The compensation irradiance for phytoplankton in nature

[1] The compensation irradiance for phytoplankton is calculated from the time course of fluorescence-derived chlorophyll-a measured on moored sensors in the North Atlantic in spring. Following the initiation of the spring bloom, the time at which chlorophyll-a begins to decrease at a particular depth in a stratified water column is used to compute the compensation irradiance from the critical depth criterion. Over the depth range of 50-110 m, the compensation irradiance is estimated to be in the range from 0.1-0.3 mol photons m(-2) d(-1).