COUPLED MOLECULAR PHYSIOLOGY AND ECOLOGY OF SOUTHERN OCEAN DIATOMS IN RESPONSE TO SHIFTING IRON AND LIGHT AVAILABILITY

• Main Author: Moreno, Carly Maria
• Other Authors: College of Arts and Sciences, Department of Marine Sciences, Marchetti, Adrian, Cassar, Nicolas, Davies, Sarah, MacGregor, Barbara, Sunda, William
• Format: Doctoral or Postdoctoral Thesis
• Language: English
• Published: University of North Carolina at Chapel Hill Graduate School 2020
• Subjects: Southern Ocean; Iron; Biological oceanography; Physiology; Ecology; Diatom; Transcriptomics; Antarctic; Antarctic Peninsula; Antarc*
• Online Access: https://doi.org/10.17615/hver-q873; https://cdr.lib.unc.edu/downloads/k3569c91d?file=thumbnail; https://cdr.lib.unc.edu/downloads/k3569c91d

Diatoms are an ecologically important group of Southern Ocean phytoplankton forming the base of polar marine food webs and contribute significantly to carbon and silica export. Changes in their physiological status can alter their growth, productivity and elemental stoichiometry, consequently affecting food web dynamics and the efficiency of the biological carbon pump. Iron and light availability are predicted to be two abiotic factors that control diatom physiology and productivity. Therefore, a better understanding of the ecological importance of iron and light limitation on Southern Ocean diatom physiology is needed to decipher the role of diatoms in polar ocean ecology and biogeochemistry. By coupling culturing methods and ‘omic techniques, my dissertation sheds light on the physiology and metabolism of ecologically relevant diatom isolates and natural diatom assemblages from the Western Antarctic Peninsula. The focus of the first two chapters of my dissertation are 1) to investigate the molecular underpinnings of the response of a Southern Ocean diatom, Fragilariopsis kerguelensis, to changing iron and light levels, and 2) to understand how the physiology and elemental composition of four Southern Ocean diatoms change in low iron conditions, focusing on a common bloom forming diatom species, Pseudo-nitzschia subcurvata. The focus of the third chapter is 3) to explore diatom cellular metabolism along the Western Antarctic Peninsula to gain insight into the environmental factors influencing diatom growth and molecular physiology. My findings suggest the physiological responses of polar diatoms to low iron availability are diverse and that certain molecular mechanisms may underpin the ecological success of polar diatoms under low iron and low light conditions, highlighting the important role of diversified photosynthetic isoforms, iron acquisition and metabolic shifts in amino acid and carbon metabolism. Furthermore, diatom molecular physiology varied across the Western Antarctic Peninsula, indicating blooming ...