Nutrient response strategies drive coastal range shifts of phytoplankton taxa

Coastal phytoplankton blooms are important drivers of regional and global marine primary production. Recently documented increases in coastal phytoplankton blooms in the first quarter of the 21st century may be a consequence in part of changing environmental conditions and have important ecological implications. Here, we explore coastal phytoplankton dynamics in Cape Cod Bay, MA, USA. We use a 20-year phytoplankton ecology dataset to identify potential drivers of the increasing prevalence of two regionally-rare phytoplankton taxa: a coccolithophore thought to thrive in the global open ocean, and a dinoflagellate genus with potentially toxic members. Using metatranscriptomics, we show that these minor phytoplankton taxa leverage unique strategies to gain a competitive advantage under nutrient limitation compared to traditionally dominant taxa and compared to a diatom taxon that became modestly more abundant over the study period. Our results highlight the ecological dynamics arising from long-term shifts in temperature and nutrient status in coastal ecosystems.