Mail Buoy

January 13 responses:

In the mission overview and daily updates, we noticed two vents named "Crab Spa" and "Trick-or-Treat." They appear to be the two main vents. Are there more vents in the area? Are these two the only vents suitable for the dive? If not, then why these two vents?

Sincerely,
Hailey from Memorial High School, Eau Claire, Wis.

Dear Hailey,

Good question! We call this general area a ”vent field,” because there are quite a few vents here. We particularly chose to study Crab Spa as it most suited for the kind of work we are doing. It is a warm-water or “diffuse flow” vent with a temperature of around 23 degrees Celsius, meaning that it emanates fluids from the sub-seafloor that represent a mixture of the very hot hydrothermal fluids and seawater. Along with the fluids, microbes living in the sub-seafloor are being flushed out. These are the microbes we are after and want to better understand. We expect that there is an extensive sub-sea floor biosphere, but we know very little about it and the importance of the organisms living in it for the ecosystem.

“Trick-or-Treat” is a similar site, which we named on Halloween in 2008. While Crab Spa is still very active and we have been sampling it frequently on this cruise, Trick-or-Treat is not active anymore. It tricked us. It happens frequently down here that vents become activated or become extinct, meaning that they stop flowing. It’s a very dynamic environment. Just a few days ago, we found another site that we named “Teddybear” because of the fuzzy white coating of bacteria on the rocks. This site emanates fluids with a temperature of 10ºC, which is still quite a bit warmer than the 2ºC in the ambient deep-ocean.

Besides the “diffuse flow” sites, there are also the impressive “black smokers” that emit superhot hydrothermal fluids. The highest temperature we found so far on this cruise was 373ºC at a site called “Bio9.” These fluids contain no life, as this is way beyond the currently known upper temperature limit of life (which is around 130ºC). The chemicals that spew out of the black smokers fuel microbial activity at lower temperatures elsewhere in the ocean, however.

All the best,
Stefan Sievert

How were the scientists and crew chosen for this mission?

Sincerely,
Hailey from Memorial High School, Eau Claire, Wis.

Hi, Hailey,

As far as the scientists are concerned, the choice was made over a few years. In the course of my lab's work, we've collaborated with many scientists around the world. When the National Science Foundation (NSF) announced a special program in 2010 to study biodiversity, we felt it would be a great opportunity to bring together all these different investigators in one project to investigate hydrothermal vents in a comprehensive way. The NSF agreed, and gave us funding, so this cruise is the culmination of this effort.

The scientists on the cruise are here because each of our areas of study covers a slightly different but complimentary piece of the vent ecosystem, and together, we hope to start piecing together a big picture of what microbes are doing at the vents. The scientists are mostly geochemists and microbiologists, since the line between chemistry and biology at the level of microbes is very thin. In a way, microbes are basically tiny chemical "engines" that can take in compounds from their environment and turn them into something else, so it's important to understand them from both a biological and a chemical perspective.

Not all scientists that are part of the project are here in board, however. For example, Ramunas Stepanauskas, a scientist at Bigelow Labs in Maine, was unable to join us, so we will bring back samples for him to perform genomic analyses on individual cells directly obtained from the environment.

Hope that answers your question!

Best,
Stefan Sievert

Dear Hailey,

The Atlantis' crew supports both the ship and number of varying science expeditions throughout the year, and so the crew choice is not expedition-specific.

Atlantis has a pool of crew personnel that rotate on and off the ship. A crew member stays aboard about three months, and then is off Atlantis for three months. When it is your turn to be onboard for your rotation, your job is to support the ship and assist the science expedition(s) taking place during your stay.

Therefore a crew member will assist two or three different science expeditions during his or her rotation, whereas science members will only be aboard for their specific science expedition.

Captain Al Lunt

How can deep-sea creatures (including microbes) survive under such high pressures where humans, land animals, and even some submarines will get crushed?

Ayush
Ms. Sheild's classes at Clarke Middle School, Lexington, Mass.

Dear Ayush,

That is a very interesting question! There is no real reason why an organism cannot survive at the high pressures at our site at Crab Spa. What really affects creatures (and submarines) that go down or up underwater is the difference in pressure between the inside and the outside of the organism or sub. The submarine is a good example. Inside, we keep the pressure at the surface level, because that's how we like it. However, as we go deeper, the pressure outside keeps increasing. So as the pressure outside increases, the difference between the outside of the submarine and the inside increases, which means that it needs to be very strong in order to hold back the huge pressure outside.

But, if somehow we could increase the pressure inside the submarine to the same pressure as outside, then the submarine would not be crushed. The animals and microbes at the deep sea vents basically use this strategy. They keep their bodies at the deep sea pressure, so there is no difference in pressure that can crush their bodies, since they are already at the same pressure.

Some creatures can actually survive fairly well when we bring them back from the vents. One example is crabs. They can still be moving around when you bring them back, and this is because as they get brought up, their bodies can change the pressure to match the environment. Other animals are not so lucky. Fish, for example, have a swim bladder inside them that helps them regulate their buoyancy. It is filled with a small amount of air. If you try to bring a fish up from the bottom, that air expands as the pressure decreases, and the bladder eventually explodes, killing the fish. This is the same idea, just the opposite, of why the submarine is crushed.

Now this is not to say that the organisms on the bottom aren’t different—they might have specific adaptations that allow them to survive better at high pressure. But those adaptations are not extremely obvious, and probably are on the level of molecules like proteins. This might be true for the microbes adapted to the deep sea—they might have a protein that works better under high pressure than proteins inside their relatives at the surface. Hope that helps!

Jesse McNichol

Can organisms chemosynthesize in light or on land? (or only in the deep sea in darkness?)
What chemicals do the microbes use to chemosynthesize?

Joey & Carter
Ms. Sheild's classes at Clarke Middle School, Lexington, Mass.

Dear Joey and Carter,

Cool question. Chemosynthesis can happen anywhere really, but is most obvious at places like vents. All you really need for chemosynthesis is two chemicals—one for energy, and another to breathe. You can think of the energetic chemical as analogous to the food we eat, and the chemical to breathe as analogous to the oxygen we use to get energy from our food.

The most common energetic chemical at these vents is hydrogen sulfide or H2S. This is the chemical responsible for the smell of rotten eggs, and is present in high concentrations at vents (on the Dive and Discover website, there is a picture of Dr. Jeff Seewald smelling for it in a vent sample). This gives energy to the microbes that live at the vents in combination with chemicals such as nitrate or oxygen, both of which the microbes can breathe, or “respire” as we call it officially. Using oxygen to breathe is called “aerobic respiration,” and using nitrate (or some other chemical) is called “anaerobic respiration.”

As for light, there is no reason why chemosynthesis can't happen in places where there is light, but where there is light there is usually oxygen. And oxygen reacts quickly with things like hydrogen sulfide, which releases the energy stored in the H2S. When that happens, there is no more energy available to the microbe. So any sort of chemosynthetic system will usually be found at the interface between an anoxic (no oxygen) zone and an oxic (lots of oxygen) zone.

If you live close to the ocean, salt marshes are a good example of this. The mud below the surface is black, stinky with sulfide, and mostly anoxic. The sulfide comes up to the surface where there is oxygen, and this is where you can see evidence of chemosynthesis. If you happen to be there, you can often see white material on the surface, which is the product of the oxidation of sulfide. In that material will be plenty of chemosynthetic bacteria! Hope that answers your questions!

Jesse McNichol

Does chemosynthesis happen in bacteria that live in places other than vents?

Eugene
Ms. Sheild's classes at Clarke Middle School, Lexington, Mass.

Dear Eugene,

Yes, it does—chemosynthesis is a very widely spread phenomenon. You can find it whenever chemical substances that can react with each other are together in the close neighborhood of a bacterium. The bacteria can use the energy released when these substances react. One can find chemosynthetic bacteria in environments such as mud flats, the waste water of chemical plants, oil wells, and rusting sunken ships in the ocean. There are many more examples worldwide. The most common reaction here at the vents is the oxidation of hydrogen sulfide (a gas that smells like rotten eggs) with oxygen. The hydrogen sulfide is provided by the vent fluids, which come out of the ocean floor and react with oxygen in the seawater near the bottom.

Horst Felbeck