At the bottom of the ocean, there is a world of light and colour that deep-sea creatures use for light and communication.
Dr Edith Widder has spent her career studying bioluminescence.
Anglerfish. Photo: Supplied / Eddith Widder
'I was totally unprepared for how spectacularly beautiful it was'
Dr Widder introduces readers to this underwater world and ponders the future of Planet Earth in her new memoir Below the Edge of Darkness.
She first saw bioluminescence as a child, chasing fireflies around her backyard.
Years later, in the depths of the oceans, she got to experience its full beauty.
After she’d finished her PhD, Dr Widder had the chance to deep dive in an atmospheric diving suit called a Wasp (developed by the oil industry to dive down to rigs 2,000 feet underwater).
It was on her first dive in the suit - in the Santa Barbara channel at 800ft below - that she first experienced being immersed in bioluminescence.
“I just was totally unprepared for how much there was or how bright it was or how spectacularly beautiful it was.”
The wonders of the deep were something Dr Widder almost missed out on, after surgery at the age of 18 temporarily blinded her.
It began with a persistent pain down her left leg, Dr Widder says.
“I always had lower back pain, I thought that’s what everyone meant when they said they were tired.”
She was sent for an x-ray and told her back was broken - the vertebrae had slipped 50 percent across from each other, pinching the nerve in her leg.
“The pain was so bad I finally had to go in for a spinal fusion, and everything went wrong. I got a blood disorder...I crumped, and I haemorrhaged everywhere, including my eyes, so when I came to, I was blind.”
Over four months in hospital, Dr Widder thought a lot about vision and light, and how much we take them for granted.
“It’s such an important input for us we can’t even quite comprehend what it’s like not to have it.
“The experience helped me when I started studying bioluminescence because in the deep ocean, where there’s no sunlight, vision is at least as important as it is on land, but it’s a wholly different visual environment.”
Red octopus Photo: Supplied / Eddith Widder
Flashes of light in the deep, dark ocean can mean either life or death, Widder says.
While people may associate light with warmth, bioluminescence is a cold light.
“All light comes from the same process; an electron gets excited up to a higher energy level and when it falls back down it gives off this packet of energy called a photon. But you can get electrons excited in different ways.”
A chemical reaction created by animals is what creates bioluminescence: “It’s a form of living light.”
“Some of these animals manufacture the chemicals themselves in their bodies, some have a symbiotic relationship with bioluminescent bacteria, some have to eat certain other animals that produce one of the chemicals that they need to produce the light.”
More than 50 percent of deep-ocean animals use light to holler, flirt and fight, Dr Widder says.
Animals use bioluminescence to help them find food by dangling a bioluminescent lure in front of themselves - as seen in Finding Nemo - or by using bioluminescence as a flashlight.
Shrimp. Photo: Supplied / Edith Widder
Angler fish use bioluminescent bacteria to produce light for them.
“They have a fishing rod sticking out of their forehead, but at the end of that fishing rod is a light organ called an 'eska' that has bioluminescent bacteria in it. So the fish provide the bacteria the perfect growth chamber and the bacteria in return produce this light that helps attract prey.”
We are exploiting the deep sea before we've even properly explored it, Dr Widder says.
“We see plastic all the time at the bottom of the ocean. We’re pulling out every last fish, just decimating the fish populations while we’re filling the oceans with our filth and plastic. It’s just unconscionable that we’re destroying the ocean before we know what’s in it.”