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.

 

My Days with the Shrimp

Deanna Hausman, The University of Texas at Austin

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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.

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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.

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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.

Catch of the Day(s)

Melanie Herrera, University of Maryland College Park

South Carolina is known for its iconic southern cuisine, including a staple of fresh seafood which fuels the buckets of shrimp & grits and “catch of the day”. In order to support this huge industry (and fill the bellies of every South Carolinian), I am conducting an experiment to figure out where this seafood is holing up prior to its demise. Dr. Harold, his graduate student, Mary Ann McBrayer, and I are out on Grice Beach collecting fishes, crabs, shrimps, and much more in order to figure what exactly is there… And what they are using to survive.

Using a seine net, we encircle marine animals in dense and sparse patches of an invasive sea grass, Gracilaria, for collection. We hypothesize that Gracilaria is helping the local economy (a surprising contribution from an invasive species) by creating refuge for young animals. On the beach, we submerge separate samples of animals (from dense versus sparse areas of Gracilaria) into a euthanizing solution to bring them up to the lab for preservation and analysis (Figure 1).

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Figure 1: An example of animals caught in separate habitats at Grice Cove. The left exhibits animals caught in a dense area of Gracilaria and the right exhibits animals caught from a sparse area of Gracialaria. Credit: Melanie Herrera

In the lab, separate samples (dense versus sparse) undergo a few transfers into different fixatives (10% seawater formalin, 25% isopropyl, and 50% isopropyl consecutively) to keep the fish from decaying. After this preserving process, fish and other animals are separated and categorized by family, genus, and species. This categorization enables us to identify and analyze what types of animals and how many of each are using different habitat. Our analysis will give us insight on what type of habitat, either patches dominated by Gracilaria or areas with more open water, benefits fish. Specifically, we will be able to identify if Gracilaria is more advantageous to young fish or if their survivorship is independent from their habitat.

So far, we have collected lots of pipefish, narrow skinny fish that resemble a hair strand-size snake, Atlantic Silversides, a fish that looks exactly like it sounds, and more shrimp than anyone needs (Figure 2). Although some of these animals do not directly contribute to the seafood industry, its presence in the Charleston Harbor can tell us a lot of things. For example, we have seen some fishes that usually stay in warmer waters in the Southern U.S. Their expanding habitat can lead us to some more hypotheses on climate change and warm weather moving northward. In addition, we can find out if Gracilaria has a stake in rearing economically important fish in the future.

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Figure 2: (From left to right) Pipefish, Atlantic Silversides, and Grass Shrimp caught for analysis.Credit: Melanie Herrera

Thank you so much to my mentor Dr. Tony Harold and his lab for his advice and guidance. Thank you to Mary Ann McBrayer for helping me facilitate this project. This research is funded through the National Science Foundation and College of Charleston’s Grice Marine Lab.