How an Aquarium Collects Curious Creatures From the Deep

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There are two types of people aboard the research vessel Rachel Carson: There’s me, quite sick and spending a good amount of time on the deck trying to keep an eye on the bobbing horizon, and there are the scientists minding the remotely operated vehicle dangling below us. Sitting in a chair with a joystick on the armrest, surrounded by glowing monitors in an otherwise darkened room, a pilot guides the SUV-sized robot through a galaxy of life—little fishes, free-swimming crustaceans, jellyfish, and other gelatinous critters that dart out of the way—stopping every so often to cross something off a species shopping list. 

Scientists with the Monterey Bay Aquarium, and its associated Monterey Bay Aquarium Research Institute, are on a methodical hunt for specimens for a new exhibit, Into the Deep, opening in the spring. It’ll be loaded with exceedingly fragile, rarely seen animals kept healthy in life-support systems that aquarists have taken years to perfect. “Some of them we call ‘wet tissue paper,’” says Wyatt Patry, a senior aquarist, speaking of the species they’re seeking. “You just touch it with your finger and it starts to tear apart. Some of the animals are that delicate.”

Video: Matt Simon

We’re about an hour off the California coastal city of Moss Landing, where the seafloor dramatically slopes off, opening up a great span of the water column below us. As soon as we parked over this spot, the deck had come alive with workers, who used a crane to gently lower the remotely operated vehicle Ventana into the water. Trailing a tether that both keeps the robot from escaping and gives the pilot real-time control, the machine immediately dove and disappeared.

Now down some 1,600 feet, the ROV begins collecting animals in two ways: via tubes and by suction. To use the tubes, the pilot inches one of two mechanical arms toward a specimen. Each wields clear tubes, oriented vertically. Once an animal slips inside a tube, doors on either end swing shut, trapping it within.

Video: © 2021 MBARI 

In the video above, the robot is using a tube to collect an umbrella comb jelly, Thalassocalyce inconstans. Comb jellies are indeed gelatinous, hence the care taken here, but aren’t actually jellyfish. They have tentacles, but instead of being studded with stinging cells, the appendages are sticky for snagging prey

Video: © 2021 MBARI 

Here’s the collection of another comb jelly, with notable tentacles and brilliant flashes of color, likely belonging to a new genus (the classification above species) that hasn’t been formally described by researchers. “We know absolutely nothing about it,” says Patry. “We don’t know what it eats; we don’t know who eats it. So that’s a real mysterious one.”

Video: © 2021 MBARI 

This train track comb jelly is producing a light show. But the flashing is not what you think. Bioluminescence is everywhere in the deep—animals glow with symbiotic bacteria, for instance, to attract prey or mates. The comb jelly’s color instead comes from tiny hairlike structures, called cilia, that propel the creature, and only we can see it: The ROV’s bright light is actually reflecting off the beating cilia. In the darkness typical to this part of the ocean, there would be no color visible.

Video: © 2021 MBARI 

The video above shows the ROV’s second method of collection, which uses a funnel with gentle suction power for animals that can withstand a bit more handling than the delicate comb jellies. The pilot just has to get the funnel right up to this golf tee jellyfish, and the suction does the rest. After passing through the funnel, the animal is shuttled into a container in the belly of the robot.

Video: © 2021 MBARI 

Here’s a Christmas tree siphonophore. Like comb jellies, siphonophores are gelatinous yet not jellyfish. They’re hydrozoans, made up of units with different functions that join together to form a colonial animal. They’ll clone themselves many times over, with some species stretching 100 feet long

Video: Matt Simon

Once these specimens have been secured, the pilot brings the ROV to the surface alongside the Rachel Carson, and the crew snags it with the crane. Patry and the other scientists rush in and unload the collection tubes, running them over to a little hut on the deck. They carefully transfer the specimens to plastic containers, which then go into coolers. 

Video: Matt Simon

Two hours later, as we tie up at a pier, they’re again hurrying the animals to a waiting van for transport to the aquarium, where the specimens will be much happier in proper life-support systems.

Video: Matt Simon

You might be wondering: If human divers get the bends when ascending from just a few hundred feet deep too quickly, is there any harm in bringing these animals up from 1,600 feet? Interestingly enough, they’re fine. And once they get to the aquarium, their displays have been matched to the water pressure, temperatures, and salinity the animals are used to. The aquarists also pass the water through special membranes that remove nearly all its oxygen, replicating the low-oxygen environment the creatures once called home. 

It’s an environment that scientists are desperate to understand, as the oceans transform under the pressures of climate change. Just as plants do on land, photosynthetic algae known as phytoplankton absorb carbon dioxide and are in turn eaten by animals, which poop out carbon-rich pellets that descend to the seafloor. Carbon is therefore taken out of the atmosphere and locked away in the depths, but scientists don’t know how that might be changing as the seas warm and acidify

“Obviously, messing with that carbon sink could be catastrophic,” says Patry. “One of the things we highlight in the exhibit is deepsea mining, which has some pretty catastrophic potential in multiple ways.” Mining equipment can churn the fine sediment on the seafloor, generating great plumes that rise up the water column. “It’s going to pretty much wipe out everything that’s gelatinous and sensitive to that,” Patry says. 

Video: © 2021 MBARI 

This video shows the ROV in pristine waters—loaded with little flecks of white detritus, sure, but those are critters busy turning that carbon into sinking pellets. They’re in no way adapted to survive clouds of mucks infiltrating their habitat. “As if killing carbon-transformers isn’t bad enough, you’re then potentially blocking out light from some of the shallower areas,” Patry says. That makes photosynthetic algae less productive. “Now you’re starting to mess with the direct carbon uptake of the ocean, especially the high-productivity zones.”

An expedition like this is both a way to gather specimens for public viewing and to better understand these organisms—to learn “who lives in the deep, what they’re doing in the deep, and what role they play in the ecosystem,” says Patry. “Every opportunity that you get like that is valuable to science.”


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