Thesis Defense: Erika Neave

The Master’s Thesis Defense of UNC Marine Sciences graduate student, Erika Neave. Presented by the Department of Marine Sciences at UNC Chapel Hill. This event will be held on Wednesday, June 19th at 10:00 am. The location of this event will be in conference room 3204 on the 3rd floor of Murray/Venable Hall on UNC-CH campus in Chapel Hill, NC and streamed live to conference room 222 at the Institute of Marine Sciences (IMS) in Morehead City, NC and online via Zoom (Meeting ID: 769-534-584).

Seminar Title: El Niño in the Galápagos Islands limits new production and causes phytoplankton succession

Abstract: The Galápagos Islands lie at the convergence of many major currents which are subject to basin scale changes in ocean circulation. The equatorial undercurrent upwells onto the western side of the Galápagos platform, but this upwelling weakens during El Niño. Annual cruises from 2014-16 show that El Niño (2015) resulted in decreased phytoplankton biomass and shifts in species composition. New production decreased in 2015 due to decreased phytoplankton biomass, while nitrate assimilation rates remained constant. Aside from affecting overall production, the El Niño to La Niña (2016) transition also caused successional shifts, which could largely be attributed to changes in the potential density of the deep layer. In 2015 parasitic flagellates, the Syndiniales, were abundant suggesting increased remineralization. Additionally, Pseudo-nitzschia, a toxic diatom, bloomed in the western region likely using specialized nutrient storage mechanisms to outcompete other diatoms. The dinoflagellate Gyrodinium had a strong presence in 2016, possibly due to its ability to form resting cysts which can seed upwelling. Correlations with deep layer water properties highlight that water mass sources are important and select for phytoplankton with certain ecophysiological strategies, dictating Galápagos phytoplankton communities and productivity.