California researchers are part of a team that has identified the largest known octopus garden in the world — just 80 miles south of Monterey.
Octopuses are generally considered solitary creatures, so it came as a surprise when the team found thousands of them congregating some 10,500 feet underwater, where heat seeping up from the base of an extinct underwater volcano helps their eggs hatch faster.
“Its location is really crucial. We didn’t know this when we first discovered it,” said Amanda Kahn, an invertebrate ecologist with San José State’s Moss Landing Marine Laboratories, who co-authored a study out Wednesday in the peer-reviewed journal Science Advances.
The findings, driven by the Monterey Bay Aquarium Research Institute, whose senior scientist Jim Barry is the lead author of the new study, build off 2018 research. At the time, scientists discovered thousands of octopuses on the seafloor near the base of an extinct volcano, the Davidson Seamount.
The latest study now confirms these deep-sea octopuses migrate to the area to reproduce — which is part of what makes this octopus gathering so special, Kahn said.
She spoke more about the findings, their significance and, of course, the connection to a Beatles song with KQED’s Brian Watt.
This interview has been edited for brevity and clarity.
Brian Watt: First off, what does an octopus garden look like?
Amanda Kahn: If you looked out over the octopus garden, you would see tens to hundreds of octopuses flipped upside down. Their beaks are pointed up and their arms wrapped around their bodies in crevices and cracks and seams along the seafloor. And if you looked closer, under those octopus arms, there would be clusters of eggs cemented to the rock. The mothers would fan water to move new water past the eggs, and they would protect those eggs as scavengers like shrimp or snails would migrate in trying to catch an egg.
So the takeaway of this study is that mating is happening here?
Correct. But not only is mating happening here at Davidson Seamount and the octopus garden, but the reason they’re coming to that particular spot is the warm water that’s seeping from the cracks and crevices. So that warmth is speeding up the development rate of the embryos. And that in turn means that they’re in that very vulnerable egg stage for a shorter period that protects them from infection or injury or predators that may come in. That warm water is really crucial for the development of the eggs and the octopus embryos.
These are called hydrothermal warm springs, and they don’t form everywhere. They form along a geological feature called a ridge-flank system, and these ridge-flank systems are places where that warm water can seep out. There are only a handful of areas where these warm hydrothermal springs have been found, and where they were found is because octopuses were identified there. So it’s a neat connection between this key geological feature and biology.
Can this study help us understand ecological habitats with respect to climate change?
The relationship between the octopus nursery and temperature is really important because warmer water is important for speeding up the development of the embryos. We estimated that in cold water it would take five-to-eight years or even longer for those eggs to develop, but instead it took just under two. So that’s really beneficial for this species, but it comes with risks. So if that water gets to be too warm or if, say, that fluid shifts and exposes the eggs to slightly warmer temperatures, then those eggs could become unviable and not hatch.