Coccolithophores are uni-cellular phytoplankton and they form an exceedingly diverse group in the phylum Haptophyta. They produce highly complex structures known as coccoliths by a biomineralisation process known as calcification. The first part of the work undertaken was to investigate the process of calcification in the coccolithophore Coccolithus pelagicus using a combination of Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and light microscopy techniques. This allowed better understanding of the formation, transit of the coccolith through the cell until its final placing in the coccosphere. The second part of the work looked at the coccolithophore Emiliania huxleyi which is divided into several morphotypes with the two most widely recognised being A and B, it can be further subdivided into further groups according to genotype by Coccolithophore Morphology Motif (CMM). The CMMs lie in the 3/ untranslated region of the coccolith-polysaccharide associated protein-GPA, which is associated with coccolith structure control and they are labelled I, II, III and IV. The work undertaken used a Scanning Electron Microscope (SEM) to investigate the morphologies of homozygous CMM I and CMMIV cell’s coccoliths. This information was used to establish a significant difference between the CMMI cells and CMMIV cells but only at certain locations. The cause for this is possibly as a result of several factors (temperature, salinity, pCO2, Ca availability and light levels) and requires further investigation.

Thesis (Ph. D.)--Rutgers University, 2009. / "Graduate Program in Oceanography." Includes bibliographical references (p. 160-173).

Thesis (Ph.D.)--Murdoch University, 2005. / Thesis submitted to the Division of Science and Engineering. Bibliography: leaves 225-252.

Thesis (Ph. D.)--Rutgers University, 2007. / "Graduate Program in Geological Sciences." Includes bibliographical references.

The carbon isotope fractionation in the coccolithophore Emiliania huxleyi constitutes the basis for the paleo-pCO₂ barometry. Under the premise that the carbon isotope fractionation is dependent on the availability of dissolved CO₂, measurements of the carbon isotope ratio of sedimentary alkenones can potentially produce a proxy record of ancient atmospheric CO₂ levels. However, recent studies, including this thesis have suggested that other factors than CO₂ may influence the carbon isotope fractionation in Emiliania huxleyi and hence the validity of the proxy. In this thesis work the effects of irradiance on carbon isotope fractionation were studied in batch cultures of non-calcifying Emiliania huxleyi. It was found that the biomass becomes more ¹³C depleted as the light intensity decreases. This is in agreement with utilization of CO₂ via passive diffusion where fractionation is a function of the rate of diffusion of CO₂ into the cell relative to the rate of carbon utilization. However, results reported in the literature for a calcifying strain show the opposite trend with a ¹³C enrichment of the biomass. These results suggest that the carbon utilization of the calcifying strain of Emiliania huxleyi differ from that of the non-calcifying strain. This is supported by observations in the literature, which indicates a connection between the process of calcification and the supply of carbon for photosynthesis. A mechanism for the effect of calcification on carbon isotope fractionation in light limited cells is presented here. The mechanism is based on the fact that the calcification and photosynthesis respond differently to light limitation. This difference leads to an imbalance in the rate of calcification to the rate of photosynthesis ratio (C/P), which ultimately affects the availability of CO₂ inside the cell. Apart from light, the availability of nutrients has also been shown to affect calcification. Nutrient starved cells will enhance calcification to the degree that the C/P ratio changes, thus affecting the internal concentration of CO₂. To study the effect of these environmental parameters on carbon isotope fractionation, C₃₇:₂-alkenones were extracted from samples of marine particulate organic matter. The particulate organic matter was collected together with information of the environmental conditions during three cruises in the North-East Pacific and during a Pacific transect from Victoria B.C. to Guam. Results from the NE Pacific show a lower carbon isotope fractionation in samples collected at the bottom of the euphotic zone compared to samples collected in the mixed layer. This may be an expression of the effect of light limitation. In this work carbon isotope fractionation shows no correlation with dissolved CO₂. Instead, a correlation with the ratio of phosphate concentration to concentration of dissolved CO₂ ([PO3/4⁻/[CO₂]aq.) was observed. Nitrate availability appears to play an important role in maintaining this relationship as in the absence of nitrate the carbon isotope fractionation is lower than can be predicted from the relationship relating carbon isotope fractionation to [PO3/4⁻/[CO₂]aq. The C₃₇:₂-alkenone based results from the Pacific transect shows a strong correlation between carbon isotope fractionation and phosphate. This correlation is independent of the concentration of dissolved CO₂, implying a nutrient dominated control of isotope fractionation. However, this control may not be typical as the transect passed through waters with very low nutrient levels. Therefore, the results seen here may be a consequence of extreme nutrient conditions. In conclusion, the results presented in this thesis challenge the classical belief that the carbon isotope fractionation in Emiliania huxleyi is a direct function of the availability of dissolved CO₂ by suggesting that the observed isotope fractionation is a result of a complex interaction between environmental factors such as irradiance and the availability of nutrients. In particular, a correlation between phosphate concentration and carbon isotope fractionation has been found. / Graduate

Neste estudo a assembleia de cocolitoforídeos de 44 amostras de sedimentos marinhos de superfície da Margem Continental Brasileira foram analisados e comparados com os parâmetros oceanográficos locais. Com o intuito de obter um melhor entendimento da área de estudo, foram incluídas as análises de 36 amostras do estudo de Boeckel et al. (2006). A partir destes dados, os padrões de abundância das principais espécies e suas afinidades ecológicas foram verificadas. E. huxleyi, F. profunda e Gephyrocapsa spp. são as espécies mais abundantes. E. huxleyi dominou as assembleias características de águas mais frias e ricas em nutrientes, Gephyrocapsa spp. as regiões com menores profundidades da camada de mistura, ou seja, estas espécies demonstram uma preferência por uma nutriclina mais rasa. Por outro lado, F. profunda, foi mais abundante nas águas quentes e oligotróficas das regiões subtropicais, revelando sua preferência por uma nutriclina mais profunda. Além disso, os resultados da Análise de Correspondência Canônica revelaram uma afinidade de C. leptoporus, E. huxleyi, C. pelagicus e G ericsonii com águas mais enriquecidas em nutrientes. Em contraste, Gephyrocapsa spp. e Helicosphaera spp. foram associadas a regiões mesotróficas. Uma vez que G. flabellatus e D. tubifera parecem estar associadas a águas com camadas de mistura mais profundas, elas podem ser utilizadas, juntamente com F. profunda, como indicadoras de uma termo/nutriclina mais profunda. A partir de análise de clusters e análise por componentes principais, 4 províncias foram identificadas e parecem refletir as características oceanográficas da zona fótica. / In this study the coccolitophore assemblages of 44 samples of marine surface sediments from the Brazilian Continental Margin were analyzed and compared with the local oceanographic parameters. In order to obtain a better understanding of the study area, were included the analysis of 36 samples from the study by Boeckel et al. (2006). From these data, the abundance patterns of the main species and their ecological affinities were verified. E. huxleyi, F. profunda and Gephyrocapsa spp. are the most abundant species. E. huxleyi dominated the assemblages characteristic of colder and nutrient-rich waters, Gephyrocapsa spp. the regions with lower mixed layer depths, in other words, these species demonstrate a preference for a shallower nutricline. On the other hand, F. profunda, was more abundant in the warm and oligotrophic waters of the subtropical regions, revealing its preference for a deeper nutricline. In addition, the results of the Canonical Correspondence Analysis revealed an affinity of C. leptoporus, E. huxleyi, C. pelagicus and G ericsonii for waters enriched in nutrients. In contrast, Gephyrocapsa spp. and Helicosphaera spp. were associated with mesotrophic regions. Since G. flabellatus and D. tubifera appear to be associated with waters that have deeper mixed layers, they may be used, along with F. profunda, as indicators of a deeper nutricline. From the cluster analysis and by the principal components analysis, 4 provinces were identified and seems to reflect the oceanographic characteristics of the photic zone.

Neste estudo a assembleia de cocolitoforídeos de 44 amostras de sedimentos marinhos de superfície da Margem Continental Brasileira foram analisados e comparados com os parâmetros oceanográficos locais. Com o intuito de obter um melhor entendimento da área de estudo, foram incluídas as análises de 36 amostras do estudo de Boeckel et al. (2006). A partir destes dados, os padrões de abundância das principais espécies e suas afinidades ecológicas foram verificadas. E. huxleyi, F. profunda e Gephyrocapsa spp. são as espécies mais abundantes. E. huxleyi dominou as assembleias características de águas mais frias e ricas em nutrientes, Gephyrocapsa spp. as regiões com menores profundidades da camada de mistura, ou seja, estas espécies demonstram uma preferência por uma nutriclina mais rasa. Por outro lado, F. profunda, foi mais abundante nas águas quentes e oligotróficas das regiões subtropicais, revelando sua preferência por uma nutriclina mais profunda. Além disso, os resultados da Análise de Correspondência Canônica revelaram uma afinidade de C. leptoporus, E. huxleyi, C. pelagicus e G ericsonii com águas mais enriquecidas em nutrientes. Em contraste, Gephyrocapsa spp. e Helicosphaera spp. foram associadas a regiões mesotróficas. Uma vez que G. flabellatus e D. tubifera parecem estar associadas a águas com camadas de mistura mais profundas, elas podem ser utilizadas, juntamente com F. profunda, como indicadoras de uma termo/nutriclina mais profunda. A partir de análise de clusters e análise por componentes principais, 4 províncias foram identificadas e parecem refletir as características oceanográficas da zona fótica. / In this study the coccolitophore assemblages of 44 samples of marine surface sediments from the Brazilian Continental Margin were analyzed and compared with the local oceanographic parameters. In order to obtain a better understanding of the study area, were included the analysis of 36 samples from the study by Boeckel et al. (2006). From these data, the abundance patterns of the main species and their ecological affinities were verified. E. huxleyi, F. profunda and Gephyrocapsa spp. are the most abundant species. E. huxleyi dominated the assemblages characteristic of colder and nutrient-rich waters, Gephyrocapsa spp. the regions with lower mixed layer depths, in other words, these species demonstrate a preference for a shallower nutricline. On the other hand, F. profunda, was more abundant in the warm and oligotrophic waters of the subtropical regions, revealing its preference for a deeper nutricline. In addition, the results of the Canonical Correspondence Analysis revealed an affinity of C. leptoporus, E. huxleyi, C. pelagicus and G ericsonii for waters enriched in nutrients. In contrast, Gephyrocapsa spp. and Helicosphaera spp. were associated with mesotrophic regions. Since G. flabellatus and D. tubifera appear to be associated with waters that have deeper mixed layers, they may be used, along with F. profunda, as indicators of a deeper nutricline. From the cluster analysis and by the principal components analysis, 4 provinces were identified and seems to reflect the oceanographic characteristics of the photic zone.

Les coccolithes, dans les cellules ou détachés, des coccolithophores sont de petites plaquettes de calcite diffusant fortement la lumière. Les efflorescences sont donc très visibles de l’espace et sont couramment quantifiées par l’algorithme Calcite de la NASA appliqué aux données des capteurs de la Couleur de l’Eau.Les coccolithes impactent aussi le produit des matières en suspension non-algales de l’ifremer (MES) largement utilisé sur le plateau continental ouest-européen. Bien que développés indépendamment, ces algorithmes sont basés sur des concepts très proches mais l’algorithme Ifremer est plus souple dans sa modélisation et permet d’établir un lien avec les particules autres que les coccolithes telles les remises en suspension ou les agrégats de particules. L'identification des blooms de coccolithophores sur 18 ans, duGolfe de Gascogne jusqu'au sud de l'Irlande, a été établie par une méthode spectrale, permettant de discriminer la fraction de MES correspondant aux coccolithes. Les blooms suivent le talus au printemps avec une progression vers le nord bien reliée à la variabilité saisonnière de la lumière. La variabilité interannuelle observée indique une légère décroissance globale des blooms, avec une année 2014 aux abondances extrêmement faibles sur toute la région.Les données des campagnes PELGAS en mai dans le Golfe de Gascogne ont mis en évidence la forte corrélation entre le produit MES et la turbidité in situ sur les blooms de coccolithophores. Ce paramètre peut être considéré comme un bon proxy pour le suivi des blooms et pour la description de leur structure verticale.Les données hydrologiques in situ montrent une occurrence plus forte des blooms dans un environnement moins stratifié, des températures plus froides et une salinité plus élevée.La sensibilité de la méthode satellite face à la présence réelle de blooms de coccolithophores a pu être évaluée grâce aux observations in situ de campagnes menées dans le Golfe de Gascogne et en Patagonie.Cette sensibilité reste variable car dépendante de nombreux facteurs intrinsèques aux blooms, liés à la proportion coccolithes/coccosphères et à leur composition taxonomique, qui s’est avérée très riche en mai2016 dans le Golfe de Gascogne. / Coccoliths, in cells or detached, from coccolithophores are calcite plates with highly backscattering signal.Coccolithophore blooms are visible from space and are currently quantified by Calcite algorithm fromNASA applied to Ocean Color data. Coccoliths impact also the Suspended Particulate Matters (SPM) product from Ifremer, well established in the Northwest european continental shelf. Although these algorithms are independent, they are based on the same basic concepts, but Ifremer algorithm is more adaptable and allows to link up with other particles than coccoliths, as the resuspended matters or aggregates.Coccolithophore blooms identification over 18 years, from bay of Biscay to South Irelands has been established by a spectral method, allowing to discriminate coccoliths from SPM. Blooms follow the continental slope northward in connection with the seasonal variability of irradiance. The interannual variability observed indicates a slight decrease of blooms, with a very poor productive year in 2014.Data from PELGAS cruises in May in the Bay of Biscay highlight the strong correlation between SPM product and the in situ turbidity in coccolithophore blooms.This parameter can be considered a a good proxy for the blooms monitoring and for the description of their vertical structure. Hydrological in situ data show a stronger occurrence in less stratified environment, with lower temperatures and higher salinity.The sensitivity of the satellite to the presence of coccoliths has benn evaluated based on in situ observations from cruises in the Bay of Biscay and in Patagonia. This sensitivity is variable due to a lot of inherent factors, to the coccoliths/coccospheres proportion and to the taxonomic composition which has been rich in May 2016 in the Bay of Biscay.

Coccolithophores are single-celled marine phytoplankton, which produce intricate calcium carbonate platelets or ‘coccoliths’. Emiliania huxleyi is the most abundant and widespread coccolithophore, and is one of the most productive calcifying species on earth, playing a key role in global carbon, carbonate and sulphur cycles. Despite much research into coccolithophore biology, the underlying function of their coccoliths is still unknown. The main aim of the research reported in this thesis was to examine the impact of calcification on metabolism in coccolithophores. Calcification is a significant global process, so it is important to discover what effect it has on the metabolism of cells. The major metabolites each have different costs and benefits to the cell, which will vary depending on the habitat and environmental conditions the cell is in. By comparing the metabolite profiles of different strains, including calcifying, non-calcifying, haploid and diploid cells, differences in metabolite composition and potential patterns related to cell type were investigated. Low molecular weight (LMW) metabolites were characterised using a combination of metabolomic techniques. In agreement with previous research, dimethylsulphoniopropionate (DMSP) was the most abundant compound, followed by mannitol and glycine betaine (GBT). Less abundant sugars, polyols and amino acids were also identified. Environmental factors were manipulated to investigate how the principal metabolites were affected by salinity, different light intensities and nutrient (phosphate and nitrate) limitation. The data revealed a striking difference between haploid and diploid cells of the same strain, with the haploid containing lower concentrations of most of the major metabolites. Thus it is proposed that haploid cells have a different osmoregulatory strategy from the diploid cells. A negative correlation was found between DMSP and mannitol, suggesting that mannitol has a dual function, not only as a major storage compound but also as a principal compatible solute. Untargeted metabolite profiling is becoming a popular tool to investigate phenotypes and varying environmental conditions. LC-ESI-QTOF-MS/MS analyses of a wide range of metabolites showed that it is an effective method to identify differences and similarities between E. huxleyi strains grown in different conditions. Strain and growth phase appear to be the more important factors in differentiating metabolite profiles. Surprisingly there were no obvious metabolite profiling differences between calcifying and non-calcifying cells. Untargeted analysis can, however, be used to identify the compounds that did display differences, and which may be important biomarkers, so warrant further investigation. A range of metabolite profiling techniques highlighted important differences between strains, which will hopefully lead onto further research into the metabolome of E. huxleyi, and the unravelling of important metabolic pathways. There has been little research into the LMW metabolites of E. huxleyi, and especially comparisons between strains. Thus the use of metabolomics is a novel way to investigate the difference between cell types and the possible functions of calcification.

Coccolithophores are biogeochemically important marine algae that interact with the carbon cycle through photosynthesis (CO2 sink), calcification (CO2 source) and burial of carbon into oceanic sediments. The group is considered susceptible to the ongoing climate perturbations, in particular to ocean acidification, temperature increase and nutrient limitation. The aim of this thesis was to investigate the adaptation of coccolithophores to environmental change, with the focus on temperature stress and nutrient limitation. The research was conducted in frame of three approaches: experiments testing the physiological response of coccolithophore species Helicosphaera carteri and Coccolithus pelagicus to phosphorus limitation, field studies on coccolithophore life-cycles with a method comparison and an investigation of the phenotypic evolution of the coccolithophore genus Helicosphaera over the past 15 Ma. Experimental results show that the physiology and morphology of large coccolithophores are sensitive to phosphorus limitation, and that the adaptation to low-nutrient conditions can lead to a decrease in calcification rates. Field studies have contributed to our understanding of coccolithophore life cycles, revealing complex ecological patterns within the Mediterranean community which are seemingly regulated by seasonal, temperature-driven environment changes. In addition, the high-throughput sequencing (HTS) molecular method was shown to provide overall good representation of coccolithophore community composition. Finally, the study on Helicosphaera evolution showed that adaptation to decreasing CO2 in higher latitudes involved cell and coccolith size decrease, whereas the adaptation in tropical ecosystems also included a physiological decrease in calcification rates in response to nutrient limitation. This thesis advanced our understanding of coccolithophore adaptive strategies and will improve our predictions on the fate of the group under ongoing climate change.