Project: MCA: Developing transcriptomics as a tool to investigate toxic diatom responses to ocean heatwave and upwelling events

NSF Award Abstract:
The diatom Pseudo-nitzschia forms large, toxic harmful algal blooms along the U.S. West Coast, killing wildlife and harming valuable ocean fisheries. Understanding the causes of these blooms and predicting their occurrence, both now and under future changing climate conditions, is critical to coastal environmental and economic health. Puzzlingly, these blooms seem to happen during periods when coastal seawater upwelling results in cold, nutrient-rich, low pH sea surface conditions, and also during times when heat wave events cause warm, nutrient-poor, high pH conditions. These two extremes are forecast to get even more intense with climate change. This project is experimentally testing how Pseudo-nitzschia responds to upwelling and heat wave events using measurements of cell growth, toxin production, and gene expression. Broader impacts of this project include training the principal investigator in new gene expression methods, graduate and undergraduate research training, high school research mentoring experiences, and outreach and communications activities aimed at the commercial fishing industry. Societal benefits include obtaining a better understanding of the causes of damaging toxic algal blooms, and how they may change in the future coastal ocean.

The toxic diatom Pseudo-nitzschia causes annual harmful blooms along the US West Coast, a region where wind-driven upwelling brings rich nutrient supplies into the euphotic zone. However, this region is also experiencing unprecedented episodic ocean heatwave events linked to global warming. Thus, future climate trends in this region suggest an exaggeration of current physio-chemical extremes between colder, more nutrient-rich, low pH upwelling, and warmer, more nutrient-depleted, higher pH heatwaves. Surprisingly, toxic Pseudo-nitzschia spp. can bloom under both upwelling and heatwave conditions, despite opposite trends in key environmental controls like nutrients, temperature, and carbonate chemistry. This project is testing how this happens by first obtaining full response curves for each of the individual factors, temperature, pCO2, phosphorus, nitrogen, and silicon for two Pseudo-nitzschia isolates. Then, these variables are combined in holistic upwelling and heatwave scenario incubation experiments, to compare how growth and toxicity is affected in both cultures and natural blooms of Pseudo-nitzschia. The PI is assessing toxic diatom responses in these experiments using her existing expertise in algal physiology, as well as by expanding her professional horizons to develop new skills in transcriptome bioinformatics in partnership with Dr. Bethany Jenkins from the University of Rhode Island. Experiments are conducted to test the physiological responses of Pseudo-nitzschia to changes in nutrient concentrations, temperature and pCO2 during simulated upwelling or heatwave occurrences, and measure expression of key metabolic pathway genes such as toxin synthesis pathways. This project is helping to understand and interpret the surprising niche flexibility of toxic Pseudo-nitzschia in a changing ocean, and at the same time offers the PI a new avenue forward for her future career development.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.