Research Product

Embryonic inland silversides, Menidia beryllina, in the early blastula stage were exposed to the water-soluble fraction (WSF) of No. 2 Fuel oil and the oil dispersants Corexit 7664® and 9527®, singly and in combination. An ordinal ranking system was used to score observed daily craniofacial, cardiovascular, and skeletal responses in control embryos and those exposed to 1%, 10%, and 100% concentrations of the WSF of No. 2 Fuel oil, the dispersants Corexit 7664® and 9527® applied at the recommended field application concentrations, and the combination of No. 2 Fuel oil and respective dispersants in seawater. The non-parametric Kruskal-Wallis analysis of variance (ANOVA) and post hoc analyses were used to identify stastically significant differences for control embryos and those exposed to No. 2 Fuel oil and dispersants. Embryos exposed to No. 2 Fuel oil in 20 o/oo salinity seawater showed significant (a less than or equal to 0.01) responses only at the 100% WSF concentration. Corexit 7664® tested singly elicited significant responses at 10% and 100% concentrations. When No. 2 Fuel oil and Corexit 7664® were combined at recommended field application concentrations of the dispersant, the oil and dispersant mixture resulted in significant (a less than or equal to 0.01) responses at 1%, 10%, and 100% exposure concentrations. In contrast, Corexit 9527® did not cause significant responses at the three test concentrations of 1%, 10%, and 100% of the recommended field application rate. However, when No. 2 Fuel oil and Corexit 9527® were combined in seawater, the 10% and 100% exposure concentrations resulted in statistically significant (a less than or equal to 0.01) embryonic responses, relative to controls. Chemical analyses indicated that both dispersants increased the total WSF of No. 2 Fuel oil in seawater.