After arriving at Green Canyon 852, the Jason group conducted a bathymetry survey of the site dubbed the 'Coral Garden.' At full resolution, the SM2000 multibeam mounted on the underside of the ROV enables scientists to spot objects as small as 0.5m. Click image for larger view and image credit.
Madrepora oculata in the foreground and Lophelia pertusa in the upper-right corner in the background. Click image for larger view and image credit.
Back to the Coral Garden
June 24, 2007
Erik Cordes
Harvard University
27° 6.56 N
91° 9.97 W
Chirostylid crab hanging onto a large bamboo coral colony at the edge of the Coral Garden dive site. (Quicktime, 2.1 Mb.)
This is an up-close view of Madrepora, one of the hard coral species found at the Coral Garden. (Quicktime, 2.1 Mb.)
Scientist noticed a impressive sea-whip at dive site Green Canyon 852 "Coral Garden". (Quicktime, 1.1 Mb.)
During last year’s cruise, we visited a newly discovered site containing a diversity of corals in a variety of shapes, sizes and colors – hard corals, sea fans, bamboo corals, and black corals to name a few. We dubbed that site in Green Canyon 852 (GC 852), the Coral Garden. Though last year’s Alvin dives were impacted by strong currents and complications with navigation, they provided an important foundation of information upon which to plan this year’s sampling activities. We hoped that this year’s return visit with the Ron Brown and Jason would provide an even better opportunity to characterize the full extent and composition of this area.
After completing two Jason lowerings for a total bottom time of approximately 77 hour and 14 min, we accomplished many of our objectives and have come away with much of the information that we wanted.
The extent of the coral area and diversity of the associated fauna is much greater than we anticipated. In addition to the Enallopsammia rostrata deep-water coral that we collected this year, we now have samples from colonies of Lophelia pertusa and Madrepora oculata from this year’s dives. We believe this may be the deepest record for Lophelia pertusa in the Gulf of Mexico (1410 m).
These deep-water hard corals create reef-like structures like the hard corals in shallow water. However, unlike shallow-water hard corals that require sunlight to produce energy, deepwater hard corals are suspension-feeding animals. The corals at GC 852 cannot photosynthesize since they live below the photic zone, at depths to which light does not penetrate.
A sea-whip located at the Coral Garden. Scientists spent several minutes examining the different organisms living in association with this single animal. Click image for larger view and image credit.
After collecting just the anterior end of the sea-whip, this close-up image centered on the central axis of the sample, was taken back onboard the Ron Brown. Click image for larger view and image credit.
A video grab from the Jason science camera’s video of the Aquapix macro-camera taking close up images of some of the organisms in the Coral Garden. Click image for larger view and image credit.
The structure created by the corals is inhabited by a number of other species, most of which we do not see at the nearby seeps. The lack of overlap between the deepwater (>1000m) chemosynthetic tubeworm and mussel communities and coral communities at similar depths is inline with our previous work at the upper slope seep sites (~ 500m depth). There is very little similarity between these communities even if they are just separated by a few meters! The species in tubeworm and mussel communities are far more tolerant of the high sulfide and methane and low oxygen conditions, typically found in seeps.
To supplement the physical samples from the coral communities at this site, we also spent considerable time taking both in-situ video and still imagery of the habitat. After the at-sea portion of this expedition is complete, we will spend numerous hours going through the imagery to learn more about the community ecology of the hard and soft corals at GC 852.
Please check back early next week after we have an opportunity to post several of favorite still images and video clips.
