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| projo.com |
Digital Extra: Mountains in the Sea |
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 A daily logbook of explorations of an underground range off Cape Cod.
Cruise Log, Day Ten: Stabilizing the system 05.19.2004
Mary Grady
ROV pilot Todd Gregory and Mark DeRoche work
to repair the manipulator arm.
Video Watch live images of the expedition, scheduled to streamed from 9 a.m. to 9 p.m. daily. NOAA will also be broadcasting live programs for an hour a day from the control van, with teachers and scientists interacting live with students on shore Late Sunday night, Hercules passed its previous depth record, on its way down to Kelvin Seamount. But around midnight, when it reached the seafloor 4,000 meters deep, it was immediately clear that all was not going well. "The manipulator arm was evidently not working," University of Connecticut scientist Peter Auster said the next morning. "And some of the foam flotation had cracked, so the vehicle lost its neutral buoyancy. Now it was negatively buoyant, and the only way to keep it off the seafloor was to run the thrusters. That just kicks up dust and we can't get good video, so there was no point in even trying to stay down there." It took about an hour for the ROV operators to stabilize the equipment and begin the ascent, so the science team got a brief look around from the landing site. "We saw a few spiky little corals, a couple of fish, some sponges," chief scientist Les Watling said. "But we didn't really get to see much." It had taken about four hours to reach the 4,000-meter depth, and it took another four to bring Argus and Hercules back on deck. The engineers immediately set to work on the problems. ROV pilot Todd Gregory drained and checked the hydraulic system, and discussions began about how to address the problems with the foam flotation blocks, one of which had ruptured. Part of the answer was to remove some of the ballast from Hercules, so it could maintain neutral buoyancy with less foam. The ROVs stayed on deck all day Monday getting checked and repaired, while the seas were building and the sky was filling with clouds. By evening, we had encountered a low pressure system and the ship was rocking and heaving. The decision was made to let everyone get a good night's sleep. Tuesday morning, Argus and Hercules went back into the water, when the front had passed and the weather was even more calm than we've seen yet, with clear blue skies and the ocean like a lake. Where are the babies? Last year, when the manned submersible Alvin visited Manning Seamount, two sets of 10 basalt blocks, each one about six inches square, were left behind on the seafloor. One set was dropped in what was dubbed "the coral forest," and the other set on the "plains" nearby. The plan was to come back at some future date and see if any new corals were growing on them. "This is all about answering the question, 'Where are the babies?', " said Lauren Mullineaux, a researcher with Woods Hole Oceanographic Institute who designed the experiment. "Because it seems when we go looking, we see only adult corals. So that raises the question, how are they reproducing? If they are slow to reproduce, then that means that if anything happens to the adults, the corals may not be able to recover." Last week, Hercules retreived half of those blocks, five from each set, and WHOI research assistant Susan Mills went right to work examining each one under the microscope. Yesterday, Mills took out a notebook of data sheets to show me what she found. "Lots of gastropods, two varieties of anemones, some kind of slimy, dirty, empty pouch that had been left behind by something, a couple of polychaetes - maybe scale worms, but I'm not certain - a couple of isopods, that looked the same on blocks from both sites. A thin worm tube, but no worm. A tube with tentacles! I'm not sure what that was, but that's what I wrote down. Some snails, maybe predatory. Most of these were things that could have just crawled onto the blocks. But we did find a caprellid, a juvenile stalked crinoid - I can show you a picture, it's adorable - and some polynoids, that had settled there." To translate: Gastropods are a kind of mollusk, a polychaete is a segmented worm, an isopod is a flat crustacean, crinoids are related to sea stars, a caprellid is a skeleton shrimp, and polynoids are worms with scales on their backs. But did they find any baby corals? "No, but that's no surprise. It's a long, slow process." Mills said it may be four or five years before anyone gets back to Manning Seamount to collect the other 10 blocks left behind, so it will be interesting to see what develops by then. 
Mary Grady
WHOI researcher Susan
Mills examines one of the basalt blocks that were retrieved by
Hercules.
Running on deep time On the surface of the Earth, all life depends on the sun. Plants create their food in chemical reactions driven by the rays of heat and light. Everything else eats the plants, or eats other creatures that eat the plants. But in the oceans, ninety-nine percent of the sunlight that falls on the surface is gone at 300 feet deep. The wavelengths of light, starting with red, then orange, yellow, green, and last of all blue, are scattered and refracted and absorbed till there's nothing left. The sun's heat is dispersed and diluted in more complex processes that depend on latitude and currents, but by about a half-mile deep it too is lost. So how do animals survive at one, two, three miles deep, in the eternal cold where the sun never shines? In some places, heat escapes through vents from the Earth's interior, to form the base of an alternative food chain. But in most parts of the ocean, it's the marine "snow," drifting down from the surface, that transports captured bits of solar energy to the depths. The snow, formed of tiny surface creatures, their dead bodies, scraps, flotsam, fish waste and debris, flurries slowly down through the water column till it eventually lands on the seafloor. The bright forward lights on Hercules reflect off the particles like headlight beams on a snowy night. "In this part of the ocean, the snow really comes only once a year, after the spring plankton bloom," says Les Watling, the chief scientist on our expedition. "So imagine if you are a deep-sea coral, for most of the year you are living in the quiet and the dark and the cold, nothing varies, there is nothing to mark the passage of time except that once-a-year plankton bloom. That's when you get fed, and you grow, and then it's all quiet again for another year. "So while the corals that are hundreds of years old seem ancient to us, a hundred years to a deep-sea coral, probably seems like nothing at all."
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