Zombie Worms and Crab Invasions

Why are the waters of the Antarctic so different from the rest of the world?
21 August 2013

Interview with 

Dr Simon Morley, British Antarctic Survey


Kate - Well, I've been looking this week at the Antarctic Seafloor. Now, this international team of scientists was really interested into the difference between wood and bone when they end up on the seafloor. Now, in the rest of the world when bones from animals drift down into the depths, they get eaten up by these weird bone-eating worms called Osedax. They're sometimes known as zombie worms. I showed them to the office a little bit earlier and they were a little bit freaked out. So, if you're about to hit search on Google, I'd sort of take one step back from your computer there. And wood, when it gets down to the bottom of the ocean, similar things happen and it gets eaten up by molluscs, but what's really interesting about these worms and molluscs that eat up this debris in the ocean is that they obviously have a huge dispersal. There are huge distances to cover for such tiny creatures in order to latch on to the next bit of bone that might randomly fall down to the depths. But can they make it Antarctica? That's what they wanted to know. So, what the team did was they got a load of wood and a load of bone - whale bones in fact - and they left them 500 meters down in the Antarctic Ocean for a year. When they brought it back up again, what they found was the whale bone was covered in these Osedax, these zombie worms, but the wood was practically in pristine condition. There didn't seem to be any wood-eating ship worms or molluscs around. But why is the Antarctic Ocean so different from the rest of the world's oceans and seas? What makes it so special? We're joined here in the studio by Dr. Simon Morley who studies the Antarctic Seabed at the British Antarctic Survey here in Cambridge. Simon, why are the Antarctic waters so different? 

Simon - The Antarctic waters are separated from the rest of the world's oceans by the polar front or the circumpolar current. So, this is a circular current that goes around the Antarctic and it goes from the surface and in places, actually goes to the seabed. So that acts as a barrier. It's a very sharp discontinuity that potentially stops larvae and other animals crossing the front.

Kate - Is cold also an issue or obviously, if this is providing a barrier, does the temperature change more dramatically?

Simon - Absolutely, yeah. This is also a very sharp change in temperature.  So, within the southern ocean, it is the coldest ocean on the planet and temperatures there, they're actually too cold for many animals from outside the southern ocean.

Kate - How does this mean the animals change?  Are they adapted differently to be able to live in those waters?

Simon - They are. Many of the animals that live in the Antarctic have these special adaptations that allow them to live in the cold. So, there's fish with anti-freeze, there's giant sea spiders that have taken the place of crabs which can't live there because it's too cold.

Kate - When we say giant sea spiders, how big are we talking here?

Simon - These can be the size of a dinner plate. They're clearly not true spiders, but they're pretty impressive beasts.

Kate - Why are we so interested in these Antarctic waters? I mean, your research obviously looks into shallower waters than this research, but is it just that these animals that live there, that survive there are so different from the other ones? Is there anything else special about that environment?

Simon - I mean, these animals that live there, so they're adapted to the cold and that makes them very sensitive to very small increases in temperature. And also, it's one of the most rapidly warming oceans on the planet. So, if you want to understand how animals are going to be affected by climate change, it is one of the best places to look.

Kate - And how are those animals being affected by climate change?  Are we already seeing differences?

Simon - We are seeing some complicated and subtle differences already, but the predictions we're getting, based on the sensitivity of these animals make us very worried about their ability to survive. Even through the next 200 or 300 years, we expect to see some major changes in the animals that live down there.

Kate - You're talking about sort of investigating these animals who live in such extreme temperatures and extreme environments. How are you doing that in the middle of Cambridge?

Simon - Yeah, so I'm lucky. Many years, I get to go to the Antarctic for a couple of months, go diving and do my research on the animals. But we also have an aquarium here in Cambridge so we can do some experiments in between, and we get animals brought back, so we can look at the effect of climate change on these animals.

Kate - I'm now terrified to one of those dinner plate sea spiders hanging around in an aquarium in Cambridge somewhere.

Simon - Not quite dinner plate-size, but there are one or two pretty big sea spiders.

Kate - That's worrying. So, you mentioned that crabs couldn't go to the Antarctic.  Is that why there are so many sea spiders about?

Simon - When the Antarctic cooled crabs have a real problem, they have magnesium in their blood and at really cold temperatures, that acts as an anaesthetic.  So, there are no crabs in the shallow water of Antarctic and we think that the sea spiders filled the gaps left by the crabs.

 Kate - So, with climate change in place, how can that change the environment of the Antarctic?

Simon - So, this is a really interesting story because very recently, a new piece of kit was deployed in the Antarctic, into the deep sea. They found crabs where they haven't previously found them. It's a really fancy bit of kit and who knows if those crabs were currently there, but weren't seen or whether they have actually moved in. We need to do more research, but there are certainly crabs just kind of hanging off in the deep water of the Antarctic and if the surface waters and the shallow waters warm as we predict then in a few years, in a few hundred years' time, the crabs could easily come back into the shallow waters.

Kate - So, you're making it sound like they're plotting which is totally playing into my fears here, but it's very exciting. This paper is obviously not just interesting because of, we find out more about the marine biology of the Antarctic but also because if wood is so well preserved, we might be able to find historic wrecks. So, Ernest Shackleton's Endurance for example sank in 1916. I grew up on stories of Antarctic adventure like Ernest Shackleton. For me, it's very exciting that we might be able to find this pristine ship lying in the bottom of the ocean. Are people sort of itching their fingers about being able to go out there and find it?

Simon - Yeah and I believe there's at least one or maybe more expeditions that are currently really interested in going to search for this wreck. Wouldn't it be amazing if bits of that wreck are still sitting there? It's pretty deep, so it's in a few thousand meters. So, it would be quite a challenge, but it would be amazing to find that.

Kate - Where can I sign up is my only question.  I mean, do they take on cabin boys?

Simon - Well, I have absolutely no idea, but you'll have to get in the queue behind me.


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