From communities to single cells: Exploring diversity and ecophysiology of marine microbes with a focus on coccolithophores
Microeukaryotes form the basis of the marine food web and play a pivotal role in marine biogeochemical processes. However, for many clades, ecological niches and inherent patterns of diversity and abundance remain poorly understood. One of the most charismatic microbial taxa are the coccolithophores...
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| Format: | Thesis |
| Language: | English |
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University of Southampton
2024
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| Online Access: | https://eprints.soton.ac.uk/490452/ https://eprints.soton.ac.uk/490452/1/Sturm2024_PhDThesis_Final_Accessible.pdf |
| Summary: | Microeukaryotes form the basis of the marine food web and play a pivotal role in marine biogeochemical processes. However, for many clades, ecological niches and inherent patterns of diversity and abundance remain poorly understood. One of the most charismatic microbial taxa are the coccolithophores, unicellular phytoplankton characterized by the production of calcite coccoliths and important contributors to microbial standing stocks. This study set out to investigate the biogeography and ecophysiology of marine microeukaryotes, focusing on coccolithophores and their elusive life cycle. Environmental sampling, culture experiments, omics techniques, and bioinformatics were integrated to elucidate the diversity and functional attributes of microbial communities. An investigation of the distribution and physiology of marine microeukaryotes in the Pacific and Indian sector of the Great Calcite Belt in the Southern Ocean, an area of particularly high coccolithophore abundance, revealed that microbial communities are strongly influenced by environmental gradients associated with frontal and mesoscale systems. However, distinct clades exhibited significant disparities in their degree of constraint, underscoring the necessity for a more profound understanding of the underlying physiology across different taxa. The lack of coccolithophore diversity revealed by broad eukaryotic 18S metabarcoding raised concerns about the underrepresentation of this group in global genomic explorations. Re-examining the area with a combination of improved genetic markers and morphological taxonomy, revealed a much higher degree of coccolithophore diversity. This underscores the limitations of current environmental DNA methodologies, highlighting the need for supplementary techniques and advancements in gene markers and reference libraries. The morphological examination of coccolithophores further unveiled novel insights into their elusive haplo-diplontic life cycle. The finding of a new combination coccosphere, a transitionary life phase, ... |
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