Comparative toxicity of ammonium and nitrate compounds to pacific treefrog and african clawed frog tadpoles

The effects of ammonium nitrate, ammonium chloride, ammonium sulfate, and sodium nitrate on survival and growth of Pacific treefrog ( Pseudacris regilla [Baird and Girard]) and African clawed frog ( Xenopus laevis [Daudin]) tadpoles were determined in static—renewal tests. The 10‐d ammonium nitrate and ammonium sulfate LC50s for P. regilla were 55.2 and 89.7 mg/L NH 4 ‐N, respectively. The 10‐d LC50s for X. laevis for the three ammonium compounds ranged from 45 to 64 μg/L NH 4 ‐ N. The 10‐d sodium nitrate LC50s were 266.2 mg/L NO 3 ‐N for P. regilla and 1,236.2 mg/L NO 3 ‐N for X. laevis. The lowest observed adverse effect level (LOAEL) of ammonium compound based on reduced length or weight was 24.6 mg/L NH 4 ‐N for P. regilla and 99.5 mg/L NH 4 ‐N for X. laevis. The lowest sodium nitrate LOAELs based on reduced length or weight were <30.1 mg/L NO 3 ‐N for P. regilla and 126.3 mg/L NO 3 ‐N for X. laevis. Calculated un—ionized NH 3 comprised 0.3 to 1.0% of measured NH 4 ‐N concentrations. Potential harm to amphibians could occur if sensitive life stages were impacted by NH 4 ‐N and NO 3 ‐N in agricultural runoff or drainage for a sufficiently long period.