Description of Work Determine the relative sensitivity of two species of amphibians (i.e. Wood Frogs Rana sylvatica, Cricket Frogs Acris crepitans blanchardi, American Toad Bufo americana) to exposure to acute and chronic levels of nitrate, nitrite and ammonia. This data will be used to evaluate the current ammonia criteria and for possible inclusion in the development of criteria for nitrite and nitrate.