Kinetics of phosphate uptake in the dinoflagellate Karenia mikimotoi in response to phosphate stress and temperature

Phosphate (Pi) and temperature are two important environmental factors affecting algal growth and the occurrence of red tide. In this paper, we conduct experiments on Karenia mikimotoi under different Pi concentrations and temperatures and propose a novel Pi uptake model by incorporating Arrhenius function and Pi-stress function into the two-stage model presented in one of our recent paper (Jiang et al. (2019)). In both Pi-replete and Pi-deplete, the model parameters are obtained by fitting the experimental data at 24 °C and validated by the experimental data at 20 °C, respectively. K. mikimotoi under low Pi condition entered into the exponential growth phase earlier compared with Pi-replete groups. Under the Pi-replete condition, K. mikimotoi continually increased, while the Pi-deplete condition showed a wave trend. The experimental results and the fitting of experimental data both show that K. mikimotoi has an obvious response to temperature. In both Pi-replete and Pi-deplete, the peak values of the cell quota of intracellular Pi and surface-adsorbed Pi at 24 °C were higher than those at 20 °C. Using the luxury coefficient and growth potential, interspecific competition between K. mikimotoi and Prorocentrum donghaiense is also discussed. These results and conclusions are helpful to understand the Pi uptake characteristics of algae at different Pi concentrations and temperatures, and could effectively explain mechanisms of interspecific competition and succession between different algae species during red tide.