Effects of Chloride on Acute Toxicity of Nitrite to Atlantic Sturgeon

The sensitivity of Atlantic sturgeon (Acipenser oxyrhinchus) to nitrite is not well understood and may have implications in the conservation of the species, particularly where water quality degradation occurs. This study examined the effects of chloride on acute toxicity of nitrite to Atlantic sturgeon fry (Acadian Sturgeon and Caviar Inc., Saint John, NB, Canada).  Fish were exposed to eight nitrite levels (0-2.58 mg/L) in each of three concentrations of chloride (0, 50, and 100 mg/L) for 96 hours in a semi-static system.

Overall, significant differences in mortality were found between the 0mg/L chloride group and both the 50mg/L and 100mg/L chloride groups, with higher mortality occurring in the 0mg/L chloride group.  Over the course of the 96-hr period, greater mortality occurred in the 0mg/L chloride groups than in either the 50mg/L or 100mg/L chloride groups.  Within each chloride group, mortality tended to increase as nitrite levels increased.

Results of the larval toxicity studies indicate that Atlantic sturgeon fry are sensitive low concentrations of nitrite.  Mortality increased as exposure time increased.  Chloride can mitigate toxicity of nitrite in fish, decreasing mortality at the upper levels of nitrite tested in this study.  In the Chesapeake Bay, the natural level of nitrite is approximately 0.07mg/L which could cause mortality and sub-lethal effects to sturgeon such as stress and decreased growth rates.  Furthermore, study results suggest that nitrite maybe a contributing factor to critically low sturgeon populations and little observed recruitment in the Chesapeake Bay. Results of this study also raise the question of impacts of nitrite on juvenile and adult Atlantic sturgeon.