Strategies among phytoplankton in response to alleviation of nutrient stress in a subtropical gyre

Despite generally low primary productivity and diatomabundances in oligotrophic subtropicalgyres, the North Atlantic SubtropicalGyre (NASG) exhibits significant diatom-driven carbon export on an annual basis. Subsurface pulses of nutrientslikely fuel brief episodes of diatomgrowth, but the exact mechanisms utilized by diatomsin response to these nutrientinjections remain understudied within near-natural settings. Here we simulated delivery of subsurface nutrientsand compare the response among eukaryotic phytoplankton using a combination of physiological techniques and metatranscriptomics. We show that eukaryotic phytoplankton groups exhibit differing levels of transcriptional responsiveness and expression of orthologous genes in response to release from nutrientlimitation. In particular, strategies for use of newly delivered nutrientsare distinct among phytoplankton groups. Diatomschannel new nitrate to growth-related strategies while physiological measurements and gene expression patterns of other groups suggest alternative strategies. The gene expression patterns displayed here provide insights into the cellular mechanisms that underlie diatomsubsistence during chronic nitrogen-depleted conditions and growth upon nutrientdelivery that can enhance carbon export from the surface ocean.