The Wildest Frontier

Into the depths of America’s national marine sanctuaries

Words by Rachel Plunkett for NOAA’s Office of National Marine Sanctuaries

Inside America’s national marine sanctuaries, the deep sea reveals ancient coral forests and hidden octopus nurseries, proving that Earth’s strangest wilderness isn’t on land, but deep in the sea. Thousands of feet below the surface, entire forests glow in slow motion: fairy-tale bubblegum corals, massive sponges the size of minivans, and ancient animals that grow by mere inches per year yet stand taller than us. Down here, life is less about speed and more about patience.

America’s national marine sanctuaries protect some of the most biologically rich and unique places in US waters. While many people picture shallow coral reefs or picturesque coastlines, these marine parks also extend into the deep ocean — places so remote that scientists are still discovering entirely new species, behaviors, and habitats.

Down here, life moves differently. It’s slower. Older. Stranger. And more fragile.

Mountains in the Dark

Seamounts are the deep ocean’s mountain ranges, places where currents slow, life gathers, and ecosystems build themselves around rock formations in the dark, transforming the open seafloor into vertical pillars of life built layer by layer over centuries, and sometimes millennia.

Rising thousands of feet from the seafloor, seamounts interrupt deep-ocean currents, concentrating nutrients and plankton along their slopes and summits. In an environment where hard surfaces are rare and food is scarce, these underwater volcanoes create structure and opportunity. Corals anchor to exposed rock. Sponges filter passing water. Fish and invertebrates gather along ledges where currents deliver a steady supply of food.

Of the roughly 200,000 seamounts believed to exist worldwide, scientists have explored only a small fraction.

Seamounts and deep volcanic features shape entire ecosystems within America’s national marine sanctuaries. In Papahānaumokuākea National Marine Sanctuary, seamounts and banks form biological stepping stones across the Northwestern Hawai‘ian islands, supporting deep-sea coral communities and endemic species found nowhere else.

In the National Marine Sanctuary of American Samoa, deep volcanic features are still shaping the future. Vailuluʻu Seamount, about 100 miles east of Tutuila, is an active hotspot volcano and the current expression of the geologic engine that formed the Samoan archipelago. When scientists mapped the seamount in 2005, they discovered a new volcanic cone forming inside its caldera. Named Nafanua, after the Samoan goddess of war, the cone and surrounding caldera continue to change, evidence that this submarine volcano is still growing and may one day form a new island.

Davidson Seamount: The Octopus Garden

About 80 miles southwest of Monterey, California, one of the best-studied seamounts on Earth rises from the darkness: Davidson Seamount, within Monterey Bay National Marine Sanctuary. Shaped by ancient layers of volcanic ash, rock fragments, and lava flows, the seamount today supports dense coral and sponge communities across its slopes and ridges.

Mother octopuses brooding their eggs at Davidson Seamount's octopus garden in Monterey Bay National Marine Sanctuary | Credit: Ocean Exploration Trust/E/V Nautilus and Chad King/NOAA

In 2018, researchers aboard Ocean Exploration Trust’s E/V Nautilus discovered something unexpected: thousands of pearl octopuses clustered in the warmth of underwater volcanic springs, brooding their eggs in a hidden nursery. It’s a sight so surreal and tender it feels like watching the planet dream.

It is proof that even in one of the harshest environments on Earth, life still finds ways to adapt and endure. 

An octopus in Arguello Canyon, near Channel Islands National Marine Sanctuary | Credit: Ocean Exploration Trust/NOAA

Other Deep-Sea Habitats

Seamounts are only one chapter of the deep ocean story.

Across national marine sanctuaries, scientists are exploring submarine canyons carved deeper than the Grand Canyon, where cold currents funnel nutrients and create highways for migrating species. On abyssal plains, vast dark expanses of seafloor, life survives on a slow snowfall of organic particles drifting from the sunlit world above. Here, sunken carcasses of whales, called whale falls, can transform otherwise nutrient-poor seafloor into decades-long blooms of life.

Bubblegum coral (Paragorgia arborea) at 4,124 feet water depth at Davidson Seamount in Monterey Bay National Marine Sanctuary. Small blue scale worms (Family Polynoidae) were often associated with Paragorgia arborea. 

Many habitats within the deep sea are a frontier for medical research. For example, deep-sea corals and sponges are natural disease fighters. They produce unique chemical compounds that scientists are studying for potential medical applications, including treatments for cancer, bacterial infections, and neurological diseases. 

In some places, Earth’s internal heat fuels entire ecosystems. Hydrothermal vents release mineral-rich fluids that support animals living in complete darkness. Chemosynthetic features like hydrothermal vents and cold seeps are ecologically rich habitats where life is powered not by the sun’s energy, but by chemistry. 

Together, these habitats form a deep-ocean mosaic shaped by geology, chemistry, and time.

Corals and sponges that make up the seafloor habitats at Santa Lucia Bank in Chumash Heritage National Marine Sanctuary, such as this deep-sea bubblegum coral (Paragorgia arborea), provide food and shelter for recreationally and commercially important fish species | Credit: NOAA 

The Frontier Beneath Us

We often talk about space as the final frontier. But in many ways, the deep ocean is closer, stranger, and just as unknown. Unlike space, it is still shaping the world that shapes us.

Inside America’s national marine sanctuaries, this frontier is not only being explored — it is safeguarded for generations to come. These deep-sea ecosystems took millennia to form, and we’ve only just begun to understand many of the species living here.

This deep-sea frogfish delighted researchers onboard Okeanos Explorer during an expedition to explore deep waters of National Marine Sanctuary of American Somoa | Credit: NOAA Exploration

Far below the horizon, in darkness older than human history, coral forests glow, octopus mothers wait patiently over their eggs, and ecosystems move at the pace of geological time.

It is a world that feels almost impossible, yet it is very real and alive. A frontier not of distance, but of depth.

A predatory sea star slowly works its way up a bamboo coral on an unnamed seamount in Papahānaumokuākea National Marine Sanctuary | Credit: NOAA Exploration, Hohonu Moana 2016

NOAA’s National Marine Sanctuary System

Safeguarding America's Premier Marine Places

From Washington state to the Gulf of America and from the Great Lakes to the Pacific Islands, the National Marine Sanctuary System protects 18 underwater parks spanning over 629,000 square miles of ocean and Great Lakes waters. By investing in innovative solutions, we strengthen these iconic places to address 21st-century challenges while supporting America's commerce and tourism. These unique locations inspire people to visit, value, and steward our nation’s iconic ocean and Great Lakes waters.

Learn more at https://sanctuaries.noaa.gov/ 

Feature Image by NOAA/Monterey Bay Aquarium Research Institute

A brittle star living on pink bubblegum coral in Papahānaumokuākea National Marine Sanctuary | Credit: NOAA Exploration