PhD Dissertation Defense: Carly Moreno

The PhD Dissertation Defense of Carly Moreno is presented by the University of North Carolina at Chapel Hill’s, Department of Marine Sciences. This event will be held on Thursday, October 29th at 1:00 pm. If appropriate the defense will have a physical location in room 3204 on the 3rd floor of Murray/Venable Hall on UNC campus in Chapel Hill, NC. The defense will be streamed online and will be available online via Zoom (Use Zoom Meeting ID: 955 0834 3530).

Title: Coupled molecular physiology and ecology of Southern Ocean diatoms in response to shifting iron and light availability

Abstract: Diatoms are an ecologically important group of Southern Ocean phytoplankton forming the base of polar marine food webs and significantly contributing 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 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 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 former, Pseudo-nitzschia subcurvata. The focus of the third chapter is 3) to explore diatom metabolism along the Western Antarctic Peninsula to gain insight into the environmental factors influencing diatom growth and molecular physiology. My findings suggest the physiological response of polar diatoms to low iron is diverse and that certain molecular mechanisms may underpin the ecological success of polar diatoms in low iron and low light, 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 centric diatoms in cold and fresher waters in the southern coastal regions, and iron limited diatom communities in shelf and slope waters. This research provides new insights into the unique molecular physiological response of Southern Ocean diatoms to variations in iron and light availability, and the environmental factors influencing diatom metabolism and their predicted response to future ocean conditions.