The Deep Submergence Vehicle Alvin is shown working at the coral site found to be impacted by the oil spill from the Macondo well in the Gulf of Mexico. Researchers, led by Penn State University biologist Charles Fisher, used a wide range of underwater vehicles, as well as comprehensive chemical-analysis techniques to determine precisely the source of the petroleum hydrocarbons they found on the corals. Credit: Image courtesy of Chuck Fisher of Penn State University and Timothy Shank of WHOI; deep-sea time-lapse camera system provided by WHOI-MISO. |
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 km from the Macondo Well and
found deep-water coral communities unharmed. However, when the ROV
explored another area 11 km 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.”
One of the impacted corals with attached brittle starfish. Although the orange tips on some branches of the coral is the color of living tissue, it is unlikely that any living tissue remains on this animal. Credit: Lophelia II 2010, NOAA OER and BOEMRE |
These
coral communities were 4,300 feet deep, 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. Because
the timing and unprecedented nature of this observation suggested that
the damage observed visually resulted from the Deepwater Horizon oil
spill, the scientists rapidly organized a second research cruise, which
began on Dec. 8, 2010, barely a month after their return to land
following their initial discovery.
Joining
this second research cruise, again headed by Fisher, was White, whose
expertise as a geochemist was key to the interdisciplinary effort. This
rare opportunity for the researchers to return to a deep-water site so
quickly for the subsequent study was made possible with 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.
To
examine the deep water, the team used the autonomous underwater vehicle
Sentry to map and photograph the ocean floor, and the deep-submergence,
3-passenger, robotic-armed vehicle Alvin to get a better look at the
distressed corals. During six dives in Alvin, the team collected
sediments and samples of the corals and filtered the brown material off
of the corals for analysis.
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.
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 Fisher’s at Penn State—yielded strong evidence that
the coral communities were impacted by oil from the Macondo well spill.
Fisher
said these findings confirm a serious impact from the spill on the
animal communities in the deep sea more than seven miles from the
Macondo well. He added, “Our ongoing work in the Gulf will allow us to
better understand the long-term effects of the spill on the deep sea,
and to constrain the footprint of the impact zone for deep-water corals
around the Macondo well.”
Source: Penn State University
