Davidson Seamount

Group of pink octopuses sitting upside down in a brooding position at Davidson Seamount
Female octopus (Muusoctopus robustus) brooding their eggs in a warm water seep at a depth of 3,200 meters near Davidson Seamount. Photo: Ocean Exploration Trust/NOAA

Davidson Seamount is located 80 miles southwest of Monterey, offshore of Central California and is 26 miles long, 8 miles wide, 4,101 feet deep at the summit, and 12,743 feet deep at the base. Davidson Seamount was added to Monterey Bay National Marine Sanctuary in 2008, and has since been recognized as one of the best explored and most protected seamounts in the world.

Seamounts are underwater mountains (often of volcanic origin), rising at least 3,280 feet from the seafloor, with submerged peaks often in the deep sea (over 650 feet). Davidson Seamount was the first geographic feature to be characterized as a “seamount” in 1938, and was named in honor of the U.S. Coast and Geodetic Survey scientist George Davidson.

Davidson Seamount has a distinctive shape. Instead of the more common conical structure of seamounts that look like circles on maps, Davidson Seamount formed over a long period of time over an earthquake fault, erupting for about one million years, creating an oblong series of cones on parallel ridges. The seamount last erupted as an undersea volcano approximately 9.8 million years ago.

Map of Davidson Seamount location
Davidson Seamount, one of the largest known seamounts in U.S. waters, serves as a model for studying deep-water ecosystems.

In the early 2000s, remotely operated deep-sea technology, developed and operated by the Monterey Bay Aquarium Research Institute, allowed for detailed surveys of formerly unvisited deep-sea habitats located only hours away from Central California harbors. The first expedition to assess deep-sea biology at Davidson Seamount took place in 2002. Research revealed a pristine area with large, ancient corals in the deep, near-freezing waters thousands of feet deep.

Repeated visits to the seamount continue to reveal new discoveries, including at least 18 species new to science (8 sponges, 1 hydroid, 4 corals, 1 ctenophore, 1 nudibranch, 1 polychaete, 1 seastar, and 1 tunicate). The Davidson Seamount Taxonomic Guide serves to illustrate and itemize at least 237 taxa (i.e., species, genus, family). Taxonomic experts continue to formally describe species for publication in the scientific literature. Environmental DNA (eDNA), the genetic material organisms leave behind in the water column, is adding to our knowledge of seamount communities.

Recent explorations have captivated the public with the discovery of deep-sea brooding octopus. Thousands of brooding deep-sea octopuses were discovered in two distinct “nesting” sites around the base of Davidson Seamount associated with hydrothermal springs. Such brooding aggregations have only been seen in one other place in the world. Similar species have been known to brood their eggs for more than four years.

Additional surveys from airplanes and large ships show the area above Davidson Seamount is abundant with large whales and seabirds (including world-record abundance of the seabird Cook’s petrel), likely because of deep-sea currents being directed towards the sea surface by the structure of the seamount.

Deep-Sea Coral and Sponge Habitats

Davidson Seamount is considered an oasis for deep-sea corals and sponges, with relatively bigger individuals and more abundant populations than found in the broader region. Deep-sea corals and sponges provide habitat for other species, and are an important indicator of critical habitat to protect from human disturbances. Monterey Bay National Marine Sanctuary and the Monterey Bay Aquarium Research Institute have a long-term collaboration to study deep-sea corals at Sur Ridge and Davidson Seamount. The goal is to increase understanding of Sur Ridge and the Davidson Seamount through characterization and ecological process studies and develop education programs for the seamount, the ridge, and similar geologic features throughout the nation.

Identifying coral and sponge communities has informed decisions on NOAA Fisheries’ designation of essential fish habitat areas and sanctuary ecologically significant areas and on the identification of Sanctuary Ecologically Significant Areas (SESA). Both Sur Ridge and Davidson Seamount are SESA. New scientific information will be used to support management decisions related to these areas and general deep-sea biology, for resource protection and education needs.

Conservation

The origin of conservation of Davidson Seamount has been bipartisan at the highest level of the federal government. Specifically, President William Clinton listed Davidson Seamount as one of three locations to launch a new era of ocean exploration and President George W. Bush announced its sanctuary designation in 2008. Information on research findings and the seamount’s protection are included in a permanent exhibit in President Bush’s Library and Museum.

The protected area within Monterey Bay National Marine Sanctuary known as Davidson Seamount Management Zone encompasses 775 square miles (2,007.4 square kilometers) of ocean waters and the submerged lands thereunder. The boundary resembles a square box centered on the summit of Davidson Seamount. Standard sanctuary regulations apply within the Davidson Seamount Management Zone (without the exemptions for seabed alteration). Taking, disturbing, injuring, or possessing any sanctuary resource below 3,000 feet (914.4 meters) within this zone is prohibited. In addition, NOAA Fisheries regulations (first effective June 2006) prohibit fishing with bottom contact gear, or any other gear deployed deeper than 3,000 feet (914.4 meters), to protect Essential Fish Habitat.

There are more than 30,000 known seamounts in the Pacific Ocean alone, but less than 0.1% of the world’s seamounts have been explored with very few protected. The Davidson Seamount “story”—its exploration, study and conservation—offers a model for future protection of offshore seamounts.

Davidson Seamount Management Zone (DSMZ): Facts and Figures
Distance from Monterey 80 mi 70 nmi 129 km
Distance from San Simeon 75 mi 65 nmi 121 km
Seamount Length 26 mi 23 nmi 42 km
Seamount Width 8 mi 7 nm 13 km
Seamount Height 7,480 ft 1.2 nmi 2,280 m
Seamount Summit (below sea surface) 4,101 ft 0.7 nmi 1,250 m
Deepest part of DSMZ 12,743 ft 2.1 nmi 3,884 m
Area of DSMZ 775 mi² 585 nmi2 2,007 km²
Area of MBNMS (including DSMZ) 6,094 mi² 4,601 nmi2 15,783 km²
MBNMS expanded to include DSMZ November 2008
Number of Corals Identified at Designation 27
Number of Taxa Identified at Designation 237
Geologic History last erupted ~9.8 million years ago

mi = statute mile
mi² = square mile
nmi = nautical mile
nmi2 = square nautical mile
ft = feet
m = meter
km = kilometer
km² = square kilometer
Coordinates of DSMZ
Point ID No. Latitude Longitude
1 35.9000 -123.00000
2 35.90000 -122.50000
3 35.50000 -122.50000
4 35.50000 -123.00000

Additional Resources

Visit the following websites for more information on the Davidson Seamount: