Deep-Ocean Impact of the Deepwater Horizon Explosion Revealed
Compelling evidence of the impact of the Deepwater Horizon oil spill on deep-sea corals will be published online in the Early Edition of the journal Proceedings of the National Academy of Sciences during the week beginning March 26. The diverse team of researchers, led by Penn State Professor of Biology Charles Fisher, used a wide range of underwater vehicles, including the research submarine Alvin, to investigate the corals. They also used comprehensive two-dimensional gas chromatography to determine precisely the source of the petroleum hydrocarbons they found.
Other researchers on the team include the paper’s lead author, Assistant Professor of Chemistry Helen White of Haverford College, Erik Cordes of Temple University, and Timothy Shank and Christopher German of the Woods Hole Oceanographic Institution (WHOI), which operates the Navy-owned submersible Alvin. Fisher, Cordes, Shank and German are co-authors of the study, along with 10 other scientists from WHOI, Penn State, Temple and the U.S. Geological Survey.
The study’s findings are significant for a number of reasons, White said.
“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, we have learned that its impacts 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 at distances 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 south west 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,” said 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.”