Over the past 30 years researchers have become aware of long-term declines in amphibian populations, often starting earlier in this century. Over this same time period, humans have dramatically increased the amount of mineralized nitrogen (N) across the planet. In the Midwest and other areas of similar latitude, early breeding amphibians enter breeding ponds in spring often before ice has completely melted. At this time snowmelt and early rains flush mineral N into surface waters, but there is very little biological uptake. Hence, amphibian embryos and young larvae are exposed to elevated concentrations of N. Preliminary evidence suggests that amphibian embryos and larvae are susceptible to mineral N at concentrations found in the environment, concentrations well below those considered safe for human consumption. In this study I will address the following research questions: 1) does exposure to elevated concentrations of mineral N as embryos and larvae in the laboratory decrease hatching and survival, and increase the time to metamorphosis and deformities in the wood frog and eastern tiger salamander, and 2) do experimentally increased concentrations of mineral N in the field decrease egg hatching, larval survival and development, and increase the frequency of deformities when amphibians are protected from predation. I expect to demonstrate that nitrogen can detrimentally affect amphibian embryos and larvae under realistic conditions and at realistic concentrations. I also expect that this research will show that exposure to mineralized nitrogen as embryos can have very large negative implications for the amphibians once they develop into larvae. My results will potentially provide major insights into the effects of mineral N on amphibian populations and freshwater ecosystems; thus, revealing a previously unrecognized factor in the declines of some amphibian populations.
