Grazing behavior and winter phytoplankton accumulation

Abstract. Recent observations have shown that phytoplankton biomass increases in the North Atlantic during winter, even when mixed layer is deepening and light limited. Current theories suggest this due to a release from grazing pressure. Here we demonstrate often-used models are linear at low concentration do not allow for wintertime increase biomass. However, mathematical formulations of as function quadratic concentrations (or more generally decrease faster than linearly decreases) can reproduce fall spring transition phytoplankton, including accumulation. We illustrate point with minimal model annual cycle designed simulate observed by BioGeoChemical-Argo (BGC-Argo) floats Atlantic. This analysis provides framework assessing hypotheses bloom formation.