ABSTRACT
Several Latin American countries currently use Artemia to evaluate the aquatic toxicity of dispersants. Test methods used to evaluate dispersant toxicity to Artemia are not uniform. The study reported here demonstrates how varying Artemia test conditions can significantly affect toxicity results for the dispersant Corexit® 9500.
The type of seawater used in Artemia toxicity tests affects 48 hour LC50 values for Corexit 9500 (lethal concentration for 50% of test organisms). Nominal LC50 values ranged from 35 to 147 ppm when natural seawater was used. Nominal LC50 values ranged from 29 to 39 ppm when a synthetic seawater prepared from Crystal Sea® Marinemix was used. Greater toxicity was observed when synthetic (reconstituted) seawater was prepared according to the U. S. Environmental Protection Agency (USEPA, 1987) Artemia dispersant test guideline. Observed nominal LC50 values ranged from 8.4 to 14 ppm.
Age of the Artemia nauplii is another test variable that can significantly affect toxicity results. The 48 hour nauplii showed greater toxicity to Corexit 9500 than 24 hour old nauplii. In tests using two types of synthetic seawater (Coral Reef Red Sea Salt® and Crystal Sea® Marinemix at 20 °C, 20 ppt salinity), nominal LC50 values ranged from 29 to 68 ppm for 24 hour old nauplii; 48 hour old nauplii had LC50 values ranging from 9 to 27 ppm. Greater toxicity was also observed in 48 hour nauplii under different salinity and temperature (Red Sea, 25 °C, 33 to 35 ppt salinity). The LC50 values were 33 and 1.6 ppm for 24 and 48 hour nauplii respectively.
