Explaining The Methane Seep Discovered In Deep Waters Off San Diego Coast
July 30, 2012 1:11 p.m.
Benjamin Grupe, Biological oceanography graduate student , a member of the seep contingent on the San Diego Coastal Expedition
Jillian Maloney, Scripps geosciences graduate student, a member of the seep contingent on the San Diego Coastal Expedition
MARK SAUER: You're listening to Midday Edition on KPBS. I'm Mark Sauer filling in for Maureen Cavanaugh. It sounds otherworldly; more than half a mile beneath the surface of the Pacific methane seeps from cracks in the ocean floor. 20 miles off the coast of San Diego a rich ecosystem has developed around the methane seep with strange aquatic worms and such we're going to hear about that. Joining me now from the Scripps institution of oceanography to take us on this undersea odyssey is Benjamin Grupe, an undergraduate student in biological oceanography. Thank you, Benjamin.
BENJAMIN GRUPE: Thank you, nice to be here.
MARK SAUER: And Jillian Maloney is a graduate student in geosciences and member of the seep contingent on the San Diego Coastal Expedition. Glad to have you, Jillian.
JILLIAN MALONEY: Thanks. Good to be here.
MARK SAUER: Ben can you tell us what is a methane seep?
BENJAMIN GRUPE: The methane seep is unique type of ecosystem and a deep-sea where methane and sulfide, these different sorts of reduced chemicals feed an ecosystem where the bacteria are actually using those chemicals for energy. So it is completely different from most ecosystems we think about, where the food chain starts with the sun and goes to plants. This is chemo synthetic, so it is chemicals coming from the seafloor, feeding the whole food web.
MARK SAUER: How interesting, how did you know a seep might exist off San Diego's coast?
BENJAMIN GRUPE: There were a few indications from previous research, from previous collections that this might be a promising area to look. There are other sorts of features like this in Southern California and bite near Santa Barbara near Santa Monica. This particular spot, Jillian actually had a contact at the USGS that knew about this area because it was an interesting fault zone. And it was we saw interesting features in the seafloor shape that made us think that it might be a good place to look for seats.
MARK SAUER: So Jillian, you were kind of the navigator here how did you help locate the specific location?
JILLIAN MALONEY: Yes so we have this information from the USGS that this was an interesting place to look and we had some other evidence of sites that we wanted to investigate further. So I study faults beneath the seafloor and we use a couple of different geophysical tools that use acoustics, soundwaves, send them to the seafloor and we are able to map the topography of the seafloor and the different sediment layers beneath the seafloor so we can look for different features that indicate seepage of methane or other fluids from the seafloor like pock marks we might see a mound and then beneath the seafloor we see a sediment layers can sometimes be disrupted which is always I hear Reese on my sediment layers the disruption and sediment layers continuing.
MARK SAUER: So it is kind of CSI, you are forensic detectives down there.
JILLIAN MALONEY: Exactly so we assist find an area that we can target them more specifically with Koror NRB or something like that.
MARK SAUER: So you found a missing mount the size of the city block as I understand how are you able to determine the size or are you able to determine the specific size.
JILLIAN MALONEY: The size we've estimated based on the survey techniques, so we mapped it acoustically so we can measure the width and the approximate height of the seafloor.
MARK SAUER: All right we've got a caller joining us from Miramar.
CALLER: What type of equipment are using for the acoustic, for that particular exercise like the boomers the use of golf when they have big flotation devices behind both boats or are using some other technique.
JILLIAN MALONEY: This is a much higher frequency than the boomers so we use a multibeam system to map The symmetry and that's about 12 kHz and the sub autumn is about three and half kilohertz. So, you can hear the ping. We heard that when we go to sleep on a boat. Pinging every 5 seconds trying to keep us awake. And so those are the frequencies that allow us to get nice high resolution images.
MARK SAUER: Sunds like a cricket, is that right?
JILLIAN MALONEY: A very large oversizeD cricket.
MARK SAUER: Let me invite callers to join the conversation. The number is toll free 1-888-895-5727. 1888895KPBS. Ben, what causes the methane seep to develop and why does it form into this mound?
BENJAMIN GRUPE: We can't say exactly what the source of this methane is. Originally it had to be some sort of organic matter and it gets changed to either physics and high-temperature pressure or biology. Microbes change it into methane. The reason that we would find it in this particular place is that either because of a fault, or because the of some sort of crap or conduit in the seafloor that methane as always percolating or seeping upward.
MARK SAUER: Okay and this is a powerful gas. Is this dangerous?
JILLIAN MALONEY: No I would say that it's dangerous. Most of the methane that's coming out is actually being used by these organisms so not much of it is escaping into the ocean and the atmosphere. If you have an increase in, people talk about gas causing instability in a (inaudible) but this is actually in a very deep sort of flat part of the oceans I would be concerned about that as a geo-hazard.
MARK SAUER: And tell us about some of these organisms. What's interesting about them and however they been able to adapt to this particular environment?
JILLIAN MALONEY: Well there are different types of microbes bacteria and Archea that are using the method for energy that is really fascinating because it's really different from our of the common sorts of organisms and energy producers we think of. There are animals that have developed symbioses with these microbes. So for example we found a particular type of two or two more that that's called a (inaudible) it doesn't have the mouth or a stomach as an organ called atrial visit and there are bacteria living inside the (inaudible). If you don't sulfide or methane, make a little bit extra for the worm and the worm does its entire life eating out another single thing.
MARK SAUER: We have another caller. George in San Diego has another technical question. Go ahead, George.
CALLER: (Inaudible) The methane you can trace is that methane going to be biological or nonbiological methane?
BENJAMIN GRUPE: It's a good question and we don't have enough measurements at this point to say what the source of that methane is. We have a return cruise in December and we are hoping to spend a few days at the site and take along some more people can work on the chemistry and hopefully will be able to sail a bit more about where the methane is coming from.
MARK SAUER: So Jillian, part of your interest I understand is finding the methane seep is that they typically happen along fault lines and what do we know about the San Diego, is it the---
JILLIAN MALONEY: The San Diego trough fault.
MARK SAUER: Explain about (inaudible) earthquake activity how often is that fault
JILLIAN MALONEY: That's something we are not totally sure but right now it's an area of ongoing research that I'm interested in and the people at the USGS are interested in. We know this fault is there this is a very specific location. It looks like the seep is that what you would consider an active fault the seafloor is little bit offset indicating there's likely been movement on it within the last 10,000 years but it's really difficult to assess at this point how frequently it moves, (inaudible), what size earthquakes it would produce.
MARK SAUER: Getting back you were talking about the organisms a moment ago found at these about methane seeps is a true they could reveal the foundation building blocks of life and shed some light on how life evolved these types of environments?
BENJAMIN GRUPE: That idea comes from, yeah the fact that when life evolved on earth there was not oxygen in the atmosphere the way there is today. So ecosystems like methane seeps, like hydrothermal vents. These are reducing ecosystems so there is very little or no oxygen. And so microbes and animals that have to deal with those conditions might be living in an environment more similar to Earth's primordial conditions. And then other ecosystems with oxygen. And so, there are, a lot of really interesting metabolisms, some that we understand some we don't and a lot of people are interested in just learning more about how organisms make a living in those reduced environments.
MARK SAUER: How interesting. And are methane seeps a fairly common phenomenon? What we know about the locations of other methane seeps?
BENJAMIN GRUPE: We know that they are a common feature of the world's oceans. They tend to occur close to shore, so along the continental margin from a few hundred meters down to a couple thousand meters so maybe a mile or little more
MARK SAUER: This is a little more than half a mile down or two thirds
BENJAMIN GRUPE: That's right about 1300 feet and there are probably about 100 seeps that have been identified worldwide and certainly many many more that we have not found yet.
MARK SAUER: And it's very convenient that they placed it 120 miles away and so close. As usual, right?
BENJAMIN GRUPE: Who knows, maybe there's more. One of the things we're excited about one of the reasons we thought it was worthwhile to spend the time looking for a seat in this area is to have Scripps institution of oceanography right here, perhaps this could become a research site where people can visit more frequently than a lot of other seeps and maybe learn more about how that environment changes over time because it really is just a couple hours away from the institution.
MARK SAUER: Are you planning to head back then soon. In December you've got another trip planned I understand what are you going to do that?
BENJAMIN GRUPE: We have an 11 day cruise in December hopefully be able to characterize the site little more take some more sediment samples if possible try and get some video down there to see what it looks like visually.
MARK SAUER: You will have the seep cam and go viral, it will be all over the place.
JILLIAN MALONEY: Hopefully, yeah
BENJAMIN GRUPE: We will see what we can get and the other thing we can mention this is part of a larger focused Chris, this is a group of graduate students at Scripps that developed the San Diego coastal expedition, and you can Google that and find our website if you want to know more about the other sites going out going on but there were physical oceanographers and chemists talking learning more about the ocean conditions another biologist learning about the different seafloor habitats off of San Diego, so this was more than just looking for seeps. It was trying to just learn more about the different sorts of open ocean ecosystems we have right here, locally.
MARK SAUER: Tell us how significant this discovery is it sounds like a pretty big deal.
BENJAMIN GRUPE: We think it's a pretty big deal. We would really like to collect some more data and get a better idea of what this particular seep really is. We don't know how similar or different it is from other seeps that have been observed in California or other places on the West Coast. But, the fact is people have suspected there might be seeps of this part of the coast for a long time and this is the first time we found one of San Diego County and so we are excited about it in think there might be some interesting things down there we don't know about yet.
MARK SAUER: I understand you look at a seep off the coast of Costa Rica. What did you find. How can you compare it to the San Diego one?
BENJAMIN GRUPE: I was part of a cruise a couple years ago that visited a couple seeps in Costa Rica and it's possible it's along the same coastline and it's possible there might be some species that might live in both places we found one type of secret clam that looks kind of similar to one from Costa Rica which was a new species there. So one of the interesting things we like to look at at seeps is a connection between different habitats because these are patches spread out through the ocean and somehow the babies of animals, the larvae have to be able to find a new habitat. So we will look to see if any of the species from Costa Rica Clay clams, like yeti crabs that were discovered there a few years ago might also show up at the scene the site.
MARK SAUER: How deep was that one in particular compared to the one here
BENJAMIN GRUPE: That was also out about 1000 m depth. About the same.
MARK SAUER: How do you go about collecting evidence to. Doing the research at the depth. It sounds like it is way down in the dark murky ocean deep.
BENJAMIN GRUPE: Well sometimes you have actual submersibles. Different types of submarine so you would use to do the research. In this case our funding came from the sea ship funds which allows us ship time, but we didn't have the funding for an actual submarine. Scripps does have a new remotely operated vehicle. Unfortunately it's depth limit is 1000 m. And this seep at 1036 m. So, Jillian was explaining how we use the geophysical tools to figure out about where this seep was, and we lowered an instrument called a multicore, which collected columns of the sediment and from what we thought was the middle of the mound so we sort of covered our eyes and blindly dropped a wire into the ocean and hit close to the right spot. But until we can see it it's hard to do a lot more than collect more blind samples and discover what's in those actual course of mud.
MARK SAUER: Tell us about the samples what exactly did you find when you got it back up and you are probably still looking at it.
BENJAMIN GRUPE: Well the first indication was a smell of rotten eggs, which is the smell of sulfide, which is really excited about because sulfide is very common at methane seeps and we saw little black spots of blood. And pieces of carbonate. The author also indications of a seep environment. As for picking through the samples we found elements of bacteria. Much larger than you would expect to see the outside of the seeping environment that was another good clue. And we found some of the other types of animals we've described. Seep clams, tubeworms, different types of polychaetes, segmented worms that we often associated with methane seeps. Some of the species returned to sequence their DNA right now so that we can get a better idea of what they might be
MARK SAUER: So this is a pretty rich ecosystem down there?
BENJAMIN GRUPE: It seems so but we only have a few course is meant to look at so at this point we've seen maybe 40, 50 different species of animals. But there's a lot of life concentrated in one place compared to the deep-sea which is more desert like.
MARK SAUER: If you Google methane seeps you see images in the Arctic about fires. That's not what we are talking about, right?
BENJAMIN GRUPE: No, that's not exactly what we are talking about. There is nothing in the tundra of the Arctic, but it is a different process of creation and release compared to these underwater seeps. That we are describing.
MARK SAUER: Do we know if it's actually leaking into the atmosphere and clearing out
BENJAMIN GRUPE: We haven't taken enough measurements to know exactly how much methane is present and whether it's coming out of the sediment. Fact is one of the really unique things about the ecosystems is that the biology by using the methane acts as a filter and it presents a great deal of methane from reaching the oceans and the atmosphere and so it will be interesting to see just how much methane might be actually seeping out. But it could be that because of the biological community, 90% of the methane or more could be turned into organic material and rocks before it ever has a chance to get into the atmosphere.
MARK SAUER: All right we are going to have to leave it there on a remarkable discovery. You can see the location of the seep and the remarkable organisms rocks the team got back from the expedition on the website KPBS.org. Thanks to Ben Grupe and Jillian Maloney for being with us today. Thank you very much.
JILLIAN MALONEY: Thank you.
BENJAMIN GRUPE: Thanks, it's been great.