Coral Reefs and Creatures of the Deep Sea

23 April 2006
Presented by Chris Smith, Phil Rosenberg.


Delving into the dark depths of science this week is Ron Douglas who describes the fascinating world of deep sea fish, bioluminescence and the sights from a deep sea sub, Jason Hall-Spencer talks about cold water corals and the threats posed by fishermen, and in slightly warmer waters David Kline reveals how Caribbean corals are suffering due to sugar pollution. Also in the show, Fran Beckerleg interviews John Ablett about a giant squid called Archie, and getting the low down on the high seas Derek finds out how a submarine works in Kitchen Science.

In this episode

Sounds Like Bad News For Speeding Motorists

Speed demon motorists watch out - the police may soon have a new weapon up their sleeves with which to trap you - and it works just by listening to sound you car makes as it speeds past a microphone. The novel trap technology, which is being developed by researchers at the University of Tennessee and Battelle Institute in Oak Ridge, relies on the doppler effect - the way a sound alters in pitch as a moving object approaches and then passes the listener - to calculate the speed of passing vehicles. And because it relies only on a passive microphone, which eavesdrops silently on a car's engine note, motorists have no chance of being able to detect it and slam the brakes on to avoid a fine. To prove that the idea works, the development team recorded the noises made by a number of moving vehicles and then calculated their speeds based on the doppler shift of the sounds made in each case. The system was right to within a few percent in 32 out of 33 of these trials. It can even work out how large an engine is, just by listening to the sounds of the pistons, and whether a vehicle is overloaded by comparing the change in road speed relative to the change in engine load as the vehicle climbs an incline.

Air Mail With a Difference

Californian company Masten Space Systems is offering a brand new service: sending random objects on a return trip to space for just ninety-nine US dollars. The lucky object will travel over 100km in altitude and will experience several minutes of weightlessness or microgravity. Upgrading your object's ticket will give it once in a lifetime exposure to the vacuum of space before making its return to the surface. But as with any special offer, there are a number of restrictions. Firstly the item must weigh less than 350 grams and be no bigger than a can of coke. Secondly, items must be legal, non-radioactive and guaranteed not to explode. If you want to send a living organism then it has to make the trip without any animal welfare issues. Maybe the pet gerbil is a bad idea then... The company are expecting to receive a range of school projects, biology experiments and the odd unusual request including firing off a late great-aunt's ashes. The first launch will be in 2008 but the ninety-nine dollar price tag is for advanced bookings so get your orders in now!

A New Catalyst Fuels Optimism For Energy Supplies

US researchers at Rutgers University in New Jersey have come up with a catalyst combo that might help to safeguard fuel supplies into the future. Alan Goldman and his colleagues have found a way to stitch together short hydrocarbon molecules, which come from coal, biomass, or refinery waste products, to make longer chains that are perfect for diesel fuel. To achieve this feat, which is known as alkane metathesis, the team have developed a pair of catalysts which work in tandem. The first knocks the hydrogens off one end of the short molecules, making them much more reactive, and the second then sticks the two pieces together to yield a longer-chain result. In some cases molecules of between 10 and 18 carbon atoms were produced, ideal for diesel. At the moment the catalysts are still under development and too inefficient to be used commercially, partly because they are too unstable and break down under the high temperatures (175 degrees C) inside the reaction vessel. But with oil prices hitting the roof, supplies dwindling and more cars than ever hitting the roads, a system that can turn plant waste into diesel, which this ultimately can, could rescue the petro-chemical industry from an uncertain future.

The Three Phases of Mars

The European Space Agency's Mars Express spacecraft has found three distinct phases in Mars' history. The orbiting satellite has used infra-red light to identify minerals that have formed on the surface. Although Mars is currently a frozen desert, we've known for decades that water must have been present at some point; a secret revealed by dried up river beds and underground permafrost. It's only now that we know the timescales involved. Just after Mars formed around 4.6 billion years ago, it boasted a dense atmosphere and plenty of liquid water. This water pooled on the surface and formed the clay beds discovered by Mars Express. However it seems that Mars' arid fate was sealed even in those early days. Radioactive elements slowly heated the planet for 600 million years until Mars erupted in a cataclysmic episode of volcanism. This released tonnes of sulphur dioxide into the atmosphere which reacted with the water to form acid rain and sulphate minerals. The volcanism died down as the planet cooled over the next 500 million years, but the planet also lost its protective magnetic field. This allowed charged particles blown out from the Sun to strip away Mars' atmosphere. For the last 3.5 billion years Mars has been a desert world with the iron in the rocks slowly rusting to create the red planet we see today. This seems a bleak place for life to try and survive, but if there is life on Mars then it will most likely be found in the ancient clay beds.

How does a submarine work?

Derek - Hello and welcome to Colchester County High School, which is where we've come this evening. A very warm welcome to you. With me is a scientist new to the kitchen science feature and who's going to do a great experiment you can do at home. Please do listen out for the details because it's very easy. Could I get you to introduce yourself?

Sheena - Hello my name's Sheena Elliott and I'm a PhD student at Cambridge University studying physics.

Derek - Ok, and just quickly, what have we got set up? What are we going to be looking at today in kitchen science?

Sheena - We've got a Cartesian diver, and what we're going to do is simulate how a submarine works in a lemonade bottle.

Derek - Fantastic and that's all coming up. Also with us is a student from Colchester County High School, so would you care to tell me your name and what year you're in please?

Amanda - My name's Amanda and I'm in upper sixth.

Derek - Excellent, thanks for coming along. We love to know from all our volunteers whether they like science. So are you doing science at school?

Amanda - I'm doing all three sciences and maths.

Derek - Ok so are you going to carry on and do more of that?

Amanda - Yes.

Derek - So we already have a convert but hopefully we'll be switching you onto science even more. Right then, to do this experiment at home, you will need some very simple things and hopefully you will have them. Firstly, a straw or a pen lid. Some kind of drinking straw or the lid of a biro will work very well. Secondly, you need a lemonade bottle. The bigger the better basically: if it's as big as two litres then that's very good and it's needs to be emptied and filled with water. Thirdly you need some blu-tac or some plasticine, and that's it. Now Sheena's going to tell us what to do with these things and how to set it up.

Sheena - First we need to take the drinking straw which we might cut up into pieces two or three centimetres long, or if not we can use our pen lid, and then we need to block up the ends. If it's pen with two ends, then we need to block it up so there's only an air pocket inside it. It's the same with the drinking straw; you just block up both ends. So what you want is an air pocket enclosed in the drinking straw or the pen lid. It has to be a very good seal. You then need to make sure that it floats, but you have to make it so that it's only just floating. You can practice in a mug of water. Put it into the water. If it floats too high then add a little more plasticine. If it sinks to the bottom then you might have to take some off and play around with it until you get it just right.

Derek - Ok, so the plasticine is weighing it down and you just need to get the right amount.

Sheena - Yes that's right.

Derek - And then what do you do with the lemonade bottle?

Sheena - You want to fill your lemonade bottle right to the very top, right to the brim, so that there's no air at the top. Then you want to put in your little pocket of air which was your straw or pen lid and just it in the top. Then you need to tighten the lid on the bottle quite hard.

Derek - Ok so that's the set up. Then what do people do?

Sheena - All people have to do is squeeze the bottle and see what happens.

Derek - So there it is then. What you have to do is get that air pocket, which could be a pen lid or a piece of straw about one inch long, and plug it at both ends with the right amount of plasticine so it just about floats. Then fill a lemonade bottle right to the top with water and put the little air pocket thing in the top and put the lid on. Screw it tight, squeeze the bottle and see what happens. Of course, you can do this at home, and we're going to be doing later on in the show. Of course, we have a volunteer who's going to be doing it, and I wonder what, Amanda, do you think's going to happen when we do this?

Amanda - I don't really know but I think it might rise.

Derek - Any reason? Why do you think that that might happen?

Amanda - I don't know.

Derek - Ok, that's fair enough because all will be explained later and Sheena will be telling us all about how this relates to real world things that we see around us. Anyway, you at home, we want you to do this too and hope you've got all the details now. If you like, then please call us with the result because there are prizes! So until later in the show, we'll be waiting poised next to this air pocket inside our lemonade bottle to see what happens. Do come back to us later at Colchester County High School. Goodbye until then.


Derek - Hello again and welcome back to Colchester County High School where we have been waiting for the last part of the show to do this experiment with a lemonade bottle, which has a kind of floating thing ready inside it. Sheena's here too, and Sheena, could you instruct Amanda about what she has to do now?

Sheena - Ok Amanda. All you need to do is step towards the bottle, put your hands around it and give it a little bit of a squeeze.

Derek - And tell us what you see.

Amanda - It's gone down.

Derek - Ok tell me more. What's gone down and how far has it gone?

Amanda - It's gone all the way to the bottom.

Derek - Ok and when you release your hands, what happens then?

Amanda - It rises up again.

Derek - So what we've seen then is that when Amanda squeezed the bottle, the bit of straw with the plasticine on the ends and the air pocket inside sank all the way to the bottom of the bottle. As soon as she took her hands away and released the pressure from the bottle, it came back up to the top. So Amanda, have you any idea why that's happened?

Amanda - I have no idea.

Derek - Well that's ok because Sheena Elliott is here who set up this experiment. So Sheena, what's happening here firstly?

Sheena - Well before we can understand what's happening we really need to know why it floats. What's the difference between something that's floating and something that's sinking? For this, we're going to turn to Archimedes' law. What Archimedes said was that for something to float, then the amount of water it displaces has to weigh more than the thing you're trying to make float. When we have our straw floating to begin with, it's obviously taking up more space of water and that water weighs more than the straw ensemble with its plasticine. Therefore it's floating.

Derek - Ok, let's just have an example here. I'm imagining something very big and very light like a big piece of polystyrene. I suppose that takes up much less weight of water if you kind of put it on the water and so it doesn't displace any and it doesn't sink.

Sheena - Yes exactly. It's all down to density because you're talking about the amount of volume it takes up and the amount it weighs. What it really comes down to is that if it's less dense than water then it will float and if it's more dense than water then it'll sink.

Derek - So we've made something there, the bit of straw with plasticine on the end, that's just about less dense than water. So what happened then when Amanda was squeezing the bottle?

Sheena - When we squeeze the bottle we're increasing the pressure inside the bottle. That's inside the whole bottle that the pressure is increasing. The thing is that water is very difficult to compress but air is comparatively much easier to compress. So by compressing the air inside the straw, you're making it smaller. So although it weighs the same, it's taking up less space so it's density has increased and has therefore increased in density relative to the water and begins to sink.

Derek - So when you squeeze the bottle you squeeze the water in the bottle, but because it can't be squeezed it has to take it out on something, and that is the straw.

Sheena - Yes exactly because the air is easier to compress than the water.

Derek - So when do we actually see this effect in the practical world?

Sheena - This is actually how fish can control their height in the water. They have little air sacs inside them and muscles to compress those. So the fish is actually changing its density by compressing these air sacs. It's also how submarines work and how their ballast tanks work. They let water in to increase their density and they pump water out to decrease their density.

Derek - So a ballast tank is really like this air pocket. They just compress it however much they want.

Sheena - Yes. That's just how they work.

Derek - Wow. Amanda does that make sense to you?

Amanda - Yes it does.

Derek - Yeah, I've always wondered how submarines and fishes managed to do that. What about you?

Amanda - Me too.

Derek - Well it's been explained. So how did you like our experiment?

Amanda - I really enjoyed it and it was totally amazing.

Derek - Will you be going home and doing the same again with everyone you know?

Amanda - I will.

Derek - Excellent, a convert! We make lots of these on this part of the show. Well thanks very much to Amanda who's at Colchester County High School and also to Sheena Elliott who will be back with us doing some more kitchen science. So that's all from Colchester County High School and we will see you again for more kitchen science somewhere in the East of England. Until then, goodbye.

- Antarctic Lake Shake Up

The Naked Scientists spoke to Professor Martin Siegert, University of Bristol

Antarctic Lake Shake Up
with Professor Martin Siegert, University of Bristol

Chris - One place people are very interested in getting into is Lake Vostok. This is a sub-glacial lake. It's a lake of water that's sealed inside the ice of Antarctica, and it's actually one of many. People think that it contains water that's been there for a very long time and might have a unique ecosystem. Life might be living there that's evolved independently form other life on Earth, at least for a long period of time which might mean that there are some interesting things in there. But then somebody came along, someone called Martin Siegert from the University of Bristol, and he's really stirred up a heap of trouble, because he's found, from looking from space, that these lakes might be communicating with each other and that lots of water is moving round.

Martin - Deep beneath the four kilometres of Antarctic ice sheet, we've discovered that a sub-glacial lake has lost, rapidly, a large part of its volume. This water has moved over 200 kilometres in to another sub-glacial lake.

Chris - How did you actually do it though? How do you know that that water has moved around?

Martin - We looked at how the ice sheet surface changes. We had a satellite that looked at ice sheet surface elevation, and we noticed that one part of the Antarctic ice sheet lowered by three to four metres over the course of a year. Two hundred kilometres away, the ice sheet surface elevation went up by about a metre. That's a very unusual change, and there are very few alternative explanations for that amount of surface change. Actually, losing that amount of mass from the centre of East Antarctica, which is a very stable ice mass, it can only be the removal of something really rapid. All the alternatives point to it being water.

Chris - Do you know what's driving that movement of water though? What's pushing it along?

Martin - The base of the East Antarctic ice sheet, much of it is at the pressure melting point. So there's water being melted from the bottom of the ice sheet and al this water will feed down into sub-glacial lakes where it collects. The sub-glacial lakes will be pressurising because water will be coming into them, and the ice sheet will be attempting to hold that back. That's an unstable situation because the ice sheet can't hold it back forever. As the pressure increases to a threshold, the water will escape, so it sort of outbursts.

Chris - People are quite interested in those lakes for the simple reason that they're viewed as time capsules in the case of Vostok and similar bodies. Your work must have those people quite worried.

Martin - Well I don't know about that. It's only been ten years since a paper was published in Nature on Lake Vostok, and since then people have been talking about these lakes as being very isolated and very distinct systems. What we're identifying now is that maybe that's not the case and that it might have to be revised. But it's still very exciting from a sub-glacial point of view. I don't think that it would harm going into to sub - glacial lakes or even belittle the types of science that could go on in those systems.

Chris - The escape of so much water at once: does that have any other consequences in terms of, say, the salinity of the surrounding ocean, animal life, that kind of thing?

Martin - We haven't shown that this water can get to the ice sheet margin, but even if it did, it's quite a large amount of water. It's 1.8 cubic kilometres of water we've seen transferred. But actually that's a very small amount in terms of global ocean values so it wouldn't have much effect.

Chris - Do you think climate change is having any kind of implication or bearing on what's happening here?

Martin - Well I don't think so. The situation that we have is the underside of the Antarctic ice sheet. And remember, this is the East Antarctic ice sheet which is the stable part of Antarctica and there really isn't very much change going on there. What we think we've seen is a process which is common, both now and in the past. This is the first time that anyone's actually seen it.

Chris - And what questions are you now gagging to answer on the basis of the intriguing observation you've got here?

Martin - Well, what we'd like to do is to find more of these processes, both in East Antarctica and in West Antarctica, because we know that a sub-glacial lake has lost mass and that water has flown underneath the ice sheet and into another lake. What we now have to try and do is understand the physics of the problem a bit better and that applies to getting more data, more observations, in order to constrain the system better than we have done up until now.

- Venus Express Success

The Naked Scientists spoke to Daniel Scuka, European Space Agency

Venus Express Success
with Daniel Scuka, European Space Agency

Phil - Now we're going to find out about Venus Express, which went into orbit around Earth's closest neighbour about two weeks ago. The European Space Agency spacecraft will look at the surface and atmosphere of Venus. Daniel Scuka from the European Space Agency was in the main control room as this crucial manoeuvre was completed. He spoke to some of the key players to find out their reactions.

Daniel - This past Tuesday April 11th engineers and scientists from the European Space Agency crowded into the dimly lit main control room at ESOC, ESA's Space Operations Centre in Germany to monitor the entry of Venus Express into orbit around the hot house planet. Positive confirmation that the spacecraft had successfully fired its main engine to slow into orbit came at 11.12am central European summer time, when ESOC mission controllers re - established the radiotelemetry link with Venus Express after a series of critical and complex manoeuvres. The dramatic activity began just after 8am, when Venus Express automatically swung itself into a slew manoeuvre to point its main engine in the direction of travel. After firing its smaller thrusters, the main engine fired for 50 minutes, reducing the spacecraft's velocity so that Venus's gravity could pull it down into the first capture orbit. You could literally feel the tension in ESA's main control room as the spacecraft dropped behind Venus at 9.45am as scheduled, causing a communications black out. Venus blocked the line of sight path between the spacecraft and the Earth. For a very long 12 minutes, radio contact was not available. Low bandwidth radio contact was re-established at 9.45am as Venus Express emerged from behind Venus, and full telemetry was back after just over an hour later. Immediately after the spacecraft's signal had been reacquired, I spoke with project manager Don McCoy, in ESOC's main control room.

Don - It went absolutely normally, so in that sense it's been an excellent mission. Given that sometimes machines don't work the way you want them to, that's a surprise. But it was very nominal, which is an indication that the satellite was very well built and well tested. The work of the crews here has been absolutely cracking, so the whole thing has worked very well.

Daniel - I also spoke with the engineer most responsible for making the manoeuvre a success: Flight Director Manfred Vorhaut.

Manfred - I think that's it's outstanding what has been delivered here by a joint effort from industry, ESTEC and ESOC and I do not want to address anybody in particular. I may say a few words about the navigators because they made sure that we aligned with Venus in the proper corridor, and finally, we did it and I'm more than happy I can tell you.

Daniel - Venus Express mission controllers now enter an intensive orbit entry period with additional engine firings and manoeuvres designed to lower the spacecraft into the final 24 hour operational orbit. Scientists will then have to wait until June 4th for the spacecraft and its instruments to be commissioned and verified and to kick off formal science investigations around the hot house planet. Venus Express is ESA's first mission to Venus and the first mission at all since 1994. For the European Space Agency, I'm Daniel Scuka reporting from the European Space Operations Centre in Darmstadt, Germany.

Phil - That was Daniel Scuka who was there for the crucial manoeuvre on April 11th.

Chris - So Phil, what are they going to be looking at now that the mission's established itself? What sorts of things will they be investigating?

Phil - Well Venus is a really interesting place but somewhere we haven't been to very much. It's covered in a layer of clouds, so we really can't see right down to the surface. There were missions previously that actually landed on the surface, but because Venus is covered with a really nasty acid rain and it's an intense atmospheric pressure down on the surface, they didn't last very long. We didn't get huge amount of data from them. We've also have probes going in making radar maps of the surface to try and get the altitude of the surface. But this mission is really going to increase our knowledge of what's going on on the surface and in the atmosphere of Venus. It's going to be a really interesting mission to watch out for.

- Deep Sea Corals

The Naked Scientists spoke to Dr Jason Hall-Spencer, University of Plymouth

Deep Sea Corals
with Dr Jason Hall-Spencer, University of Plymouth

Chris - Tell us about your research because you're looking at corals principally aren't you?

Jason - Yes, but I'm looking at deep sea corals. Previously people thought that corals only occurred in the tropics making great big coral reefs. But we've just discovered some really huge ones off the coastline of the UK.

Chris - I imagine a lot of people of thinking, myself included, what actually is coral?

Jason - It's related to an anemone but it's got a hard skeleton, like we've got a skeleton inside of us. These corals have got a hard chalky skeleton too. What's peculiar about them is that they've got stinging cells. They've got harpoons that inject their prey, and that's what they use to catch their prey.

Chris - But when you see this big chunk of coral reef, is all of that one massive alive organism or is this an ants' nest with lots of little things that co-operate to make one big colony home for themselves?

Jason - It's more like an ants' nest I suppose because each individual polyp, that is the individual anemones that make up the reef, make up a great big skeleton together. They are like ecosystem engineers because they make these reefs to catch their prey.

Chris - And how big is each of those polyps then?

Jason - Well each one is about the size of your thumb nail. But if you're the size of their prey, such as a little tiny flea, that's a large mouth ready to catch you and rip your head off.

Chris - So how did they evolve? Where did these polyps come from?

Jason - We think they came from things like Hydra. they've got lots of tentacles; they've all got stinging cells; and they're all related to things like jellyfish. These are sedentary jellyfish: jellyfish which live on the bottom and then form a skeleton.

Chris - So why's it significant that some live deep and some live shallow?

Jason - We didn't think that large reefs were formed in deep water. We thought that they had to be living in shallow water to catch enough light to feed their symbiotic bacteria that live in their skeletons. But it turns out that we've just been able to discover some large reefs of the coast of Ireland and Scotland and Norway, and that's very significant. You'd think that people would know the deep sea quite well but in fact there are large reefs there that no-one knew about until about five years ago.

Chris - Tell us a bit about that symbiotic relationship, in other words two organisms living side by side to mutual benefit.

Jason - Symbiosis is when two different unrelated organisms benefit each other. In the case of the corals in the tropics, there's an algae that lives inside its tissues that captures light and makes sugars. That benefits the corals themselves. The corals benefit the algae by being a highly armoured vehicle in which they can live.

Chris - Is it just a protection thing or does the coral do anything else for the algae?

Jason - The coral provides the algae with its waste products, which are nitrogenous. The algae would otherwise find this very hard to get hold of.

Chris - Because algae are plants aren't they.

Jason - Yes.

Chris - And when you go deep down in the ocean, what sort of depths are the corals you're looking at growing at?

Jason - Typically, the ones I'm looking at are a kilometre down.

Chris - That's a long way. How much light is there down there?

Jason - there's no light. We lowered some polystyrene cups down to that depth and they're crushed down to the size of a thimble, so there are huge pressures.

Chris - How do the corals withstand that kind of pressure?

Jason - It's because they don't have any air pockets in them. We have air pockets in us and so does a polystyrene cup. If I was lowered down on a rope to a kilometre depth, I'd implode. My skull would be crushed because I've got sinuses in there that are air pockets. But because there are no air pockets in a coral, it can withstand any depth.

Chris - If they can't get any light or have any algae, how do they get their energy? How are they metabolising?

Jason - Well the jury's still out on that actually. Lots of geologists think it's because they get their energy from methane seeps or from hydrocarbons that are coming out of the sea bed. I'm of the opinion that they live at depths where plankton comes down from the surface and concentrates into a thick soup. That could benefit the corals at depth.

Chris - A lot of people say that there are some interesting things lurking in the ocean depths that might benefit mankind in terms of medicine. Are there any examples you can think of for these corals, or is it relevant?

Jason - There's an intensive search on. The French in particular are looking for chemicals that can help with cancer in sponges that live in the deep water, but to my knowledge we haven't discovered that yet.

Chris - So why are these corals important?

Jason - They form habitats that are very important for the breeding, feeding and daily lives of fish. They form part of the life history of these deep sea fish populations. Unfortunately, these deep sea corals are very easily damaged if you tow fishing nets through them. The fish are attracted to the corals to feed and breed, but they also make the corals vulnerable to fishing equipment.

Chris - It's pretty deep a kilometre though. What kind of fish are knocking around a kilometre down?

Jason - There are all sorts. They've got unpleasant names like Black Scabbard Fish or Pudgy Cusk Eel. They're things that if you put them on your plate they look revolting. But what people do is that they fillet them, and then put them into school dinners in France for example. You wouldn't know if you bought it in a supermarket for example, that it was necessarily a deep sea fish.

Chris - Where are these reefs principally located? Around the UK?

Jason - It seems, although we don't really know because we haven't looked at most of the sea bed, that they're concentrated where the sea bed used to be glaciated in the past. So where icebergs trundled down the coast line of Europe, they scarred the sea bed with deep trenches and left behind lots of piles of stones that were scraped off the mountains. It seems that these piles of stones are in the way of strong ocean currents and: a) provide the corals with a substrate to live on; and b) the food that they need to survive.

Chris - Are they threatened then now that we're going out there with massive great nets and indiscriminately ploughing the sea bed?

Jason - Unfortunately yes, they are highly threatened at the moment. We've got to the stage where lots of the shallow water fish, for example cod, are much less abundant than they were in the past. So people are looking deeper and deeper to catch deeper fish populations. This is the frontier of new exploration. Places that haven't been touched since the last ice age are now being trawled through with heavy trawling gear.

- How Tropical Corals Are Succumbing To Sugars

The Naked Scientists spoke to Dr David Kline, Smithsonian Tropical Research Institute, Panama

How Tropical Corals Are Succumbing To Sugars
with Dr David Kline, Smithsonian Tropical Research Institute, Panama

Chris - Thank you for joining us. Tell us about your work and what you're looking at in relation to coral.

David - I work at the Smithsonian Tropical Research Institute in Panama and I've been studying how tropical reefs have been declining. Throughout the world, reefs are declining at a scary rate. It's estimated that 20% of the world's reefs have already been effectively destroyed. A provisional 50% are under long term threat of collapse and the situation is even worse in the Caribbean. I've been looking at how all the different types of pollution we throw into the ocean change the relationship between the corals and their symbionts. Besides the algal symbionts, I'm also looking at bacteria that live in the coral tissue and how the pollutants affect these bacteria and potentially lead to diseases and mortality in the coral.

Chris - So are those bacteria bad for the coral?

David - Actually just like the algae, when they live in the corals at controlled levels they're actually quite good for coral. Corals are dependent on them. These bacteria could protect the corals from harmful bacteria, they can provide them with vitamins and other limited nutrients that they wouldn't be able to obtain otherwise. So in normal conditions, these bacteria are actually quite important for the health of the corals.

Chris - So when you chuck in a nice healthy dose of pollution, what's the impact on the coral then?

David - The main components of pollution that people monitor on reefs are nitrates and phosphates. These don't affect the bacteria on the corals directly. But what is affecting the bacteria are simple sugars. There are high levels of simple sugars associated with sewage and also with run-off from agriculture. These sugars are the perfect food for these bacteria. The bacteria can then grow so fast that they overwhelm the coral causing disease and mortality.

Chris - There must be knock-on effects. Jason was talking about how his reefs were home to a huge variety of fish. That must also be true in the shallows.

David - Yes that's very true. The coral reefs in the tropics are a nursery for many of the commercial fish species that we eat and they are the home of many invertebrates that we eat such as lobster and conch. When those corals start to die you lose the biodiversity and that includes these fish and animals that we eat.

Chris - The key question that will be going through a lot of people's minds now must be is it too late, or can we still remedy this?

David - I'm more on the optimistic side because I think that there are a lot of things we can do. There are sewage treatments that could definitely be improved. In the Caribbean less than 10% of the sewage is treated before being released onto the reefs, so sewage treatment is a big thing we can do. Marine reserves are being set up that can help bring back the fish and reducing fishing pressures. It's been shown that marine reserves can have really big impacts in improving the health of reefs. We can also try to reduce carbon dioxide emissions by using fuel efficient cars and try to drive less. With carbon dioxide emissions you get global warming, and with global warming as the oceans heat up it can disrupt a lot of these symbiotic relationships leading to the bleaching effects that we've been seeing all around the world.

- Creatures of The Deep Sea

The Naked Scientists spoke to Dr Ron Douglas, City University, London

Creatures of The Deep Sea
with Dr Ron Douglas, City University, London

Chris - Tell us about your research.

Ron - I'm interested in what animals are down there and what it is they do. The problem is that it's very difficult to make observations on living animals in the deep ocean. You have two ways of catching animals. Mainly I'm interested in fish. You can send down nets but it's very difficult to fish with nets because they're the size of a football goal. If you say the average depth of the ocean is about 4000 metres and you want to fish there, you have to let out fifteen kilometres of cable. That takes maybe twelve hours to get down and get up and what you end up with is a bucketful of organisms, most of which are dead. The alternative is to go down in a submersible, but a submersible also has problems because it's noisy, it has lights and you're going to scare things away. It's rather akin to deciding to look at lion behaviour and going out in a Land Rover at night with the lights flashing and the stereo on full blast. You're not going to see meaningful behaviour. So really all we see in the deep sea in submersibles are the dumb, the deaf, the stupid and the dead.

Chris - Can we define first what deep sea actually is, because Jason said that he's been plumbing the depths at one kilometre. How deep is deep in your book?

Ron - The average depth of the ocean is 4000 metres, but the deepest point is around 11000 metres. Deep sea is usually defined as that area below where photosynthesis can occur, which is usually 200 metres.

Chris - And beyond that point there's not enough light for anything to be meaningful.

Ron - There's not enough light for photosynthesis. Humans can perceive light if you go down in a submersible and switch off all the lights. You can see some sunlight down to about 700 or 800 metres. The animals that live there are a little bit more sensitive and can see sunlight down to about 1000 metres. What we must remember is that 80 to 90% of animals in the deep sea produce their own light; that is they are bioluminescent. If you go down into the deep ocean and switch off the lights inside a submersible, as the sunlight fades, it'sreplaced with a bewildering array of flashes. It's rather like being in a firework display as all the animals are talking to each other and illuminating each other with their bioluminescence.

Chris - Anybody who's been underwater will notice how blue - dominated the underwater environment is because, I think I'm right in saying, water scatters and gets rid of red light and only blue light comes down. So by the time you get very deep you're in a blue world, and therefore the animal that are knocking around down there are optimised to see blue and not reds.

Ron - Absolutely right. If you go diving even off the coast of Britain, if you cut yourself you don't bleed red but you bleed this alarming green gooey stuff. This is because all the long wavelengths or the red light has been absorbed by the water. So as you go down the water column, after about 200 or 300 metres, all you're left with is blue light. Almost all the animals down there have eyes that are only sensitive to blue because that's the stuff that's transmitted furthest.

Chris - But what about the animals that have exploited this evolutionary niche and are now producing their own light which is red, which means that they can essentially focus a search light on all their prey because their prey aren't sensitive to the red light? The fish that makes the light can see them beautifully.

Ron - That's right. Most bioluminescence, as I've said, is blue and almost all fish are therefore sensitive to blue. But there are three species of deep sea fish which have the lovely name of dragon fish because of their large teeth and jaws, that are able to produce light and their eyes are sensitive to that red light. They can use this for a number of purposes. For instance, they can illuminate prey and the prey won't know that they're being looked at because they're not sensitive to the red light. It's rather like a sniper scope in the army. The other thing is that these animals can talk to each other without their potential predators knowing that they're there. So if you like it's a teenagers dream: as much sex as you like but nobody knows that you're at it because you can flash your red lights at each other but you're quite immune from detection by anyone else.

Chris - The statistic I said earlier was that three quarters of the Earth's surface is covered with water and we know more about the surface of the Moon and Mars than we do about the deep sea. What about the deep sea and the trenches? They're about seven kilometres down some of them and when was the last time that someone went there? How do we know what's down there?

Ron - The statistic you say that three quarters of the world is covered in ocean is absolutely right, but what you have to realise is that life on land is really two dimensional. Everything happens within a few metres of the ground. But as I said, the average depth of the ocean is 4000 metres, so the volume of habitat available is absolutely enormous, and in fact 99.9% of all available living space on the planet is deep ocean. We know incredibly little about it. To answer your question, the only two people that have ever been to the bottom of the ocean at 11000 metres are Don Walsh and Picard in 1960, and nobody has ever been back since.

Chris - How do such animals withstand such tremendous pressure?

Ron - They can withstand this pressure because they do not contain air spaces. They won't implode like Jason would if he went down one kilometre below the ocean.

Chris - How much weight of water have they got sitting on them and when you bring them to the surface, why don't they do the converse and explode?

Ron - Again, they don't explode because they don't have any air spaces in them. They don't have these swim bladders that most shallow water species have. So if you bring them up they don't explode.

- Archie The Giant Squid

The Naked Scientists spoke to Fran Beckerleg interviews John Ablett at the Natural History Museum, London

Archie The Giant Squid
with Fran Beckerleg interviews John Ablett at the Natural History Museum, London

Chris - Time now to catch up with what Fran Beckerleg has been up to at the Natural History Museum this week where she went and introduced herself to Archie, who's a giant squid.

John - Archie was actually caught by some fishermen off the coast of the Falkland Islands. When they actually caught it in their net they realised that what they'd got was so important that they took it to a research station who immediately realised that it was too big for them to handle. So they donated it to us.

Fran - What's so special about this specimen?

John - Giant squid are very rarely known. Most of the giant squid around the world have either come from specimens washed up on to the beach, in which case they're very badly damaged so there's very little of them left, or they come from the stomachs of sperm whales and are very badly digested. So to have a specimen in such good condition, so complete, is really amazing and it really is quite a large specimen.

Fran - How did you go about preserving such an enormous animal?

John - When it arrived at the museum, it was actually frozen. So the first thing we had to do was to defrost it. This was quite difficult because the mantle, which is the thick body, took a long time to defrost while the arms and the tentacles defrosted very quickly. So it was a vigorous regime of keeping the tentacles frozen with ice packs while hosing down the mantle area. Once the whole specimen was defrosted, that took around three days, we had to inject it with a preservative called formalsaline. This is a mixture between formaldehyde and salt water and this stops it from rotting from the inside out.

Fran - How far down in the sea do giant squid normally live?

John - Like a lot of things with giant squid, we're not really sure about the way they live. It was only at the end of last year that they were sighted for the first time in the wild. Two researchers from Japan actually filmed them. Estimates by studying specimens that have been found and also from sperm whales which are the main predator, we think that they probably live at a range of about 200 metres to 1000 metres.

Fran - It must be pretty high pressure down there. Do they have any special adaptations that help them to live that deep?

John - They actually fill the tissues of their skin with ammonia, which most squid would excrete. This allows them to get neutral buoyancy in the deep waters. Also they don't have any areas you can compress like most fish that live at the surface, so they're quite stable animals.

Fran - And it must also be pretty dark down there. How do they find their way around?

John - Giant squid actually have the largest eye of any animal. In this specimen it's about 23 centimetres across. Lots of people ask me why they have such a big eye at such great depth, and again, we don't really know. Lots of animals down there are bioluminescent and produce lots of flashes, so one thought is that they might have these large eyes to capture some of the flashes deep down to either avoid or find to eat.

Fran - Do you know what kind of things giant squid eat?

John - Yes there have been quite good studies on the stomach contents of giant squid. They seem to eat a mixture of cod and hake, slightly smaller squid, and there have even been reports that they might be cannibalistic, but we're not sure how true that is.

Fran - Is Archie a fully grown giant squid or are there bigger squid than Archie?

John - The biggest reported giant squid is about 18 metres, which is nearly double this size. That was in 1880 in Newfoundland. It was quite a long time ago so it's not 100% certain how true that is, but giant squid tend to be around this size with a maximum average size being around thirteen metres.

Fran - And what's going to happen to Archie now?

John - Well hopefully she'll be on display forever, not only for the public but also to researchers. So if scientists from around the world want to study the specimen then they'll be able to come here and visit it.

Chris - That was Fran Beckerleg, our roving Naked Scientist reporter down at the Darwin Centre at the Natural History Museum in London, catching up with John Ablett to hear about the giant squid Archie that they have on display there.

- Science Update - Fish

The Naked Scientists spoke to Chelsea Wald and Bob Hirshon From Aaas

Science Update - Fish
with Chelsea Wald and Bob Hirshon From Aaas

Chris - Time now to go across the ocean to the guys at Science Update, Chelsea Wald and Bob Hirshon.

Chelsea - This week on Science Update we'll be talking about fish. Many species of the world's fish have been over - fished to a tiny fraction of their original numbers. In order to help rebuild one population, scientists in Florida are undertaking an ambitious underwater surveillance programme.

Bob - High tech listening devices, surgically implanted transmitters, tracking thousands of subjects without their knowledge. Is it a controversial homeland security programme? Well maybe. But what we're talking about is a fish research project. University of Miami marine biologist Jerry Alt and his colleagues are implanting acoustic transmitters into thousands of Florida grouper in and around a marine reserve. Then they're re-releasing them and listening to them with underwater microphones.

Gerry - The transmitter itself is pinging about every twenty seconds or three times a minute. Each pinger has a unique acoustic code so we can identify individual fish.

Bob - By understanding how the grouper use the protected waters, the researchers hope to figure out how to replace their over-fished population while still keeping area fisheries well stocked.

Chelsea - Fortunately there are still some places that fishing nets can't reach. One of them is the abyssal plain; the ocean floor located about 4000 metres under the surface. The total darkness and intense pressure there have made it a very challenging place for researchers to get to know.

Bob - Yes, scientists at Scripps Institution of Oceanography in La Hoya California have now taken the first long term look at the abyssal plain and what they found was surprising. The population of a fish called the grenadier tripled in fifteen years. Marine biologist David Bailey says that this boom is likely the result of natural ocean cycles like El Nino that affect the production of nutrients on the surface.

David - How productive the surface waters are affect how much food arrive on the sea floor, which affects the fish we're working on.

Bob - He says that so far there's little sign of human influence on these fish populations; a rarity anywhere on the planet.

Chelsea - So let's hope it stays that way. For next week's science update: a riddle. What's brown, sounds like a bell and can cure the energy crisis?

Bob - I don't know? What is brown, sounds like a bell and can help cure the energy crisis?

Chelsea - Well you'll just have to tune in next week to find out. Until then, I'm Chelsea Wald.

Bob - And I'm Bob Hirshon for AAAS the science society. Back to you Naked Scientists.

- Why are some planets surrounded by rings?

Why are some planets surrounded by rings and not encased in a sphere of debris? Shouldn't gravitational pull act in all directions?

Why are some planets surrounded by rings?

If you take Saturn with its rings, Saturn is not a perfect sphere. This is because it's spinning and its mass gets thrown outwards. This makes it a bit wider than it is tall. Because of this, there's a concentration of mass around the centre, which means that stuff is more attracted to the area at Saturn's equator than anywhere else. So even if you started of with a spherical sphere of debris around the planet, then eventually as they bump into each other and jostle each other, it will all settle down into a ring. This extra mass around the centre provides that extra bit of pull and forms rings instead of a sphere. This is exactly the reason that the planets in our solar system form the planar structures that they do. This is also why moons tend to be in the equatorial plane. It's all the same theory.

- How does a lie detector work?

How does a lie detector work?

How does a lie detector work?

They're not really very accurate and you can get around them. It's called glavanic skin response. A lie detector works by measuring changes in skin conductance on the basis of sweating. It uses the fact that when you lie, your skin usually goes up in its conductivity because you sweat, and you sweat because you're nervous. This is also linked to blushing. There's another group of researchers who in the past few years have been looking at another way to tell if you're lying, which is studying closely the blood flow across the face. Although this is probably still undergoing tests, they found that when people tell a lie, the blood flow around the eyes specifically changes and increases blood flow. Even if your eyes aren't sensitive enough to pick it up, a clever camera can. So you can look at the heat or thermal changes in someone's face and tell whether they're trying to hide something. This would be useful, say, at the airport. If someone's checking in and says no when asked if there's anything in their bag, this may be a way to flush out the liars without having to do anything invasive.

What is global dimming?

When you put particles into the air, such as from cars, industry and volcanoes, the particles reflect some of the sun's rays back into space and stop it coming through into the atmosphere. The sun is the key source of warming and energy input into our planet. So actually in real terms when you have a big volcano, despite the fact that it releases an enormous amount of heat, it releases an enormous amount of ash. That correspondingly cools the planet. Most people might think that volcanoes would heat the planet up, but they actually cool it down for quite a long time. A recent piece of research in the journal Nature showed that Krakatoa, which blew up over Indonesia about 100 years ago, still has a legacy living on in the oceans today. Over 100 years later we can still see a cold body of water and lower sea level because of that.

- Is there any life at the bottom of deep ocean trenches?

Is there any life at the bottom of deep ocean trenches?

Is there any life at the bottom of deep ocean trenches?

The basic problem with the ocean trenches, we're talking 9, 10, 11000 metres, is that it's incredibly hard to sample animals from down there. People have only been down there once and they saw fish. There are no nets that can go that far down but so far four species of fish have been found in these trenches but 90% of the creatures down there are holothurians, which are basically tubeworms. So there is a lot of life down there and there are also bacteria that live on the sea floor. The problem is that we haven't found most of it yet. It's not that it's not there; it's just so difficult to actually see it.


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