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Harmful algal blooms (HABs) are becoming more prevalent throughout the world’s aquatic systems. These blooms have been the subjects of numerous studies because they can cause human health issues and economic impact through fish kills, contaminated shellfish and decreased tourism. Much research has focused on the “bottom-up” aspect of these blooms; namely, the potential role of increased nutrient input into coastal waters from anthropogenic sources causing increased growth in harmful algal species. However, there are also potential “top-down” controls affecting the rate at which harmful algal species are consumed by grazers. The aim of this project was to determine protozoan grazer population fluctuations and their grazing impact on HAB species through field monitoring and laboratory grazing experiments. Protozoan grazers were chosen because their growth rates could potentially keep up with those of HAB species. Declines in grazer populations before the onset of a bloom could be indicative of a release of the HAB from a “top-down” grazing control. Field samples taken during bloom and non-bloom events helped elucidate any microplankton community changes. After establishing that there appear to be changes to the grazer population before and after a bloom, ingestion experiments including direct epifluorescence microscopy and DNA analyses were conducted to determine if it is possible that a chosen protozoan grazer can ingest a HAB species. Finally, experiments were conducted to determine whether the HAB species was a favorable food source for the grazer. Population growth experiments in which grazers are fed a HAB species, 50:50 mixture, or normal culture food source were used to determine the survival and growth rate of the grazer. Although certain ciliates and heterotrophic dinoflagellates were found to feed on HAB species in the lab and in natural bloom samples, the HAB species as a food source produces lower grazer growth rates than on control food. Protozoan grazers may be a more effective control during bloom initiation than after the bloom has been established. / text

161 miospore species and 122 microplankton species are described from 106 samples in six sections of the Lower Colorado Group and its equivalents in central and west-central Alberta. Two miospore species, and two genera and twenty-five species of microplankton, are newly described. The miospore and microplankton assemblages are used as a basis for division of the Lower Colorado Group into several time-stratigraphic units. The age of the Group is determined as Upper Albian (latest Lower Cretaceous). A method for defining recurrent microplankton species groups is developed and applied to assemblages from two of the sections. The distribution of the recurrent groups formulated is shown to be correlated in part with palynological, lithological and other data. Application and extension of the results and conclusions of this investigation should prove useful in understanding many aspects of western Canadian Cretaceous stratigraphy and in the investigation of microplankton occurrence patterns from other deposits. / Thesis / Doctor of Philosophy (PhD)

During 1999 ex-situ microcosm experiments were carried out at Dunstaffnage Marine Laboratory, Oban using natural assemblages of microplankton (< 200 m in size) in a series of enrichment experiments using continuous culture techniques to determine q - the yield of chlorophyll from dissolved available inorganic nitrogen (DAH\I), during and after an enrichment event. The experiments lasted between 11 and 14 days and produced a time series of q after an enrichment of either 12 M ammonium or 12 M nitrate. Allother essential nutrients, vitamins and trace metals were added in excess so that only DAIN would limit chlorophyll synthesis. Experiments were carried out during Spring, Summer and Autumn and environmental regimes in the growth room were set-up tomimic ambient conditions at the sampling site for each season. Water samples were collected every 2 days and were analysed for chlorophylls a, b and c, chlorophyll a breakdown products, carotenoids, dissolved inorganic nutrients and particulate nitrogenand carbon. Identification and enumeration of microplankton was also undertaken. During 2 of the experiments nitrogen isotope techniques were used to determine uptake rates for nitrate and ammonium. The results indicated that the microplanktonic response to an enrichment event could be divided into 3 phases: Phase I q - a rapid uptake of DAINand the synthesis of large quantities of pigments; Phase H q - DAIN became limiting and there was a decline in q caused by nutrient limitation and an increase in grazing pressure; Phase II q - after declining q remained fairly stable. Nitrogen tied-up in autotrophicbiomass was transferred to the heterotrophs as grazing pressure and algal death increased accompanied by a calculated rise in dissolved organic nitrogen through degradation processes (assuming mass conservation of nitrogen was occurring in the microcosms),and, presumably, regenerated DAIN. There were seasonal differences in q caused by changing environmental conditions such as light, temperature and background nutrient concentrations. Seasonal changes in the community structure of microplankton collected from the sampling site could also have affected the value of q. During the Summer and Autumn Experiments ammonium enriched microcosms produced lower values of q compared to nitrate enriched microcosms but further investigation is needed to clarify the reasons for this. The method used to estimate chlorophyll or nitrogen had an effect on the value of q. Refined values of q have been produced for use in the screening model used to predict potential eutrophication in the UK.