Phytoplankton physiology controls global ocean biogeochemistry (and climate)

<p><span class="">The similarity of the average nitrogen-to-phosphorus ratios</span><span class="">&#160;(N:P)</span><span class="">&#160;in marine dissolved-inorganic and particulate-organic matter indicates tight links between those pools in the World Ocean. Here we analyse the&#160;sensitivity of marine biogeochemistry to variations in phytoplankton N and P subsistence quotas in an optimality-based ecosystem model coupled to the UVic Earth system model. Our results reveal distinct&#160;feedbacks between changes in the N and P quotas,&#160;</span>N<sub class="">2</sub><span class="">&#160;</span><span class="">fixation, and denitrification that loosen the coupling between dissolved and particulate N:P.</span><span class="">&#160;&#160;</span><span class="">We demonstrate the&#160;importance of particulate N:C and P:C for regulating dissolved N:P on the global scale, with oxygen concentration being an important mediator. Our analysis also reveals a potential interdependence between phytoplankton&#160;stoichiometry and global equilibrium climate conditions.</span></p>