The Hidden World of Seamounts (Making Waves podcast, 5.13.10)
Making Waves podcast: Tune in to our extended interview with Dr. Peter Etnoyer, NOAA marine biologist, about the hidden world of seamounts.
Lophelia, Candidella, and solitary cup corals with brittle stars, crinoids, and various sponges found during a 2004 NOAA expedition to a seamount chain off the coast of New England.
A new estimate of the total number of large and small seamounts found around the world suggests that these massive underwater mountains collectively form one of the largest habitats on Earth — encompassing more of the planet’s surface than South America.
In a report published in the April issue of the journal Oceanography, lead author Dr. Peter Etnoyer, a NOAA marine biologist, compared the global footprint of seamounts with that of terrestrial habitats such as deserts, tropical forests, or tundra.
'This is the first time that we've actually tabulated the global areas of marine and terrestrial habitats in one place," Etnoyer said.
The results surprised Etnoyer's team of researchers. Taken together, seamounts encompassed about 28.8 million square kilometers of the Earth's surface. That’s larger than deserts, tundra, or any other single land-based global habitat on the planet.
Seamounts — undersea mountains formed by volcanic activity — were once thought to be little more than hazards to submarine navigation. Today, scientists recognize these structures as biological hotspots that support a dazzling array of marine life.
While it has been long known that seamounts are abundant around the world, only rough estimates of the total number of these geologic features exist. That's in part because seamounts are located in deep waters, invisible to the naked eye. It's also in part due to the vast size of the ocean.
The biological richness of seamount habitats results from the shape of these undersea mountains. Thanks to the steep slopes of seamounts, nutrients are carried upwards from the depths of the oceans toward the sunlit surface, providing food for creatures ranging from corals to fish to crustaceans.
"I like to think of seamounts as a riot of life above in the water column and below in the benthic habitats. I think of them as Hawaii, but underwater," he said, "Everything you might see around Hawaii in the shallow waters is something you’d also see around a seamount in the deep, cold, dark waters."
Many people are surprised to learn that corals, in particular, are found in such deep, dark, and cold places. Etnoyer said that these slow-growing, fragile animals can live for extraordinary lengths of time. Some of the black corals found on the Cross Seamount in Hawaii, for example, may be up to 4,000 years old.
While large and small seamounts may be a prominent feature of our planet, Etnoyer said that only around 250 individual seamounts have been biologically sampled. And since each one of these seamounts are so large, the biological samples collected from manned and unmanned submersibles are miniscule.
Documenting the abundance and variety of life on one single seamount, he said, is "like trying to describe a a Monet painting from three bristles of a brush."
"We couldn’t hope to understand its enormity if we dove on it every day for a year. We still would have sampled a very small amount. So these are truly massive features, and that's why, when you add them all up, they are larger than the continent of South America. It's just an enormous and unknown habitat."
Etnoyer is a marine biologist with NOAA's Center for Coastal Environmental Health and Biomolecular Research, part of the National Centers of Coastal Ocean Science.