Phosphorus uptake and growth of blue-green alga, Microcystis aeruginosa

The specific uptake rate Q(p) of orthophosphate (expressed throughout as phosphorus) and the specific growth rate mu of Microcystis aeruginosa were measured using batch-precultured cells, whose growth phase, and intracellular and extracellular phosphorus concentrations f(p) and P, respectively, had been changed. When the cells from phosphorus-rich precultures were used, smaller values of Q(p) (0.1-0.3 microg P mg dry wt. (-1) h (-1)) were observed. However, if phosphorusstarved cells were used, the initial value of Q(p) was enhanced to more than ten times those smaller values referred to above, but declined rapidly with time after the transfer. Q(p) leveled off at around t = 4 h, when f(p) approached the maximum value, even if phosphorus was still available in the medium. A new correlation was presented here with respect to Q(p) as a function of P and f(p) as follows: [Qp = Qp,max P/Kp + P (fp,max-fp)/fp,max-fp)] Although numerical values of parameters involved in the equation depend on physiological state (or preculture history) of the cells, the above equation could account not only for phosphorus uptake, during which changes in phosphorus content in the cells were observed, but also for initial rates of uptake presented previously by other workers. mu Values were confirmed to be a hyperbolic function of f(p) as has been suggested by previous workers.