TOXIC CONCENTRATION OF FREE AMMONIA TO BRACHIONUS CALYCIFLORUS PALLAS, A ROTIFER PEST SPECIES FOUND IN HIGH RATE ALGAL PONDS (HRAP's)

Abstract

Laboratory tests on Brachionus calyciflorus Pallas indicate that at low concentrations of free ammonia (< 7 mg l ⁻¹) pH levels up to 9,85 could be tolerated for 96 h without apparent ill effect. Free ammonia concentrations > 14,4 mg l ⁻¹ (as N) could not be tolerated by this species. It is recommended that ammonium hydroxide be added to HRAP's in order to elevate the concentration of free ammonia above this level.