Harmful Algal Bloom-Forming Organism Responds to Nutrient Stress Distinctly From Model Phytoplankton

O_LIResources such as nitrogen (N) and phosphorus (P) play an important role in primary production and constraining phytoplankton bloom dynamics. Models to predict bloom dynamics require mechanistic knowledge of algal metabolic shifts in response to resource limitation. For well-studied model phytoplankton like diatoms, this information is plentiful. However, for less-studied groups such as the raphidophytes, there remain significant gaps in understanding metabolic changes associated with nutrient limitation. C_LIO_LIUsing a novel combination of metabolomics and transcriptomics, we examined how the harmful algal bloom-forming raphidophyte Heterosigma akashiwo shifts its metabolism under N- and P-stress. We chose H. akashiwo because of its ubiquity within estuarine environments worldwide, where bloom dynamics are influenced by N and P availability. C_LIO_LIOur results show that each stress phenotype is distinct in both the allocation of carbon and the recycling of macromolecules. Further, we identified biomarkers of N- and P-stress that may be applied in situ to help modelers and stakeholders manage, predict, and prevent future blooms. C_LIO_LIThese findings provide a mechanistic foundation to model the metabolic traits and trade-offs associated with N- and P-stress in H. akashiwo, and evaluate the extent to which these metabolic responses can be inferred in other phytoplankton groups. C_LI