Deep below the ocean’s surface, in the icy darkness of the bathypelagic zone, lies a hidden gem known as the “Octopus Garden.” This unusual nesting site for thousands of “pearl” octopuses (Muusoctopus robustus) is located on the Davidson Seamount off the coast of California. Discovered in 2018, it has since attracted the attention of scientists and marine life enthusiasts alike. Now, a team led by marine scientist James Barry of the Monterey Bay Aquarium Research Institute (MBARI) has uncovered the secret behind this mesmerizing phenomenon – the heat emanating from the volcano accelerates the development of octopus eggs, increasing their chances of survival. The study is published in the journal Science Advances
Through numerous dives and careful observations, Barry and his team unraveled the delights of the Octopus Garden. Armed with advanced marine technology and collaborating with local researchers, they were able to study this unique habitat in unprecedented detail. The findings shed light not only on the lives of these mysterious creatures, but also on the importance of protecting deep-sea habitats from climate change and other threats.
The octopus garden seemed to defy expectations thanks to its unusual location in the cold depths of the ocean. Located 3,200 meters (10,500 feet) below the surface, it is in the permanent darkness of the bathypelagic zone. Despite such inhospitable conditions, the researchers were amazed to find 4,707 nesting females in a 2.5-hectare area in the center of the site. They estimated that there could be as many as 20,000 octopuses, both males and females, in the entire nursery.
Octopuses, like many other marine life, are cold-blooded organisms. The average temperature of 1.6 degrees Celsius (35 degrees Fahrenheit) in the abyss of Mount Davidson significantly slows their metabolism. Under these conditions, pearl octopus eggs typically take five to eight years to hatch.
Over the course of three years, the research team conducted 14 dives using a remotely operated vehicle. They carefully studied and documented the octopuses’ behavior, noting their distinctive features and observing where mother octopuses lay and protect their eggs. During their observations, they noticed a faint shimmering of water in the seamount, indicating the presence of warmer water mixing with cooler water. This led them to discover a previously unknown hydrothermal system.
The researchers found that octopus nests are usually located in crevices where heat seeps in from beneath the seafloor, heating the water to a relatively warm 11 degrees Celsius (51 degrees Fahrenheit). This temperature proves more favorable for octopus metabolism and egg incubation. By tracking individual octopuses, the experts found that the heat of the volcano shortened the incubation period for pearl octopuses to about 21 months. The accelerated growth has a favorable effect on both the embryos and the metabolism of the mothers.
Although it remains unclear whether heat is a prerequisite for octopus nesting, its benefits are undeniable. A shorter incubation period greatly reduces the risk of predation, while incubating octopuses are still vulnerable and cannot defend themselves or escape. Ultimately, this increases their chances of survival in the long term.
The octopus garden serves as a reminder of the hidden wonders that lie beneath the bottom of our oceans. It emphasizes the interconnectedness of unique habitats and the need to protect them. By understanding and protecting these fragile ecosystems, we can ensure the continued existence of extraordinary creatures like the pearl octopus.