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Thesis (Ph.D.) in Oceanography--University of Maine, 2007. / Includes vita. Includes bibliographical references (leaves 155-172).

Thesis (M.S.)--Eastern Illinois University, 2008. / Includes bibliographical references (leaves 46-49).

Thesis (Ph. D.)--University of Washington, 1998. / Vita. Includes bibliographical references (p. [118]-136).

Thesis (M. Phil.)--University of Hong Kong, 1992.

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

Our view of phytoplankton has historically revolved around their inability to control their location in space. The term phytoplankton itself underscores this particular difference between phytoplankton and their sessile terrestrial counterparts. Yet there are other differences between land plants and the phytoplankton that are perhaps equally important, beyond this sessile-planktonic dichotomy, to their growth, survival, and productivity. For example, phytoplankton are microbes and thus are short-lived, with generational scales on the order of days or less. An intriguing question to ask is how today���s pelagic ecology would differ, had this temporal difference between plants and phytoplankton been initially emphasized, perhaps by naming these microbes phytoephemera instead? This dissertation addresses certain aspects of the ecology of phytoplankton that result from their having short generational scales. Because they are so short lived, phytoplankton need to adjust their photosynthetic physiology to cope with more rapid changes in irradiance than may matter to longer-lived plants. Photoacclimation on the hours-plus time scales has been studied extensively in the phytoplankton, because its temporal scales match those of vertical mixing processes in the ocean. Yet most phytoplankton exhibit faster photosynthetic responses as well, down to the time scales of seconds. These photosynthetic responses have received considerably less attention in phytoplankton ecology. This dissertation specifically examines these rapid, seconds-to-hour scale photosynthetic responses in phytoplankton. First, the physiological bases of rapid photosynthetic regulation were examined using a numerical model that shows how specific physiological changes in phytoplankton photosystems either constrain or enhance light harvesting. This model is stochastic, and thus replicates certain nonlinear aspects of light harvesting better than equation-based analytical models. Also in this dissertation, a laboratory study is described that examined rapid photosynthetic regulation in three model phytoplankton. Results suggest that rapid photosynthetic regulation is not only constrained to higher eukaryotic phytoplankton, but also occurs in the two dominant marine photosynthetic prokaryotes, Synechococcus and Prochlorococcus. Finally, rapid photosynthetic responses were examined in field assemblages at Station ALOHA in the North Pacific. This ocean region experiences considerable cloud cover, which may result in a strong degree of rapid photosynthetic responses, even in near-surface assemblages. / Graduation date: 2007

Thesis (M.S.)--University of North Carolina at Wilmington, 2005. / Includes bibliographical references (leaves: [69]-73)

Thesis (Ph. D.)--University of Hong Kong, 2001. / Includes bibliographical references (leaves 192-206).

published_or_final_version / abstract / toc / Ecology and Biodiversity / Doctoral / Doctor of Philosophy