Conservation & Science

Safeguarding seamounts: the hidden Yosemites of the deep

At the bottom of the ocean, amid vast, pitch-dark expanses of mud, there are a few exceptional, rocky places: undersea mountains. Here, the muddy seafloor and burrowing worms give way to bedrock and beautiful gardens of corals and sponges.

Seamounts are islands of biological diversity in the deep sea, home to rich marine communities of often long-lived animals. Photo courtesy MBARI/NOAA

Seamounts, as these peaks are known, “are the Yosemites of the deep sea that nobody sees,” says Dr. Jim Barry, a marine ecologist at MBARI—the Monterey Bay Aquarium Research Institute. “Under the surface, right off the horizon, is this wonderful world that’s been developing, slowly but surely, like a sequoia forest.”

Some seamounts are covered with ancient corals and deep-sea sponges that stand a meter tall and resemble oak trees. They’re also home to anemones, clams, small crustaceans and all manner of fishes. Many of these creatures rely on smell instead of vision to find food in these inky waters, at least half a mile deep.

Life on seamounts is of interest to marine scientists and to biotech researchers who hope to develop new pharmaceutical products based on properties in sponges, mussels and microbes. Photo courtesy MBARI

Seamounts are a frontier for scientific discovery, both for basic research, designed to fill knowledge gaps, and for applied research aiming to solve practical problems. Biotech companies, for instance, are interested in unique chemicals produced by deep-sea microbes, sponges, and mussels, which hint at pharmaceutical applications from antibiotics to fighting cancer.

Only a few seamounts are legally protected, like national parks are on land. One of those is Davidson Seamount, 80 miles southwest of Monterey and part of Monterey Bay National Marine Sanctuary. But the Trump administration is in the process of reviewing Davidson Seamount’s designation, with an eye for potentially stripping its protection and opening it up for new offshore oil and gas drilling.

California’s peculiar volcanoes

How rare are seamounts? Dr. David Clague, a senior scientist at MBARI, estimates that 90 percent of the ocean floor is a flat plain.

The Davidson Seamount, off California’s Big Sur coast, is one of 10,000 to 15,000 of these undersea mountains found around the world. Map courtesy oF MBARI

“It just happens to be punctuated with 10,000 to 15,000 submarine volcanoes,” he says. “These range in size from tiny volcanoes that erupted probably just once or twice, to places like Hawaii that breach the surface and form an island.”

There are several ways seamounts form, David says. The majority are small and appear near mid-ocean ridges, usually a mile or so from the active heart of the ridge. Hawaii’s volcanoes are a more unusual type that forms linear chains.

Along the California coast, the process that created Davidson Seamount—and other nearby seamounts with names like Pioneer, Guide, Gumdrop, San Marcos, San Juan and Rodriguez—is also uncommon. Their existence is tied to the formation of the San Andreas Fault a few tens of millions of years ago.

California’s seamounts, David says, are “very peculiar volcanoes.”

In some places, the rocky surface of seamounts is coated with life. In other places, geologists can easily collect rocks to learn about the volcanic origins of seamounts. Photo courtesy NOAA/MBARI

A volcanologist who works alongside marine biologists, David began surveying seamounts to test the capabilities of MBARI’s remotely operated underwater vehicles, or ROVs, which are used to collect small animals and rocks. A single ROV dive can yield up to 35 samples of rocks, and the animals living on them.

These specimens proved interesting enough to keep David coming back to seamounts for years.

“The animals are so thick and so big, they actually get in the way of me being able to do geology, because I can’t get to the bottom,” David says. “I’ve never dived anyplace else where that is the case.”

Life regenerates over centuries

Jim, the marine ecologist, studies life on the rocks that David pulls up from the deep. Not all undersea mountains are oases of life, Jim says, but Davidson Seamount is one.

Davidson is a 26-mile-long, 8-mile-wide mountain, nearly 7,500 feet tall from base to crest. Yet its summit is still more than 4,000 feet below the sea surface.

Ancient deep sea corals, some several feet across, are among the MBARI discoveries on the Davidson Seamount, an underwater mountain off the Big Sur Coast. Photo courtesy NOAA/MBARI

It’s home to an incredible variety of life, including corals that can live for thousands of years and predatory sponges on stalks. Jim says places like this, and the life they support, are both rare and fragile.

In some parts of the world, deep-sea bottom trawling for fish like orange roughy has obliterated the tops of some seamounts, Jim says. A colleague lost his research site this way: “There was nothing left. It was a pavement. And [the life] won’t be back for centuries—that was the end of the study.”

Over the longer term, he adds, animals living on the bottom of deep ocean basins may struggle to survive. That’s because the ocean is absorbing excess carbon from our burning of fossil fuels, challenging the physiology of deep-sea species with many secondary effects that ripple through the food web.

Deep-sea corals like this one off the U.S. Atlantic Coast, are vulnerable to drops in dissolved oxygen warming waters and changing in ocean chemistry, all driven by global climate change. Photo courtesy NOAA

The dissolved oxygen content of the oceans interior is dropping, due mainly to the warming of ocean waters, Jim says. This reduces the vertical mixing of oxygenated surface waters to depth, which is likely to be very important as well.

“As we make the ocean more acidic, with less oxygen, that can be a huge challenge for animals living in the deep sea,” Jim says.

Because the water thousands of feet down is only a few degrees above freezing, life on seamounts moves slowly. Damaged habitats can’t regenerate overnight, or even within a human lifetime.

“When you wipe these corals out, it’s not like you’re cutting down a wheat field and it’s going to come back in a year or two,” Jim says. “It’s going to be centuries.”

Fertile waters

In places with strong ocean currents, the steep slopes of seamounts can steer the flow of nutrients upward, feeding plankton and krill near the surface—and everything else that feeds on them.

Seamounts are magnets for whales, sharks, seabirds and schooling fishes because the flow of currents along their slopes concentrates nutrients that sustain a rich food web. Photo ©Emily Simpson

“There are often many more whales and birds above a seamount than next to one,” says Dr. Andrew DeVogelaere, research coordinator for Monterey Bay National Marine Sanctuary. In other words, removing safeguards for biologically productive places like seamounts could lead to a loss of biodiversity across the entire ecosystem.

That’s one of the reasons the Aquarium spoke up last summer to defend national marine sanctuaries, including Davidson Seamount.

We asked Aquarium members, email subscribers and social media followers to join us, and you did: Nearly 10,000 people clicked through our link to the federal public comment portal. The administration’s next steps are pending.

“We’ll continue to defend our blue parks in 2018, and to support policies that protect extraordinary places like Davidson Seamount from the unacceptable risks of new offshore oil and gas development,” says Aimee David, the Aquarium’s director of ocean conservation policy strategies. “We’re proud to be a part of the movement away from fossil fuels and toward a prosperous, clean-energy future.”

— Daniel Potter


One thought on “Safeguarding seamounts: the hidden Yosemites of the deep”

  1. You are right, we should not have any developments of oil fields along the California coast it is too beautiful to ruin. I have visited the Aquarium at its beginning and took people there, it is a learning experience for all of us who did visit many times. Mr. Trump needs to visit that area instead of golf courses. I am sure that he will be impressed. Ariane Lesmez


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