LERNER, D. T.*; MCCORMICK, S. D.; University of Massachusetts, Amherst; Conte Anadromous Fish Research Center: Physiological and behavioral effects of nonylphenol and 17β-estradiol on larval survival and smolt development of Atlantic salmon, Salmo salar

Nonylphenol (NP) is widely found in effluents from sewage treatment plants and industrial sites due to its use in detergents, plastics, cleaning products, and pesticides. A direct consequence of this widespread use is its presence in rivers and estuarine systems. In this study, we examined the effects of estradiol (E2) and environmentally relevant concentrations of aqueous NP on larval survival and smolt development of Atlantic salmon. Larvae were exposed for three weeks to 10 or 100 ppb NP, 2 ppb E2, or vehicle. Animals were maintained at ambient conditions for one year and then assessed for endocrine, osmoregulatory, and behavioral disruption of smolt development. Fifty percent of larvae treated with 100 ppb NP succumbed to mortality, with less than 5% mortality in each of the other groups. Between one and two months post-treatment E2 and 10 ppb NP treatment resulted in mortality 4 to 5 times greater than controls, indicating a delayed mortality effect. These groups also exhibited decreased gill Na⁺, K⁺-ATPase activity and salinity tolerance as smolts as well as a greater stress response when challenged with a handling stressor as evidenced by increases in plasma cortisol and decreases in plasma chloride in freshwater. Seawater preference of smolts exposed to E2 or 10 ppb NP as larvae was significantly reduced. These results indicate that E2 and environmentally relevant levels of aqueous NP can compromise smolt physiology and behavior and elicit stress hypersensitivity one-year following exposure. These impacts of early exposure suggest that NP and E2 can have long term, �organizational� effects on life history events in Atlantic salmon.