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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Oil Spills, Climate Change, and Grass Shrimp

Cheldina Jean, American University

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The problem: The Deepwater Horizon oil spill that occurred in April 2010 is known as the nation’s most detrimental offshore environmental disaster. Over the course of almost three months, approximately 134 million gallons of crude oil was released into the Gulf of Mexico. Tens of thousands of marine organisms, including dolphins, sea turtles, 93 bird species, and marine plants such as mangroves, whose roots hold together the eroding coasts of Louisiana and South Florida, were negatively affected by this calamity.

Estuarine organisms, particularly sensitive early life stages, are particularly vulnerable to oil pollution given the stressful environmental conditions of their habitat. Estuaries experience daily tidal fluctuations in light penetration, temperature, and salinity; and the range of these factors is expected to increase with global climate change. My project this summer consists of testing the effects of oil on the early life stages of estuarine organisms under various environmental conditions. This research will help us understand how their populations may be affected.

Grass shrimp are commonly found in estuarine waters of South Carolina and along the Gulf and Atlantic coastlines. Grass shrimp are detritivores, playing an important role in the salt marsh by recycling the nutrients of decaying matter back into the food chain. They are also an important prey species for commercially and recreationally important marine organisms, such as spotted sea trout and red drum (Coen & Wenner, 2005). This research project focuses on the role abiotic stressors such as ultraviolet light, temperature, and salinity play on the survival of grass shrimp (Palaemonetes pugio female grass shrimp embryos and larvae exposed to oil.

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Gravid (egg carrying) female grass shrimp (Source)

Crude oil is a complex mixture of chemicals, including a group of compounds called polycyclic aromatic hydrocarbons (PAHs). Some PAHs are chemically altered in the presence of ultraviolet (UV) light, causing an increase in the toxicity of oil (Alloy et al., 2017). In addition, thermal stress from rising global temperatures may affect the ability of marine organisms to metabolize and detoxify contaminants they take up (DeLorenzo et al., 2009). Salinity is another environmental factor to consider because it can alter the solubility of chemical contaminants and thus change the level of chemical exposure.

Every oil spill has different conditions surrounding it, so it is important to understand how factors such as UV light, temperature, and salinity affect oil toxicity in the early life stages of estuarine organisms. Although we cannot eliminate oil pollution in the ocean, the results of this research will help us understand how multi-stressors and oil affect the early life stages of aquatic organisms and will help governments and citizens take action in oil spill response and remediation.

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.

Literature Cited:

  1. Alloy, M., Garner, T. R., Bridges, K., Mansfield, C., Carney, M., Forth, H., … & Bonnot, S. (2017). Co‐exposure to sunlight enhances the toxicity of naturally weathered Deepwater Horizon oil to early lifestage red drum (Sciaenops ocellatus) and speckled seatrout (Cynoscion nebulosus). Environmental toxicology and chemistry, 36(3), 780-785.
  2. Coen, L., & Wenner, E. (2005). Grass shrimp. South Carolina State Documents Depository.
  3. 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.