This thesis addresses the idea that colony formation effectively increases the size of a phytoplankter thereby reducing grazing losses by deterring ingestion by zooplankton. It was initially hypothesized that colonies of Dinobryon (Ochromonadales, Chrysophyceae) deter zooplankton grazers, and that their spring population declined either because of a drop in the mean colony size of the Dinobryon population or from an increase in the abundances of large zooplankton grazers capable of ingesting large colonies. From January to May 1983 a small dystrophic lake was sampled weekly at three discrete depths at two stations. In the samples collected from one station, two species of Dinobryon, D. cylindricum Imhof and D. diverqens Imhof, as well as all zooplankton species were enumerated and morphometric variables of Dinobryon colonies were measured. The results showed that, alone, each of the original hypotheses could not account for the population and colony size dynamics of the Dinobryon species present in the lake. A new hypothesis was generated from the results which suggested that Dinobryon colonies minimized grazing losses to small grazers because of increased size and to larger grazers by fragmentation upon capture. Subsequent evaluation of the assumptions of this new hypothesis, using both the original data and new data from the second station, added further support to the hypothesis. / Science, Faculty of / Botany, Department of / Graduate

Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references (leaves 137-150). Also available on the Internet.

Thesis (Ph. D.)--University of Missouri-Columbia, 1999. / Typescript. Vita. Includes bibliographical references (leaves 137-150). Also available on the Internet.

The response of macroinvertebrate and protozoan colonization dynamics to industrial pollution was determined in a thermal organic effluent and in a metals effluent. The relationship of the time course data to the MacArthur-Wilson model is considered, along with Pinkham and Pearson's community similarity index and traditional community structural parameters. The response of both communities is similar with respect to equilibrium number of taxa at both sites; however, the fitted rate constant, G, was accelerated in the organic effluent for the protozoans. The macroinvertebrate G in the same effluent showed a dose response. There were no differences in rate between stations in the metals effluent for either the protozoans or the macroinvertebrates, although the equilibrium number of taxa was decreased downstream. Community similarity indices shows similar macroinvertebrate and protozoan communities at all three stations in the organic system at equilibrium, although some differences occur in the early stages of colonization. The communities in the metals effluent are most often significantly different at the downstream station, which was the most impacted. Community diversity indices indicate the same results for the equilibrium community as do the other methods of evaluation. While community colonization studies have been suggested as a method of water quality assessment, colonization dynamics and particularly the fitted rate constant, G, may be misleading unless considered in conjunction with equilibrium information. / Master of Science