Oil Spills, Climate Change, and Grass Shrimp

Cheldina Jean, American University


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.


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.



My Days with the Shrimp

Deanna Hausman, The University of Texas at Austin

me with ray





In “What can baby shrimp teach us about oil spills,” I discussed the problem of UV enhanced toxicity of oil. In other words, the fact that UV rays can cause molecules in oil known as PAHs to become more harmful than they would be otherwise. I also discussed the fact that this summer, I will be studying the effects of oil toxicity on grass shrimp, or Palaemontes pugio, an important estuarine species that cycles nutrients through the food chain. Because oil spills are always complex, and organisms can be exposed to oil in many different ways, from the sediment they walk on to the water they swim through, a variety of experiments are needed to get a better understanding of this issue.


A few of the many PAHs- the compounds in oil that harm marine life Photo from: http://www.crawfordscientific.com/newsletter-2008-12-dedicated-HPLC-GC-columns-PAH-analysis.htm

The first and simplest of the experiments I conducted was the developmental test. In this test, I basically mixed oil and seawater in a giant blender, then took out the water with the oil dissolved in it. Then, I made several dilutions, creating several concentrations of the oily water. Then, I took 6-well plates and filled them up, and placed a single, 24-hour old shrimp in each well. Then, I put these plates in an incubator under UV and non-UV light, and waited for 4 days. After that, I moved the shrimp into clean water, counted how many died, and am currently monitoring them to see how the oil exposure in early life impacts their ability to grow into healthy juveniles.


Shrimp being monitored after initial oil exposure

Another experiment I conducted essentially followed the same procedure as above, but instead of watching them as they grew, I analyzed the shrimp after their 96-hour oil exposure to see whether the oil affected the concentration of a hormone, known as an ecdysteroid, that controls their molting. Essentially, if the concentrations of this steroid are off in a shrimp it can’t grow properly, so it’s very important!

I’m also conducting an oil sheen test. In this experiment, I place 40 larval shrimp in an aquarium, some caged on the bottom and some swimming freely, and then place an extremely thin oil sheen on top. One aquarium goes under UV light and the other goes under fluorescent light, and after exposure I analyze whether the sheens have had a harmful effect. Whether thin oil sheens are toxic is something that’s not very well understood in this species, so it will be very interesting to see the results.

Finally, I’m conducting an experiment to see what occurs when oil is mixed in with sediment. Essentially, this involves putting sediment from an estuary in a jar, adding oil, and tumbling it around so that the oil is completely mixed in. Then, the sediment is placed into beakers along with water and 24-hour old shrimp, and put under UV and non-UV light for 24 hours, in order to see what mortality occurs. This will perhaps be the most informative experiment, as grass shrimp spend most of their time on the seafloor, so if they’re going to be exposed to oil, it will likely be from the sediment they’re walking on.

In short, I have my hands full this summer! It will be very interesting to see the results. Hopefully, this will increase our knowledge of the harmful impacts oil spills can have to estuarine organisms, and allow NOAA and oil spill analysts to make better predictions of the long-range impacts of oil spills. Ultimately, this may help them make better clean-up decisions.

Thank you to my mentors, Dr. Marie Delorenzo and Dr. Paul Pennington, for their guidance. I’d also like to thank Katy Chung for all her help and expertise. This research is funded through the National Science Foundation.