PhD Proposal Defense: Weida Gong

The PhD Proposal Defense of Weida Gong is presented by the Department of Marine Sciences. The main location of this event will be in conference room 3204 on the 3rd floor of Murray Hall on UNC campus in Chapel Hill, NC. The defense will be streamed live to room 222 at IMS in Morehead City, NC. This event will be held on Wednesday, September 19th at 9:00 AM.

Title:  Development of molecular approaches to characterize the taxonomic composition and physiological status of natural eukaryotic phytoplankton communities

Abstract: Contributing around half of global primary production, phytoplankton are a central component to ocean biogeochemical cycles. Changes in physiological status can alter phytoplankton growth, productivity and elemental stoichiometry and consequently affect food web dynamics and the extent of carbon export. The growth of harmful algal bloom species can have substantial ecological and economical impacts. Recent studies have also shown specific phytoplankton can contribute disproportionally to carbon export. Therefore, a complete understanding of the coupling between phytoplankton physiology and taxonomic composition with their environmental surroundings is necessary to decipher their roles in shaping ocean ecology and biogeochemistry. By measuring the abundance of genes and transcripts within phytoplankton, novel molecular approaches are providing a new means to explore their functional and taxonomic profiles within naturally mixed assemblages. The focus of my dissertation is to apply metagenomics, metatranscriptomics and amplicon sequencing techniques to shed light on eukaryotic phytoplankton metabolic activities and compositional profiles and assess their influence on community dynamics and carbon export processes. I have done so in two contrasting environments – in the highly dynamic and eutrophied Neuse River Estuary and the iron-limited Northeast Pacific Ocean. In addition, I compare results from amplicon sequencing to conventional taxonomic identification measures to evaluate the strengths and limitations and apply a read-depth approach for 18S rDNA copy number correction to provide a more quantitative characterization of phytoplankton taxonomic composition. This research improves current knowledge of phytoplankton’s responses to variations in environmental surroundings and will aid in developing predictive understanding of phytoplankton ‘s influence on ocean ecology and biogeochemical cycles.