments in an apparatus containing four acrylic tubes (100cm x 4.5cm). Passing ice-water through coils wrapped around the tubes created a distinct thermocline (6.3-20.5°;C) in the tubes. There was no discernible effect on the position of D. pulicaria in a cylinder due to chemicals released by three different fish species—Lepomis macrochirus (bluegill sunfish), Lepisosteus osseus (longnose gar), and Pimephales promelas (fathead minnow). Light had a significant effect on lowering Daphnia position in the last set of trials and limited data suggest this light effect was limited to columns containing water from bluegill sunfish and minnows. Although the results of this study are not definitive, future studies should reexamine the interaction of species-specific kairomones and light cues on Daphnia behavior.

Keywords

Bull Shoals Lake, DVM, kairomone, predation, zooplankton

Subject Categories

Biology

Copyright

© Jason Carlisle Wolf

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