Carbon fixation in eukaryotic marine algae: Evolution of photosynthetic machinery and isotopic footprints

Thesis

Photosynthesis in the world's oceans by marine algae is responsible for approximately 50% of CO2 fixed into organic carbon. Aquatic primary producers are intricately linked to the climate system due to their reliance on CO2 as a substrate for photosynthesis and role in the removal and export of carbon from the surface ocean to marine sediments. The evolutionary history of marine algae was shaped by changes in the climate system. As a result, fossilized marine algae and modern representatives of ancient groups have the potential to unlock information about the Earth’s climatic past. To use this information and fully understand the role of marine algae in the carbon cycle, however, it is essential to develop an in-depth understanding of CO2 fixation in these organisms. In this thesis I look at carbon fixation in biomineralizing marine algae from a geological and a biological perspective. First I apply a carbon isotope proxy for CO2 to organic material preserved in marine diatom frustules from an extremely transformative period in geological history, the Eocene-Oligocene boundary. Subsequently, this thesis aims to address gaps in our understanding of carbon fixation in eukaryotic marine algae. I present a novel dataset of kinetics of the carbon fixing enzyme, Rubisco, in eukaryotic algae, investigate the role of a pyrenoid-based carbon concentrating mechanism, and identify plastic changes in carbon fixing machinery in response to changing CO2. The findings from this thesis refine our understanding of primary production in the oceans and how we apply algae-based CO2 proxies to understand ancient climates.

Authors: Heureux, AMC

• Publication date: 2016
• DOI: 10.5287/ora-4ro9azb54
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: carbon fixation; climate; marine algae; photosynthesis
• Subjects: Earth Sciences; Plant Sciences