Acute Toxicity of Salt Cavern Brine on Early Life Stages of Striped Bass (Morone saxatilis).

Abstract

A plan to create solution-mined salt caverns for natural gas storage by discharging brine into the Shubenacadie River estuary poses a potential risk to an "endangered" stock of striped bass. Toxicity of brine made from both salt-core and artificial sea-salt "Instant Ocean" was assessed by 1-h acute toxicity tests at both 19°C and 12°C, the typical thermal range in June, post-spawning. The short test duration was justified given the rapid dilution of the brine in the macrotidal estuary. The median lethal concentration (LC50 1h) 95% confidence intervals of salt-core brine at 19°C for eggs was 51-60 parts per thousand (ppt); yolk-sac larvae 34-55ppt; first-feeding stage larvae (6-8mm total length, TL) 37-44ppt, and 30-46ppt for large larvae (14-20mm TL). Among juveniles, the median lethal concentration was significantly higher compared to larvae: 51-58ppt for early juveniles (4-cm fork length, FL) and 63-67ppt for juveniles 12-cm FL. The toxicity of brine made from either Instant Ocean or salt-core was similar. At 12°C, yolk-sac larvae salinity tolerance was 30% lower than at 19°C, whereas other life stages exhibited a similar response to 12°C and 19°C. The threshold observed effect concentration (TOEC) of the salt-core ranged from 24.4ppt on large larvae to 59.7ppt on 12-cm juveniles. In conclusion, a very low direct threat to striped bass is estimated for the discharge of brine into the Shubenacadie River estuary.