Impact of oceanic frontal divergence on phytoplankton community composition

As phytoplankton reproduce and compete, their motion is often prescribed by ocean currents. These currents therefore influence the distribution and diversity of phytoplankton, although the details of this biophysical interaction are not well characterized due to observational and computational limitations at small spatial and temporal scales. Here, we combine observations, simulations, and theory to consider the impact of realistic flow fields with resolved submesoscale dynamics on plankton community composition. We find that the regions of divergence in our flow field can substantially modify competition events in simulations, and propose that submesoscale frontal divergence is a plausible explanation for observed taxonomic variability in oceanic fronts. The change in community composition of neutral competitors is linearly related to the divergence, with regions of positive divergence supporting local populations and regions of negative divergence suppressing them.