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.

PAHs

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.

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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.