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

Phosphate (P-i) 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 P-i concentrations and temperatures and propose a novel P-i uptake model by incorporating Arrhenius function and P-i-stress function into the two-stage model presented in one of our recent paper (Jiang et al. (2019)). In both P-i-replete and P-i-deplete, the model parameters are obtained by fitting the experimental data at 24 degrees C and validated by the experimental data at 20 degrees C, respectively. K. mikimotoi under low P-i condition entered into the exponential growth phase earlier compared with P-i-replete groups. Under the P-i-replete condition, K. mikimotoi continually increased, while the P-i-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 P-i-replete and P-i-deplete, the peak values of the cell quota of intracellular P-i and surface-adsorbed P-i at 24 degrees C were higher than those at 20 degrees 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 P-i uptake characteristics of algae at different P-i concentrations and temperatures, and could effectively explain mechanisms of interspecific competition and succession between different algae species during red tide.