A DYNAMIC REGULATORY MODEL OF PHYTOPLANKTONIC ACCLIMATION TO LIGHT, NUTRIENTS, AND TEMPERATURE

A new regulatory model can describe acclimation of phytoplankton growt h rate (mu), chlorophyll a:carbon ratio and nitrogen:carbon ratio to i rradiance, temperature and nutrient availability. The model uses three indices of phytoplankton biomass-phytoplankton carbon (C), phytoplank ton nitrogen (N), and chlorophyll a (Chl). The model links the light-s aturated rate of photosynthesis to N: C, requires that Chi a synthesis be coupled to nitrogen assimilation, and includes several regulatory features. The:je include feedback inhibition of the nitrogen assimilat ion rate by increases in the N: C ratio, as well as regulation of Chi a synthesis by the balance between Light absorption and photosynthetic carbon fixation. The model treats respiration as the sum of the maint enance metabolic requirement and the cost of biosynthesis. In addition , the model can account for accumulation and mobilization of energy re serves (i.e. variability of N: C) and photoacclimation (i.e. variabili ty of Chi: N and Chl:C) in response to variations in irradiance and nu trient availability. The assumptions of the model are shown to be in a greement with experimental observations and the model output compares favorably with data for cultures in balanced and unbalanced growth.