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Title: Calcification, photosynthesis and nutrient uptake in coccolithophores
Author: Berry, L. S.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2002
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Emiliania huxleyi is the most abundant coccolithophore in the World's oceans today. These organisms have the ability to calcify and photosynthesise, and may represent an important oceanic sink for dissolved inorganic carbon. As a result, they have the potential to influence the oceanic carbon cycle. It has been proposed that calcification may improve carbon acquisition under CO2 (aqueous) limiting conditions, but may involve high Ca2+ transport costs. In this thesis, results presented show that calcification increases in E. huxleyi (strain L) in response to low phosphorus and/or nitrate, high external pH, and high dissolved inorganic carbon. This information was used to produce calcifying and non-calcifying cells of the same strain allowing comparisons, which avoided the genetic and psychological differences between strains. Calcification correlated with an increase in photosynthetic efficiency (Φ>PSII), relative electron transport rate (REFPSII) and the proportion of photons captured and converted to chemical energy (qP). The mechanisms underlying these correlations are unknown, but may involve the H+ produced during calcification being used to supply an internal CO2 source. High calcifying cells were found to have a lower internal pH than low-calcifying cells, and were able to take up HCO3-. This may influence CO2 availability within the cell, or nutrient requirements and assimilation. Results from X-ray microanalysis and Electron Energy Loss Spectroscopy indicate that the endomembrane system may provide an efficient pathway for Ca2+ transport to the coccolith vesicle. Potentially, this avoids transport of Ca2+ against a concentration gradient, and resolves what was thought to be one of the major cost-aspects of calcification. The most likely advantage of calcification is that it may allow low levels of photosynthesis to occur efficiently, thus increasing survival time during co-limitation by CO2, phosphorous and/or nitrate. Calcification may enable the cell to reduce the nutrient requirements for photosynthesis, or allow internal nutrient recycling.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available