At night, on the side of the bow away from the moon, we can look over the edge of the ship’s rails and see something magical. The dark ocean, cut by the bow of the ship, suddenly turns sparkly blue-green and the wake glows as if filled with millions of fire flies.

We are churning the ocean and disturbing thousands of microscopic organisms, called plankton, which live near the ocean surface. The cold, deep Humboldt Current water, upwelling around the Galápagos, fills the upper ocean with plankton.

When disturbed, some plankton emit light or bioluminescence. “Bio” is another word for life and “luminescence” means light. “Bioluminescence is always such a treat to see,” Kate Buckman says.

Bioluminescence occurs in many different types of marine animals and in invertebrates on land. For example fire fly species have unique signals they flash to identify their mates. But mammals, reptiles, birds and amphibians lack this glow-in-the-dark capability.

For fish and animals living in the deep-sea, light can attract prey. It may also be useful for communication. But how this light process works in each species and why it is important remains a mystery for scientists to solve. Bioluminescence results from oxidation of special types of organic compounds. But, because deep-sea animals are hard to observe and study, not much is known about this process.

“Deep sea biologists have many theories,” Kate says. “If a predator is chasing an animal that starts glowing brightly, the predator may be distracted. Many kinds of jelly fish under attack will release a bioluminescent tentacle as a trick, leaving the rest of the jelly to escape.”

In Antarctica, when the weather is calm, some single-celled organisms travel in caravans on the surface of the ocean. “We saw a trail of plankton on the water and passed right through the middle of them,” Eric Wakeman says. “On either side of the ship, waves of plankton as far as we could see on the horizon were glowing.”

As Revelle steams on through the night, surveying the seafloor, we are treated to our own private light show on the surface.

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