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SEAS: Student Experiments At Sea

Ask-a-Scientist

Thank you for submitting excellent questions for our scientists at sea. You can read about their research in the Updates From Sea section of the library.

This year's student questions!

How do deep-sea organisms get to the hydrothermal vents in the first place?

How long do hydrothermal vents last?

Can we use heat from hydrothermal vents?

Are there any vent organisms that help cure disease?

Why didn't the bologna sandwich decompose?

Where does the 'poison' near hydrothermal vents come from?

How can you tell the age of a mussel?

Have you noticed any bacterial mats at the new volcanic site?

How many black smokers are in the area you are studying?

Are there any patterns to the eruptions on the ocean floor?

How would light affect a deep-sea mussel?

What is the temperature of the environment of a deep-sea mussel?

What happened to the mussel exclusion cages?

What is life like at 9°N - any other people or animals around?

Did anything survive the new eruption in that area?

How do deep-sea organisms get to the hydrothermal vents in the first place?

Q: Our first question involves deep-sea organisms. How do these deep-sea microbes and animals get to the hydrothermal vents in the first place?
(Ms. Carolyn Sheild's 7th grade Life Sciences, Clarke Middle School, Lexington, MA).

Costa Vetriani

Dr. Costa Vetriani, Rutgers University

A: Microorganisms are very small (micron range) single-cell organisms, hence they very easily disperse in the oceanic environment. When they find a suitable environment, they start using the resources (nutrients) and divide. The fact that very often we find similar bacteria at deep-sea vents that are geographically distant supports the idea that microorganisms disperse very easily, and then the environment selects for specific types (for example, sulfur-metabolizing bacteria). Another reservoir of microorganisms adapted to the deep-sea vent environment (high temperature, anoxic conditions) may exist underneath the ocean crust; these microorganisms may then be flushed out by the flux of hydrothermal fluids.

Abby Fusaro

Abby Fusaro, Woods Hole Oceanographic Institution

A: Great question and one I'm very interested in myself! There are two ways I could address your question--one, how did animals first ever arrive at hydrothermal vents, or two, how do animals that like to live at hydrothermal vents travel from vent to vent. For the former question, we have an idea that hydrothermal vent animals first came from cold methane seep environments, another type of chemosynthetic environment, like in the Gulf of Mexico. Through evolutionary time, these seep animals could have gained adaptations that helped them to prefer life at deep-sea vents. We can understand this process through the relatedness of present-day vent and seep animals.

For the latter question, there are several answers. Firstly, there are mobile fauna, like fish, octopuses, and crabs, which visit the hydrothermal vents. Some of these animals are dependent on hydrothermal vents to live, whereas others are just visitors which swim or crawl from other areas of the deep sea. The visitors might be attracted by the higher availability of food associated with other life at vents. Then, there are animals like mussels, which while observed to move with amazing speed and can clear out of an area which they don't like, do not typically make long distance journeys. These animals and animals (such as tubeworms) that are attached to the sea floor when they are adults, actually have another stage of their life during which they can move about in the water. In fact, fish and crabs have an early form after hatching, as well. During this young phase of life, the animal is called a larva. Some larvae are able to weakly swim while others are primarily transported by currents through the water. These currents bring some types of larvae to the surface water to feed in the plankton. Other currents may transport the young animal in a layer of water that originated from the hydrothermal vent, called a buoyant plume, below the ocean's surface. However, the big question then, is how these young vent animals find their way back to a hydrothermal vent to grow up. This question is one we still do not have a complete answer for, but we have some ideas. Part of our research on this cruise is to understand where new animals come to the vents from after an eruption and what causes the larvae to settle (drop) out of the water to a new vent. We hypothesize that microbial films or mats may be provide a biological or chemical cue to which new vent colonists are attracted. Stay tuned as we learn more ourselves!

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How long do hydrothermal vents last?

Q: My students had another question. How long do hydrothermal vents last? Thank you,
Ms. Carolyn Sheild (7th grade Life Sciences, Clarke Middle School, Lexington, MA).

Rich Lutz

Dr. Rich Lutz, Rutgers University

A: How long a vent last depends upon a number of things. First, it depends upon where it is located. On what we call "fast spreading mid-ocean ridges, such as the East Pacific Rise where we are currently diving, vents usually last on the order of years or decades before they are buried by new lava flows that occur quite frequently. In contrast, on "slow spreading" mid-ocean ridges, such as the Mid-Atlantic Ridge, some of the vent areas are as old as 50,000 years - at "slow spreading" centers, lava flows are generally rare relative to those on the East Pacific Rise. Secondly, vents can spontaneously "shut down" due to "clogging" of the hydrothermal vent system which can occur when minerals precipitate inside the vents. It is difficult to predict just how long it takes vents to "clog" in this manner and we have a feeling that when one vent does shut down due to "clogging", another vent might form not too far away. How long a given vent takes to clog may ultimately depend upon the chemical composition of the vent fluids which vary from site to site.

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Can we use heat from hydrothermal vents?

Q: Has anyone ever thought of trying to use the heat from the hydrothermal vents to generate energy for us to use? -Kendyl Yonamine (Mrs. Grace's 7th grade science class, Palos Verdes Intermediate School, CA).

George Luther

Dr. George Luther, University of Delaware

A: Good question. Yes, some people have thought of that possibility. Unfortunately, to transfer that heat over 2000 meters up to the surface through all that cold water would result in much heat loss and would not be economically viable - unlike geothermal sources near or on the earth's surface. It might be possible to use heat near the vents for small items although the amount of energy that could be harvested in a short period of time may not be sufficient for most purposes. Also the materials needed to get the heat would be very expensive and difficult to manufacture because they would need to be placed at the hottest sources and be able to withstand extreme temperatures. But who knows what engineers will come up with next.

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Are there any vent organisms that help cure disease?

Q: Are there any organisms that are living at the hydrothermal vents that can help cure diseases? - From the 7th grade students in Ms. Benjamin's class at Palos Verdes Intermediate School, CA.

Costa Vetriani Rich Lutz

Dr. Costa Vetriani and Dr. Rich Lutz, Rutgers University

A: Scientists are always looking at nature to discover opportunities for new medicines, and the deep sea is no exception. The unique organisms that live at hydrothermal vents in the deep sea aren't very well understood yet, but they may help us to develop new medicines as we uncover their secrets for living in such a challenging environment. Bacteria are a great example - many bacteria make biochemical compounds that will kill other bacteria around them to protect themselves or avoid competing for resources such as food or space. People already use some of these compounds as drugs called antibiotics to kill bacteria that can make us sick. But antibiotics aren't effective forever - eventually bacteria can become resistant to them and we need to find new ones.

Bacteria found at hydrothermal vents may be a new source of antibiotics or other drugs. In order to find out, we need to collect bacteria from vents, grow and multiply them in the lab (which can be difficult), and then isolate and identify them by individual species using their unique genetic codes. We can then test the compounds made by one species of bacteria on other harmful cells, such as other bacteria and cancer cells. If any of the compounds kill the harmful cells they can be identified and tested further to see if they may be useful for the development of a new drug. Keep in mind, however, that bacteria aren't the only organisms that may make compounds useful for drugs - other hydrothermal vent animals such as worms, fish, shrimp and crabs could potentially be sources of useful compounds that can improve our health, given that they live in unusual, extreme environments.

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Why didn't the bologna sandwich decompose?

Q: A student learned from her research on hydrothermal vents that a biologist accidentally left behind a bologna sandwich at one of the vents. They found it in nearly the same condition a year later. How could that be? Wouldn't it decompose? The website also said the tubeworms that had died the year before had not decomposed either.
- From the 7th grade students in Ms. Benjamin's class at Palos Verdes Intermediate School, CA.

Rich Lutz

Dr. Rich Lutz, Rutgers University

A: Actually, the "infamous" deep-sea bologna sandwiches got to the ocean bottom when the Alvin sub accidentally sank in 1968. As the sub was being lowered into the water from the support ship R/V Lulu, some cables broke and the sub slid into the water and began to take on water. Fortunately, the pilot and scientists were just getting into the sub when the accident occurred, so they were all rescued before it sank below the surface. The sandwiches that had been packed for lunch in the sub, however, were not so fortunate and sank with the sub to a depth of 5,000 feet. When the sub was recovered ten months later, the scientists were surprised to see that the sandwiches were soggy but still intact.

Why didn't the sandwiches decompose? Well, one reason is that they had been wrapped and packed inside a box, which prevented them from quickly being eaten by fish, crabs, or other animals. But why didn't bacteria start to decompose them? There could be several causes, including 1) there may not be many bacteria in areas of the deep sea away from hydrothermal vents, and 2) near-freezing temperatures in the deep sea may cause bacterial decomposition there to occur very, very slowly.

As for the tubeworms, the tubes of dead tubeworms decompose slowly (and could perhaps take a year to decompose), while the soft tissues of a dead tubeworm either decompose rapidly or are eaten by other organisms such as crabs or fish. Just yesterday (1/17/2007), we found on the bottom a tremendous clump of tubes of dead tubeworms that had met their demise during the last seafloor eruption, so these empty tubes have managed to persist for approximately a year. Good questions!

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Where does the 'poison' near hydrothermal vents come from?

Q: Where does the poison near hydrothermal vents come from? -(Ms. Sheild's 7th grade science class, Clarke Middle School, MA).

George Luther

Dr. George Luther, University of Delaware

A: Well, that depends on what you mean by 'poison'. A chemical called hydrogen sulfide is often found at vents and can be very poisonous to people and other animals that breathe oxygen. This chemical is formed when seawater is forced deep into cracks in the seafloor and comes into contact with rocks that are heated to high temperatures by the pressure of the earth. The high temperatures cause sulfates in the seawater to be changed to hydrogen sulfides, which are then carried back up to the seafloor through the fluids of hydrothermal vents.

Why is hydrogen sulfide poisonous to people and other animals that breathe oxygen? Normally, the red blood cells in our bodies pick up oxygen in our lungs and carry it around to different areas of our bodies. But hydrogen sulfide can bind with our red blood cells better than oxygen, so if we breathe a high enough concentration of hydrogen sulfide for too long, we could die from not getting enough oxygen.

However, for some bacteria that live near vents, hydrogen sulfide isn't a poison - it's a necessity! These bacteria can break down the hydrogen sulfide into sulfur and combine it with carbon dioxide to make energy. Some animals such as tubeworms and mussels also rely on hydrogen sulfide by including these special bacteria in their bodies to provide them with sugars and other compounds in a special relationship called symbiosis. So, while we have to eat food to get our sugars for energy, these animals have bacteria that make food inside them - how cool!

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How can you tell the age of a mussel?

Q: Are deep-sea mussels' ages determined by the "shell rings" as fresh water mussels? What is the oldest mussel you have identified? Does this then mean it is also the largest? How is it possible that mussels can withstand the amount of pressure in the deep sea?
- Students of Ms. Judy Tryon's 7th grade Science class, Central Middle School, Qunicy, MA.

Rich Lutz

Dr. Rich Lutz, Rutgers University

A:Unlike some fresh water mussels, it is not possible to determine the age of deep-sea mussels using "shell rings". The main reason for this is that the annual rings on the shells of some fresh water mussels are caused by the seasons - the rings typically grow thicker in the summer when the mussel is growing more quickly, and thinner in the winter when it's growing more slowly (or not at all). However, this method cannot be used in the deep-sea because there is little or no effect of seasons in that environment.

While we have not been able to accurately age deep-sea mussels, we have been able to "age" deep-sea clams by determining the thickness of the outer layer of their shell. Once the outer layer of their shell is made, it doesn't get any thicker (even though the inner layers of the shell do), and gradually dissolves at a regular rate over time. Knowing this, you can determine how old a deep-sea clam is by measuring the thickness of its outer shell. The oldest clams that we have found are about 25 years old. Interestingly enough, the oldest blue mussels, which are commonly found along the east coast of the U.S, are also about 25 years old. The largest mussels are not necessarily the oldest mussels, just as the oldest humans are not necessarily the largest or tallest humans.

As for withstanding pressure, mussels are able to withstand the high pressures of the deep sea because they do not have any "air spaces" in their bodies so there is nothing for the high pressures to "compress".....unlike styrofoam cups, which have a lot of air (that's why they're so light and that's why they "shrink" or "compress" when we send them down with Alvin).

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Have you noticed any bacterial mats at the new volcanic site?

Q: Have you noticed any bacterials mats at the new volcanic site?
- Ms. Diedre Young's students, St. Joseph Catholic School, Pine Bluff, AR.

Costa Vetriani

Dr. Costa Vetriani, Rutgers University

A: Yes, our microbiology group here on the cruise has noticed many areas of new bacteria. In fact, we're seeing many more mats of bacteria than we did before the eruption a year ago.

Bacteria are among the first organisms to arrive and grow at new vents after an eruption. Many of the new colonies of bacteria we've seen here at the East Pacific Rise site appear as patches of white on the black rocks around the opening of vents. It appears that these types of bacteria thrive at new vents where the fluids have high levels of hydrogen sulfide.

The last time that a major eruption occurred here at the East Pacific Rise (in 1991), scientists weren't able to do the same types of detailed studies we're doing now of the bacteria that are present after an eruption. Unfortunately, that means that we don't have any previous results to compare to the measurements we are taking now. But it's also exciting to think that our measurements will not only be useful to us and other scientists now, but also in the future as we continue to monitor the bacteria at the vents to see how they change over time.

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How many black smokers are in the area you are studying?

Q: How many black smokers are in the area you are studying? How tall is the largest one? - Ms. Jill Fekete, Clarke Middle School, Lexington, MA.

Tim Shank

Dr. Tim Shank, Woods Hole Oceanographic Institution

A: The first question is a little tricky to answer since we study several different locations in a fairly large area of the seafloor - and some locations may contain a number of smaller black smoker chimneys. The short and simple answer is that that there are about fourteen sites or areas that are identified because they have relatively large black smokers. The largest of these smokers is found at a site called 'P' Vent, and is about 17 meters (~55 feet) tall.
Note: there is a bathymetric map of this area of the seafloor from 2005 with the vents marked in the Field Notes posted with the mussel data collected on the last SEAS cruise. Although things have changed since the eruption, this map can give you a general sense of the area.

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Are there any patterns to the eruptions on the ocean floor?

Q: Are there any patterns to the eruptions on the ocean floor?
- Ms. Jill Fekete, Clarke Middle School, Lexington, MA.

Danielle Stroup

Danielle Stroup, Graduate Student, Lamont-Doherty Earth Observatory

A: That's a great question. When 9°50'N East Pacific Rise erupted in 1991, marine geophysicists were interested in predicting when the next eruption episode would occur. Eruptions help create much of the new oceanic crust at the mid-ocean ridge axis and are characterized as periods of intense shaking of the seafloor in the form of earthquakes. During an eruption, many small earthquakes occur within a short amount of time, and sometimes earthquakes happen so close together, it is hard to tell them apart!

In 2003, scientists from Lamont-Doherty Earth Observatory placed eleven ocean bottom seismometers (OBSs), or instruments that record small earthquakes, on the seafloor in an effort to predict the next eruption. In April 2006, scientists tried to recover the instruments from the seafloor and two of the ocean bottom seismometers were stuck! Usually scientists are upset when their instruments are stuck on the seafloor, but for marine geophysicists, we took this as a good sign because the ocean bottom seismometers were stuck in newly formed basalt caused by an eruption! Data from 2003-2006 were analyzed (OBSs are deployed and recovered each year), and scientists noticed that earthquakes were happening more often as the months went on, and that many earthquakes occurred on January 22, 2006. The earthquakes showed us that an eruption event took place around noon on January 22, 2006, only fifteen years after the 1991 eruption. Most of the seismic activity had occurred in the Northern area of our study sites (9 degrees, 50 minutes north).

The pattern we see is that most earthquakes occur on the ridge axis and we're wondering how much lava flowed out. We are actually figuring this out during this cruise! Ocean bottom seismometers are still recording data on the seafloor, and scientists wonder if an eruption will happen in another fifteen years.

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How would light affect a deep-sea mussel?

Q: Would light affect a deep-sea mussel if it were exposed to it for any given amount of time?
- Kim Moody from St. Joseph Catholic School, Pine Bluff, AR).

Rich Lutz

Dr. Rich Lutz, Rutgers University

A: Interesting question. It's hard to know if light would affect a deep-sea mussel if it were exposed to it for a period of time. We've never been able to expose deep-sea mussels to light for a lengthy period of time because they don't survive for very long when brought to the surface. The only way deep-sea mussels survive (and this would be for a relatively short period of time) is if we re-pressurize them, and this is usually done in the dark. There are deep-sea scientists at UC-Santa Barbara working on ways to keep deep-sea animals alive when brought to the surface, so that we can study their physiology.

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What is the temperature of the environment of a deep-sea mussel?

Q: What is the temperature of the environment of a deep-sea mussel?
- Kim Moody from St. Joseph Catholic School, Pine Bluff, AR).

Rich Lutz

Dr. Rich Lutz, Rutgers University

A: Mussels are found in areas where the hydrothermal vent fluid is coming up through cracks in the seafloor. We refer to these areas as "diffuse flow". The temperature of the environment of a deep-sea mussel can range from 2-25°C. This environment is quite different from the high temperature chimneys, or what we refer to as "focused flow", where temperatures can range from 350° to almost 400°C. Dr. Karen Von Damm from the U. New Hampshire has temperature data from these EPR chimneys collected over 12 years.

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What happened to the mussel exclusion cages?

Q: What happened to the mussel exclusion cages since the eruption, and do you have any idea how far from the ridge area the new rock extends?
- Kathryn Kelsey, Seattle Public Schools, Seattle, WA.

Tim Shank

Dr. Tim Shank, Woods Hole Oceanographic Institution

A: We haven't seen any signs of the cages anywhere, so we're assuming they are likely buried under several meters of fresh basalt. The eruption appears to have resulted in lava flow and fresh basalt rock extending up to a kilometer away from the ridge trough, although this distance varies depending on the specific location.

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What is life like at 9°N?

Q: What is life like at 9°N - any other people or animals around?
- Ms. Jill Fekete, Clarke Middle School, Lexington, MA..

Eric Simms

Eric Simms, SEAS Education Coordinator, Scripps Institution of Oceanography

A: Life here at 9°N can feel quite isolated at times, but we're definitely not alone. To my knowledge, we have sighted only one other ship since we arrived here at the research site three weeks ago. However, we do have some other animal life to keep us company out here. You can often spot flying fish leaping from the water when the ship spooks them, and if the deck lights are on at night you can usually see small squid (about a foot long) swimming at the surface next to the ship, looking for a meal. These smaller animals sometimes attract larger predators such as mahi mahi and white tipped sharks. We also have the company of several kinds of seabirds - boobies, gulls, petrels - that stay close to the ship, and occasionally land on the decks to rest. And we've even seen two sea turtles swim by - one of them was a juvenile that wasn't much bigger around than a softball. So, we've been seeing lots of life out here both at the surface and on the bottom at the vents. Right now, we're waiting for the Alvin to return from it's dive for a look at some deep-sea fish that have been collected - can't wait!

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Did anything survive the new eruption in that area?

Q: Did anything survive the new eruption in that area? - Ms. Diedre Young's students, St. Josephy Catholic School, Pine Bluff, AR.

Tim Shank

Dr. Tim Shank, Woods Hole Oceanographic Institution

A: We haven't found too many animals that survived in the areas that we studied before the eruption - most of them were probably killed by the lava. A few small patches of mussels that survived have been found, but many of them don't appear to be very healthy.

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Questions from previous years:

How can you distinguish male and female mussels?

What could our shallow-water mussels have been eating?

What websites and books can we look at to learn more about mussels?

How can you distinguish male and female mussels?

Q: My students had a few questions while they were doing the mussel lab. These mussels were salt-water, farm-grown mussels from Prince Edward Island, purchased at a grocery store. How do you tell male from female in mussels? We know the basics, but can you only tell the sexes while the mussels are breeding/producing egg and sperm? Thank you,
Carolyn Sheild (7th grade Life Sciences, Clarke Middle School, Lexington, MA).

A: Well, it depends on which kind of mussels you have. With some species, such as Bathymodiolus childressi (the mussel found at cold seeps in the Gulf of Mexico), you can't tell the sex without looking at a microscope slide of the gonad (or getting them to spawn) to see whether the mussel has eggs or sperm. If you see eggs, the mussel is female. If you see sperm, the mussel is male. On the other hand, if you are dissecting Mytilus trossulus (one of our local mussels here in Oregon), for instance, the ripe gonad of the males and females are slightly different colors. The females have a bright orange gonad and the males have a milky orange gonad. I don't know if this particular difference in coloration would hold true for the type of mussels the Clarke middle school students have, but if they do have mussels with ripe gonads and can see two different colors, they could try dissecting a piece out and using a microscope to look for eggs in order to establish which color is male and which is female. This is the best I can think of without knowing which mussels they have.
Shawn Arellano (Graduate Student, Oregon Institute of Marine Biolog)y

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What could our shallow-water mussels have been eating?

Q: Our second question is about the stomach of the mussel. Many of the stomachs were "full" when we opened them. In fact, it didn't seem to be the stomach directly, but two "pouches" one next to each shell when we opened the mussel. Do mussels have two stomachs? Or is this part of intestines or what? The pouches were full of black stuff. What could they have been feeding on? (We know they are filter feeders). Our teacher looked at the "gut contents" under the microscope, but said it just looked like little jagged particles—mud? The store said the mussels are farm grown (on ropes) so we can't imagine that this is mud.
Carolyn Sheild (7th grade Life Sciences, Clarke Middle School, Lexington, MA)

A: Good question. And good guess. First of all, mussels have one stomach. It's very simple, tubular, and shaped somewhat like an ice cream cone. However, they do have a pair of lateral digestive glands associated with the stomach. The glands secrete enzymes that aid in digestion. It's hard to say precisely what you were looking at without seeing it, but I'd guess that you were looking at the digestive glands. The 'mud' was probably just part of the gland. Keep up the good work.
Chuck Fisher, Biology Professor, Penn State University

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What websites and books can we look at to learn more about mussels?

Q: My class is currently writing their papers and we are having difficulty finding information on the deep-sea mussels. Could you direct us to some websites that would be beneficial for my class?
Ms. Diedre Young and students

A: Good question. I checked with some of our scientists and we don't really know of particular websites devoted to deep-sea mussels. However a quick Google search on 'deep-sea mussels' yields quite a lot of on-line material. For example, the NOAA Ocean Explorer wesite has information from Dr Craig Young and Dr. Cindy Van Dover. There's also a journal article by Dr. Bob Vrijenhoek on how mussels get their symbionts (and it's downloadable). The Venture Deep Ocean website also has an article about deep-sea mussels.

The other great resource is Dr. Cindy Van Dover's book The Ecology of Deep-Sea Hydrothermal Vents. You can get it on Amazon. It's an excellent reference in general for research in this arena. Dr. Van Dover did a wonderful job compiling most of the latest research into a very readable text. Hope this helps.

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