For Immediate Release
March 26, 2012
Office of College Communications
Woods Hole, MA—Six scientists from Woods Hole Oceanographic Institution (WHOI) have contributed to a new report finding "compelling evidence" that the Deepwater Horizon oil spill has impacted deep-sea coral communities in the Gulf of Mexico.
Their study, “Impact of the Deepwater Horizon oil spill on a deep-water coral community in the Gulf of Mexico," published today in the journal Proceedings of the National Academy of Sciences USA, utilized a wide range of underwater vehicles, including the submarine Alvin, to investigate the corals and comprehensive two-dimensional gas chromatography to determine precisely the source of petroleum hydrocarbons found.
Lead author Helen White, an assistant professor of chemistry at Haverford College and a graduate of the MIT-WHOI Joint Program in oceanography, was part of a diverse team of researchers, led by Charles Fisher from Penn State University, that included Walter Cho from Gordon College, Erik Cordes from Temple University, Tim Shank and Chris German from WHOI, and six other scientists from Penn State, Temple, and the U.S. Geological Survey.
The study’s findings are significant for a number of reasons, White says. “These biological communities in the deep Gulf of Mexico are separated from human activity at the surface by 4,000 feet of water. We would not expect deep–water corals to be impacted by a typical oil spill. But the sheer magnitude of the Deepwater Horizon oil spill and its release at depth make it very different from a tanker running aground and spilling its contents. Because of the unprecedented nature of the spill, its impacts, we have learned, are more far-reaching than those arising from smaller spills that occur on the surface.”
The study grew out of an initial research cruise to the Gulf led by Fisher in late October 2010—approximately six months after the Deepwater Horizon oil spill. This expedition was part of an ongoing study funded by the Bureau of Ocean Energy Management and the National Oceanic and Atmospheric Administration’s Ocean Exploration and Research program. Using the remotely operated vehicle (ROV) Jason II, the team examined nine sites greater than 20 kilometers from the Macondo Well and found deep-water coral communities unharmed. However, when the ROV explored another area 11 kilometers to the Southwest of the spill site, the team was surprised to discover numerous coral communities covered in a brown flocculent material and showing signs of tissue damage.
“We discovered the site during the last dive of the three-week cruise,” says Fisher, a biologist and the chief scientist of this mission. “As soon as the ROV got close enough to the community for the corals to come into clear view it was clear to me that something was wrong at this site. I think it was too much white and brown, and not enough color on the corals and brittle stars. Once we were close enough to zoom in on a few colonies, there was no doubt that this was something I had not seen anywhere else in the Gulf: an abundance of stressed corals, showing clear signs of a recent impact. This is exactly what we had been on the lookout for during all dives, but hoping not to see anywhere.“
These coral communities were at a depth of 4,300 feet, in close proximity to the Macondo well, which had been capped three months previously after spilling an estimated 160 million gallons of oil into the Gulf. The timing and unprecedented nature of this observation suggested that the visual damage resulted from the Deepwater Horizon oil spill.
The team was determined to find answers. On December 8, barely a month after returning from sea, the scientists set out on a second cruise to the Gulf.
It is rare for researchers to get the opportunity to return to a site so quickly. Making that trip and the subsequent study possible was funding from the National Science Foundation’s RAPID Collaborative Research grant program, which aids scientists seeking to respond quickly to urgent issues such as natural disasters or crises resulting from human activity; for example, an oil spill.
Joining this second research cruise, again headed by Fisher, was Helen White, whose expertise as a geochemist was key to the interdisciplinary effort. “It is easy to see the impact of oil on surface waters, coastlines and marine life, but this was the first time we were diving to the seafloor to examine the effects on deep sea ecosystems,” says White, who directs the new Tri-College Environmental Studies Program at Haverford College.
To examine the deep water, the team employed the autonomous underwater vehicle, Sentry, to map and photograph the ocean floor and the deep submergence vehicle, Alvin, to get a better look at the distressed corals. Alvin holds a pilot and two passengers, and is equipped with viewports and cameras. Alvin also has robotic arms that can manipulate instruments to collect samples. During six dives in Alvin, whose manipulator claws were modified with a cutting blade, the team collected sediments and samples of the corals and filtered the brown material off of the corals for analysis. “Collecting samples from the deep ocean is incredibly challenging, and Alvin is crucial to this kind of work,” says White, who got the chance to observe the corals up close onboard the submarine during one of the scheduled dives.
Because oil can naturally seep from cracks in the sea floor of the Gulf, pinpointing the source of petroleum hydrocarbons in Gulf samples can be challenging to scientists, especially since oil is comprised of a complex mixture of different chemical compounds. However, there are often slight differences in oils that can be used to trace their origin. To identify the oil found in the coral communities, White worked with Christopher Reddy and Robert Nelson at WHOI using an advanced technique called comprehensive two-dimensional gas chromatography, which was pioneered at WHOI by Reddy and Nelson for use in oil spill research. The method, which separates oil compounds by molecular weight, allows scientists to essentially “fingerprint” oil and determine its source.
Dr. Walter Cho, a postdoctoral investigator in the laboratory of Dr. Timothy Shank at WHOI and an assistant professor of biology at Gordon College, participated in both the cruises and analyzed the invertebrate associates of the deep-sea corals—identifying them using morphological and molecular techniques, as well as characterizing changes in their behavior and morphology. "I was studying the animals that lived on the corals, mainly brittlestars. I identified them based on their morphology as well as molecular data comparing how they changed in their appearance and behavior between the different cruises."
This exacting petroleum analysis coupled with the analysis of 69 images from 43 individual corals at the site, performed by Pen-Yuan Hsing, a graduate student of Charles Fisher’s at PSU, yielded strong evidence that the coral communities were impacted by oil from the Macondo well spill.
“These findings will have a significant impact on deep water drilling and the monitoring of oil spills in the future,” White says. “Ongoing work in the Gulf will improve our understanding of the resilience of these isolatedcommunities and the extent to which they are affected by human activity. Oil had a visible effect on these corals and it is important to determine if they can rebound.”
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