RESPONSES OF EMBRYONIC AND LARVAL INLAND SILVERSIDES, MENIDIA-BERYLLINA, TO NO-2 FUEL-OIL AND OIL DISPERSANTS IN SEAWATER

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(R) and 9527(R), singly and in combination. An ordinal ranking system was used to score observed dai ly craniofacial, cardiovascular, and skeletal responses in control emb ryos and those exposed to 1%, 10%, and 100% concentrations of the WSF of No. 2 Fuel oil, the dispersants Corexit 7664(R) and 9527(R) applied at the recommended field application concentrations, and the combinat ion of No. 2 Fuel oil and respective dispersants in seawater. The non- parametric Kruskal-Wallis analysis of variance (ANOVA) and post hoc an alyses were used to identify statistically significant differences for control embryos and those exposed to No. 2 Fuel oil and dispersants. Embryos exposed to No. 2 Fuel oil in 20 parts per thousand salinity se awater showed significant (alpha less than or equal to 0.01) responses only at the 100% WSF concentration. Corexit 7664(R) tested singly eli cited significant responses at 10% and 100% concentrations. When No. 2 Fuel oil and Corexit 7664(R) were combined at recommended field appli cation concentrations of the dispersant, the oil and dispersant mixtur e resulted in significant (alpha less than or equal to 0.01) responses at 1%, 10%, and 100% exposure concentrations. In contrast, Corexit 95 27(R) did not cause significant responses at the three test concentrat ions of 1%, 10%, and 100% of the recommended field application rate. H owever, when No. 2 Fuel oil and Corexit 9527(R) were combined in seawa ter, the 10% and 100% exposure concentrations resulted in statisticall y significant (alpha less than or equal to 0.01) embryonic responses, relative to controls. Chemical analyses indicated that both dispersant s increased the total WSF of No. 2 Fuel oil in seawater.