Nebeker, Alan V. and Gerald S. Schuytema. 2000. Effects of ammonium sulfate on growth of larval Northwestern salamanders, red-legged frog and Pacific treefrog tadpoles, and juvenile fathead minnows. Bulletin of Environmental Contamination and Toxicology 64:(2)271-278.
Ammonium-nitrogen fertilizers are used in large quantities in agricultural areas of the United States, including the grass-seed fields of the Willamette Valley of western Oregon, and research has shown that they are a potential threat to larval amphibians living in the treated areas. Nitrogen fertilizer use over the past 50 years in the United States has increased from less than 0.45 million metric tons per year to more than 9.98 million metric tons per year. Ammonia has been found to be toxic to fish, invertebrates and amphibians. Hecnar showed that four amphibian species were affected by ammonium nitrate at levels that are commonly exceeded in agricultural areas globally. Acute tests gave 96-hr LC50's ranging from 13.6 to 39.3 mg/L NO3 -N. In chronic tests chorus frog and leopard frog tadpoles had significantly lower survival at 10 mg/L NO3 -N. We previously have shown that the toxicity of ammonium nitrate, ammonium sulfate and ammonium chloride in static-renewal tests is essentially the same for the Pacific treefrog, Pseudacris regilla, due to the ammonium ion. Where the use of ammonium compounds is widespread, chronic effects could be important. We have conducted 10-day static-renewal tests with embryos and tadpoles of P. regilla and have shown significant effects as low as 6.9 mg/L NH4 -N for embryos and 24.6. mg/L for tadpoles. The purpose of this study was to determine effects of ammonium sulfate in flow-through tests, a representative of several ammonium compounds used to add nitrogen to the soil, on growth of three native amphibian species and one introduced fish species. The four species are all residents of the Willamette Valley of western Oregon. The Northwestern salamander Ambystoma gracile and the Pacific treefrog Pseudacris regilla continue to thrive in lowland areas. Historically, the red-legged frog Rana aurora was more common than it is today, and the fathead minnow is a relative newcomer to the valley.