A deep-sea shrimp spews bioluminescent chemicals at its predator, a viperfish.

A deep-sea shrimp spews bioluminescent chemicals at its predator, a viperfish. Edith Widder


A Scientist Reveals the Bioluminescent Magic of the Deep-Sea World

In an interview with Yale Environment 360, marine biologist Edith Widder talks about her pioneering research into the world of bioluminescent organisms in the deep oceans and warns of the dangers, from trawling to oil drilling, that imperil this hidden realm.

Until recently, the depths of the world’s oceans remained almost entirely unexplored. But advances in submersible technology are increasingly giving scientists a window into this little-known universe. One of the leaders in this exploration is marine biologist Edith Widder, who has extensively studied bioluminescent, or light-producing, organisms that use this trait to communicate, defend themselves, and hunt in darkness. Among other things, Widder has worked with engineers to develop highly sensitive deep-sea light meters and special cameras, like the remotely operated Eye-in-the-Sea, which allow for real-time monitoring of the seafloor.

In an interview with Yale Environment 360, Widder — author of the recently published book Below the Edge of Darkness: A Memoir of Exploring Light and Life in the Deep Seatalks about the surprising strategies that bioluminescent creatures employ to survive in a world without light, explains why deep-sea research remains woefully underfunded, and laments that with the advent of deep-sea fishing, mining and oil drilling, “we’re exploiting the [deep] ocean before we even know what’s in it. Those of us that have been in submersibles and seen … these gorgeous undersea gardens filled with bioluminescent corals that have just been turned into rubble [by trawling], it’s gut-wrenching.”

Edith Widder.

Edith Widder. Tom Smoyer

Still, despite the deteriorating state of the world’s oceans, Widder, co-founder of the Ocean Research and Conservation Association, said she remains hopeful that the assault on marine environments can be turned around: “Explorers have to be optimists. You’re constantly facing setbacks and difficulties and problems. And you have to be a problem solver.”

Yale Environment 360: You almost died after surgery when you were a freshman in college. You temporarily went blind. Does your professional interest in light stem in any way from that experience?

Edith Widder: There’s no question that vision becomes so precious when you’re deprived of it. I do think that my experience of being blind helped me when I was trying to think about what life must be like for animals in that world of so much darkness with just occasional flashes of light, which is what my world was like for a while.

e360: The deep sea is sometimes referred to as a world of eternal darkness, but when you made your first deep dive, you write that it was like the Fourth of July down there.

Widder: Well, I knew there would be bioluminescence. I didn’t discover it by any means. I just was completely unprepared for how much there was, for this fireworks display that surrounded me and was set off by any movement.

e360: Why do so many bioluminescent creatures light up when you bump into them?

Widder: There are a lot of animals that release their luminescent chemicals into the water to distract a predator. But for others, it can signal, “Don’t eat me or you’ll be sorry because I’ll sting you” or “I’m poisonous.” Some dinoflagellates use an especially bright light as a burglar alarm where it’s a scream for help with light. If something is attacking them, they make this light that will attract larger predators that will attack their attacker.

e360: You write that bioluminescent fish are the most successful vertebrates on the planet. Is the ability to produce light a big part of that success?

Widder: A huge part — 99.5 percent or more of the living space on the planet is the ocean. But the ocean is so different from the terrestrial realm because there are no trees or bushes to hide behind. Animals have to figure out how to hide in a place without hiding places. A lot of animals produce bioluminescence from their bellies that exactly matches the color and intensity of the sunlight above them. These fish are using their bioluminescence for camouflage [from predators below].

Atolla vanhoeffeni, a bioluminescent deep-sea jellyfish.

Atolla vanhoeffeni, a bioluminescent deep-sea jellyfish. Edith Widder

It’s called counter-illumination. They’re so clever at it. They have filters that match the color perfectly. They have lenses that make sure that the angular distribution of the light exactly matches that of the sunlight coming down through the water. If a cloud goes over the sun and dims the sunlight, they dim their belly lights. It’s the perfect cloaking device.

e360: That’s amazing and so counterintuitive — using light to hide from predators! Why is light so critical to survival in the deep sea?

Widder: As the ocean began to fill up with faster-swimming and more aggressive predators, there was a lot of selection pressure on animals to evolve enhanced vision and enhanced visual signals to live in the darkness. That’s where bioluminescence comes in.

e360: That would also account for the fact that bioluminescence is more common in the ocean than it is on the dry land?

Widder: Right. A few have it, like fireflies and a few earthworms, centipedes. But it’s really rare on land because there are plenty of hiding places. There’s isn’t the selection pressure on land that there is in the ocean to develop bioluminescence.

e360: There are some really strange creatures down there. You write about the saber-toothed viperfish, which employs several different types of bioluminescence for different purposes, and the stoplight fish, which emits both blue and red lights. Do you have a favorite?

Widder: Well, the stoplight fish is definitely high on my list. When I was trying to develop the Eye-in-the-Sea camera system and trying to find an illumination system that would work, that would allow me to see the animals, but not be seen by them, I copied the stoplight fish, so I feel like I owe it something.

e360: Why does the stoplight fish have two different color lights?

The Eye-in-the-Sea camera system.

The Eye-in-the-Sea camera system. Edith Widder

Widder: Where most animals down there only see blue light and only emit blue light, the stoplight fish can emit and see red light. It uses red light like a sniper scope to sneak up on animals that it can see, but they can’t see it. It could also use it as a private communications channel to attract a mate without attracting larger predators.

e360: And the blue light?

Widder: The blue light would be the high beams that would probably be used for hunting prey.

e360: Beyond finding mates, what other kinds of communication are going on?

Widder: We see these fairly elaborate and very different flashes in different animals. We’re never going to know for sure what they’re communicating, unless we can sit down there and observe the way naturalists do on land — you hide behind a blind and you watch for a period of time. We don’t have that opportunity in the deep sea, so that’s why I’ve concentrated on trying to develop observation systems that we can leave in the ocean and that can sit down there quietly and be invisible.

e360: You wrote about one undersea camera that’s on all the time recording what’s going on.

Widder: They basically put a power bar in the bottom of Monterey Canyon, so you could plug in different experiments. I had my camera plugged in down there for eight months, which was a really long observing time.

e360: Do we have any idea how many species are still unknown to science?

Widder: Really, we don’t. Because there are creatures like the giant squid. We had never seen one alive until 2012. It’s just too fast and too wily to be captured in our nets or be seen from our submersibles. We only know about them because they happen to float when they die. There could be a tremendous number of animals that we’ve never seen.

A giant squid caught on camera in 2012.

A giant squid caught on camera in 2012. Edith Widder

e360: It’s said that the seafloor is less well mapped than the dark side of the moon. Why this lack of exploration? Is it just too technically difficult and expensive to get down there?

Widder: Clearly not. If we can spend trillions of dollars going to Mars, that is not the challenge. Deep-sea exploration has always been chronically underfunded. NASA was basically written a blank check in the ’60s because we had to beat the Soviets. The same has not been true of the ocean, so the oceans have been left largely unexplored.

The usual routine is to explore and then exploit an environment. We’ve managed to do it backwards in the ocean. We’re exploiting the ocean before we even know what’s in it. We’re just dumping enormous amounts of trash and plastic pollution and chemical pollution and nutrient pollution into the ocean, and at the same time we’re pulling out every last fish. We’ve got invasive species everywhere. We’re trawling the bottom of the ocean.

e360: In some cases, I imagine when you destroy that ecosystem on the bottom, through trawling, for example, it really will never come back.

Widder: These gorgeous undersea gardens that are filled with bioluminescent corals, they’re magical places that took more than 1,000 years to grow. We’re wiping them out with one bottom trawl for one haul of shrimp. Those of us who have been in submersibles and seen one of these gardens that have been turned into rubble, it’s gut-wrenching. That ecosystem will never sustain life again in our lifetimes or many lifetimes into the future. It’s all just happening out of sight and out of mind.

An anglerfish using a bioluminescent lure to draw its prey.

An anglerfish using a bioluminescent lure to draw its prey. Edith Widder

Now we’ve got seafloor mining that is coming online. China is building up for deep-sea drilling and mining operations. We’ve got destruction of estuaries and wetlands, which are the nurseries for the ocean. And then loss of coral reefs and sea ice habitat. It just goes on and on and on. And we don’t even have a user’s manual for our ocean yet, let alone a repair manual.

This is a huge part of our life-support system. The ocean has been buffering us against our own stupidity, absorbing all of the carbon dioxide that we’ve been pumping into the air and all of the extra warmth that’s resulted from that. But it can’t do it anymore. So the pH is dropping because when carbon dioxide dissolves in seawater, it forms carbonic acid. And then once the ocean acidifies, a lot of important calcifiers, like corals, can’t build their skeletons anymore. All of these things are leading to a tipping point that we may not be able to recover from.

e360: When you dive in submersible vehicles, into the deep ocean, do you sometimes think, “I’m one of the first people on Earth to ever see this incredible life. And if we humans don’t get our act together, I may be one of the last people to see this.”

Widder: It’s a tragedy of immeasurable proportions. My sadness is also that we just don’t seem to be able to convey just how serious this is. People don’t understand what it means to live on an ocean planet. The fact that we could be altering the chemistry of the ocean, which represents 300 million cubic miles of volume, is staggering. And we’ve done it in only about a century.

We don’t have a strong enough connection with what it means to live on this planet. This is the only rock in the universe that we know of right now that can sustain life. It’s a miracle that it does it. It’s just absolutely an astonishingly complex system that has all of these fantastic checks and balances evolved over millions of years. And we’re changing them in an incredibly short period of time.

e360: Could you tell us a bit about the organization that you helped found in 2005, ORCA, the Ocean Research and Conservation Association?

Widder: I live on this amazing 156-mile-long estuary on the East Coast of Florida, which once was designated as the most biodiverse estuary in the United States. Like a lot of estuaries, it’s under stress these days, and we’re starting to have a lot of toxic algae blooms and brown tides, things that are making it impossible for the sea grass to survive, which means the manatees are now starving. The system is collapsing.

The bamboo coral Keratoisis flexibilis lights up when touched.

The bamboo coral Keratoisis flexibilis lights up when touched. Edith Widder

Estuaries are a tiny percentage in area of the ocean, but they have a huge impact because so many animals spend some portion of their life cycle there. A lot of animals come into the estuaries to have their babies, so their babies will have someplace to hide. Sea grass meadows and mangrove roots are critical habitat. We’re seeing a tremendous destruction of these enormously important ecosystems.

When I started ORCA, my focus was on developing real-time water quality monitoring systems. So we created these pollution maps that looked like weather maps, where red is toxic and blue is non-toxic. We have a fish monitoring program where we’re collecting fish from the estuary and testing them for toxins and heavy metals. We’re trying to develop new passive pollution sensors that are low cost and easy to deploy, that people can use anywhere.

e360: What do you say to young people about the ocean that we are leaving them? Do you find it hard to be hopeful?

Widder: Occasionally, but I really work at it. Because I think that a lot of kids are getting so turned off by the doom and gloom that they just think it’s hopeless. I really try to foster that need for exploration. Because explorers have to be optimists. You’re constantly facing setbacks and difficulties and problems. And you have to be a problem solver. What we need right now is problem solvers who are going to have to explore the planet as it is and figure out how to deal with these problems.

This interview has been edited for length and clarity.