The midnight zone begins half a mile beneath the ocean, and is an area so deep that no sunlight can reach it. Few humans have seen the animals who live there — until now.

A groundbreaking exhibit at the Monterey Bay Aquarium is bringing deep-sea animals from the midnight zone up to the surface and into public view for the first time.

“What’s really cool about this exhibit is that we are the only humans on Earth right now that are likely looking at some of these animals,” said Allen Protasio, exhibit guide at the Monterey Bay Aquarium.

[pullquote size='small' citation='Samantha Muka, aquarium historian and professor, Stevens Institute of Technology']‘We should be completely astounded by the technological things that they’ve done. It probably couldn’t have been done even 10 or 15 years ago. It’s that cutting-edge.’[/pullquote]The midnight zone is cold and dark, and can only be explored by remote operating vehicles (ROVs) controlled by pilots in submarines. The deep sea is rich with strange and often bioluminescent creatures, many of them delicate and unable to withstand the drastic transition to the low pressure, bright lights and high temperatures at the surface. Monterey Bay researchers have experimented for over a decade with ways to bring elusive deep-sea life safely up from the depths.

The exhibit takes visitors on a descending tour of the abyss, starting with a model of Monterey Bay’s underwater canyon. Some parts of the canyon are more than a mile deep, and the canyon comes remarkably close to shore. Visitors can meander through a darkened gallery of tanks displaying gelatinous creatures from the shallower end of the midnight zone, known as the midwater, which ranges from 650 feet to 3,300 feet deep.

A rust-colored crab with an oval body and white markings on its shell and legs rises up on four legs, two legs extended out above and in front of its body like an orchestra conductor. The crab is on a sandy floor inside an aquarium, with models of whale bones on the ground and looming in the background. — The Japanese spider crab is the size of a small dog. (Tyson V. Rininger/Monterey Bay Aquarium)

In the midwater gallery, screens show dazzling ROV footage of shimmering bioluminescence. A goopy string adorned with stingers — a creature known as a siphonophore — floats suspended in its tank.

Tommy Knowles, a jellyfish expert and one of the scientists who developed the exhibit, described his favorite midwater creature — a crimson dome bedazzled with ridges of strobing rainbow lights.

“This is the bloody belly comb jelly, Lampocteis,” Knowles said. “It’s one of the most delicate jellies in the world. It’s like a sparkly bowl of Jell-O.”

Knowles and other scientists tinkered with the acidity, light and temperature to achieve conditions that were just right for each deep-sea animal on display.

“We should be completely astounded by the technological things that they’ve done,” said Samantha Muka, aquarium historian and professor at the Stevens Institute of Technology in Hoboken, New Jersey. “It probably couldn’t have been done even 10 or 15 years ago. It’s that cutting-edge.”

While the deep sea is known for its high pressures, the aquarium scientists found that some deep-sea creatures could survive the ascent if they were given time to acclimate to the lower pressure and higher temperatures, not unlike the delicacy required when human divers return from high-pressure depths.

Inside a deep sea exhibit, black boulders looking like pieces of charcoal, pocked with lines and small holes line the ground. Growing on these boulders are tall, pale orange corals with trunks like a tree and branches like a curved fan. — Corals and sponges that grow on underwater mountains, or “seamounts” develop so slowly that damaged habitats could take centuries to recover. Drilling, mining, and fishing can put corals, sponges, and the animals they shelter at risk. (Tyson V. Rininger/Monterey Bay Aquarium)

“They’re the only people right now that know how you can push these animals, like the plasticity of their pressure needs at the moment,” said Muka. “They already know more about those deep-sea animals than we’ve ever known about them ever.”

While it took years of trial and error to figure out each deep-sea creature’s specific requirements, achieving low-enough oxygen levels proved to be a particular challenge. Many deep-sea creatures from an area known as the oxygen minimum zone need as little as 5% of the oxygen found at the ocean’s surface to survive. Some displays required developing new methods to strip oxygen out of seawater.

“We had to use equipment that I don’t think has ever been used in aquariums before,” Knowles said. “It was used in food production, for stripping gasses out of liquids.”

The exhibit is more than a technological marvel or a way to show off exotic animals. In addition to educating the public, it serves as a reconstructed ecological system that allows scientists to study deep-sea environments without the expense and difficulty of submarine voyages. This combination of public outreach and basic science is a hallmark of the Monterey Bay Aquarium.

“They’re basically setting up a long-term laboratory for those scientists to be able to study those organisms,” Muka said. “In some sense, it is the ultimate reason for the public aquarium to exist.”

Because it is so challenging to access and study, deep-sea biology is still in its infancy. Although scientists are only beginning to understand deep-sea environments, those environments are already under threat from human influence, such as deep-sea drilling, mining operations, climate change and microplastic pollution.

Deep-sea creatures feed on marine snow, tiny flecks of rotten flesh and other debris that drift down and eventually reach the sunless depths. But now, much of that snow is made up of tiny bits of microplastic.

To demonstrate how microplastic pollution affects deep-sea animals, the exhibit includes an interactive game that shows how hard it is for these animals to survive. Players take control of different deep-sea creatures and must avoid getting eaten or stung, all while chasing down and gobbling up bits of marine snow. If a player survives the game, the screen displays the percentage of plastic they consumed along with their marine snow meals — often more than half.

“As those plastics break down smaller and smaller, they get into the food chain,” said Protasio. “And these deep-sea critters may not be able to distinguish between what’s marine snow and what’s microplastic.”

At the deep end of the exhibit, visitors reach the muddy plains of the sea floor, studded with microhabitats. In one seafloor tank, spiny Japanese spider crabs the size of small dogs crawl over a model of a sperm whale skeleton settled into the mud. Cartilaginous ghost sharks lurk, and elephant fish probe for food with their long snouts.

[pullquote size='small' citation='Tommy Knowles, jellyfish expert, Monterey Bay Aquarium']‘In one sense they’re so foreign to us, they’re very alien. But in another sense, they are earthlings.’[/pullquote]While every other animal in the exhibit lives behind glass, giant deep-sea isopods with 14 legs huddle in a touch tank. They look like roly-polys from your garden, except they’re ghostly pale and as big as bread loaves. Isopods can thrive in a vast range of depths and environments, from just 550 feet below the surface to as deep as 7,000 feet. They can switch between crawling along the muddy plains of the seafloor to swimming with muscular flaps called pleopods.

Because the deep sea is so different from what we’re used to, it can seem far away, and has often been compared to another planet. The creatures who call it home, with their many limbs and glowing, gelatinous bodies, might strike some visitors as otherworldly.

“In one sense they’re so foreign to us, they’re very alien. But in another sense, they are earthlings,” said Knowles. “I feel like the alien, coming in with my submarine with bright lights. They’re probably wondering, ‘What is that?!’”

The Monterey Bay Aquarium has successfully brought a glimpse of the midnight zone into the light. The exhibit provides scientists with new tools to keep learning about the earthlings who call it home, and reminds us just how close we are to our deep, dark neighbors.

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