Estimation of Cochlodinium polykrikoides growth potential using a dialysis membrane

We developed a test to measure the growth potential of C. polykrikoides using a dialysis membrane and artificial seawater. Nitrite nitrogen and inorganic phosphorus in the medium were almost completely removed when the medium was dialyzed against artificial seawater for five or more 6-hour cycles using a dialysis membrane (Spectrum's Spectra/Por 7 Membrane) with a molecular-weight cut-off of 50,000, regardless of the presence of C. polykrikoides. The phytoplankton grew well even after dialysis. To estimate the growth potential of C. polykrikoides, a minimum initial concentration of > 100 cells/ml is required. Methods using short-term starvation culturing of C. polykrikoides to measure growth potential were determined to be ineffective; instead, controlled tests using artificial seawater are recommended. The dialysis membrane used in this study can also be employed to measure the algal growth potential of other phytoplankton species.