BY THE OPTIMIST DAILY EDITORIAL TEAM
Most of the deep seafloor is cold, dark, and barely mapped. The Monterey Bay National Marine Sanctuary covers more than 6,000 square miles of ocean along California’s central coast and is better studied than most of it. Even there, researchers from the Monterey Bay Aquarium Research Institute somehow missed a gathering of 20,000 octopuses until 2018.
The site is now the largest known deep-sea octopus congregation on Earth, which raises an obvious question about what else is down there. It sits on a field of hydrothermal springs, and that’s the key. The springs warm the water above what the surrounding seafloor offers, which speeds up metabolism and egg development in the pearl octopuses (Muusoctopus robustus) drawn to the heat. Normally, female octopuses in the deep sea spend years brooding their eggs. At this site, they do it in about 1.8 years.
Why 20,000 octopuses gather here
Pearl octopuses are pale purple, roughly grapefruit-sized, and not especially known for company. Something about the thermal conditions here has drawn more than 20,000 of them to roughly 6.2 acres of seafloor. Using underwater mapping technology, researchers counted about 6,000 in a 2.5-hectare area and extrapolated the rest.
The dens they build use whatever is on the seafloor nearby: stones, shells, and whatever human objects have settled down there over time. After brooding their eggs, the females die, and their bodies become food for other animals in the area. The whole cycle keeps the local food web running on what the octopuses themselves leave behind.
What protection made this discovery possible
The octopus garden sits inside the Monterey Bay National Marine Sanctuary, which restricts oil and gas exploration, seabed mining, and other activities that can damage the seafloor. Hydrothermal fields in the deep sea are fragile and not well understood. Without protected status, this one could have been disturbed or destroyed before anyone knew what was living there.
This congregation went undetected until 2018 in one of the most closely monitored stretches of deep ocean in the world. Hydrothermal springs aren’t unique to this part of California, and the ocean has a lot of floor. The question the garden raises is how many other congregations, in thermal fields no one has mapped yet, are still down there.
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