Glittering seas: the science of ocean bioluminescence

Imagine eating a piece of fish that looks, smells and tastes completely normal, but a few hours ater you're stuck in the toilet, vomiting and with tingling in your arms and legs. Well, this can happen if the fish you eat is contaminated with ciguatera toxin. This affects fish in tropical waters that eat a dinoflagellate species of algae that make the toxin. It affects between 20-60 thousand people every year and is the most common form of food poisoning caused by a natural toxin.Testing fish for the toxin has up until now been a lengthy and time consumingprocess, involving injecting purified samples into mice, and watching to see ifthey become ill. Now Kentaro Yogi and his colleagues in Japan have developeda much faster and effective way of testing for the toxin, which has also allowedthem to identify 15 different forms of the toxin present in fish species caught in different areas, as well as identifying differences in the dinoflagellates responsible for producing the toxin.The team used liquid chromatography tandem mass spectrometry to analyse thetoxins, which were extracted and purified in a similar way to the mouse bioassaymethod. The peaks obtained from the analysis were compared with known referencesamples of the toxins and they accurately showed the separate toxins found. Theteam believe that with the production of more reference samples of the various toxins from extraction from natural sources and through synthetic chemistry, this method of detection could become widespread and would improve the speed and accuracy of testing for this unpleasant toxin.

Edith- In fact in the open ocean environment most of the animals make light. Youdrag a net out there and most of the animals you bring up are producing light and in some cases 80-90% of the animals. And it's fish, shrimp, squid, jellyfish, and they use it to help them survive. They use it to help them find food, to attract mates, and to defend against predators in all kinds of amazing and bizarre ways.

So for finding food you have things like the luminescent lures or built in flashlights to help them see in the dark. For finding mates they can flash certain species-specific patterns or have light organs that are shaped in a unique fashion that allows one species to identify another.

And then for defence there's just a huge range of different ways of using bioluminescence. For example, quite a few animals can release their bioluminescent chemicals into the water just the way a squid or an octopus release an ink cloud. These animals will release their light into the face of a predator, temporarily blinding the predator while they swim away into the darkness.

Helen- So there are all sorts things marine animals do with their homemade light- but how do they make it in the first place?

Essentially it comes down to a reaction between a substrate and an enzyme - generically referred to as luciferin and luciferaze - but, it's not as simple as that.

Edie- We think bioluminescence has evolved maybe 40 separate times, maybe as many as 50 separate times. It's a really unusual example of convergent evolution because there are very different chemistries in different animals. Some animals use the same chemistries and it's even across species and across phyla. But they're extremely different depending on different cofactors and different enzymes and different substrates. It's just very unusual in that respect.

For most of these animals they're making the chemicals that produce light out of the food that they eat. And usually some derivation of amino acids, enzymes or proteins. They hold these chemicals usually in cells in their bodies and when they want to make light there's some activator usually a nerve action potential that triggers the release of something, maybe calcium or hydrogen, that's the missing element that then allows the light reaction to occur.

Some animals get their light form bioluminescent bacteria. So they have a symbiotic relationship with the bacteria. But the fish sometimes need to turn that light off and so they'll often have mechanical shutters that can close down around the light in some fish the light organ actually rotates back into the head just light the headlights on your Lamborghini.

Helen- Edie has spent a lot of time miles down beneath the waves, studying the glowing creatures of the depths, and she told me about the first time she went down in a submersible. Up until this point she'd only been conducting her research on bioluminescent organisms in the lab.

Edie- I went down to 880 feet, it was an evening dive, I turned out the lights and I was just blown away by the amount of light a saw. The bioluminescence light show was breathtakingly beautiful, but I also knew enough about it at this point to know how energetically costly it was to produce this light. And I thought, this has got to be one of the most important processes in the ocean, I couldn't understand why more people weren't studying it. And it completely changed the course of my career.

So, a lot of the reason I came to understand that it wasn't being studied more is there weren't tools available for studying it. Clearly you have to do a little bit more than go down and say, 'Oh wow everything glows!'. And so I started working with engineers to develop instruments that could better quantify bioluminescence in the ocean. I also doing more work from submersibles and eventually developed a technique that uses video image analysis to identify the animals by the type of flashes they produce. And it's turned out to be a very powerful tool for mapping the 3D distribution patterns of animals in the ocean.

Helen- Even with the advancing technologies for venturing into the depths in person, Edie began to think about what she was missing.

Edie- Of the 100s of dives I've made in submersible I've always felt like how muchis there out there that I'm not seeing because we're scaring it away with our bright lights and noisy thrusters.

And so I wanted to develop a camera that could be left quietly on the bottom of the ocean that was battery powered but unlike cameras that had been used in the past I wanted it to be completely unobtrusive. So I used red light, sort of the way people studying nocturnal animals use infra red light on land, trouble is you can't use infra red in the ocean because its absorbed so quickly in the water. So we used far red light and then a camera that was super sensitive to compensate for the fact that so much of that light is absorbed.

And so now we've started to study these animals in their natural habitat. I also developed an optical lure that imitates certain bioluminescent displays. That's proved very valuable in working out this language of light and what kind of displays different animals respond to.

Helen- As well as learning about the fascinating lives of glittering deep ocean species, Edie has also started applying her bioluminescence research to helping solve some of the problems facing the oceans.

Edie- One of the big ones is tracking pollution. We have a lot of problem with non point-source pollution which is things like fertiliser and pesticides running off crop land, animals waste out of animal feed lots, toxic cocktails of hydrocarbons that run off our roads every time we have a rain storm. Just all kinds of things that are running off the land and having a very profound effect on coastal ecosystems.

And so I felt like what we really want to do here is make pollution visible. So we're actually using bioluminescence to do that. We use bacterial bioluminescence.

The reason bacteria glow all the time is that the bioluminescence is linked to the respiratory chain - so the breathing of the bacteria. And any pollutant that interferes with that, dims the light.

So the bioluminescent bacteria are akin to a canary in a coalmine. Miners used to take a canary down with them before they had sensors that could detect the poisonous gases that they had to be concerned about. They knew when the canary stopped singing or keeled over that they better get out of there very quickly. And that's what's known as a broad-spectrum bioassay. You're not measuring for a specific pollutant but a whole range of them. And that's what the bacteria do for us.

So we take sediment samples. When you're talking about water pollution most ofthe water pollution actually resides in sediments. So we take sediments and test the bacteria against these sediments and figure out where the toxins are accumulating in the environment.

And then we've also developed a water quality monitoring system called a Kilroy - because we hope these guys are going to be everywhere - that allows us to track the pollutant back to its source.

My dream is to get a pollution layer onto Google earth so that people can see the pollutants in their own back yards and in their favourite waterways and then work together to figure out what we can do to solve these problems.

Find out more:

ORCA(Ocean Research and Conservation Association)

Edith Widder
TED talk

Helen-我几乎选择了我的一个前马烟花kers the bioluminescent dinoflagelates that glow in the sea when you go diving at the right time in the right place and they just flash these fantastic lights when you move.

Sarah-I think those are in the beach, aren't they, in that film when they go swimming in that lagoon and you move your hands through water and it startles them and they produce all these teeny lights.

Helen-Yeah, it is absolutely brilliant. And it does happen like that, it really does. You can basically have a lot of fun pretending to be an underwater wizard because you can throw fireballs, it's fantastic. I have been swimming one time at night and come out and it stuck to my skin. So that if you actually then draw with your finger on your skin it glows again, it's like you are covered in this crazy paint. It is fabulous.

I am not choosing them, so I am cheating,slightly. Those dinoflagelates only flash when they are disturbed. But there is another phenomenon in the ocean that glows constantly and that is a thing called the milky seas effect.

It is a surreal night time phenomenon that mariners have puzzled over for hundreds of years. It's called milky because it looks white but is actually blue and but is such a low light that your eyes just use your rods which don't distinguish color, so it looks white.

It went unexplained for a long time, and it's still pretty mysterious; but, we think, the latest theories are, that it is caused by a type of bioluminescent bacteria,Vibrio harveyi. And these glowing seas have been spotted from space, this is fantastic.

This is all thanks to a meteorologist called Steve Miller, back in 2003 he was basically pondering the idea "could you see glowing seas from space", could we do this, is it possible. Everyone said no don't be stupid, it's far too brief, it's not bright enough, there is no way you could do it. But he was determined to see if he could figure this out.

So, like all good scientists he went straight to the internet and hunted around for descriptions of the milky seas effect. He found a report from the ship SS Lima, from Jan 1995 when it was in the Northern Indian Ocean and it went something like this:

"22:00 local time on a clear, moonless night a whitish glow was observed on the horizon and, after 15 min of steaming, the ship was completely surrounded by a sea of milky-white color with a fairly uniform luminescence. The bioluminescence appeared to cover the entire sea area, from horizon to horizon . . . and it appeared as though the ship was sailing over a field of snow or gliding over the clouds.."

Isn't that wonderful?

So, basically Steve got this report and then he wanted to figure out if thatparticular milky sea could be spotted from space. So, he teamed up with some other researchers including bioluminescence expert Steve Haddock from the Monterey Bay Aquarium Research Institute.

They sifted through satellite images, and low and behold, there was the milky sea spotted from space in exactly the right place and the right time as SS Lima's description. It turned out to be an enormous patched of glowing sea, it measured over 15,000 square kilometers, the size of the county of Yorkshire if you are a Brit or the state of Connecticut if you are in the US, everyone else will just have to figure out how big that is.

A satellite image showed that it glowed on 3 consecutive nights, between the 25 and the 27^thof January. Check this out, weirdly it is the same date, the 27^th, although a hundred years earlier that the passengers on board the Nautilus, in Jules Verne's novel20,000 Leagues Under the Sea, in a very similar part of the ocean sailed through a milky sea. How weird is that?

It only happens in the right conditions, and that is when there is a huge concentration of bacteria. It estimated that this particular milky sea had 40 billion trillion bacteria, and that is quite a lot. In fact, if you had a grain of sand for every one of those bacteria you'd cover the entire planet to a layer of 10cm thick in sand. It's huge.

不管怎样,我有一个快速和史蒂夫·密尔聊天er the other day and he said since that2005 paper came out describing the satellite spotting of the milky sea in the Indian Ocean he has had lots of reports from sailors of milky seas but so far hasn't had satellite images to match it up. Because we're really talking extremely low light levels here, you've got to have very sensitive satellite images.

But the good news is, in October just past, NASA launched a new satellite called NPP and its carrying a new, improved low light sensor. So that does increase the chance of it spotting the milky sea from space and it perhaps gives researchers a chance to dash out on a ship and grab some of the sea water in the same place. And Steve told me if that happens he is going to put down his science hat and just frolic around in the glow.

Sarah-But, is that safe? Could you get infections from those kinds of bacteria or is it a safe thing to go swimming in?

Helen:That is a really good question. These are bacteria that are all the way through the oceans, just at very low concentrations compared to milky seas. But no, I think I might have to ask Steve that one, perhaps get him to go first and see what happens.

Find out more:

Milky Seas from Space- website with more info and links to Steve Miller and Steve Haddock's 2005 paper

Helen- In the mollusk group there are lots of glowing squid and octopus and so on. But in fact for gastropods, the seashells, there is really hardly any bioluminescence except for a little brilliant creatureHinea brasiliana, also known as the clusterwink, which has to be the best name for a creature.

Basically they are called that because they group together in crevices at low tide, these live on the coast of Australia. Apparently once the tide comes in they wake up and scoot around busily, but when the tide comes in they all cluster together, hence the name cluster wink.

It's a family Planaxidae, when they are just sitting there in the day light they look like little yellow shells, fairly normal yellow shells. But put one in the dark and poke it and it glows bright green. It is basically a kind of burglar alarm, the idea is that is it shouting out for help and essentially saying "help, help I'm being attacked" to attract perhaps other predators of the thing that is attacking them and to basically make themselves look bigger.

A study came out earlier this year that looks into how this happens. They have two blobs of light emitting cells inside their bodies but it comes out like a whole glowing shell, a bit like a light bulb essentially.

Turns out this is caused by the crystalline structure of the shell that is specificallyfiltering and diffusing the light to amplify it and it does it better than any commercially available material that we use to do similar things. It only works with green light, red and blue justgets stuck they don't get transmitted through the shell.

只是真的很棒,现在研究人员trying to bio-mimic this structure to try and make things that we can use for ourselves. And they are also looking at other members of the Planaxidae family to work out how this particular fireworks trick evolved.

Find out more:

Deheyn and Wilson (2011).Bioluminescent signals spatially amplified by wavelength-specific diffusion through the shell of a marine snail.
Proc. Roy. Soc B.