Can a predatory fungus (Zoophagus sp.) endanger the rotifer populations in activated sludge?

We investigated the influence of the predatory fungus Zoophagus sp. and temperature on the number of rotifers inhabiting activated sludge. When a sample of sludge was subjected to the fungus, the number of Lecane inermis and bdelloid rotifers was reduced at 15 °C and 20 °C, whereas at 8 °C the effect was not significant. The effect of Zoophagus on two Lecane and one bdelloid species, in conditions optimal for rotifers, confirmed the negative effect of the fungus on rotifer density. In the L. inermis treatment, the number of living rotifers was three times lower than in the control. These results demonstrated that the massive occurrence of predatory fungus may endanger the population of rotifers (organisms considered capable of significantly improving the quality of the effluent from wastewater treatment plants).