Exploring the Gulf of Mexico Deep Reefs with Megan Cook
July 17, 2013
By Megan Cook, Mission Blue Young Explorer
Megan will rejoin the E/V Nautilus in the Gulf of Mexico in late July further exploring hydrocarbon influx sites. Participate as the team explores the Gulf of Mexico Deep Reefs Hope Spot by sending in questions to www.NautilusLive.org or by following on Twitter or Facebook. ~ Ed.
Where is your favorite coral reef? I’m willing to bet you answered somewhere tropical and warm, where the sunshine glitters into clear, shallow water bathing polyps and divers alike. Nearby there might be a beach scene where drink umbrellas wouldn’t be out of place. That would have been my answer too, until last month…
Descending to the seafloor took the ROV Hercules over an hour. From the control van of the E/V Nautilus, I sat with my watch team from the Corps of Exploration as HD video poured in from the ROV Hercules. Colonial tunicates and other jelly-filled drifters glided into and past the frame. Through most of the water column it appears to be snowing; white plankton or dead tissue literally rain down into the deep. After the first fifteen minutes, the sunlight was gone. The ROVs hung in inky blackness; the temperature dipped below 4C and the water column above pressed nearly 1500 pounds on every square inch of every surface. A hard target was ahead on the sonar. This seascape was far removed from the coral scenes I knew, and yet as the ROV lights’ milky beams glanced the sea floor, ghostly fronds with tiny outstretched polyps combed the current at the edge of our view.
The rocky slab was covered in sunset-colored tufts. These feathery bundles and tall fans sprouted up like branching limbs. Growing in a world devoid of sunshine these deep water corals can’t rely on algae hitchhikers who use sunlight to feed their shallow water cousins. These corals have to catch every meal they eat. The thick bases of each colony braced feeding polyps into the current, sifting from the local superhighway of food and oxygen.
I had no idea what to expect from a deep sea community as the dives began, but as the camera inched closer I realized that my coral reef definition needed to expand. This deep sea reef was every bit as vibrant as reefs I’d snorkeled on. Among the coral bases were sea urchins and sea cucumbers. Shrimp and squat lobster climbed among the branches snapping at lunch and clams pinched themselves closed each time a conger eel fidgeted in his dugout home. The deep sea reef was so oddly familiar and yet entirely unique. The diversity and abundance of life made the reefs recognizable to any ocean enthusiast, like a familiar scene played by a new cast of characters. I go back to my original question- and definitely need to put deep sea reefs at the top of my favorites list.
Our chief scientist Dr. Erik Cordes of Temple University, a Principal Investigator in the ECOGIG consortium, led our exploration team to the deep sea reefs of the Gulf of Mexico. ECOGIG is a project funded by the Gulf of Mexico Research Initiative bringing together the nation’s best deep sea specialists to understand the ecosystem-wide impacts of oil and gas. Our mission was not only to explore these spectacular undersea communities, but to collect monitoring data to understand changes and community health through time. Cordes and team have been monitoring reefs in the Gulf for more than ten years, including publishing the first paper on definitive impacts to corals from the 2010 BP Deepwater Horizon/Macondo well blowout.
I was thrilled to join this expedition as a science communication fellow from the Ocean Exploration Trust. The Nautilus is a platform fitted with the most advanced technologies available to bring together the highest level science teams to go places on the seafloor never explored before. Exploration streams 24 hours/day over the internet to inspire young explorers and engage audiences around the world. Only a handful of people have the experience of seeing these habitats in person, but thousands more were part of the ECOGIG science team’s work through telepresence.
If you missed any of the action from the deep, here are some of the moments that amazed me in this alien deep world.
Old geezer corals:
Without the sunlight for photosynthesis, these corals survive entirely by capturing small prey and detritus in their tentacles. There isn’t an enormous amount to eat down here; life at this depth settles into slow-motion. Some of the sea fan colonies might be 500-600 years old while a black coral might live to 4,000 to 6,000 years old! Gorgonian corals lay down a protein called gorgonin in their bases, similar to rings in a tree trunk.
Corals: Condos for deep sea life
Both hard and soft corals thrive in the deep sea forming huge colonies and attracting all types of associated life. Wrapped tightly around the branches are brittle stars’ arms easily confused as worms or the novelty curly straws from a big-gulp soda. These opheroids, related to starfish, may spend their entire tendrillar life on a single branch of coral. Brittle stars eat the mucus coating a coral secretes, ridding its host of debris and bacteria.
These reefs are also important habitat for juvenile fish, both commercial and sport-fished throughout the Gulf of Mexico. Throughout the exploration we saw many fish species including tuna, orange roughy, and barrelfish.
Beyond photosynthetic depths, food becomes an increasingly scarce resource. The deeper we went, the smaller the fish got and the lower the diversity of large-bodied organisms. This fish was one of the most incredible creatures which crossed our path. With this tiny tadpole-body and huge upward facing mouth, this deep sea fish is ready to take advantage of any unsuspecting snacks that swim by. Additionally muscles take a lot of energy to maintain. The species isn’t wasting any extra energy on muscle mass with this thin frame and tadpole-tail.
RolyPolys that could beat up your housecat!
One of the biggest surprises of the expedition was the deep sea isopod sighting. This armored crustacean looks just like its terrestrial cousin you would find in the garden, the roly-poly. They also can roll themselves into a tight, plated ball when startled. In major contrast, the giant isopod can grown to over 14 inches long. An important scavenger, giant isopods eat anything from sponges and worms to whale falls.
Regional champion diversity
There are more coral species in the deep sea of the Gulf of Mexico than you could ever find snorkeling or diving in the shallows. There are more than 100 species of deep water coral in this region. Nearly a third (21) of the octocorals (67+) have been added to the list in only the last three years. During thirteen days of exploration, our team sighted most of those sampling 13 different species for further study. Several of our dives took us to regions of the seafloor never seen by human eyes. Even in relatively well-known monitoring zones, all it takes is a 90-degree turn to be charting new ground.
Shallow water coral live in preferred zones because of their tolerance for sunlight and wave action. In the deep, corals are instead found striated by water temperature. It’s impossible to lump all deep sea communities together as the species make-up is likely totally separate at 500m or 2000m. Around 500m temperature and water chemistry are well suited for mounding tumbleweed-like Lophelia to overtake rocks and surfaces. One dive site, Roberts’ Reef, has had Lophelia growing there for at least 300,000 years. Black corals (which are deceptively sunset toned) prefer colder, deeper water. These are the longest-lived family of corals forming thousands of year old communities. At over 2400m deep the ROVs were still illuminating large, healthy stands of soft coral.
Because coral polyps have no inner air spaces like ear drums in humans or swim bladders in fish, they handle changes in pressure well. So long as the temperature remained within their preferred range, live coral samples were raised from the deep and airlifted to research universities where they will continue to build our understandings of this unique place.
Tracking damage from the 2010 Deepwater Horizon oil spill
Cordes and his team had been working at some of these deepwater sites before the 2010 BP oil spill. Since the spill and in collaboration with ECOGIG partners, the team now returns frequently to image both affected and non-visually affected corals to track health over time. The value of a long-term data series like this cannot be underestimated. Because of the life history of so many slow-growing, slow changing creatures in the deep sea data will need to be collected for decades. The effects of our actions above the surface and under it will play out for years and changes may be hard to detect until decades of data are available. With the tiny percentage of exploration already completed, the deep sea is thick with opportunity for new generations of explorers to make their impacts.
The team collected high-resolution digital images of coral colonies, live coral samples, water samples, physical and chemical water profiles, and sediment for microorganism and bacteria research. The work understanding the deep sea is truly just beginning. Every dive has real potential for discovering something groundbreaking and building a better understanding of our planet.
I hope you’ll join me on the seafloor to see these deep water corals for yourself. More images and highlight videos are available online. Live exploration is streaming live from the deep around the clock at www.NautilusLive.org.