Biodiversity at Davidson Seamount:

Exploring National Marine Sanctuaries

By Rachel Plunkett

Davidson Seamount used to be an active underwater volcano, but it stopped erupting approximately 9.8 million years ago. The feature, located 80 miles southwest of Monterey, California, was first mapped in 1933 and was the first undersea feature to be characterized as a “seamount.” In 2002, researchers from NOAA, Monterey Bay Aquarium Research Institute, Monterey Bay Aquarium, and Moss Landing Marine Laboratories set out to explore the seamount utilizing the remotely operated vehicle (ROV) Tiburon—an underwater robot that was considered new technology at the time. The expedition was historical, revealing that the geological feature was an oasis of biodiverse marine life amid a flat ocean seafloor.

soft corals in a dark ocean
Researchers exploring seamounts such as Davidson have found that as vertical relief from the seafloor increases, animal life explodes. Photo: NOAA/MBARI
several pink, branching corals
Deep-sea corals like this bubblegum coral are beautiful, long-lived, and fragile. Photo: NOAA/MBARI

Researchers returned to Davidson Seamount in 2006 in hopes of understanding more about the ancient coral gardens that exist there, and to explore why deep-sea corals thrive in some areas but not others. “We were blown away by the size, age, and diversity of the deep-water corals we saw during our 2002 Davidson cruise,” said Andrew DeVogelaere, sanctuary research ecologist and chief scientist for the 2006 expedition. “Indeed, the discoveries we made during that cruise prompted members of the public to propose that Davidson Seamount be protected as part of Monterey Bay National Marine Sanctuary. We wanted to go back to learn why so many extraordinary corals thrive there and to determine their age and growth patterns.” The exploration and subsequent scientific findings from these two expeditions led to the expansion of Monterey Bay National Marine Sanctuary in 2008 to protect the seamount.

Since then, NOAA and its partners have conducted more than 20 surveys at/over Davidson Seamount, and it is considered one of the best explored and most protected seamounts in the world. Recent expeditions aboard Ocean Exploration Trust’s Exploration Vessel (E/V) Nautilus allowed people across the world to tune in live and witness exciting discoveries such as the two “octopus gardens” at the base of the 12,743-foot-deep mountain. The octopus gardens are nesting sites for brooding deep-sea female octopuses attracted to the warm 50 degrees Fahrenheit water seeping from the inactive volcano’s vents.

octopus positioned upside down on rocky substrate
Muusoctopus positions itself upside down in a brooding position. Photo: OET/NOAA

“One of the tenets of exploration is to expect the unexpected,” said Chad King, research ecologist for Monterey Bay National Marine Sanctuary. “We had no idea that there were thousands of octopus mothers taking advantage of warm water escaping the seafloor, which accelerates the development of their eggs. The fact that two major discoveries were made simultaneously points to the fact that we have so much more to discover in our own sanctuary.”

Why is it Important?

The fragile and ancient deep-sea coral forests at Davidson provide habitat for some rare and endemic species—meaning they can’t be found anywhere else on the planet. Many of the species found living at seamounts grow and reproduce very slowly, which makes them highly vulnerable to unsustainable deep-sea fishing practices and mineral exploration. To protect this fragile ecosystem and the resources found there, taking, disturbing, injuring, or possessing any sanctuary resource from more than 3,000 feet below the sea surface within the Davidson Seamount Management Zone is prohibited. But many previously existing fisheries are still able to operate in waters above the seamount, making the protections compatible with commercial fisheries that contribute to the Blue Economy by providing jobs and food security.

whale bones with marine life growing on them
During an expedition to Davidson Seamount in October 2019, a new species of bone-eating Osedax worm was discovered on the carcass of a dead whale. When found in great numbers, the worms look like a pink, fuzzy carpet covering the whale’s bones. Photo: OET/NOAA
a pink sponge with long branches
Asbestopluma monticola is a white, branched, predatory sponge. Their velcro-like structures (spicules) help to capture small prey that float by. The holotype was recovered from the summit of Davidson Seamount in 2006 using MBARI’s ROV Tiburon. Photo: NOAA/MBARI

Since 2002, seven species observed at Davidson Seamount have been formally described by scientists and are new to science, and about 13 others are awaiting further analysis. Undoubtedly, more remain to be discovered during future expeditions. These findings make the protected seamount a valuable place for researchers to continue learning more about how these unique geologic formations deep in the ocean contribute to ecological quality and ocean productivity.

According to the International Union for the Conservation of Nature, roughly 200,000 seamounts exist throughout the world, and over 30,000 seamounts are known to exist in the Pacific Ocean alone, but less than 300 of the world’s seamounts have been explored and relatively few are protected.

Rachel Plunkett is the writer/editor for NOAA’s Office of National Marine Sanctuaries