Research Seminar: Rob Lampe

A research seminar presented by UNC-CH Department of Marine Sciences graduate student, Rob Lampe.

Seminar Title: Investigating distinct strategies by bloom-forming diatoms to frequently-encountered shifts in their environment.

Abstract: Diatoms are a highly diverse and prominent group of eukaryotic phytoplankton that perform approximately one-fifth of the carbon-fixation on Earth. As modern molecular techniques advance, they are quickly providing insights into the evolution and metabolic adaptations contributing to the ecological success of diatoms at a high taxonomic resolution. Here I present two studies that couple gene expression with physiological measurements from natural phytoplankton assemblages to examine these adaptations. The first one examines the response to upward vertical transport by a subsurface community acting as a seed population for blooms during coastal upwelling events. We show that certain bloom-forming diatoms exhibit a distinct transcriptional response that coordinates a rapid physiological shift-up response. These diatoms appear to frontload genes involved in nitrogen assimilation and utilization in order to outcompete other groups for available nitrogen sources when upwelling occurs. The second study investigates the use of the iron storage protein ferritin along natural iron gradients in the North Pacific Ocean. Mesocosm experiments with iron addition or removal were conducted within coastal waters and along a nearshore to offshore transect. Bulk phytoplankton biomass was affected by low iron concentrations, but pronounced community shifts were not observed. Pseudo-nitzschia spp. display high ferritin expression that varies temporally and with iron status in contrast to other genera; however, iron-to-carbon ratios were similar in the predominantly non-ferritin containing genus Chaetoceros, highlighting possible differences in iron storage strategies. Together, these studies provide insight into the evolution and ecology of certain diatom genera and form the basis for laboratory experiments further investigating phytoplankton responses to these phenomenon.