Earth & Sky

The following individual was interviewed for today’s show. Our thanks to:

Cindy Lee Van Dover
Biology Department
College of William & Mary
Williamsburg, VA

Interview with Cindy Van Dover:

ES:

CVD: My name is Cindy Van Dover. I’m an assistant professor at the College of William and Mary.

ES: Thanks for talking with Earth and Sky. Could you please tell our listeners about your work studying deep sea biodiversity?

CVD: Well, that’s a big subject ? deep sea biodiversity (laughs). My advisor as a graduate student is Fred Grassly, who has really led the field of deep sea biodiversity, and he studied the *** sediments, which make up most of the abyssal plains. And in those muds ? all mud sediments – there are hundreds of species within a meter squared. So in a square meter you can have a hundred species. They’re little tiny things, often little small crustaceans, small worms, small mollusks, snails, and clams. And it’s truly remarkable. And the deep sea, we think has a very high diversity, at least at moderate depths, a couple of thousand of meters. My own work is on diversity in mid ocean ridges, which are where the hot springs are, the hydrothermal vents. So I’ve been looking at diversity within habitats in hydrothermal systems. And it’s quite different, that we have a much lower diversity. We get very diverse kinds of animals, but the actual numbers of species are lower than in the non-vent, deep sea habitat.

ES:

CVD: Sure. Hotbeds on the sea floor are analogous, they’re the submarine equivalent of hot springs on land. So if you’ve ever been to Yellowstone and seen Old Faithful, you’ve seen hot springs. And the same kind of thing happens on the sea floor. In the case of land, rainwater percolates down to the crust, to the ground, and gets heated up, reacts with the underlying rocks, and becomes chemically modified. So the same thing goes on in marine systems, except that instead of rainwater, of course, it’s sea water. It percolates down through the crust, and these mid ocean ridges where we find the hot springs, they’re the mountain ranges that girdle the globe. They’re volcanic systems, so they have hot rock. So the sea water becomes heated, it becomes chemically modified. In particular it gets enriched in sulfide, that compound that makes that rotten egg smell. And sulfide turns out to be very important to the animals that live at the hot springs in the deep sea. So, what we find where these hot springs are little islands of very high biomass, a lot of animals, and when these were discovered in 1977, the big question was how could you support so much biomass in the deep sea. Because the traditional story was that everything lives on the rain of small, dead bodies of plants and animals from the surface waters where there is sunlight down to the sea floor. So by the time it gets there there’s not much left that’s very good. So how could these hot springs be supporting all of these animals? And the answer was in the this concept of chemosynthesis and the role of microorganisms, bacteria. Take the chemicals coming out of these vents, this sulfide in particular, and combine it with oxygen from sea water and carbon dioxide, so all of these things are what we call inorganic compounds. And the bacteria then make organic material from it. And then that’s the food, that’s what everything else lives on in the vent. So it’s all driven by microorganisms using chemicals, hence the term chemosynthesis, in contrast to getting the energy for making organic material from sunlight, which is photosynthesis.

ES:

CVD: The hot springs in the deep sea, by deep I mean 2000 meters, a mile and a half down, are on these mountain ridges which are basalts, they’re formed by lava, mountain forming kinds of systems. And the way we get there is by taking submersibles, we call them human occupied submersibles now, as opposed to manned submersibles, we take the submersibles down to the sea floor. One in particular that Americans use a lot is Alvin, our deep submergence platform. Alvin is a three person submarine. She dives with one pilot and two scientists. And so it dives day in and day out. So if you are the lucky scientist that gets to go down that day, you get in the sub at eight in the morning, and descend. It takes maybe an hour and a half to get down to the sea floor. You have five hours of working on the bottom. The way we do it is that the scientists talk to the pilots and explain to them what we want, and then the pilot takes all the samples. And so there has to be really good communication between the scientist and pilot. And it’s all done with manipulators outside. The sub itself is at one atmosphere. And so you want to maintain the integrity of the sphere. You can’t just reach out and grab something because of the high pressure. So it’s all done with manipulators. So it takes a year or two for a pilot to become really good at getting samples. And they just work the manipulator and do whatever you ask them. They can do some very complicated tasks. We’ve become very adept at working the deep sea. I started 20 years ago, and it was difficult to even find the same place a second time reliably, and sampling was very difficult. Now we know how to get down there and work in these environments, and our main limitation now is that we have one manned submersible, one submersible for the entire country for all the researchers who’d like to work on the sea floor. And so we’ve added a tool, these unmanned vehicles called remotely operated vehicles. They allow us to sit on a ship and watch video cameras and then a little robot goes around and does the same work that ALVIN might. And it has a lot of advantages, but it tends to have some disadvantage too. There’s a lot to be gained by seeing the site, having that three-dimensional sense of the habitat. It’s challenging, but it’s not impossible to do this kind of work on the sea floors. And it’s just a fascinating, beautiful place to be.

ES: What is something that surprised you while researching the ocean floor?

CVD: I’m always stunned by the geology, the formations. These sea floor habitats are spectacular. They’re very three-dimensional. So when you’re diving on a hot spring, you’re also steering around these volcanic structures. So there can be columns and pillars. Black smokers are just the most amazing things in the universe. They’re where the high temperature fluids come out of chimneys on the sea floor at 350 degrees Celsius or hotter. They’re beautiful things to see. And the first time you see them, they’re surprising. I’ve seen them over and over and over again, and they’re still stunning features. I think they’re more spectacular than any geyser on land. I’m sure I’m biased, but they’re really lovely. The animals, the vibrant colors? you would not believe how rare the tube worm is. You can watch all the video in the world, and until you’re down there and see it with your eyes, with these bright lights from the submarine, It’s just incredible how much color the animals that live in the hot springs can have. Some things are surprising, where when we go exploring a new site. It’s very exciting because we go into some place, a remote region where we haven’t dived before, and we don’t know what we’re going to find. I was out last April at a site called the Blake Ridge. We knew there were mussels there, big mussels, but we didn’t know what else. So we had a great time exploring, looking around. It’s like going to some new planet and seeing what lives there.

ES: I can’t help but to ask, is it true that you occasionally get sea sick before you dive?

ES: I am prone to sea sickness, yes. I know a ot of people who sail, and I just don’t do day trips on a sailboat. I don’t go out for a day trip because I get so sick. I can be non-functional. But when you go out to sea, to study a hot spring with a research expedition, you go for weeks at a time. And then it works out OK. I get on, and I’m sea-sick the first day, and I just make sure that I’ve got all the work done that I’ve needed to get done to get done for that first day, organizing of things. And I kind of just take it easy that first day. And then, fortunately, it goes away.

ES:

CVD: The agenda for the group of people studying hot springs is really varied. My particular lab ? I teach undergraduates and Masters students ? I’ve taken on a project that involves them in the research project very easily, even at that kind of level. And it’s a biodiversity project. And the main thing we’ve been doing is going – essentially around the world ? at the same habitat in different site and asking the question: how many species are there? What are the patterns of distributions of species? It’s biogeograpy, essentially. And then we try and understand, get some ideas of what might be causing some of the differences we see. So we know that when we go to different ocean basins, and look at vent sites on the Mid-Atlantic Ridge, and compare what’s there with a vent site on the East Pacific Rise in the Pacific, the fauna is completely different. So they’re completely different species living with the mussels. And the diversity levels are different. There are fewer species on the Mid-Atlantic Ridge then on the East Pacific Rise. So we get into those kinds of questions, asking who is where, and how come, and what controls these kind of distributions on a very large scale. And then we also go into individual sites and look at spatial change and variation, how species change over time, getting at some very fundamental information, that for terrestrial systems, we’ve known about for centuries because it’s easy to look. But for these deep water systems, it’s the first time we’re getting this spatial resolution of where bigeographical provinces begin and end, and what might be some of the things that cause boundaries that restrict species to certain regions, all the details of the spatial relationships between species.

ES:

CVD: Biodiversity is an interesting topic because I think ? I don’t know, but I think that some people have the impression that when we talk about biodiversity, more is better. And in fact in some systems it’s natural to have low diversity. So in intertidal zones in coastal systems you have low diversity, but that’s good. We like it. We like all those animals who live in the intertidal zones on our coastlines. So the diversity we have at hydrothermal vents is low, but that’s not a bad thing. It’s a good, healthy environment. What’s very interesting about what we see at the vents is that animals almost always have some type of adaptation to the habitat. It’s one of those extreme environments, and that means that they all have to be somehow coping with – well sulfide itself is typically poisonous for organisms ? so they all have some physiological mechanisms that allow them to cope with the sulfides so it doesn’t poison them. They have to deal with heavy metals, we all know about heavy metal pollution in shallow water. These guys live with it day after day, so they have special adaptations that allow them to cope with it, and we’re very interest in how they do that. There may be low diversity in the number of species, but there are other measures, like how diverse are the different adaptations they have, and different ways of making a life in the system, and so it’s just the natural state to have the low diversity and the species coexist just fine.

ES: So what motivates you to study deep sea wildlife?

CVD: I have always been interested in weird animals. That’s how I got into studying invertebrates in the first place. There’s all these things like horseshoe crabs. When I went to the beach as a kid we used to see crabs and snails and things. They look different from humans or vertebrates, mammals. So I wanted to know what they used all those legs for. Sometimes they have four pairs of eyes. Why should they have four pairs of eyes? Their eyes didn’t look like ours. And so all those weird things I liked and wanted to understand. And I had the sense that the oddest things would be out in the deep sea, once I actually understood that there was such a thing as the deep sea. And so even before hydrothermal vents were found, I was interested in what was going on in deep water. And, of course, these vents were found. These are the oddest animals around, and they’re just amazing to study and learn how they’re coping with that environment. So that’s certainly a motivation. I’m pretty much a veteran in this business and have done a lot of dives ? over a hundred dives and many, many cruises, more than I care to count. Now, a motivation for trying to get field grants is ? yes, I still want to ask scientific questions ? one of the best things for me, getting my students out to sea and getting them in the submarine and getting them down to the sea floor to see these things. If nothing else, that’s probably my biggest motivation now is to be able to teach others what I know and watch them go on and ask the same set of questions.

ES: Can you tell me about some of the things that are threatening the deep-sea ecosystems?

CVD: In general, the deep sea is certainly subject to insult from coastal activities. It’s an open system. What you do on the coastline gets into the deep sea, and we can see these signals. I did a project at dumpsite 106 in New Jersey. When that was first started the thought was that the sewage sludge they were dumping there wouldn’t even get into the deep sea. It would be dispersed and diluted in the upper water column and no one would see it. And in fact, it does get down to the sea floor and we can find evidence of it entering into the food web. The deep water trolling ? I’ve heard it referred to as mining. Because, you take these animals, and they don’t replace themselves once you take them, their age structure is such that they’re really quite old when they get fished ? like the orange roughie, there’s other stories like that. And I’m sure that there’s plenty of other things that I’m not thinking of for the deep sea. Specifically for hydrothermal vents, there’s issues of mining, the vents themselves where the hot fluids come out have minerals ? copper, iron and zinc in particular. Some places where there are abundances of gold and silver, and so there is a threat of mining, especially in the western Pacific. Tourism is perhaps an issue, although the tourism that might go on in hydrothermal vent is pretty elitist and pretty low impact. Maybe one of the biggest threats to hydrothermal vents is the scientific research that goes on. The scientists, as a community, we’re well aware of this issue, and we’ve been policing ourselves pretty well on this in terms of making sure that we don’t over exploit systems and consider what it is that we’re doing, where we set up observatories and really do intensive research. I guess those are the things that come to mind first, that it in fact it might be the scientist that have the potential to threaten these systems.

ES: What’s special about deep-sea ecosystems?

CVD: It’s unknown. It’s vast, and things that are that vast, small things that go on there are multiplied by huge numbers. So something that might be affecting water chemistry can have a big effect on a global scale, because the system is so big. I don’t have a specific example, but one can imagine that there’s things going on in the biology, the geology and the overlying sea water that controls aspects of what the oceans are like. Certainly, in the sense of being unknown it has hundreds, if not millions of species that have never been seen, let alone described. And if we’re really going to go do things down there, we really need to know what’s there. We only just discovered hydrothermal vents in 1977, and we’re only beginning to appreciate methane hydrate systems are like. These are vast areas of the continental margins where there’s methane resources which, are arguably exploitable, certainly host very interesting animal communities, and they have the potential to have global climate impact or have major effects if the climate starts to warm, big pulses of methane might be released. So we’re just finding these out now. Who knows what else is out there. It’s one of those things where we can’t even imagine what we don’t know about the sea floor.

ES:

CVD: Absolutely. I just mentioned the methane hydrates, those are amazing. There’s also, we call it a seep. Seeps are a catch-all phrase for lots of different kinds of ways of generating hydrogen sulfide. We don’t get the sulfide just from hot springs. But there are other kinds of habitats. And wherever you have that sulfide, you support a whole bunch of odd kinds of animals. Whale skeletons ? when a whale carcass falls to the sea floor, scavengers come in and eat the flesh. Then the bones lie there on the sea floor and they’re lipid rich, and those lipid ooze out and the microorganism, the bacteria come into play. And then they start generating some sulfide, and then the sulfide animals come in. So there’s little islands, oasis of life around whale skeletons. There’s a shipwreck that was found in the Atlantic that has tube worms growing out. It’s organic, it carried a cargo of hemp I think it was. And the hemp was rotting, and microorganisms were consuming it, and in the process generating sulfide. And then these sulfide animals came in to live off it. So there’s just amazing kinds of things that we find on the sea floor in just the past two decades, so there must be more out there.

ES:

CVD: It’s frontier. It doesn’t have any solutions for immediate, human kind social activities. There’s so much basic knowledge to learn about how our planet functions. I think that’s a big thing to appreciate, that we’re getting a pretty good handle, maybe, of what’s going on on land and in the upper water columns. Because we can go out there and measure them easily. We can use satellites to see what’s going on on a global scale. We don’t understand globally what’s going on in the deep ocean. And so I think we’re going to be learning amazing things over the next couple of decades as we go in and explore the deep waters. Stand by for discoveries.