The Alvin submersible begins
its descent to 1,200 meters
Photo courtesy of Gavin Eppard, WHOI
To borrow a baseball term, recently the Minerals Management Service (MMS), along with the NOAA Ocean Exploration, went deep.
How deep? About seven times farther than the longest of Barry Bonds’ blasts -- 3,280 feet (1,000 meters) -- to the floor of the Gulf of Mexico.
Specifically, the project, “Expedition to the Deep Slope,” used manned submersibles in May-June to explore and survey for the first time the hard bottom habitats and seeps located on the lower continental slope of the Gulf.
The intent was to learn more about the chemosynthetic communities that are commonly associated with near surface or surface gas hydrates, which have been suggested as a clean-burning fuel for the future.
And while the Gulf was the region targeted, the team involved in studying a resource that could eventually have global significance was truly international: “Deep Slope” attracted scientists from as far away as France, Germany and Russia.
AAPG member Harry Roberts, co-chief scientist at Louisiana State University (where he teaches and advises graduate students in the Department of Oceanography and Coastal Sciences), said the project was unique not just because of what they were looking for, but how they went looking for it.
“Very little direct observation and sampling using a manned submersible had been done” in past expeditions of this type, said Roberts, who was on the trip. “The objectives were to study the communities and surface geology and geochemistry of natural hydrocarbon seeps and vents.”
MMS, part of the Department of the Interior, oversees the production of about 23 percent of the natural gas and 30 percent of the oil produced in the United States, and is generally responsible for the management of offshore energy and minerals on the 1.76 billion acres of the Outer Continental Shelf. It spent more than $3 million on this expedition trying to find “essential” information on “the ecology and biodiversity of these deep-sea communities,” said Penn State professor Chuck Fisher, another of the project scientists.
The Gulf’s northern and northwestern continental slope are the most mature deepwater oil and gas provinces in today’s oceans -- and clearly, the Gulf is prolific. But naturally occurring fluid and gas expulsion processes not only produce unusual chemosynthetic communities, they also can cause geohazards. As such, federal law requires oil and gas companies to both avoid and protect the chemosynthetic communities.
It’s not unlike the warnings given by your local utility company: Call before you dig.
“It is to everyone’s benefit,” says Roberts, who believes that good working relationships between the groups are essential, “to follow the rules currently on the books that protect the environment, but to also allow for aggressive exploration and production to move forward into even deeper water of the Gulf.”
A Complex Environment
 This stunning octopod seemed
quite interested in Alvin’s port
manipulator arm. Those inside the
sub were surprised by the
octopod’s inquisitive behavior.
Photo courtesy of Bruce Strickrott
Adding to the urgency of understanding what’s down below is the fact that seven of the top 20 oil fields in the United States (ranked by liquids proved reserves) are now located in federal deepwater areas.
According to MMS, deepwater fields in the Gulf of Mexico contribute 1 to 1.6 million barrels of oil a day produced in federal waters in the Gulf of Mexico.
Two teams -- consisting of 25 scientists, including microbiologists, physiologists, ecologists and a middle school science teacher -- used an R/V Atlantis and the Alvin submersible to dive on sites, as Roberts mentioned, never visited “in person” before. A professional crew based at Woods Hole Oceanographic Institution maintained and operated the Alvin.
Once there, the collection of scientists tried to answer the following:
- Where are chemosynthetic habitats located?
- What is the diversity of animals living in these exotic communities?
- How do these species interact with each other and with their environment?
- How are chemosynthetic communities in different parts of the world’s ocean connected?
- How do physical and biological processes facilitate or hamper these connections?
Currently, there are 15 structures operating in water depths greater than 1,000 feet, and Roberts says most of the work in the last decade has concentrated on the upper slope, above that height.
“We really didn’t know if chemosynthetic communities would be plentiful below this depth,” he said. “They are!”
Specifically, he says, “The diversity of animals was greater than we expected. Many new deepwater life forms are now in the process of being described and entered into the scientific literature.”
Some of the areas explored are those that will soon be drilled for oil and gas by energy companies, Roberts said.
Efficient Effort
Roberts said this trip was not only a success, but efficient.
“Little time was wasted traveling over featureless mud bottom,” he said, as all sites selected had seepage and chemosynthetic communities.
Both cross-slope and along-slope variability in chemosynthetic communities, as well as geologic characteristics, were tested, and the results emphasized the dynamic geologic framework of the northern Gulf’s continental slope, where the interplay of salt that deforms when loaded with sediment has created many “leak points for oil and gas to reach the modern seafloor.”
Roberts, whose work specializes in developing a detailed understanding of both the geologic and biologic impacts of fluid and gas expulsion on the modern sea floor, said these sites support unusual biologic communities as well as exotic surficial geology such as mud volcanoes, rocky mounds and hardgrounds, and brine streams and lakes.
Data will now be studied, but already the enthusiasm is evident for the project’s next step.
“Many of the organisms were new species,” he said. “We will go back next year.”
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