Selenium toxicokinetics, chronic toxicity, and interaction with salinity stress in white sturgeon

Regulatory agencies are currently lacking the scientific data needed to guide management decisions on the maximum selenium (Se) loading into the San Francisco (S.F.) Bay-Delta to minimize the risk of Se toxicity in white sturgeon (Acipenser transmontanus). A series of studies investigating the toxicokinetics of Se, chronic toxicity of Se, and interactive effect of Se and salinity stressors in white sturgeon was conducted to provide the data needed to manage Se loading into the S.F. Bay-Delta.; A combined technique consisting of esophageal intubation, dorsal aortic cannulation, and urinary catheterization was used to obtain a basic understanding of the toxicokinetics of Se in white sturgeon. White sturgeon (1-2 kg) were intubated with 0, 250, 500, or 1000 mug Se/kg body weight in the L-selenomethionine form. Mean plasma Se, red blood cell Se, and urinary Se excretion rates were positively correlated with the size of the intubated Se dose.; The chronic toxicity of Se in white sturgeon (25-30 g) was determined by dietary exposure to 0.4, 9.6, 20.5, 41.7, 89.8, and 191.1 mug Se/g diet for 8 wks. Sturgeon growth but not survival was negatively affected during Se exposure in sturgeon fed above 20.5 mug Se/g diet. Selenium accumulated in all sampled tissues in a dose-dependent manner and histopathological lesions were observed in the liver and kidneys of sturgeon fed above 9.6 mug Se/g diet.; Sturgeon exposed to dietary Se for 8 wks were transferred into brackish water to determine the interactive effect of Se and salinity stressors on osmoregulative capacity and survival. Sturgeon fed above 41.7 mug/g diet for 8 wks experienced decreases in survival when transferred into 15 ppt brackish water although sturgeon survival was not affected when exposed to Se and salinity stressors separately.; While these studies suggest a maximum threshold of approximately 10 mug Se/g diet to prevent dietary Se toxicity, further studies are needed to determine how extended exposure (>8 wks), multiple stressors, and sensitivity of different life stages may influence the toxic potency of Se in white sturgeon.