Every summer, the University of Texas Marine Science Institute (UTMSI) admits Research Experiences for Undergraduates (REU) interns to participate in exciting research, giving them valuable experience that will prepare them for careers in marine science. After choosing a research topic and mentors, they spend the summer working on their projects and give a final presentation at the REU Symposium at the end of the summer.
Chris Payne, a marine biology major from Boston University, is one such student. He decided to work with DROPPS because he realized the value of studying oil spills and wanted to help be a part of the solution to this complicated problem.
There have been many studies on how oil affects macrofauna, but not as many studies on the impacts it has to the base of the marine food chain: plankton. These tiny organisms are important for many reasons. Plankton are important contributors to primary and secondary production. Also, toxic species can cause harmful algal blooms when they are in large numbers. They also form important links in the marine food web, and finally, they provide organic matter to deep sea ecosystems through marine snow.
|Chris Payne presents at the REUfest|
2015 Summer Symposium
Credit: Lalitha Asirvadam
Chris’ research focused on these questions: What effect does oil and dispersant have on natural plankton populations? How do changes in oil and dispersant concentrations affect natural plankton communities? Chris worked closely with his mentors, Dr. Brad Gemmell and Dr. Ed Buskey from DROPPS, to try and find answers to these questions.
In preliminary experiments, Dr. Gemmell has looked at the dinoflagellate Prorocentrum and its ciliate grazers. He exposed them to oil and dispersants and observed changes in populations. His results indicated that dispersants inhibit ciliate growth which led to population increases in dinoflagellates. Chris wondered if similar results can be seen in natural plankton populations.
His study consisted of three experiments: two using nearshore water and one using offshore water. The water was filtered to remove large zooplankton. Each experiment used three treatments: filtered sea water, seawater with crude oil, and seawater with crude oil and dispersant. Both offshore and nearshore experiments were exposed to 20 µL Lˉ̄ ¹ of crude oil, while an additional treatment was conducted for nearshore water with 50 µL Lˉ̄ ¹ concentration of oil. A 20:1 ratio of crude oil to dispersant was used in all three experiments. For the nearshore experiments, 10 mL samples were taken daily and Chris counted diatoms, dinoflagellates, and ciliates using microscopy, FlowCAM, and flow cytometry. The offshore samples had to be settled in 50 mL settling chambers and were counted using microscopy.
For the 20 µL Lˉ̄ ¹ crude oil nearshore experiment, Chris found no significant differences among the total populations of the control, oil, and oil plus dispersant treatments. The 50 µL Lˉ̄ ¹ nearshore experiment, however, showed significant differences among the total populations of each treatment.
In summary, Chris observed that oil and dispersants have a negative effect on diatoms; however, dinoflagellates appear to be resistant to the toxicity of oil and dispersants. In addition, higher concentrations of oil have a more significant impact on plankton populations while offshore populations were more affected by 20 µL Lˉ̄ ¹ concentration of crude oil than the nearshore populations. And finally, a population of small (approximately 2 micron) organisms becomes much more abundant in oil and oil + dispersant treatments. It may be that small nanoplankton (such as Synechococcus) are resistant to oil and dispersant.
Chris gave his final presentation on August 5, 2015. He said that he learned a lot and enjoyed his time as an REU student at UTMSI. He is currently thinking about a future in marine conservation.
Research sponsored by the Gulf of Mexico Research Initiative