Growth of Oscillatoria agardhii in Chemostat Culture: 1. Nitrogen and Phosphorus Requirements

Abstract

The blue-green alga O. agardhii Gom. was cultured in a chemostat with N or P as limiting factors. The experiments were carried out at continuous light with an intensity of 37 .mu.E [Einstein] m-2 .cntdot. s-1 and a temperature of 24-26.degree. C. Specific rate is supposed to be a function of external mutrient concentration. Growth constants of Oscillatoria were estimated by fitting Monod''s and Mitscherlich-Baule''s equations to the data. The fits gave the following results: maximum specific growth rate, .cxa..mu. = p.5/day, half-saturation constant for N, Ks = 0.5 .mu.g l-1 and halfsaturation constant for P, Ks = 1 .mu.g 1-1. The mean value of the N content was 6% of DW [dry weight] and the mean value of the P content was 0.26% of DW. The yield coefficient for N (YN) varied between 12 and 26 DW/mgN and for P (YP) between 270 and 560 mg DW/mg P. The low values of Ks for O. agardhii are reasonable by comparison with field data. It is shown by examples of growth curves of a green alga [Selenastrum capricarnutum] and a blue-green alga that the succession of different algae can be partly due to differences in these constants.