November 23, 2009
Researchers find startling array of life in the ocean's abyss.
To date a total of 17,650 species are now known to live in frigid, nearly lightless waters beyond the photic zone—where enough light occurs for photosynthesis—approximately 200 meters deep. Nearly 6,000 of these occur in even harsher ecosystems, below depths of 1,000 meters or 0.62 miles down.
Just this year, CoML voyages to the Mid-Atlantic Ridge have collected remarkable specimens.
At 1,700 – 4,300 meters: Coryphaenoides brevibarbis, with tiny bones in its ear, known as otoliths, that have growth bands countable like tree rings to reveal the fish’s age. Comparison of age with size shows its growth rate and thus the amount of food in the neighborhood. Called the rat-tail, the fish lives on crustaceans it catches just above the seafloor. Photo courtesy of Rebecca Hunter.
The Mid-Atlantic Region expedition collected the largest 'dumbo' octopus to date. The specimen measured nearly two meters (six feet) across and weighted approximately 13 pounds. . As well as catching the largest specimen of Dumbo octopus ever recorded, researchers believe they may have also discovered a new species of Dumbo octopi.
Dumbo octopi, so named because they sport large fins that look like elephant's ears, are primitive animals also known as cirrate or finned octopus. They are one of the larger animals that inhabit this dark world.
Discoveries like these have been occurring every year since CoML began its expeditions in 2000. For example, in 2007 a voyage to the Gulf of Mexico uncovered an oil-eating tubeworm. At 990 meters, a robotic arm on the deep sea vessel lifted up a tubeworm from a hole only to find that as the species was lifted away from the hole, crude oil spilled both from the worm and the hole. Scientists now know that this unique species actually feeds on the chemicals contained in crude oil.
'New' Dumbo (Grimpoteuthis sp.). Photo courtesy of David Shale.
At this depth species are discovered by high tech instruments like remotely operated vehicles or autonomous underwater vehicles, known as ROVs and AUVs respectively. Species are caught on camera, sonar, or scooped up by robotic limbs. Some species are even caught using trawls and dredges, which require several kilometers of cable to reach the ocean's floor.
"The deep sea is the Earth's largest continuous ecosystem and largest habitat for life. It is also the least studied," says Chris German of Woods Hole Oceanographic Institution and ChEss (Biogeography of Deep-Water Chemosynthetic Ecosystems) co-chair. It is the least-studied because until recently there were few ways of actually reaching such depths, and even now the works is far from cheap or easy.
"Every deployment is a trip into the unknown, with often seasick scientists struggling to work amid high winds and 10 meter swells," says Mireille Consalvey of the New Zealand National Institute of Water and Atmospheric Research, and CenSeam (Global Census of Marine Life on Seamounts) project manager. "It can be a tough environment down there. I recall once the abject fear when our video imaging system snagged for 40 minutes on a rock face—the slow, scary process of recovering it, and the shared worry that our valued recording equipment would arrive at the surface battered and bent. Thankfully, the recorder survived the ordeal better than many of us and yielded brilliant new footage of this remote realm."
The payoffs, however, for so much time, energy, and funding can be huge. Recently scientists have discovered that the mud at the ocean's floor may be as diverse as "tropical forests".
Jumbo Dumbo (Cirrothauma magna). Photo courtesy of Mike Vecchione.
"The abyssal fauna is so rich in species diversity and so poorly described that collecting a known species is an anomaly," says Census of Diversity of Abyssal Marine Life expert David Billett of UK's National Oceanography Centre. "Describing for the first time all the different species in any coffee cup-sized sample of deep-sea sediment is a daunting challenge."
According to Robert S. Carney of Louisiana State University such discoveries overturns our very understanding of diversity: "Some scientists have likened deep mud's biodiversity to that of tropical forests. In college I was taught that high biodiversity is a function of habitat diversity - many nooks and crannies. It is, however, hard to imagine anything as monotonous, nook-less and cranny-less as deep-sea mud."
Carney is co-leader with Myriam Sibuet of France of the Census project COMARGE (Continental Margin Ecosystems on a Worldwide Scale), which studies life along the world's continental margins.
Yet even deep-sea ecosystems—miles below the surface—have been impacted greatly by human activity.
"There is both a great lack of information about the 'abyss' and substantial misinformation," explains Carney. "Many species live there. However, the abyss has long been viewed as a desert. Worse, it was viewed as a wasteland where few to no environmental impacts could be of any concern. 'Mine it, drill it, dispose into it, or fish it - what could possibly be impacted? And, if there is an impact, the abyss is vast and best yet, hidden from sight.' Census of Marine Life deep realm scientists see and are concerned."
Of CoML's fourteen field projects—to explore and catalogue the world's marine life—five of them are heading beyond the layer of light. These field projects alone incorporate 344 scientists from 34 countries.
When the census finishes up next October, CoML will have undertaken 210 expeditions in these harsh and surprising ecosystems below the light of the sun.
At 2,000 to 2,500 meters: A bizarre, elongated orange animal identified as Neocyema -- only the 5th specimen of the fish ever caught and never before on the mid-Atlantic Ridge. Photo courtesy of David Shale.
What appears to be an ancient gold treasure is a magnified crustacean, a tiny copepod collected this year from the Atlantic abyss (© Büntzow/Corgosinho).
At 1,000 meters and below: abundant colorful coral. Photo courtesy of NIWA, New Zealand's Ministry of Fisheries & Foundation for Research Science and Technology, and Land Information New Zealand.
Cute Dumbo (Grimpoteuthis discoveryi). Photo courtesy of Mike Vecchione.
At 2,750 meters in the Northern Gulf of Mexico: an odd transparent sea cucumber, Enypniastes, creeping forward on its many tentacles at about 2 cm per minute while sweeping detritus-rich sediment into its mouth. Photo courtesy of Larry Madin, Woods Hole Oceanographic Institution.