A warm garden in the deep sea with octopuses lying like jewels on the bottom

Biologists also call the place in this photo ‘Octopus Garden’: an undersea hot spring that serves as a nursery for baby octopuses, in the deep sea far off the coast of California. Thousands of octopuses fall from the species every year Mouse octopus robustus down to a depth of about 3,200 meters, to mate, lay eggs and then die. The place was only discovered in 2018.

Nowhere else in the world are there so many octopuses together American researchers write in Science Advances that this high squid density is due to the hydrothermal vents at that location. While the surrounding deep sea has a temperature of about 1.6 degrees Celsius, around the springs it is a pleasant 10.8 degrees Celsius. The heat promotes the development of the embryos and thus shortens the incubation time and breeding success: the faster the eggs hatch, the greater the chance that they will not be eaten prematurely or succumb to an infection, for example.

And although the incubation time in Octopus Garden is still around 1.8 years, that is surprisingly fast for that depth: in places in the deep sea where the temperature is actually below 2 degrees Celsius, you can expect the embryos to hatch as quickly as take five to eight years to develop. Each female lays about sixty eggs, which she firmly cements to the rocks around the source.

The fact that the adult octopuses come to the hot springs has another indirect advantage, the researchers write. Because the journey is a one-way trip for them – the males die immediately after mating, and the females after the eggs hatch – their remains increase the local carbon content. This is beneficial for food abundance and therefore for biodiversity. Sea anemones, fish and shrimp, among others, feed on the dead squid.

In English, these octopuses are also called ‘pearl octopuses’: from a distance they look remarkably like precious jewels.