Its mauve, suction cup-covered arms gently unfold to grab an egg shaped like an elongated ping-pong ball. A jet of water from a siphon next to the octopus's head ensures that the unhatched cubs get enough oxygen.

From a distance, she is surrounded by hundreds of females, living up to her nickname. The pearl octopus (Muusoctopus robotus) resembles a spherical gem that sits on the ocean floor. This is the largest known assemblage of eight-armed molluscs on Earth, numbering approximately 20,000 individuals, and has been witnessed by people all over the world in astonishingly high resolution. “Oceans” episode BBC series Planet Earth III.

This view would have been amazing enough even if it were from shallow water, including tropical coral reefs and kelp forests. But these octopus mothers tend to their eggs in freezing cold and darkness, about 2 miles below the surface. of the deep sea.

“The fact that there is life there is amazing in itself,” says the producer and director. Will Ridgeon They spent two years photographing the octopus, collaborating with scientists and technicians at California's Monterey Bay Aquarium Research Institute (MBARI).

The octopus farm, as the site is now known, is located on a hill in the eastern Pacific Ocean, 160 km (100 miles) southwest of Monterey Bay, near a giant underwater mountain called Davidson Seamount. This place was discovered during his expedition in 2018. live streamed over the internet.

It was the first time I had ever seen so many creatures in one place, let alone in the deep sea. (Octopuses are notoriously solitary animals and tend to be cannibalistic when kept together in captivity.) ).

Ridgeon watched the livestream of the discovery and immediately knew it was a story to be filmed in a new BBC series.he teamed up with Dr. Jim Barrya senior scientist at MBARI, began regularly visiting octopus farms in 2019 to learn more about why so many octopuses congregate in certain areas.

“The question is, why is it there?” Barry says. Barry and his colleagues gathered specialized tools and began a series of detailed studies. They created a photomosaic of his 2.5-hectare (about 27,000 square feet2) portion of the property and stitched together high-resolution images that allowed them to count the octopus population.

They also installed time-lapse cameras on the ocean floor, taking close-up photos every 20 minutes at a time for months to show what the octopuses were doing, and Barry's team gradually expanded the octopus park's largest began to unravel some of the mysteries.

work remotely

Ridgeon took part in an expedition to an octopus farm early on. Initially, filming took place during lockdown, so he participated via live video link from his bedroom in Bristol, England (with occasional interruptions from his five-year-old daughter).

Once COVID-19 restrictions allowed, Ridgeon joined Barry and his team aboard MBARI's vessel, the research vessel Western Flyer. However, no one visited the octopus farm directly. All surveys and filming were done using a car-sized remotely operated vehicle (ROV) equipped with a camera and a robotic arm.

The dive began around 6 a.m., and the ROV was lowered into the ocean through a hole in the Western Flyer's hull called the moonpool. “It's very James Bond,” Ridgeon says. The descent to the octopus garden can take up to two hours, and the ROV will remain there all day.

The pilot controls the ROV via a cable connected to a control room on the ship on the ground, and everyone watches the video feed to see what's happening below.

“You forget you're looking at a screen,” Ridgeon says. “You think you're there,” says the MBARI engineer. He worked with the BBC to find the ideal camera setup to photograph the octopus garden. It was not possible to use footage from a camera fixed to the ROV due to too much vibration.

“I think the BBC will do a little bit about that.” [shivering]“But not as much as we had,” Barry says. ROVs “shudder” not because of the cold temperatures of the deep ocean, but because the thrusters must be activated constantly to ensure they stay close to the ocean floor (ROVs are positively buoyant, so if they fail they will ). .

To get around this, Barry and Ridgeon used a separate 4K camera mounted on a specially designed stand that could be placed on the ocean floor.

“I think that's the secret behind the images,” Ridgeon says. Unlike the ROV cameras used by scientists, which can only reach within a few meters of objects on the ocean floor, the 4K camera's focal length of about 20 centimeters (7 to 8 inches) allows it to precisely navigate between octopuses. can be captured.

But it was difficult to use. It took up to 40 minutes to get into position, and the team had to hope it wouldn't fall over and the action would happen in front of it. Ridgeon operated the camera from the ship using his PlayStation controller, which MBARI engineers adapted for the job. “At first it's like trying to film him with his hands tied behind his back,” Ridgeon said.

Another challenge with deep-sea photography is light. “Put the light as far away from the camera as possible, ideally around the sides so it’s three-quarters backlit. [the scene]That way, there are no reflections from any debris in the water,” explains Ridgeon.

Those “fragments” are marine snow. These are organic particles that constantly rain down from the shallow ocean above. Marine snow is made up of dead plankton and their feces stuck together by microbial glue, and is the main food source for deep-sea animals. However, it makes filming difficult as the movie can look like it was shot in a snowstorm.

To see through the snowstorm and achieve the desired three-quarters backlighting effect, the MBARI team built a lighting system that the ROV could hold on its side, away from the camera. “That's how we got some really great shots,” Barry says.

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Accelerate development

As Barry's investigation and BBC filming progressed, the team made some surprising discoveries. First, no medium-sized octopus ever visited this location, and there were no signs of it feeding. It was only a fully grown adult octopus.

They were here to breed and for no other purpose. It may be called an octopus farm, but this place is definitely an octopus farm. The researchers also collected evidence that incubating females use on-site hot springs to speed up the development of their offspring.

For octopuses, there is a strong relationship between temperature and hatching time. The colder it is, the longer it will take and the more dangerous it will be. This is because there are scavengers that prey on unborn, unprotected octopus eggs.

Temperature studies have shown that the seawater surrounding each octopus nest can reach 10°C (50°F), much warmer than the 1.6°C (34°F) seawater just a few meters away. It was shown. By observing specific octopuses (identifiable by scratch and scar patterns) in the field, Barry and his colleagues determined that their eggs take an average of 1.8 years to hatch.

During this time, the female does not move but is constantly fighting off predators and guarding her approximately 60 eggs. “Once you plant an egg on a rock, that's it. You can't leave that spot,” Barry says. At just under two years, it's not the longest parenting period for an octopus. This record is given to another species that other MBARI scientists discovered nearby, Graneledon boreopafica, clinging to the sides of Monterey She Canyon 1.4 km (just under a mile) deep. I did.

Researchers watched one female incubate her eggs for four and a half years, longer than any other recorded animal. However, she was growing her eggs in water that was much warmer than the octopus park's ambient temperature of 1.6 degrees Celsius. Without the hot springs, the eggs in the octopus garden would take more than 10 years to hatch. When this site was discovered, biologists were surprised to find octopuses nesting there.

But geologists were fascinated by warm water seeping through the ocean floor, something they had never seen before. These springs are much cooler than the red-hot hydrothermal vents that form at the edges of tectonic plates where new molten ocean floors are created.

Although the enormous pressure will not cause the water to boil, the temperature around the vent can reach hundreds of degrees. These were first discovered in his 1970s, and plumes of hydrothermal water rise up to hundreds of meters in the water column, making them relatively easy to detect with temperature probes. In contrast, hot springs are more difficult to find because they form away from these tectonically active regions and have much cooler temperatures.

But geologists believe they could exist in the thousands and are highly stable, likely remaining in the same location for hundreds or even thousands of years. Therefore, biologists believe that more octopus farms may be established around these springs.

birth and death

In the final scene of the “Octopus Garden” episode Planet Earth III, a cluster of tiny sucker-like arms appears beneath the brooding female, then a wobbling young octopus swims away into the darkness like a mini-umbrella. More chicks follow and begin life at sea.

No one knows where they're going…yet. “That's what I want to understand next,” Barry says. The hatchlings are large for a newborn octopus, at about 6 cm (2 inches), so they have the best chance of survival. But as anyone who has seen the Octopus documentary knows, this comes at a heavy cost to mothers.

“These mothers are trying so hard to protect their bloodlines, and they're just dying out,” Barry says. Her father died a few years ago, shortly after mating. On the screen, we see the women's eyes cloudy and their bodies wrinkled. Ridgeon saw what happened next, but she decided it was not suitable for an evening television audience.

Dead octopuses are quickly attacked by scavengers such as fish, snails, sea anemones, and shrimp. For Barry, this is another important part of his discovery at the octopus farm. The nesting season is asynchronous, with octopuses hatching and mothers dying throughout the year. Approximately 9 each day. The female octopus' body nourishes the rest of the ecosystem and helps supplement the energy input from marine snow by 72 percent.

“This is clearly a huge food subsidy for the local ecosystem,” Barry says. “That wouldn't happen in shallow water,” he added. Because there is a lot of food around. But in the more barren depths, nothing goes to waste.

The BBC has finished filming at the octopus farm, but Barry's research continues. One of the things he wants to know is the age of the sea anemone. These are giant orange flower-like animals that make the octopus garden look like a real garden.

Barry studies sea anemones, which live for decades in shallow coastal waters, and finds that deep-sea species can survive for centuries, in contrast to octopuses, which are relatively short-lived. That's what I'm thinking.

“They're like sentinels that just sit there while the octopus cycles,” he says. There are many more questions Barry would like to answer. “Are octopuses confined to this breeding form in warm areas, or are they able to breed elsewhere with cooler ambient temperatures? Is there fidelity to specific nest sites? ?Will they return to their place of birth?'' he asks.

No one knows how far the octopuses travel before they reach the garden or how they found them, but Barry said he was surprised by the large number of dead and dying octopuses floating around. I suspect I smelled it. “We'll definitely be back,” he says.

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