In-situ observations of phytoplankton phenology, net primary production (NPP), net community production (NCP), and NCP to NPP ratio in the North Atlantic Ocean with Argo profiling floats

The seasonal phytoplankton dynamics in the western subpolar and temperate North Atlantic Ocean (40° N to 60° N) were examined using bio-optical measurements on Argo profiling floats. Overall, the Argo results agreed well with satellite remote sensing estimates and the phytoplankton phenology could also be reproduced by an eddy-resolving version of Community Earth System Model (CESM) ocean component. The seasonal phytoplankton dynamics in this area result from interactions between “bottom-up” (e.g., resources for growth) and “top-down” (e.g., grazing), which involve both biological and physical factors. The observed phytoplankton phenology patterns are broadly consistent with the disturbance recovery hypothesis (DRH). Net primary production (NPP) and net community production (NCP) were also estimated with float-measured bio-optical and oxygen data. The mixed layer NPP ranges from 0.2 to 12.7 mmol m^-3 d^-1 (Carbon-based Productivity Model) and 0.1 to 6.2 mmol m^-3 d^-1 (Vertically Generalized Production Model), respectively. Mixed layer NCP is between -0.3 to 0.8 mmol m^-3 d^-1. The NCP to NPP ratio shown significant seasonality with high values in summer and negative values in winter.