Oil Spills, Climate Change, and Grass Shrimp

Cheldina Jean, American University

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Getting down and dirty for egg carrying grass shrimp in Leadenwah Creek. Photo: Katy Chung

The Approach: In my previous post, I discussed how grass shrimp (Palaemonetes pugio) larvae can be used to test the effects of oil when paired with environmental conditions such as ultraviolet light (UV), temperature, and salinity. In the environment, salinity, temperature, and different levels of light can affect the health and survival of organisms. UV light is one of the three types of radiation the sun emits. Crude oil is made up of polycyclic aromatic hydrocarbons (PAHs), which are formed from the incomplete burning of fossil fuels. When oil spills happen, UV light can change the PAH chemistry, making oil up to 100 times more toxic to marine organisms (Alloy et al., 2017).

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Upclose image of grass shrimp eggs. If you look closely, you can see the black eye spots of the embryo. Photo: Cheldina Jean

In the environment, grass shrimp experience salinities ranging from 0-36 parts per thousand (ppt), temperatures ranging from 2 °C to 37 °C (DeLorenzo et al., 2009), and various levels of UV light, all depending on season, precipitation, and tides.  For this research project, we collected adult grass shrimp with eggs from Leadenwah Creek, which is located on Wadmalaw Island, Charleston, SC. Seawater from the Charleston Harbor estuary was filtered and used for all of the test conditions. The oil we use in our tests was obtained through NOAA from the DeepWater Horizon oil spill.

 

 

We are looking at two different types of oil exposures for this project:

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Undiluted HEWAF. Photo: Cheldina Jean

  1. High Energy Water Accommodated Fraction (HEWAF), which is dissolved oil in seawater. The HEWAF is diluted to concentrations of 0.25%, 1%, 4% for our different tests. 
  2. Thin oil sheen, which is a thin layer of fresh oil placed on the surface of the water.

Standard laboratory testing conditions for grass shrimp generally consist of a salinity of 20 ppt, temperature of 25 °C, and fluorescent lighting (DeLorenzo et al., 2016).

 

 

For both oil exposure scenarios (HEWAF and sheen) we set up larval shrimp under combinations of the different environmental conditions: UV or no UV (using UV light bulbs or cool-white fluorescent bulbs, respectively) temperatures of 32 °C (90 °F) and 25°C (77 °F), and salinities of 10 ppt, 20 ppt, and 30 ppt.

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Temperature HEWAF test under UV conditions. Photo: Cheldina Jean

Newly hatched larvae were acclimated in the different temperatures and salinities before each test. Every 24 hours, the amount of larvae that survived and the amount that died were recorded. Each test ran for 96 hours and on the 96th hour, water quality (temperature, dissolved oxygen, salinity and pH) was recorded.

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Field Collection! (Featuring Shelby, myself, and two Hollings Scholars). Photo: Katy Chung

Next, we will use statistical analysis to evaluate our results. Stay tuned!

I would like to thank my mentor Marie DeLorenzo and co-mentor Katy Chung for guiding me through this research. This project is supported by the Fort Johnson REU Program, NSF DBI-1757899.

 

 

 

Citations:

  1. Alloy, M., Garner, T. R., Bridges, K., Mansfield, C., Carney, M., Forth, H., … & Bonnot, S. (2017). Coexposure to sunlight enhances the toxicity of naturally weathered Deepwater Horizon oil to early life stage red drum (Sciaenops ocellatus) and speckled seatrout (Cynoscion nebulosus). Environmental toxicology and chemistry, 36(3), 780-785.
  2. DeLorenzo ME, Wallace SC, Danese LE, Baird TD (2009) Temperature and salinity effects on the toxicity of common pesticides to the grass shrimp, Palaemonetes pugio. J Environ Sci Health B 44:455–460.
  3. DeLorenzo, M. E., Eckmann, C. A., Chung, K. W., Key, P. B., & Fulton, M. H. (2016). Effects of salinity on oil dispersant toxicity in the grass shrimp, Palaemonetes pugio. Ecotoxicology and environmental safety, 134, 256-263.

 

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