Deep Seafloor Seep Habitats Probed

Getting to the Bottom of the (Organic) Matter

During the previous two years the Minerals Management Service (MMS) and the NOAA Ocean Exploration had expeditions to the continental slope in the Gulf of Mexico to explore and survey areas heretofore not seen.

Deep, deep areas.

The “cruises,” as they were called, used manned submersibles to explore first-hand the hard-bottom habitats and seeps located distances 3,280 feet down.

The intent of the expeditions – one aboard the Alvin in 2006, and most recently, the Jason, in 2007 – was to learn more about chemosynthetic communities that are associated with surface gas hydrates, which may be used as a clean-burning fuel in the future.

Specifically, there was work done on the chemosynthetic habitats, the diversity of the animal communities, their interaction with the environment and the biological processes that facilitate or hamper these connections.

Harry Roberts, an AAPG member and Boyd Professor in the Department of Oceanography and Coastal Sciences and director of the Coastal Studies Institute at Louisiana State University, was on both cruises.

The findings, he said, show that these chemosynthetic communities are, in fact, supported by sulfide and hydrocarbons.

Planning Pays Off

Before the expeditions, Roberts, in conjunction with AAPG members Bill Shedd and Jesse Hunt (both of MMS), reviewed large volumes of 3-D seismic data held by the MMS New Orleans office and used for regulatory purposes of the agency.

Roberts says both, especially Shedd, were invaluable in helping plan and direct dives.

Image Caption

Getting ready to go deep: Scientists preparing for another dive in the Alvin, a mission to better understand the dynamics and characteristics of the Gulf of Mexico slope. Photos courtesy of Harry Roberts

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During the previous two years the Minerals Management Service (MMS) and the NOAA Ocean Exploration had expeditions to the continental slope in the Gulf of Mexico to explore and survey areas heretofore not seen.

Deep, deep areas.

The “cruises,” as they were called, used manned submersibles to explore first-hand the hard-bottom habitats and seeps located distances 3,280 feet down.

The intent of the expeditions – one aboard the Alvin in 2006, and most recently, the Jason, in 2007 – was to learn more about chemosynthetic communities that are associated with surface gas hydrates, which may be used as a clean-burning fuel in the future.

Specifically, there was work done on the chemosynthetic habitats, the diversity of the animal communities, their interaction with the environment and the biological processes that facilitate or hamper these connections.

Harry Roberts, an AAPG member and Boyd Professor in the Department of Oceanography and Coastal Sciences and director of the Coastal Studies Institute at Louisiana State University, was on both cruises.

The findings, he said, show that these chemosynthetic communities are, in fact, supported by sulfide and hydrocarbons.

Planning Pays Off

Before the expeditions, Roberts, in conjunction with AAPG members Bill Shedd and Jesse Hunt (both of MMS), reviewed large volumes of 3-D seismic data held by the MMS New Orleans office and used for regulatory purposes of the agency.

Roberts says both, especially Shedd, were invaluable in helping plan and direct dives.

Further, as to this working environment between MMS and NOAA, Roberts was impressed and heartened.

“Both were very supportive of the objectives of the overall project,” Roberts said, “and went out of their way to help the researchers meet their research goals.”

Having a better understanding of the Gulf’s deepwater regions is important – some might say necessary – because seven of the top 20 oil fields in the United States (ranked by liquids proved reserves) are 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.

Roberts, a marine biologist, says he chose the specific dive sites based on analysis of 3-D seismic data.

Further, Roberts believes the Alvin, where he was co-chief scientist with Charles Fisher from Penn State, could be classified more as reconnaissance, while the Jason is designed more for detailed sampling and photo documentation.

Both provided data that is still coming in.

Bonus Coverage

And now that more of the data is in … what’s new?

First, a little history. “The objective was to extend our knowledge of chemosynthetic communities and the hydrocarbon seep/vent environments that support them from the upper slope (<1,000 meters water depth) to the deepest parts of the northern Gulf,” Roberts said.

In fact, according to MMS, 50 percent of leased acreage in the GoM is in water greater than 1,000 feet.

The widespread existence of these hydrocarbon seep habitats and the specialized communities supported by them on the little-known middle and lower parts of the continental slope were, in fact, evident and abundant.

“We found that both strike and dip variability in geology and geochemistry of deep seep settings supports surprisingly high density and diversity in both macrofauna and microfauna.”

Roberts said that by the end of the latest cruise it was apparent that hydrocarbon seepage supports abundant production of biomass in the deepest parts of the Gulf and that the specialized communities are not confined to the upper slope.  

“In the process of making these discoveries concerning the biology, we as geologists and geophysicists significantly improved our knowledge of the seafloor,” he said, “and what the remotely sensed 3-D seismic data was telling us about migration pathways and seafloor response.”

That’s All, Folks (?)

Perhaps somewhat surprisingly, as productive as the expeditions were, there are no plans for future ones.

Roberts said at current, funding will support only data analysis, interpretation and report writing.

He adds, however, that MMS has another study on deepwater corals that could dovetail with this project very well.

“The team of geoscientists who worked on this project feels confident that the methodologies used on previous dive-related studies and improved on the CHEMO III study could be used effectively to find the most probable deepwater coral habitats.”

All in all, Roberts was impressed by the deep-diving ROV.

“This was only my second time … and I must say I was impressed with the capabilities,” he said. “It had a full complement of cameras and sampling capability.”

While his scientific experiences on both the Alvin and the Jason have been and will continue to be chronicled, he does have a preference – albeit a purely personal one.

“The one thing I like about the Jason is that four hours into the dive when you had to go to the toilet, you just got out of your chair in the recording van and walked to the ship’s toilet.

“This is not easy to do when you’re submerged 8,000 feet in Alvin.

More About Harry Roberts

Harry Roberts leads a group of geologists and geoscientists who will present both a poster and paper at the GCAGS Annual Convention, which will be held Oct. 21-23 in Corpus Christi, Texas.

The poster “Exploration of the Deep Gulf of Mexico Slope Using DSV Alvin: Site Selection and Geologic Character” will be presented by the group from 9-11 a.m. on Tuesday, Oct. 23.

A paper on the same subject will be given at 4:30 p.m. that same day.

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