Lethal and Sublethal Effects of Nitrogen Fertilizer Ammonium Nitrate onCommon Toad (Bufo bufo) Tadpoles

The impact of elevated ammonium nitrate concentrations onthe survival and development of common toad (Bufo bufo) tadpoles wasinvestigated in the laboratory. 1,704 mg/L and 1,637 mg/L nitrate (equivalentto 2,198.7 mg/L and 2,112.3 mg/L ammonium nitrate) were recorded as 96 h and168 h LC50s respectively. These are well above field levels (10-250 mg/L)observed in freshwater in Britain. The exposure of tadpoles to nominalconcentration of 100 mg/L nitrate for 24, 48, and 72 h caused a significantdecrease in their activity but no clear reduction in food consumption ordelay of the development. In subchronic exposures at the nominalconcentrations of 50 and 100 mg/L nitrate, the metamorphosis started earlierand took less time to complete than in the control. However, some of theresults were equivocal, at 50 mg NO3/L the metamorphs weresignificantly larger than the controls, while at 100 mg NO3/Lmetamorphs were not significantly different from the controls. Certaindeformities and unusual swimming patterns were also found in tadpoles exposedto various concentrations of ammonium nitrate.