A theoretical and experimental examination of the predictions of two recent models of phytoplankton growth

Abstract

An analysis of the theoretical models of phytoplankton growth developed independently by Bannister (1979) and Shuter (1979) shows that the models are mathematically identical in their predictions regarding steady-state light limited growth rates, respiration rates and chlorophyll: carbon ratios if one takes n = 1 and m = ∞ in the Bannister model. The chief advantages of the Bannister model are its ability to predict short-term photosynthesis versus light curves, and its adaptability to L : D cycle growth conditions. The latter capability of the model is greatly facilitated if n = 1. The principal advantages of the Shuter model are its ability to describe nutrient-limited steady-state nitrogen: carbon and phosphorus: carbon ratios, and its ability to predict the interactive effects of temperature, light and nutrient limitation on phytoplankton composition. A comparison of the models with nutrient and light limited growth rate and composition data for the marine diatom Thalassiosira weissflogii shows good agreement in all cases except for RNA: C and ATP: C data. The latter two composition ratios do not appear amenable to description by the model. An examination of the Shuter model shows that it predicts a hyperbolic relationship between nitrogen :carbon (or phosphorus: carbon) ratios and nutrient-limited growth rate of exactly the form proposed on empirical grounds by Caperon & Meyer (1972), and that the hyperbolic function reduces to the form earlier proposed by Droop (1968) in the limit of high light intensity. The predicted light and temperature dependences of the parameters in the hyperbola are shown to be in qualitative agreement with recent experimental data.