A secret deep-sea oasis where 20,000 octopuses lay their eggs

A purple-red arm covered with suckers spreads gently, reaching toward a nest of elongated ping pong ball-shaped eggs. Water squirted from a siphon on the side of the octopus’s head ensures that her unhatched young receive adequate oxygen.

She was surrounded by hundreds of other women who, from a distance, lived up to their name. The pearl octopus (Muusoctopus Robustus) resembles a spherical gem on the sea floor.It’s the largest known aggregation of eight-armed molluscs on Earth, numbering around 20,000 individuals, and people around the world witnessed the phenomenon in stunning HD on an episode of the BBC series Oceans Earth Pulse III.

It would be surprising enough if this sight came from somewhere in shallow seas, tropical coral reefs or kelp forests, but these octopus mothers are caring for them in the cold and darkness nearly 3 kilometers (2 miles) below the surface The eggs of the deep sea.

Producer and director Will Ridgeon, who spent two years filming the octopus and working with scientists and engineers at the Monterey Bay Aquarium Research Institute (MBARI) in California, says life does, in fact, exist It’s amazing.

The site, now known as Octopus Garden, is located in the eastern Pacific Ocean, 160 kilometers (100 miles) southwest of Monterey Bay, on a small hill near a huge underwater mountain called the Davidson Seamount. The site was discovered in 2018 during an expedition broadcast live online.

This is the first time so many of these creatures have been seen 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 was watching the discovery live and knew immediately it was a story to film for a new BBC series. He teamed up with MBARI senior scientist Dr. Jim Barry, who began visiting the Octopus Garden regularly in 2019 to learn more about why so many octopuses congregate at that particular site.

The question is, why is it there? Barry said. Barry and his colleagues assembled specialized tools to conduct a series of detailed studies. They created a mosaic of photos of a 2.5-hectare (nearly 27,000-square-foot) portion of the site, stitching together high-resolution imagery that allowed them to count individual octopuses.

They also installed time-lapse cameras on the seafloor, taking close-up photos every 20 minutes for several months to show the octopuses in action. Gradually, Barry’s team began to unravel some of the biggest mysteries of the octopus garden.

telecommute

Richion was involved in Octopus Garden adventures early on. Initially, filming took place during lockdown, so he joined via live video link from his bedroom in Bristol, England (occasionally interrupted by his five-year-old daughter).

When COVID-19 restrictions allowed, Ridgeon joined Barry and his team aboard MBARI’s research vessel, the Western Flyer. But none of them had ever visited the Octopus Garden in person. All research and filming was done using a car-sized remotely operated vehicle (ROV) equipped with a camera and robotic arm.

The dive begins around 6 a.m. with the ROV lowering into the sea through a hole in the hull of the Western Flyers called the moonpool. It’s a lot like James Bond, Riggin said. The descent into 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 that connects it to a control room on the surface vessel, where everyone can watch video to see what’s going on below.

Richion says you forget you’re looking at a screen. You thought you were there. MBARI engineers worked with the BBC to find the ideal camera settings for filming the octopus garden. It was not possible to use the lens of a camera fixed to the ROV because the vibration was too great.

The BBC could solve some of the problems [shivering]”But not as many as us,” Barry said. The ROV trembles not because of the frigid temperatures of the deep ocean, but because its thrusters have to constantly work to ensure it stays near the ocean floor (the ROV has positive buoyancy, so if it fails, it will float back to the surface).

To solve this problem, Barry and Ridgeon used a separate 4K camera on a specially designed mount that could be placed on the ocean floor.

‘I think that’s the secret behind these images,’ Riggin said. Unlike the cameras on the ROV used by scientists, the 4K camera has a focal length of about 20 centimeters (7-8 inches) and can reach directly into the middle of the octopus.

But it is difficult to use. It takes 40 minutes to position, and then the team has to hope it doesn’t tip over and that the action will take place in front of it. Ridgeon operated the camera on board using a PlayStation controller modified by MBARI engineers for the task. Richion said it was like trying to film with your hands tied behind your back at first.

Another challenge when photographing in the deep ocean is light.You want the light to be as far away from the camera as possible, preferably to the side so you are three-quarters backlit [the scene]so you’re not reflecting off all the debris in the water, Richion explains.

These fragments are organic particles of marine snow that are constantly falling from the shallow ocean above. Marine snow is made from dead plankton and their feces held together by microbial glue and is a major food source for deep-sea animals. But this made filming difficult, as the movie looked like it was shot in a snowstorm.

To see through the snowstorm and achieve the required three-quarter backlight effect, the MBARI team built a lighting rig that the ROV could position away from the camera and to the side. Barry says that’s how we get some really great photos.

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Accelerated development

As Barry’s research and BBC filming progressed, the team made some startling discoveries. For one thing, no medium-sized octopuses ever came to the site, and there were no signs of feeding. It’s just a fully grown, mature octopus.

They come here just to reproduce and have no other purpose. It may be called the Octopus Garden, but the site is undoubtedly an octopus nursery. The team also gathered evidence that incubating females are using local hot springs to accelerate the development of their young.

For octopuses, there is a strong relationship between temperature and hatching time. The colder the weather, the longer it takes and the more dangerous it is, as scavengers wait to eat the unborn, unattended octopus eggs.

Temperature detectors show that the water temperature around each octopus nest can reach 10 degrees Celsius (50 degrees Fahrenheit), much higher than the 1.6 degrees Celsius (34 degrees Fahrenheit) in the water a few meters away. By watching specific octopuses hatch in the field (individuals can be identified by the pattern of scratches and scars), Barry and his colleagues found that their eggs took an average of 1.8 years to hatch.

During this time, the female does not move but constantly fights off predators and protects her approximately 60 eggs. Once you plant your eggs on a rock, you’re stuck in that spot, Barry said. At less than two years, this isn’t the longest an octopus has ever taken to hatch. The record belongs to Graneledone boropacifica, a different species that other MBARI scientists discovered nearby, clinging to a depth of 1.4 kilometers (less than a mile) on the side of Monterey Canyon.

They found that one female incubated her eggs for 4.5 years longer than any other animal on record. But she raised her eggs in water that was much warmer than the 1.6 degrees Celsius ambient temperature of the octopus garden. Without hot springs, octopus garden eggs can take ten or more years to hatch. When the site was discovered, biologists were surprised to find octopuses nesting there.

However, geologists are fascinated by the warm water seeping out of the ocean floor, which has never been seen before. These springs are much cooler than the searing hydrothermal vents that form at the edges of tectonic plates, where new molten seafloor forms.

Although the intense pressure prevents the water from boiling, the temperature around the vents can reach hundreds of degrees. First discovered in the 1970s, they are relatively easy to detect with temperature probes because plumes of hot water rise hundreds of meters into the water column. In contrast, hot springs are far away from these tectonically active areas, are much cooler, and are harder to find.

But geologists believe there may be thousands of them, and they are likely to be highly stable, lasting hundreds or even thousands of years in the same spot. As a result, biologists believe there may be more octopus nurseries around these springs.

birth and death

In the final scene of the episode “Octopus Garden” Earth Pulse IIIA swarm of tiny sucking tentacles appears beneath a brooding female, then a bobbing baby octopus swims off into the darkness like a mini umbrella. More hatchlings follow and begin life in the ocean.

Where they went, no one knows yet. That’s the next thing I want to figure out,” Barry said. For newborn octopuses, the larvae are large, about 6 centimeters (2 inches), giving them the best chance of survival. But anyone who has watched the Octopus documentary knows that this comes at a huge cost to mothers.

Barry said these mothers were staunch defenders of their children, but they just withered away. The fathers died shortly after mating a few years ago. On screen, we see the female’s eyes glaze over and her body becomes wrinkled. Richion saw what happened next but decided it was inappropriate for an early evening TV audience.

The octopus carcass was immediately devoured by fish, snails, sea anemones and shrimps, and for Barry it was another important part of his discovery in the octopus garden. The nesting season is asynchronous, with approximately nine octopuses hatching and the mother dying each day of the year. The female octopus’s body helps feed the rest of the ecosystem, supplementing 72% of the energy input from ocean snow.

Barry says this is clearly a large food subsidy to the local ecosystem. He added that this would not be the case in shallow water because there is a lot of food around. But in the barren depths, nothing goes to waste.

The BBC has completed filming at Octopus Gardens, but Barry’s research continues. One thing he was curious to know was how old the anemone was. These giant orange flower-like animals make the Octopus Garden look like a real garden.

Barry studied sea anemones that live in shallow coastal waters for decades and suspects that deep-sea species can survive for centuries, in contrast to octopuses, which live relatively short lives.

He said they were like these sentinels that sat there as the octopuses rode by. Barry still had a lot of questions he wanted answered. Are octopuses locked into warm places for this type of reproduction, or can they still reproduce elsewhere with cooler temperatures? Is there fidelity to a specific nesting site? Will they return to the place where they were born? he asks.

No one knows how far the octopuses travel to reach the garden, or how they find it, although Barry suspects they smell the scent of so many dead and dying octopuses. Well, I will definitely go back, he said.

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