A. Sciandra et P. Ramani, THE STEADY-STATES OF CONTINUOUS CULTURES WITH LOW RATES OF MEDIUM RENEWAL PER CELL, Journal of experimental marine biology and ecology, 178(1), 1994, pp. 1-15
Continuous cultures of the chlorophyte Dunaliella tertiolecta R.W. But
cher were stabilized for different sets of dilution rates d and nitrat
e concentrations so in the renewal milieu. Cell concentrations at equi
librium were compared to the theoretical concentrations obtained using
differential equations postulated in Droop's model. The experimental
data were in agreement with the theoretical when the rate of nutrient
renewal per cell exceeded a certain limit R. Coupling different values
of d and s(o) where the limit R is not attained - for example, low va
lues of d with high value of s(o) - algal density at equilibrium is in
ferior to the theoretical density. Algal mass, calculated from cell vo
lume, is also inferior to theoretical mass, although to a lesser exten
t. It is suggested that when the rate of renewal R (which is probably
species specific) is insufficient, the population of cells is inhibite
d by the emergence of unfavourable factors (e.g. insufficient eliminat
ion of toxic excretion, predominant bacterial activity). In these extr
eme experimental conditions, as the population is not uniquely limited
by the limiting factor, the hypotheses supported by the Droop's model
and the continuous culture theory become non-verifiable.