Modelling steady-state growth and photosynthesis rates of Oscillatoria rubescens continuous cultures in relation to temperature and irradiance

Abstract

The lacustrine blue-green alga (= Cyanobacterium) Oscillatoria rubescens D.C. was cultured in chemostats with temperature and light intensity as the only limiting factors. The experiments were carried out under combinations of three temperatures 10, 20 and 30°C and three irradiances 6, 18 and 30 μE m −2 s −1 . Dilution rate, photosynthesis rate and a large number of abiotic and cellular factors were regularly measured to determine steady-state periods and the level of the associated variables. Various mathematical models were fitted with series of data by a non-linear regression method derived from Marquardt's method. Four models for calculation of specific growth rate and photosynthesis rate are presented. The last one computes growth rate from calculated photosynthesis: μ = μ maxpmaxI /[ KpKi + I ( Kp + Pmax )], with Pmax =100 + 257 T and K1 = 300/chl a . Values of adjusted parameters are discussed. One conclusion confirms that values of maximal growth rates and half-saturation constants frequently considered in the literature as absolute species characteristics should always be considered as relative to associated prevalent growth conditions.