The marine picocyanobacteria Prochlorococcus and Synechococcus are dominant in the surface waters of subtropical gyres. Despite inhabiting similar ecological niches, these two species are able to sustain their coexistence through the specialization in the uptake of different nitrogen substrates at low concentrations. As the marine nitrogen biogeochemical cycle responds to ocean acidification and warming, as well as upper ocean deoxygenation and stratification, shifts in the relative abundances of Prochlorococcus and Synechococcus are expected to occur. In this study, a global biogeochemical ocean model is coupled with an ecological model in order to predict the steady-state global distributions of Prochlorococcus and Synechococcus. Additional simulations using a biogeochemical ocean model  provide a framework for predicting the coexistence dynamics of these two species in the ocean under changing concentrations of nitrate and ammonium.

cyanobacteria, nitrogen, ecological model, biogeochemical model