Hydrothermal seep-dwellers: large tubeworm “bush” with more than 14,000 tubeworms. Credit: Lisa Levin/NSF |
Decades
ago, marine scientists made a startling discovery in the deep sea. They
found environments known as hydrothermal vents, where hot water surges
from the seafloor and life thrives without sunlight.
Then they found equally unique, sunless habitats in cold areas where methane rises from seeps on the ocean bottom.
Could vents and seeps co-exist in the deep, happily living side-by-side?
No one thought so. Until now.
That’s
exactly what researchers uncovered during a submersible expedition off
Costa Rica. They’ve coined a new term to describe the ecosystem: a
hydrothermal seep.
A
description of the scientists’ findings, including a large number of
deep-sea species that previously had not been described, is published in
a paper by Lisa Levin of the Scripps Institution of Oceanography in La
Jolla, Calif., and colleagues.
The paper appears in the March 7, 2012, issue of the journal Proceedings of the Royal Society B: Biological Sciences.
Levin and the team were surprised to find a hybrid site in an area where only cold seeps had been reported.
“The
discovery shows that we still have much to learn about hydrothermal
vents and methane seeps and about the vast depths of the oceans,” said
David Garrison, director of the National Science Foundation’s (NSF)
Biological Oceanography Program, which funded the research.
“We need to re-think the boundary,” he said, “of where a vent begins or a seep ends.”
The
most interesting aspects of the site, said Levin, “are the presence of
vent-like and seep-like features together, a vast cover of tubeworms
across large areas, and a wealth of new species.”
Called
Jaco Scar, the site lies at a tectonic plate margin off Costa Rica.
There an underwater mountain, or seamount, is moving under the tectonic
plate.
Jaco Scar’s animals range from those that inhabit hot vents or cold seeps, to species that exist in both settings.
In addition to tube worms, the team documented deep-sea fish, mussels, clam beds and high densities of crabs.
Because
so little is known about the deep ocean, the researchers say it’s
likely that other hybrid or “mosaic” ecosystems remain undiscovered,
possibly with marine life specialized to live in such environments.
“Plenty
of surprises are left in the deep sea,” said Levin. “There are new
species, and almost certainly new ecosystems, hidden in the oceans.”
The human presence in Alvin, a submersible, deep-diving research craft was key to the findings.
“The
site had been visited by other researchers using remotely-operated
vehicles,” said Levin, “but it wasn’t until human eyes saw shimmering
water flowing under a tubeworm ‘bush’ that we really understood how
special Jaco Scar is.”
Co-authors
of the paper include Greg Rouse, Geoffrey Cook and Ben Grupe of the
Scripps Institution of Oceanography; Victoria Orphan and Grayson
Chadwick of the California Institute of Technology; Anthony Rathburn of
Indiana State University; William Ussler III of the Monterey Bay
Aquarium Research Institute; Shana Goffredi of Occidental College; Elena
Perez of the Natural History Museum in London; Anders Waren of the
Swedish Museum of Natural History; and Bruce Strickrott of the Woods
Hole Oceanographic Institution.
The research was also supported by the Center for Research in Marine Sciences and Limnology, University of Costa Rica.
