APPLIED ISSUES The effect of ammonium nitrate on the feeding and development of larvae of the smooth newt, Triturus vulgaris (L.), and on the behaviour of its food source, Daphnia

1. Larvae of the smooth newt, Triturus vulgaris, were exposed to four concentrations of ammonium nitrate in artificial pond water (50, 100, 200 and 500 mg 1-^?1) under controlled laboratory conditions. 2. Larvae exposed to a 50 mg 1-^?1 solution of ammonium nitrate showed no significant difference to control larvae in feeding rate, mass at metamorphosis or time to metamorphosis. However, larvae exposed to 200 or 500 mg 1-^?1 ammonium nitrate, for a single period of 24, 48 or 72 h, were significantly smaller than controls at metamorphosis. Larvae exposed to 100 mg 1-^?1 had a significantly higher feeding rate than those reared under control conditions or those exposed to 200 or 500 mg 1-^?1 ammonium nitrate, but this was not reflected in their size at metamorphosis, which was not significantly different from the controls. Larval survival remained high in all trials. 3. In separate trials, Daphnia, used as a food source for the newt larvae, were exposed to the same series of ammonium nitrate concentrations. Daphnia behaviour was affected by exposure to 200 and 500 mg 1-^?1 ammonium nitrate, and in both cases animals were significantly more likely to be found at the top of the water column than those exposed to 50 or 100 mg 1-^?1 ammonium nitrate or the control medium.