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Metabolic Physiology of Healthy and Bleached Corals

  • Author(s): Linsmayer, Lauren
  • Advisor(s): Tresguerres, Martin
  • et al.
Abstract

Coral reef productivity is based upon the relationship between the coral host and its symbiotic dinoflagellate. While it is well known that the photosynthetic symbionts are metabolically significant to the host, very little is known about host metabolism. Metabolism is central to sustaining energy-consuming physiological processes such as calcification, growth, and reproduction. Availability of oxygen (O2) to cells/tissues determines the balance of aerobic (oxygen-requiring) and anaerobic (oxygen-independent) metabolic pathways, which have different energy yields. The main objectives of this work were to characterize the aerobic and anaerobic metabolism of the coral host during diel (daily) cycles and during coral bleaching (as an oxygen-stressed state to the host). In Chapter 2, I measured the diel O2 concentrations of coral tissues and found that corals are hyperoxic during the day and near-hypoxic throughout the night. Using enzyme assays, I found that the aerobic and anaerobic metabolic capacities of the host are mostly unchanged between day and night, while the concentrations of anaerobic end-products fluctuate significantly. Using analytical chemistry techniques, I provide the first definitive evidence that corals produce the anaerobic end-products strombine and alanopine. In Chapters 3 and 4, I found that coral bleaching in several different species creates a common situation of constant hypoxia in host tissues regardless of how bleaching was induced (thermal or menthol treatment). However, bleaching alters aerobic and anaerobic metabolism of the host in a species-specific manner. I hypothesize that the ability of some coral species to up-regulate anaerobic metabolism during bleaching could confer higher survival rates than merely undergoing reductions in aerobic metabolism. Finally, in Chapter 5, I examine broad-scale changes in daily coral metabolism using untargeted proteomics and metabolomics. My findings suggest that changes in daily coral metabolism are regulated on the metabolite-level as opposed to changes in protein amount. Together, this research helps us better understand basic coral energy metabolism under healthy and stressed states, which is useful both in building a mechanistic understanding of coral energy budgets, as well as in understanding how corals might fare in the face of increasing frequency of bleaching events.

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