Defining the Ecological and Physiological Traits of Phytoplankton Across Marine Ecosystems

Harriet Alexander, Ph.D., 2016
Sonya Dyhrman and Elizabeth Kujawinski, Co-Advisors

In this thesis, I developed and applied novel analytical tools and bioinformatic pipelines to characterize the physiological response of phytoplankton to their environment at several levels of taxonomic grouping. An in silico Bayesian approach was designed to identify stable reference genes from high-throughput sequence data for use in metatranscriptome studies. Using a metatranscriptomic approach, the role of resource partitioning in the coexistence of two closely related diatom species in an estuarine system was examined, demonstrating that co-occurring diatoms in dynamic environments have apparent differences in their capacity to use nitrogen and phosphorus. The second field study used simulated blooms to characterize the traits that govern the bloom dynamics of the diatom, haptophyte, and dinoflagellate functional groups in oligotrophic systems. Results indicated that the mechanistic basis for the success of one functional group over another might lie in the efficiency of transcriptome modulation following a nutrient pulse. The final study examined the balance of phenotypic plasticity and strain diversity in the success of the coccolithophore Emiliania huxleyi. This work demonstrates the breadth of information that can be garnered through the integration of molecular approaches with traditional biological oceanographic surveys, with each illuminating fundamental questions around phytoplankton ecology and bloom formation.