Thesis (M.S.)--Oregon State University, 2011. / Printout. Includes bibliographical references (leaves 71-79). Also available on the World Wide Web.

Submitted by Natalia de Souza Gonçalves (natalia.goncalves@ufpe.br) on 2016-09-19T14:05:55Z No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese_Eveline Aquino_final_versão entregue_após biblioteca.pdf: 2444824 bytes, checksum: 611daa8ff08eb71508238b15067ae577 (MD5) / Made available in DSpace on 2016-09-19T14:05:55Z (GMT). No. of bitstreams: 2 license_rdf: 1232 bytes, checksum: 66e71c371cc565284e70f40736c94386 (MD5) Tese_Eveline Aquino_final_versão entregue_após biblioteca.pdf: 2444824 bytes, checksum: 611daa8ff08eb71508238b15067ae577 (MD5) Previous issue date: 2016-03-15 / CAPES / A dinâmica espaço-temporal do fitoplâncton está relacionada a um conjunto de variáveis ambientais. As camadas de estratificação vertical e a presença de ilhas oceânicas podem influenciar na distribuição desses organismos. Esse estudo objetivou investigar a distribuição e composição da comunidade fitoplanctônica nas águas oceânicas do arquipélago de Fernando de Noronha (Atlântico Sul Equatorial, Brasil), como um fator biológico indicativo das condições oceanográficas, evidenciando sua relação com as variáveis abióticas e sob influências da proximidade do arquipélago e da estratificação vertical, bem como registrar as populações de Ornithocercus sp. que apresentam diferentes horários e estágios de reprodução, sendo esta última uma abordagem complementar. Para tanto, as amostras da água foram coletadas ao longo de seis pontos, em escalas espacial (horizontal e vertical) e temporal, a saber: em diferentes distâncias do arquipélago, em duas posições geográficas (nordeste e sudoeste), em seis profundidades (entre 1 e 130 m), em dois períodos do dia (diurno, noturno e nictemeral) e durante dois anos (2010 e 2012). Foram coletadas as variáveis abióticas, como sendo os nutrientes inorgânicos dissolvidos, temperatura e salinidade. A clorofila a fitoplanctônica foi determinada, bem como a densidade celular, riqueza de espécies, abundância relativa, frequência de ocorrência, diversidade e uniformidade. Como resultados, horizontal e verticalmente, foram identificadas 115 espécies fitoplanctônicas, representadas essencialmente por dinoflagelados (>60% do total), seguidos por diatomáceas, cianobactérias e dictiofíceas. Foi registrado um decréscimo gradual da densidade de 1 m a 130 m e, portanto, mais elevada na camada de mistura. Por outro lado, não houve efeito significativo da estratificação para a clorofila a. Os dinoflagelados Oxytoxum gracile Schiller e O. laticeps Schiller foram dominantes, para todos os tratamentos em estudo. A alta dominância de dinoflagelados indica a estabilidade da água, devido à estratificação. Nitrato e fosfato estiveram relacionados com O. laticeps, favorecendo a sua dominância. A diversidade e composição de espécies, horizontal e verticalmente, foram homogêneas, sugerindo não ocorrer efeito de massa insular durante o período em estudo e para os tratamentos amostrais aplicados. / The spatio-temporal dynamics of phytoplankton is connected to any environmental variables. The layers of vertical stratification and the occurrence of oceanic islands can induce the distribution of these organisms. This study aimed to investigate the distribution and composition of phytoplankton in the ocean waters of Fernando de Noronha archipelago (South Atlantic, Brazil), as an indicative biological of oceanographic conditions and their relationship with abiotic variables and under archipelago's proximity influences and vertical stratification, as well as record the populations of Ornithocercus sp. under different timings and reproduction stages and this is a complementary approach. Samples of water sampled over six points in spatial (horizontal and vertical) and temporal scales: at different distances, in two geographic positions (northeast and southwest), six depths (between 1 and 130 m), different periods of the day (daytime, night and nyctemeral) and two years (2010 and 2012). The abiotic variables were sampled (dissolved inorganic nutrients, temperature and salinity). Chlorophyll a was determined, and the phytoplanktonic density, species richness, abundance, frequency of occurrence, diversity and uniformity. In horizontal and vertical scale, were identified 115 phytoplankton species, represented by dinoflagellates (> 60% of the total), followed by diatoms, cyanobacteria and dyctiophyceans. Were observed a gradual decrease in density from 1 m to 130 m and higher density in the mixing layer. Were dominant Oxytoxum gracile Schiller and O. laticeps Schiller in all samples. The high dominance of dinoflagellates indicates water stability due to stratification. On the other hand, there was no significant effect of stratification for chlorophyll a. Nitrate and phosphate were in significant relationship with O. laticeps, benefiting its dominance. The diversity and species composition, horizontal and vertical, were homogeneous, suggesting that no occur insular mass effect during the study period and for the applied sample treatments.

Submitted by Caroline Falcao (caroline.rfalcao@ufpe.br) on 2017-05-25T16:17:50Z No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) DISSERTAÇÃO FINAL SAWANA BORGES.pdf: 1343555 bytes, checksum: 626a5657eff4bd97ecd102c75073d331 (MD5) / Made available in DSpace on 2017-05-25T16:17:50Z (GMT). No. of bitstreams: 2 license_rdf: 811 bytes, checksum: e39d27027a6cc9cb039ad269a5db8e34 (MD5) DISSERTAÇÃO FINAL SAWANA BORGES.pdf: 1343555 bytes, checksum: 626a5657eff4bd97ecd102c75073d331 (MD5) Previous issue date: 2014-02-26 / As áreas recifais que se utilizam do turismo são susceptíveis às mudanças em sua fauna e flora como impactos negativos. Alguns cnidários são importantes bioindicadores de alterações físico-químicas no ecossistema. Devido a isso, foi realizada a análise da microbiota simbionte do zoantídeo Palythoa caribaeorum na Praia de Porto de Galinhas (PE) para avaliação da influência temporal e do pisoteio nesse organismo. As amostras foram coletadas mensalmente no período de junho a dezembro do ano de 2012, em áreas com pisoteio e sem pisoteio. Foram analisadas as variáveis de densidade populacional, índice mitótico, diâmetro celular e clorofilas a e c das zooxantelas e altura, quantidade e volume dos pólipos de P. caribaoerum associadas com alguns parâmetros abióticos (pluviosidade, temperatura, salinidade, pH e nutrientes). Foi observada variação significativa do índice mitótico, com maior média no período chuvoso (9.38 ± 0.62%) e diâmetro celular, com maior média no período de estiagem (11.30 ± 0.91μm). A pluviosidade, a salinidade, o pH, o fosfato e o silicato exerceram uma influência significativa no índice mitótico e no diâmetro celular das zooxantelas. O volume dos pólipos apresentou diferença significativa temporal, com maiores valores no período chuvoso e também influenciou no índice mitótico e no diâmetro celular desses simbiontes. A clorofila a variou de forma significativa entre os dois períodos estudados, apresentando maiores valores no período chuvoso. A biomassa clorofiliana (clorofilas a e c) foi influenciada pela pluviosidade, salinidade, volume dos pólipos e pelos sais nutrientes nitrito, fosfato e silicato. O pisoteio dos banhistas sobre os recifes não demonstrou influência sobre as variáveis estudadas, apesar do escossistema recifal sofrer intensa atividade turística. O zoantídeo P. caribaoerum indicou uma forte adaptação aos estresses ambientais, apresentando métodos para compensar a influência da variação dos fatores abióticos, não sofrendo intervenções na capacidade fotossintética dos seus simbiontes. / The reef areas that use tourism are susceptible to changes in flora and fauna as negative impacts. Some cnidarians are important bioindicators of physicochemical changes in the ecosystem. Because of this, analysis of the symbiotic microbiota zoanthid Palythoa caribaeorum in Porto de Galinhas Beach (PE) to assess the temporal influence and trampling were applied in this organism. Samples were collected monthly from June to December of the year 2012, in areas with and without trampling. The variables of population density, mitotic index, cell diameter and chlorophyll a and c of zooxanthellae and height, number and volume of polyps were analyzed for P. caribaoerum associated with some abiotic parameters (rainfall, temperature, salinity, pH, and nutrients). Significant variation in mitotic index was observed, with the highest average in the rainy season (9.38 ± 0.62%) and cell diameter, with the highest average in the dry season (30.11 ± 0.91μm). Rainfall, salinity, pH, phosphate and silicate exerted a significant influence on the mitotic index and the cell diameter of the zooxanthellae. The volume of polyps showed significant temporal differences, with higher values in the rainy season and also influenced the mitotic index and the cell diameter of these symbionts. The chlorophyll a was significantly different between the two study periods, with higher values in the rainy season. The chlorophyllian biomass (chlorophyll a and c) was influenced by rainfall, salinity, volume of polyps and the nutrient salts nitrite, phosphate and silicate. The trampling of bathers on the reefs showed no influence on these variables, although the reef escossistem suffer intense tourist activity. The zoanthid P. caribaoerum indicated a strong adaptation to environmental stresses, presenting methods to compensate the influence of the variation of abiotic factors, not suffering interventions in the photosynthetic capacity of their symbionts.

The purpose of this study was to assess whether nutrient absorption rates by water hyacinths are affected by low-salinity levels. In a controlled experiment, water hyacinths demonstrated the ability to absorb a significant amount of nutrients in low-saline waters while maintaining a slowed growth rate and shortened life span. Nutrient rates were reduced by an average of 36% in ammonia nitrogen and 48% in reactive phosphorus in the tanks of 4.45 parts per thousand (ppt) salinity. Growth rate in the experimental tanks of 4.45 ppt was observed at 33% slower than that of the control. The high salinity comparison tank of 7.0 ppt experienced complete mortality after three days. Phytoremediation practices through the use of an aquatic invader, water hyacinths, can be used to reduce large-scale fish kills along the eastern U.S.’s major estuarine systems, focusing on Florida’s waters. Toxic dinoflagellates and other harmful algal blooms have been plaguing the contributing waterways of North Carolina and the Chesapeake Bay and are the main causes of these massive fish kills. The characteristics and trends that these upstream estuarine systems are following could serve as a warning for Florida. An analysis of Florida’s fish kill database, as well as patterns and trends of the fish kills in North Carolina and the Chesapeake Bay, were used to determine areas at an increased risk for toxic dinoflagellates and harmful algal blooms to occur. Areas are proposed for water hyacinths to be implemented in a controlled method to reduce massive fish kills in Florida’s waters.

Thesis: Ph. D., Joint Program in Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Biology; and the Woods Hole Oceanographic Institution), 2016. / Cataloged from PDF version of thesis. / Includes bibliographical references (pages 124-131). / Dinoflagellates are a diverse group of single-celled eukaryotic phytoplankton that are important for their unique genetics and molecular biology, the multitude of ecological roles they play, and the ability of multiple species to produce toxins that affect human and ecosystems health. Two dinoflagellate genera, Alexandrium and Gambierdiscus each contain species that can cause human poisoning syndromes, although the methods of toxin transfer, accumulation, and exposure are very different. Gambierdiscus is a benthic organism that produces lipophilic ciguatoxins that can bioaccumulate in coral reef fish and cause ciguatera fish poisoning (CFP) in human consumers. Alexandrium is a planktonic species that produces saxitoxins that can directly accumulate in shellfish and cause paralytic shellfish poisoning (PSP) in humans. Both genera contain multiple species that vary dramatically in toxicity and physiology. Through transcriptomic analysis, this thesis describes the genetic diversity present across dinoflagellates that produce saxitoxin, elaborating on differences in their complement of genes within the saxitoxin biosynthesis pathway. This study demonstrated retention and expression of some of these saxitoxin genes by non-toxic species within Alexandrium, as well as in Gambierdiscus, which does not produce saxitoxins. Furthermore it confirmed the presence of certain transcripts only in toxin-producing species. This thesis then developed novel fluorescence in situ hybridization (FISH) probes that can be used to identify and enumerate six Gambierdiscus species, thereby enabling the community composition of Gambierdiscus to be examined in a quantifiable manner. The probes were tested in the laboratory on cultures, and then successfully applied to field samples from Florida Keys and Hawai'i. Gambierdiscus species are diverse in both their toxicity and optimal temperature ranges for growth. Analysis of Gambierdiscus community composition in an area of variable temperature allowed the characterization of species shifts that were driven both by a seasonal increase in mean seawater temperatures and spatial variability of temperature experienced between tidal pools. Overall this thesis advances the knowledge of dinoflagellate genetics and ecology, aids in the characterization of species harmful to public health, and provides tools and approaches to help monitor and manage harmful effects from these species, including some that are projected to increase with climate change. / by Kathleen Johnson Pitz. / Ph. D.

Thesis (Ph. D.)--Joint Program in Biological Oceanography (Massachusetts Institute of Technology, Dept. of Biology; and the Woods Hole Oceanographic Institution), 2005. / Page 296 blank. / Includes bibliographical references. / Marine thecate heterotrophic dinoflagellates likely play an important role in the consumption of primary productivity and in the trophic structure of the plankton, yet we know little about these species. This thesis expanded our understanding of the autecology and evolutionary history of the Protoperidinium and diplopsalids. The distributions of Protoperidinium species off the southwestern coast of Ireland were influenced by physical oceanographic conditions coupled with the availability of preferred prey. The distributions of individual Protoperidinium species varied widely from the distribution of total Protoperidinium, indicating differences in ecologies among species. Certain species of Protoperidinium co-occurred with known preferred phytoplankton prey species. Concentrations of other Protoperidinium species were not related to those of any particular phytoplankton species, indicating that these Protoperidinium may rely on phytoplankton or other food sources beyond those already known, may not be species specific selective feeders, or may have become uncoupled from their preferred prey. The description of the sexual and asexual life history of Protoperidinium steidingerae provided the first account of the life history of any Protoperidinium species. / (cont.) Asexual division occurred by eleutheroschisis within a temporary, immotile cyst, yielding two daughter cells. Daughter cells were initially round and half to two-thirds the size of parent cells, then rapidly increased in size, forming horns before separating. Sexual reproduction was constitutive in clonal cultures, indicating that the species may be homothallic. Fusing gametes were isogamous, and resulted in a planozygote with two longitudinal flagella. Hypnozygotes had a mandatory dormancy period of ca. 70 days. Germination resulted in planomeiocytes with two longitudinal flagella. Nuclear cyclosis may occur in the planomeiocyte stage. A high level of morphological diversity among life history stages of P. steidingerae has led to mis-classification and taxonomic inaccuracy of Protoperidinium species identified from field samples. The large subunit ribosomal DNA (LSU rDNA) molecular phylogeny of the heterotrophic dinoflagellates revealed that the genus Protoperidinium appeared to be recently diverged within the dinoflagellates. In maximum parsimony and neighbor joining analysis, Protoperidinium formed a monophyletic group, evolving from diplopsalid dinoflagellates. / (cont.) In maximum likelihood and Bayesian analyses, however, Protoperidinium was polyphyletic, as the lenticular, diplopsalid heterotroph, Diplopsalis lenticula Bergh, was inserted within the Protoperidinium clade basal to Protoperidinium excentricum (Paulsen) Balech, and Preperidinium meunieri (Pavillard) Elbrichter fell within a separate clade as a sister to the Oceanica section and Protoperidinium steidingerae Balech. In all analyses, the Protoperidinium were divided into two major clades, with members in the Oceanica group and subgenus Testeria in one clade, and the Excentrica, Conica, Pellucida, Pyriforme, and Divergens sections in another clade. The LSU rDNA molecular phylogeny supported the historical morphologically determined sections, but not a simple morphology-based model of evolution based on thecal plate shape. LSU rDNA gene sequences are frequently used to infer the phylogeny of organisms. The many copies of the LSU rDNA found in the genome are thought to be kept homogenous by concerted evolution. In Protoperidinium species, however, there was high intragenomic diversity in the D1-D6 region of the LSU rDNA. For each species, the clone library was usually comprised of one highly represented copy and many unique sequences. / (cont.) Sequence differences were primarily characterized by single base pair substitutions, single base pair insertion/deletions (indels), and/or large indels. Phylogenetic analysis of all clones gave strong support for monophyly of the polymorphic copies of each species, and recovered the same species tree as an analysis using just one sequence per species. Analysis of LSU rDNA gene expression in three species by RT-PCR indicated that copies with fewer substitutions and fewer and smaller indels are expressed, and that 50% or more of the copies are pseudogenes. High intraspecific and intraindividual LSU rDNA sequence variability could lead to inaccurate species phylogenies and over-estimation of species diversity in environmental sequencing studies. This thesis has explored the ecology, life history, molecular phylogeny, and intraspecific DNA sequence variability of marine thecate heterotrohic dinoflagellates using a wide range of methodologies, including field sampling, culturing, microscopy, morphological analyses, histological staining, and molecular biology. The work here has broadened our understanding of the Protoperidinium and diplopsalids, providing new insights into the ecological and evolutionary relationships of these heterotrophs with other plankton species. / by Kristin Elizabeth Gribble. / Ph.D.

The occurrence of phytoplankton taxa, with special focus on harmful algal bloom (HAB) taxa, was monitored for one year off the central coast of California to examine both their co-occurrence and physical and chemical variables influencing their temporal patterns. Bi-weekly samples were taken from October 6, 2008 to October 5, 2009 in San Luis Obispo Bay, CA. Canonical correspondence analysis (CCA) of weekly samples indicated that 46.1% of the variability in species abundance was explained by the variables in the model, higher than previous reports. Cluster analysis divided phytoplankton communities into HAB and non-HAB groups of species, while shared distribution analysis identified specific co-occurring species of HABs. The HAB dinoflagellate group consisted exclusively of HAB taxa, including Cochlodinium polykrikoides Margalef, Dinophysis acuminata Claparède & Lachmann, and Alexandrium spp., and was correlated with a homogeneous water column and high nitrate concentration during the fall and winter seasons. The domoic acid producing diatoms Pseudo-nitzschia seriata (Cleve) H. Peragallo complex and Pseudo-nitzschia delicatissima (Cleve) Heiden complex grouped with several other non-HAB diatoms, and were correlated with warm, thermally stratified waters of the summer season. These results contradict the classic diatom / dinoflagellate succession theory and suggest that event-scale processes influencing water column stability within seasons may influence the distribution of HAB species in near shore upwelling dominated regions.

This study documents the occurrence of dinoflagellate, chlorophyte, and acritarch cysts from the Upper Cretaceous upper Cusseta, Ripley, and lower Providence Formations in the USGS Fort Gaines core, drilled in Clay County, Georgia. A total of 75 taxa were identified, consisting of 36 genera, 61 species, and 5 subspecies of dinoflagellates, 3 genera and 4 species of chlorophytes, 3 genera and 4 species of acritarchs, and 1 problematical protozoan. 15 of these taxa are unpublished. The study's cyst assemblage was statistically analyzed to ascertain paleoecologic patterns. The results from cluster analysis and detrended correspondence analysis indicate the presence of four cyst associations. The <i>Deflandrea pannucea</i> association is interpreted as indicative of low salinity related to nearby river discharge. The <i>Deflandrea</i> sp. A association is confined to the inner shelf. The <i>Exochosphaeridium bifidum</i> and <i>Glaphyrocysta reticulosa</i> associations alternate under normal marine conditions. The associations correlate well with observed lithologies and lithologic change. Comparison of this study's assemblage with other Late Cretaceous assemblages provides limited information, since many biostratigraphically-important species are not present in this study. However, comparisons with Wilson's (1974), Benson's (1976), and Firth's (1984) zonations suggest a Lower Maastrichtian age for all strata in this study. / M.S.

O dinoflagelado unicelular marinho fotossintetizante Gonyaulax polyedra tem sido utilizado como modelo para o estudo de relógios biológicos. Neste organismo já foram descritos os ritmos de: migração vertical, divisão celular, atividade de superóxido dismutase e nitrato redutase, bioluminescência e capacidade fotossintética. Investigamos a variação circadiana dos pigmentos carotenóides e de RuBisCo II e PCP, as quais estão intimamente ligadas ao processo fotossintético. Experimentos de supressão de espécies reativas de oxigênio (EROs) por carotenóides foram preparados e mostraram que extratos de carotenóides de G. polyedra são capazes de suprimir o O2(1&#916;g) (oxigênio singlete) in vitro confirmando o importante papel destes no controle das EROs nestas algas. Os extratos metanólicos apresentaram vários pigmentos, tais como clorofila a, &#946;-caroteno e peridinina em diferentes concentrações. A peridinina representa 80 % do total de carotenóides enquanto que o &#946;-caroteno somente 4%. As análises dos cromatogramas de HPLC mostraram que a razão peridinina/clorofila a não varia ao longo de 24 h porém, por outro lado, o &#946;-caroteno apresenta uma variação significativa na sua quantidade, com níveis duas vezes maiores no meio do dia em comparação com os níveis no meio da noite. Esta variação é conservada mesmo quando as células são mantidas em condições de luz constante. A curva de dose-resposta para a síntese de &#946;-caroteno induzida pela luz mostra uma resposta linear com 45 minutos de exposição a luz branca. A indução é máxima quando utilizamos as células do meio período da noite (CT 18) que após esta exposição apresentam níveis de &#946;-caroteno semelhantes as células do meio do dia. Esta alteração de fase no CT 18 sugere que este pigmento pode ser um dos compostos-captadores de luz envolvidos no mecanismo de ajuste de fase por luz em G. polyedra. Culturas de G. polyedra do meio da noite foram expostas à diferentes irradiações (azul, vermelha e verde) e os seus pigmentos extraídos e analisados. Em outra série de experimentos, as células foram mantidas durante o período de claro (12: 12 h) sob diferentes irradiações (vermelha, verde e azul) por 36 horas e os seus pigmentos analisados. Os resultados sugerem que a síntese foto-induzida e a oscilação circadiana do &#946;-caroteno estão ligadas a um fotorreceptor de luz azul/ verde. Nas condições utilizadas não foram observadas variações significativas no conteúdo protéico da RuBisCo II e da PCP ao longo do dia. As análises de RNA total da RuBisCo II mostram que não há variação nos seus níveis quando as células são coletadas no meio do dia e no meio da noite. Quando expostas a condições adversas, G. polyedra apresenta a capacidade de encistar. Embora se conheça bem este mecanismo de defesa, existem poucas informações sobre o estado fisiológico destas células. Células encistadas induzidas por dias curtos apresentam uma alteração na composição de pigmentos com diminuição nas quantidades de &#946;-caroteno e de clorofila a e aumento da quantidade de peridinina, indicando um rearranjo do aparato fotossintético nesta situação, com a peridinina desempenhando um papel mais estrutural. Em consequência, embora o conteúdo protéico de RuBisCo permaneça inalterado, os níveis protéicos de PCP se encontram diminuídos nas células encistadas. / Gonyaulax polyedra, a marine dinoflagellate which has been used as a model to study the biological clock, displays numerous circadian processes, such as bioluminescence, cell aggregation, cell division, superoxide dismutase and nitrate reductase activities and photosynthesis. In this alga, the photosynthesis is maximal in the middle of the day and minimal in the middle of the night. We investigated the pigments content and the amounts of two proteins related to the photosynthesis: ribulose- 1,5- bisphosphate carboxylase/ oxygenase form II (RuBisCo II) and peridinin: chlorophyll a: protein (PCP) in a 24 h cycle. Using the thermal decomposition of 1,4-dimethylnaphtalene endoperoxide, it was shown that the carotenoids could act as effective quenchers of synglet oxygen in G. polyedra. G. polyedra pigments were extracted every three hours over 24 hours. The amounts of peridinin and chlorophyll a remain constant over the day while the levels of &#946;-carotene oscillate, being two times higher at the day than at the night phase. This variation persists when the cells were kept under constant dim light. The dose-response curve for light-induced &#946;-carotene synthesis showed a linear response up to 45 minutes of light exposure, after which night-phase cells contained the same levels of &#946;-carotene as day-phase cells. Cells exposed to light pulses at different times displays the highest &#946;-carotene induction in the middle of the night. This may suggest that &#946;-carotene may be one of the light-harvesting compounds involved in the light induced phase-shift in Gonyaulax polyedra. To identify which was the photoreceptor involved in &#946;-carotene synthesis, cell of the middle of the night-phase (CT 18) were exposed for 45 minutes to different irradiations (red, blue and green) and their pigments extracted and analysed. Also, cells were grown under red, blue and green light during the light phase (12 h light: 12 h dark ) for 36 hours and their pigments analysed. The results suggested that the circadian oscillation and the photoinduced response synthesis of &#946;-carotene, are related to a blue light receptor. The amounts of RuBisCo II and PCP do not change over the circadian cycle when the cultures were grown under constant dim light. The levels of these proteins also remain constant when cells were kept under ither white light or different light qualities (red, blue and green ) in light: dark (12: 12 h) regime. The G. polyedra RuBisCo form II transcrits levels are the same in middle-day and middle-night cells, suggesting a post-translational control for this enzyme in this organism. Adverse environmental conditions elicit the encystment of G. polyedra. Our results showed an alteration in pigment composition of cysts. An increase in peridinin levels and a decrease in &#946;-carotene and chlorophyll a content were observed. Although RuBisCo form II protein levels remained constant, there was a reduction in the amounts of PCP in cysts. This suggests an important role in thylakoids structure stabilizer for free peridinin.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Biology, 2017. / Thesis: Ph. D., Joint Program in Oceanography/Applied Ocean Science and Engineering (Massachusetts Institute of Technology, Department of Biology; and the Woods Hole Oceanographic Institution), 2017. / Cataloged from PDF version of thesis. / Includes bibliographical references. / Blooms of the dinoflagellate Alexandrium catenella cause paralytic shellfish poisoning syndrome and present an expanding public health threat. They are inoculated through the germination of benthic cysts, a process regulated by internal and environmental factors, most importantly temperature. Less understood is the effect of temperature conditioning on cyst dormancy cycling, which inhibits germination for long periods. This thesis characterizes the temperature-dependence of both dormancy and germination in natural A. catenella cyst populations from Nauset Marsh (Cape Cod, MA, USA), a small estuarine embayment, and relates these processes to the phenology of blooms there. Through laboratory germination assays, it is shown that dormant A. catenella cysts require a quantifiable amount of chilling to exit dormancy and attain quiescence (i.e. become germinable). A series of experiments compares germination rates of quiescent cysts across a range of temperatures through laboratory experiments and field incubations of raw sediment using plankton emergence traps (PETs). Emergence rates of A. catenella germlings measured by PETs increased linearly with temperature and were comparable to germination under constant laboratory conditions. Total emergence fluxes were much lower than expected, suggesting that germination occurs in a much shallower layer of sediments than typically assumed. The results are synthesized to develop a temperature-dependent model to examine the sensitivity of A. catenella bloom phenology to dormancy-breaking by winter chilling. Notably, the chilling-alleviated dormancy model accurately predicted the timing of quiescence (January) and the variable bloom phenology from multiple blooms in Nauset. Once cysts became quiescent and began to germinate, however, temperatures were typically too cold for growth to exceed losses so there was a several-week lag until bloom development. Years with warmer winters and springs had shorter lag periods and thus significantly earlier blooms. Ecologically, dormancy-breaking by a chilling threshold is advantageous because it prevents the mismatch between conditions that are favorable for germination but not for the formation of large blooms. Synchronized germination after winter chilling also promotes promotes efficient conversion from the cyst seedbed to the spring bloom inoculum. The dormancy mechanism characterized here may be present in other cyst-forming dinoflagellates, but there is likely plasticity that reflects the temperature regime of each habitat. / by Alexis Dal Fischer. / Ph. D.