RESUMO
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 1 h) 95% confidence intervals of salt-core brine at 19 °C for eggs was 51-60 parts per thousand (ppt); yolk-sac larvae 34-55 ppt; first-feeding stage larvae (6-8 mm total length, TL) 37-44 ppt, and 30-46 ppt for large larvae (14-20 mm TL). Among juveniles, the median lethal concentration was significantly higher compared to larvae: 51-58 ppt for early juveniles (4-cm fork length, FL) and 63-67 ppt 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 24.4 ppt on large larvae to 59.7 ppt 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.