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Logbook
July 11, 1999

Contents:

• News from Thompson
• Participant Perspective
• Logbook from Teacher at Sea
• Question/Answer from shore to sea

Science Report - Saturday, July 11
Ships Location: 45 56.0/130 00.8

"Chapstick corers" invented for dive 501 to collect volcanic glass chips.

ROPOS dive 501 successfully completed two major geological traverses across the 1998 lava flow and collected 14 rock samples with a combination of the manipulator arms, the suction sampler, and newly invented "chapstick corers" (which have a wax cup for collecting volcanic glass from the surface of rock, like the rock corer does that we lower from the ship, but these look like giant chapstick tubes and can be used by the ROPOS manipulator arm). (photo right) After ROPOS dive 501, three moorings with miniature temperature recorders (MTRs) and nephelometers (which measure the level of particulate matter from hydrothermal plumes) were deployed in the southern part of Axial caldera. These moorings will make continuous measurements at several heights above the seafloor to monitor the plumes over the vent sites during the next year. Everyone is suddenly vividly aware that we have less than 2 days left before the Thompson has to return to port. The remaining ROPOS dives will be at the ASHES vent field, in the southwestern part of the caldera. ASHES is another high-temperature vent site with several black-smoker chimneys that expel water at up to 348 degrees C (which is actually the boiling temperature for seawater at this depth!). ROPOS dive 502 is currently on the bottom at ASHES and will collect fluid samples at the vents and biological samples with the suction sampler.

Listing of all Science News postings

Christian Levesque
University of Quebec

What I am particularly interested in is to understand what organisms eat at vents. As we are still discovering species that were previously unknown, we definitely don't know yet what the food chains look like. Understanding the feeding relationships between different species gives us insight into how they live together, why some species are most often found together and not with others, why and how the different populations of organisms evolve through time, how perturbations such as a new hot fluid source will affect the fauna, etc. Vent ecology is still a very young discipline, and these are among the first steps to try and understand a little better these ecosystems.

Since it is impossible to stay at a vent many hours and look close enough at animals to see what they actually eat and in what amount, the best way to elucidate feeding relationships is to use what we call tracers. Among those are stable isotopes of carbon, nitrogen and sulfur, and molecules like fatty acids. This might all seem a little complex, but its based on a simple idea: you are what you eat. These molecules or isotopes are found in certain amounts in each organism, and the animals that eat those will retain these molecules they took from their preys. Your cells are made of carbon, nitrogen, and molecules that come from the cereals, the carrots, the milk (and even the broccoli or spinach!) that you eat! Its exactly the same with palm worms or limpets at vents - although they probably don't have as much choice as we do in the grocery store!

Listing of all Perspectives postings

Thompson Teacher at Sea Log

Teachers Log #20 7/11/99

While observing the scientists prepare for a dive I noticed that all containers for sampling vent fluids and organisms were first filled with seawater. The reason this is done is to prevent the containers from being crushed by the pressure of the water as the ROV makes its way to the bottom. In fact, I'm told that if there is any air within the containers as they descend, that at about 15 meters below the surface they would implode and be crushed. Why does this happen?

When I stand out on deck, the air above me is pushing down with a force equal to one atmosphere of pressure. I don't even notice it. In fact, we all take it for granted. Imagine that I jump in (boy this water is cold) and swim downward, I feel the pressure in my ears. The rest of my body does not register this small amount of pressure increase. If I went deeper, say 1500 m down, any part of my body that contained air would collapse and be flattened. Not a pleasant thought. As you increase the depth of your dive, the pressure is a cumulative factor. For each 10 m (32 feet), you add one more atmosphere (atm). At 1500 m, where we are diving, the pressure is roughly 150 atm or just over 2200 lb. per square inch. This is one reason we use ROPOS to do our bidding at the bottom. Even it sometimes suffers from the extreme pressure below. All of the equipment on ROPOS has to be specially designed to operate in this high pressure environment.

There has been an increased level of artistic creativity around the ship. Styrofoam cups and wig heads are becoming major art projects. Late in most cruises, students mostly, but also some of the more grizzled veterans of the sea, go about creating souvenirs for themselves and loved ones back home. After designing and coloring the cups and wig heads, they are bagged and strapped to the ROVs cage. When they come back to the surface, they are very small because as they drop through the water column, increasing pressure forces out the air trapped within the foam. Some, come up shriveled and misshapen while others look like perfect miniatures. They make for great conversation pieces.

Bye for now.

Logbook of all Teacher At Sea postings

Questions from HMSC auditorium audience:

This is a more detailed answer to the questions posed on 7/10/99:

Q:Do they know what species of crab it was that was captured on dive R498 and what is know about its life history? How big is it and what was done with it?
A: It is a known species: Macroregonia macrocheira. This species was first described from two male specimens collected on the Emperor Seamounts by Japanese trawlers. It is a majid crab related to the king crab. Large males can reach a leg span of 1 meter. We have studied the habits of this animal as it is one of the few normal deep-sea animals that is able to tolerate the toxic sulphides at vents. The males range widely in the deep-sea while we tend to find females and juveniles clustered around the vents. They will pull tubeworms and snails from the edges and move off to eat them. Males are agressive and often fight each other - and even attack a submersible. We see females with incubating eggs at the vents. I believe they are an important predator and a mechanism that 'transports' vent productivity into the surrounding deepsea.

All Questions/Answers from sea
Send Your Question to NeMO
(oar.pmel.vents.webmaster@noaa.gov)

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