Studies on growth and phosphorous uptake kinetics of Karenia mikimotoi at the different phosphorous levels

Abstract:

We conducted a series of conditional experiments to explore the changes in cell densities, volume and phosphorous uptake kinetics of Karenia mikimotoi at three different inorganic phosphorus levels. The results showed that the growth of K. mikimotoi was significantly affected by inorganic phosphorus levels, the cell densities in high-phosphorous (HP) group were significantly (P<0.05) higher than those in medium-phosphorous (MP) and low- phosphorous (LP) groups starting from the 12th day until to the end of experiment. On the contrary, the cell volume of K. mikimotoi which grew in LP group was significantly (P<0.05) greater than those in MP and HP groups from the 6th day, however, it was non-significantly different between MP and HP group (P>0.05). The relationship between inorganic phosphorus absorption rate and initial phosphorus concentration was preferably fitted by the Michaelis-Menten equation. According the equation, the maximum inorganic phosphorus absorption rate of K. mikimotoi (ρ_max) was 18.587 fmol/(cell·h) and the half-saturation constant (K_s) was 0.490 μmol/L. Given the fact that inorganic phosphorus content was low (approximately 0.10 μmol/L) in the East China Sea when dinoflagellates red tides occurred, and K. mikimotoi have strong affinity for inorganic phosphorus and continuous growth potential in low phosphorus condition indicate that dinoflagellates have more competitive nutriment absorption ability than diatom, which may promote the succession of the diatom and dinoflagellates red tides in the East China Sea.