In my two previous posts, I discussed my research studying the effects of UV light on oil toxicity. Well, around two months and hundreds of larval shrimp later, my research has come to an end! And I’m discovered quite a lot of interesting things.

The first thing we discovered was just how much more toxic UV light makes oil. The average percent mortality for the various concentrations is shown in the following graph. This graph shows that UV light makes the three highest oil concentrations significantly toxic, while none of the concentrations tested were significantly toxic under non-UV light. After these data were analyzed, we determined that UV light essentially makes oil around 4.3 times more toxic than it would be under non-UV light.

initial mort

After 30 days, there was even more mortality, as shown in the following graph. This graph shows that after 30 days, all the shrimp exposed to the 3 highest concentrations of oil under UV light died, and only 1 of the shrimp exposed to the lowest concentration of oil under UV light hadn’t died. All the concentrations of oil were significantly more toxic under UV light. This study shows that even after shrimp are removed from oil, being exposed to oil can cause significant harm.

latent mort

Other studies showed that early oil exposure can harm shrimp development. Further studies looked at the dry weights of the shrimp at the end of 30 days and the concentration of ecdysteroid molting hormone at the end of 96 hours of oil exposure. This found that oil exposure increased the dry weight for some concentrations, and certain concentrations reduced the concentration of molting hormone. The reduced molting hormone is especially troublesome, because this hormone is very important in shrimp growth and development. Having reduced ecdysteroid could be inhibiting shrimps’ ability to properly grow.

Other experiments I conducted were on thin oil sheens. What I found was very mixed. There was higher average mortality in the shrimp exposed to the oil and to the oil and UV light, however, it wasn’t statistically significant. Therefore, more research is definitely needed.

In the future, some interesting research to conduct would be to look at the sublethal effects caused by lower concentrations of oil, and studying different species responses to the thin sheens. From the beginning, the goal of this work has been to better understand the harm caused by oil spills so that we can better respond to them, and I hope my work this summer has filled in some of the gaps!
A huge thank you to my mentors, Dr. Marie Delorenzo and Dr. Paul Pennington. I’d also like to thank the NSF, The National Centers for Coastal Ocean Science and the Grice Marine Lab for supporting this research.


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