Old Chlorella cultures are known to be toxic to zooplankton (Edmondson
1957). In our experiments ,we ensured fresh supply of algal
diet to rotifers. In treatments containing up to 50% M. aeruginosa,
both rotifers grew at densities comparable to 100% Chlorella. This
suggests that in nature at least some quantity of M. aeruginosa is
consumed, but only when the strain is not highly toxic.
Therefore
changes in the cyanobacterial abundances in nature are not only
related to physico - chemical variables but are alsolikely due to
grazing from zooplankton (Scholtenetal.2005).