No description available.

Phytoplankton populations are integral to the structure and function of aquatic ecosystems, and phytoplankton are an excellent study system for exploring ecological questions. Reservoirs often exhibit high horizontal (inflow to dam) and vertical (surface to sediments) environmental heterogeneity, which plays a large role in determining phytoplankton population dynamics. In this thesis, I explore how three bloom-forming phytoplankton taxa, the dinoflagellates Peridinium and Gymnodinium, and the cyanobacterium Planktothrix, respond to horizontal and vertical environmental gradients, respectively. First, I monitored recruitment, or the process of leaving the sediments and entering the pelagic life stage, of dinoflagellates across a horizontal reservoir ecosystem gradient. Surprisingly, coupling of dinoflagellate biology with reservoir physics and chemistry varied along this continuum; recruiting cells were sensitive to reservoir physics (e.g., flow rate, solar radiation) in the upstream riverine zone, while recruitment was related to reservoir chemistry (e.g., dissolved oxygen, nutrients) in the downstream lacustrine zone. This study indicates that upstream habitats should be monitored when studying reservoir phytoplankton dynamics. Next, I investigated the environmental drivers of the vertical distribution and biomass of a hypolimnetic cyanobacterial bloom over two consecutive summers. I collected high-resolution in situ phytoplankton data, and measured environmental variables throughout the water column. Across both years, the vertical distribution of this population was determined by light availability, while the cyanobacterial biomass was predicted by both light and nutrients. These two studies demonstrate that changing physics and chemistry across environmental gradients can regulate phytoplankton dynamics in reservoirs, and phytoplankton monitoring should include more spatially comprehensive sampling approaches. / Master of Science

This study documents the occurrence of dinoflagellate cysts from the Middle Eocene Tallahatta and Lisbon Formations in the Baldwin County, Alabama, Core. This is part of a larger project being conducted by the ARCO Depositional Sequence Analysis Group to gather paleontological, sedimentological, paleomagnetic, geophysical, and geochemical data from the Alabama Coastal Plain for the purpose of calibrating the Tertiary time scale with the sequence stratigraphy of the Gulf region. A total of 101 taxa were identified, including 55 genera, 91 species, and 10 subspecies. Statistical analyses were run on the data collected to identify paleoecologic patterns and to relate these patterns, if possible, to sedimentary sequences. Diversity curves generated from the data show that there is usually a rise in diversity at sequence boundaries and at introsequence surfaces. Q-mode cluster analysis and detrended correspondence analysis indicate that samples tend to cluster within sequences. R-mode cluster analysis was performed and live informal cyst associations are discussed. Comparison of this studies assemblage with ranges published by Goodman and Stover (1975, 1983), and Edwards (1982) confirm the Middle Eocene age assigned to these units. / Master of Science

Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (leaves 32-38). / v, 38 leaves, bound 29 cm

Thesis (M.S.)--University of North Carolina Wilmington, 2009. / Title from PDF title page (February 22, 2010) Includes bibliographical references (p. 48-51)

The small dinoflagellate Azadinium spinosum produces azaspiracid (AZA) toxins which can contaminate filter feeding shellfish to dangerous levels. Toxin-contaminated shellfish flesh, when consumed by humans, can cause acute intense illness and chronic health issues. Shellfish biotoxins are monitored in Scottish shellfish by Food Standards Scotland (FSS), and the concurrent monitoring of harmful phytoplankton in the water column acts as an important early warning system of future shellfish toxin contaminations. Since A. spinosum is very small (12-16 μm long) it is difficult to identify using a light microscope, therefore molecular techniques have been developed to detect species-specific environmental DNA from phytoplankton samples. In this thesis the application and verification of quantitative real time polymerase chain reaction (qPCR) is discussed in detail and documents its first use in Scottish waters to survey A. spinosum abundance and seasonality. The limit of detection of the method was found to be 2000 ±5600 cells L-1, however it is unclear whether this is adequate for regulatory monitoring because it is not yet understood how cell density in the water column relates to AZA shellfish toxicity. The qPCR probe and primer sequences were also found to be too specific to detect all strains of the A. spinosum species, as new strains have been isolated since their development. This is a significant hindrance to the application of the tool for monitoring which will need to be addressed in the future through the isolation of local A. spinosum strains. Over a year long sampling period, A. spinosum was detected only twice (maximum cell density of 2545 ±5600 cells L-1, August 2014) off the Shetland Islands. The seasonality of the species in Scottish waters could not be assessed with so little data, however other observed harmful species of importance to shellfish regulatory monitoring are discussed; of particular note an unusual bloom of Dinophysis acuta as its association with a temperature front at the mouth of Loch Fyne. This thesis critiques the use of this qPCR technique for A. spinosum detection at high-throughput. The issues which have been highlighted do not prevent its future use by FSS, but highlight specific areas of development which need addressed before national monitoring can occur.

Interest in the effect of fish farming practices on the marine environment has arisen because there is concern that the wastes that fish farms produce may be contributing to eutrophication in coastal areas and the problem of harmful algal blooms. The focus of this thesis is an examination of phytoplankton distribution and abundance in relation to tuna fish farms in Boston Bay and near-shore Spencer Gulf. This is the first study in South Australia to define the short-term biomass fluctuations of chlorophyll and in vivo fluorescence, identify phytoplankton species distribution and abundance, including two potentially toxic dinoflagellates, and describe patch distribution relative to tuna fish farms in Boston Bay and the near-shore waters of Spencer Gulf. An ecological interpretation of phytoplankton distribution and abundance is determined and shows that community composition was different in lower Spencer Gulf compared to Boston Bay and upper Spencer Gulf sites. Pico- and nanophytoplankton were often the most abundant organisms. Diatoms and gymnoids were most common. Season and currents predominantly influenced the distribution of phytoplankton in Boston Bay and Spencer Gulf. Individual species may be influenced by inputs from the fish farms. Chlorophyll levels were different between the Spencer Gulf and Boston Bay sites and no differences were recorded, using mean levels of chlorophyll, between tuna cages and controls. Chlorophyll levels were higher east of Boston Island in autumn of 1999. Chlorophyll levels appeared to show a slight increase between years. This may have been an anomalous natural variation and future research may investigate this in the long term. In addition, Principal Components Analysis (PCA) was used to investigate differences between treatments and the functional grouping model supported an ecological interpretation of the factors from the PCA. A total of 131 taxa of phytoplankton were identified in this study. The 14 dominant taxa were used in the PCA and of these, 9 were diatoms. Phytoplankton abundance was not different between tuna cages and controls. However, when examining individual species, Karenia mikimotoi was more prevalent at tuna cages, close to shore, east and west of Boston Island than at other sites. PCA showed how different species bloomed together and were seasonal. Karenia brevis and K. mikimotoi featured predominantly in the PCA with K. brevis the dominant organism during summer and autumn along with Gyrodinium spp. and smaller gymnoids. K. brevis blooms were most likely influenced by water temperatures and fixation of nitrogen from a Trichodesmium erythaeum bloom. K. mikimotoi bloomed bimodally and may be influenced by ammonia excreted from fish from the tuna farms but , on the other hand, may be limited by the high salinities of South Australian waters. Currents in the region distribute both organisms. The final aspect of this study assessed finer temporal and spatial sampling using directional transects around tuna cages and controls using in-vivo fluorescence and size fractionated chlorophyll. The chlorophyll a sampling showed little spatial variability within a site in the 1000 m2 that the sampling area covers but far greater temporal variability (days). In contrast, fluorescence `mapping' expands the window of variability both spatially (within a site) and temporally (along transects and between days). This has given a spatial definition, which is unavailable from a single point sample, and thereby leaves room for much greater interpretation. Small patches are evident from the fluorescence mapping where this is impossible to detect from the single point samples. Therefore, the fluorescence `mapping' and patch definition show that the trend is widespread (spatially) and quite persistent (temporally) around the fish farm area. Size fractionated chlorophyll samples provided further insight into phytoplankton dynamics in this study where diatoms were favored over dinoflagellates and were responsible for the larger fraction of chlorophyll found at the tuna cage one (TC1) site. We suggest that seasonal fluctuations, high nutrient input from the farm activities and turbulence may be responsible for the different chlorophyll/fluorescent structures found at TC1. Future research may look at the long-term regional impact on phytoplankton size structure, biomass and communities from fish farm activities. As a good part of this journey involved counting phytoplankton using the Utërmohl technique, a short paper, published in the Journal of Plankton Research, on reducing the settling time of this method, is presented in Appendix.

Karenia brevis is the major harmful algal bloom-forming species in the Gulf of Mexico, and produces neurotoxins, known as brevetoxins, that cause large fish kills, neurotoxic shellfish poisoning, and human respiratory distress. Brevetoxins are polyethers that bind voltage-sensitive sodium channels, opening them for prolonged periods of time. Clonal cultures of K. brevis exhibit unique brevetoxin profiles, which not only differ from one another, but also change when subjected to different environmental conditions. The brevetoxin structures were elucidated 30 years ago without any breakthroughs for the biosynthetic pathway. These unique ladder-like polyethers have 10 (PbTx-1) or 11 (PbTx-2) rings, indicating that they are synthesized as secondary metabolites by polyketide synthases. The extensive size of the genome and the lack of histones and nucleosomes combined with the additional regulatory step of a trans-splicing spliced leader sequence make normal molecular techniques ineffective in determining the genes involved in toxin synthesis. The goal of this project is to identify a potential link between toxin, gene, and function. One objective is to take the next step towards identifying the genes associated with the synthesis and regulation of brevetoxins and to help elucidate the hypothesized gene clusters of multi-protein enzymatic complexes involved in brevetoxin production, one for each backbone. The second objective is to make an effort to determine the in vivo function of the costly brevetoxins by identifying possible ion channels, which could be osmotically regulated by the toxins. Genes for polyketide synthases (PKS) were identified in K. brevis, obtained from Expressed Sequence Tag (EST) libraries. In this work, reverse transcription polymerase chain reactions (RT-PCR) were used to generate pools of complementary DNA (cDNA), which was used in real-time quantitative polymerase chain reactions (qPCR) to give relative amounts of PKS transcripts. K. brevis clones have shown a significant increase in toxin production after a rapid shift from high salinity to low salinity, indicating a regulation of brevetoxin synthesis. To gain a better understanding of regulation of toxin production during algal blooms, we compared the toxin levels under different conditions to the transcript levels of PKS genes, as determined by quantitative RT-PCR. In a separate line of investigation, an in silico analysis of the EST library was performed to identify ion channel genes expressed by K. brevis, which may be the in vivo binding site of brevetoxin. The information generated from this project will help to elucidate the effects of environmental variations on toxin production and the biological function of toxin production -- valuable information for the shellfish industries and public health.

Thesis (M. Phil.)--Hong Kong University of Science and Technology, 2003. / Includes bibliographical references (leaves 118-130). Also available in electronic version. Access restricted to campus users.

Thesis (Ph. D.)--Oregon State University, 2008. / Printout. Includes bibliographical references. Also available on the World Wide Web.