The past two months have gone by so quickly! I have been working with Dr. Rodrigo Almeda this summer and I am happy to say that my project has turned out well. I’m hoping to attend a couple conferences to present the research that I have conducted this summer. I’m extremely thankful for the support I’ve received from my mentors as well as from my fellow REU-ies. My abstract below explains my project in more detail.
Petroleum is one of the most common pollutants released into marine environments. The use of dispersants is a common response to oil spills, as occurred during the Deepwater Horizon oil spill in the Gulf of Mexico in 2010. However, little is known about the toxicity of chemical dispersants and dispersant-treated crude oil to zooplankton. In addition, increasing evidence suggests that UV radiation (UVR) may play an important role on the toxicity of crude oil. The objectives of this study were to determine; (i) if the dispersant Corexit 9500A increases the acute toxic effects of crude oil to copepods (ii) the effects of UVR on the toxicity of crude oil to copepods. We investigated the lethal and sublethal effects of crude oil alone, dispersant-treated crude oil and chemical dispersant and, the influence of UVR exposure, in adults and nauplii of the copepod Acartia tonsa and Pseudodiptomus pelagicus. At the ratio of dispersant to oil commonly used in oil spills (1:20), the combination of oil and dispersant increased mortality and reduced egg production, hatching success, and egestion rates in adult stages of A. tonsa, compared to crude oil alone. Copepod nauplii survival and growth rates were significantly lower when exposed to dispersant-treated crude oil than to crude oil alone. Median lethal concentration (i.e., concentration required to kill half the members of a tested population, 48 h) for copepod nauplii decreased from 1.9 µL L-1 without UVR to 1.2 µL L-1 with UVR. Similarly, we found that toxicity of crude oil and crude oil plus dispersant increased from 24% to 66% and from 67% to 100%, respectively, under UVR exposure. Overall, our results showed that copepod nauplii are highly sensitive to crude oil, and that toxicity of crude oil to zooplankton increases with the use of dispersant and under UVR exposure.