Toxicity of Desalination Brine of Varying Ionic Compositions on Embryonic Development of Japanese Medaka (Oryzias latipes)

Desalination of seawater and brackish groundwater is a promising sustainable solution to meet growing water needs of California and throughout the US. However, the environmental impacts of brine disposal need to be evaluated. Brine disposal into freshwater embayments is often less dilute than disposal to coastal marine environments, resulting in a large increase in salinity. Fish embryos and larvae are especially sensitive to changes in salinity. Furthermore, different ionic compositions of different brine may vary in developmental toxicity. Limited research has been performed on the impacts of hypersalinity on chronic embryonic vertebrate development, particularly on sublethal adverse effects. To investigate these effects, embryos of Japanese medaka (Oryzias latipes), an euryhaline, model organism, were treated at fertilization with five treatments: 1. Freshwater; 2. Artificial seawater (17, 35, 42, 56, and 70 parts per thousand (ppth)); 3. Brine from a desalination facility at Monterey Bay Aquarium, CA, diluted 75%, 50%, and 25% with 35ppth artificial seawater to simulate mixing (39, 42, 46 and 50ppth); 4. River water modeled after the San Joaquin Valley, CA, and prepared in the lab (13, 17, 21 and 26ppth); and 5. Artificial San Joaquin River water diluted 75%, 50%, and 25% with artificial seawater to simulate mixing (13, 19, 24, and 30ppth). Survival, hatch, day to hatch and deformities were recorded. No significant difference was observed between artificial seawater and Monterey Bay aquarium brine and the EC50 values varied between 45-55ppth. These values suggest that under approprioate mixing conditions brine disposal into the open ocean would not be toxic to Japanese Medaka development. However, San Joaquin River water (primarily sulfate, sodium and calcium) decreased survival post hatch in comparison to artificial seawater and desalination brine suggesting that these ions may be more larval toxic.