Dive and Discover : Expedition 4 : Mail Buoy

Central Indian
Ridge
Expedition 4:
Mar 27-May 1, 2001

Mail Buoy
April 1, 2001

Hi: I wanted to ask you what happens to the water when an underwater volcano explodes. My name is Yazmine and I think volcanoes are cool. I made a volcano with the instructions. I wanted to know how many species are in the ocean.

Sincerely
Yazmine

Hello Yazmine:
Interesting questions! What happens to the water when an underwater volcano erupts depends a lot on the depth of water. What causes the explosions that you see when a volcano erupts on land is water boiling and turning to steam, and other gases escaping. However, at mid-ocean ridges, the water is usually very deep (2000-4000 m or about 6000-12000 feet). At these seafloor depths, the water is prevented from boiling by the pressure of all the seawater above. So lava flows out of deep seafloor volcanoes and over the surrounding ocean floor without having explosions.

The other question you asked was related to the number of species in the ocean. I assume you mean species of organisms associated with hydrothermal vents rather than in the whole ocean! There have been well over 400 new species (and in fact, it may be 500 by now) described from vents.

Hope you will continue to follow our expedition!
Susan Humphris

Dive and Discover:
At Waring we notice that your research area is at the intersection of three tectonic plates. Does the movement of the plates in this area differ from the spreading centers common to places where two plates meet? Did you expect to see more vents in this area?

Thanks, Susan

John, Neil and the Oceans Class

Hello John, Neil and the Oceans class:

Very observant! Our research area does indeed include an intersection of three tectonic plates -- see the diagram. The plates are the African plate, the Indian plate, and the Antarctic plate, and the point where they all meet is called the Rodriguez Triple Junction. The plates are separated by the three mid-ocean ridges named in the diagram. Each ridge is a junction between two plates and ocean crust is being formed there by volcanoes. But it is important to know that the rate at which seafloor is being created at these three ridges is NOT the same. The Southwest Indian Ridge is spreading much more slowly that the Central or Southeast Indian Ridges.

We don’t know really whether there are more vents at a triple junction. If you look at a bathymetric map, you can see that the seafloor at the triple junction is quite deep suggesting there is less volcanism to create new crust in that area. So -- if there are fewer volcanoes, there are probably fewer heat sources to drive hydrothermal circulation. Therefore you might expect fewer vents.

Hope you will stay tuned as we begin our research!
Dan Fornari and Susan Humphris

This is a message for Bob Collier from Suzanne and Ted in New Jersey. How cold it the water at depth?

Good luck and safe diving.
Ted

Suzanne and Ted in New Jersey:
Thanks for the note of encouragement and watching the web site. I just looked at the temperature of the bottom water, measured today with our CTD instrument. At 4000 meters depth (almost 2.5 miles down), it is 1.4 degrees C (almost 35 degrees F). But then the surface water is almost 80 deg F, so we rather enjoy the cold water running on our feet as we collect samples after the CTD returns. If the Jason is successful finding hydrothermal vents, then we are working with water temperatures up to 400 degrees C!

Enjoy the spring because we will certainly miss it (and say hello to Vermont).
Bob Collier

I am curious about the molecular analysis you will conduct on biological samples taken from the vent sites. What types of evidence are you looking for at the molecular level? What methods will you use to analyze the samples? Thank you for taking the time to let us share in your expedition.

Don
Boston, MA

Hi Don:
There are several microbiologists on board so two of them have sent you answers.

1) Don- My group is interested in the identifying the microorganisms that reside in the spongy mineral black smoker chimneys. These chimneys are wonderful places for heat loving microbes (thermophiles) to reside, since they get all their energy and carbon (food) provided by the hydrothermal fluid, AND they have a place to attach (most microbes like to hold onto something, -their little home...).

Unlike most biologists that can identify animals by looking at them, microbiologists need to use different methods to identify microbes. Under the microscope they just all look like blobs or little rods. We either try to grow the organisms in tubes in the lab, a difficult task since we have to second-guess what they ‘eat’, or we use molecular methods to identify them. We extract the DNA from our chimney sample, and then use PCR (the polymerase chain reaction) to look for the ‘fingerprint’ of the microbe. In our case, we look for a gene (the small subunit rRNA gene) that is important for the organism’s survival, and that also occurs in all life (we even have it!). Using this molecular approach, we have found whole branches of life that we never knew existed. Branches of life that are as different from one another as you and I are from insects!

Anna-Louise Reysenbach

2) For the vent animals, we will be using information from their genetic material (the first step - DNA extractions - we can do at sea, the rest will be done in lab). This will tell us the identity of these animals and whether they are the same, or similar, to other known vent animals, or whether they are entirely new species. New species are obviously very exciting but the same species at different vent sites (including new sites in the Indian Ocean) are also very interesting. One of the great mysteries is how vent animals get from one site to the next or even move between ocean basins. By comparing different populations of the same species we can track gene flow (i.e. movement over evolutionary time scales) of these animals.

Thanks for the great question,
Shana Goffredi