The influence of crude oil and oil dispersant on the embryonic development of Gulf killifish

The interactive effects of weathered oil and dispersant on the embryogenesis of the Gulf killifish were tested using laboratory mesocosms that were constructed using water spiked with oil, dispersant, or in combination. Treatment waters were generated at nominal salinities of 12 and 18 g/L. Control water was left undisturbed. Dispersant water was mixed at 22 mL of Corexit 9500 dispersant to 80 L of treatment water. Oil water was initially mixed at an approximate 1:4 oil:water ratio by volume and the dispersant was used at a 10:1 oil:dispersant ratio to generate oil/dispersant water. Treatment waters at the previously mentioned nominal salinities were weathered for 1, 4, and 16 weeks in treatment mesocosms. Embryos were monitored for hatch percent, mortality, and embryonic heart rate. Images of embryos were taken at hatch to screen for the presence of developmental abnormalities.