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Current Research

Molecular Responses of Phytoplankton in Upwelling Regimes

Coastal upwelling regimes along the eastern boundaries of the Pacific and Atlantic Oceans are the most biologically productive areas of the ocean. These regions are characterized by equatorward wind patterns that cause cold, nutrient-rich water to upwell to the surface and stimulate enormous blooms of phytoplankton. Due to the dynamic nature of upwelling, these phytoplankton communities are subject to tremendous natural variations in abiotic stressors. Upwelled water is naturally high in carbon dioxide and more acidic which quickly changes with photosynthetic activity forming large gradients at the surface. Reduced availability of the essential micronutrient iron can also be limiting to phytoplankton growth in some areas depending on the level of interaction between upwelled water and iron-rich sediment. The end result is a complex biogeochemical mosaic which may be perturbed by climate change.

Phytoplankton in these regions also undergo a ‘conveyer belt cycle’ in which deep subsurface populations are upwelled with the nutrient rich water. This processes forces the community to cope with intense changes in light, but likely provides a substantial seed stock for surface blooms. These blooms are well characterized as being dominated by large chain-forming diatoms. Through a combination of shipboard incubations in the California Upwelling Zone and laboratory-based experiments, we seek to couple levels of gene expression with chemical and physical measurements to address the following research questions:

  1. How do different types of phytoplankton respond to being upwelled, and what is unique to diatoms that allows them to preferentially benefit?
  2. How will phytoplankton responses to upwelling change facing increased pH and iron stresses as a result of climate change?

Past Research

The Production and Fate of Domoic Acid in Marine Snow Aggregates

Pseudo-nitzschia is a ubiquitous diatom known to produce the neurtoxin, domoic acid (DA). The phytoplankton genus has been implicated in harmful algal blooms worldwide. A previous study suggests that DA not only affects organism feeding in the upper water column where the blooms occur but that DA is also rapidly transported to depth. No photodegredation of the toxin in absence of light and lower temperatures at depth can allow for transport to the seafloor where DA becomes available for consumption by benthic organisms. The objectives of this study are to understand DA production during Pseudo-nitzschia growth and DA fate during aggregate (marine snow) formation and decomposition.

Funded by an undergraduate research grant from the Division of Academic & Student Affairs (DASA) at North Carolina State University.