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Under the Sea

Vast fuel reserves and mineral resources lie in the ocean depths. But so does a world we could destroy before ever understanding it.

Fanged fish, 12-foot crabs, and colossal squid lurk in the ocean depths, swimming through shipwrecks and deep, dark trenches. Most people don’t think of the deep sea—defined as 600 feet or more below the surface—as a thriving ecosystem. But it’s actually the world’s largest, teeming with mysterious life forms and covering more than 60 percent of the earth’s surface.

And it needs protection. Advances in technology are bringing the mining industry to new depths in the search for precious minerals and fossil fuels. Ocean scientists worry that we’ll make a mess of the place before we even truly understand what’s going on down there—and how the deep-sea environment interacts with the rest of the planet.

A recent study published in the European Geosciences Union journal details some of those deep-sea ecosystem services, including the ocean’s crucial ability to absorb a huge amount of the carbon pollution we emit. “We still need to realize that it’s an environment,” says lead author Andrew Thurber, a marine ecologist at Oregon State University, “and begin to think about why it’s important.”

What’s Down There?

We know the depths are home to fish and other organisms adapted to high pressure, low-light environments. They often depend on organic matter falling from higher in the water column (imagine if your food fell from the sky). Deep-sea dwellers also glow, using bioluminescence to attract prey and protect themselves.

Jelly mushrooms? Spiny killer sponges? Yeti crabs? Most of these creatures are super weird, and scientists discover roughly 100 new ones every year. New to us, anyway—Thurber says many of these organisms are hundreds of millions of years old.

Photo: Mandy JouanYeti crab

As fishermen deplete shallower stocks, however, they have been dropping their nets lower, about 200 feet lower every decade. Right now we fish 27 species in the deep sea, including orange roughy and Chilean sea bass. Because we don’t quite understand how these ecosystems operate, scooping up large numbers of a particularly tasty species can have big repercussions to the food web—consequences we might not even notice are happening. 

And if we continue to fish with abandon, we could throw the whole ecosystem out of whack, compromising one of its biggest benefits: the ability to absorb carbon dioxide. The deep sea and its fish (like smoothheads) hold at least a quarter of all the carbon we’ve released into the atmosphere since the start of the Industrial Revolution, reducing the rate of climate change.

Unfortunately, as the oceans absorb more carbon, they become more acidic, which then breaks down the shells and skeletons of many marine organisms. Without their protective layers or internal structures, they’ll die.

Risky Business

We already know what can go wrong with deep-sea exploitation. Remember the Deepwater Horizon blowout? That 2010 mega-oil spill—the largest in history—occurred 5,000 feet below the surface of the Gulf of Mexico. The gusher flowed for 87 days, spilling 206 million gallons of oil before we could stop the leak. An October Proceedings of the National Academy of Sciences study shows that a layer of oil from the spill—what researchers are calling a “bathtub ring”—still coats 1,250 square miles of the ocean floor. This could account for as much as 16 percent of the total oil that spewed from the well. And that oil is smothering corals and causing heart defects in large fish like yellowfin tuna and amberjack. 

Energy companies routinely drill in the deep sea now, mainly for oil and gas. By 2023, as much as 40 percent of the world’s oil production could come from these waters. Despite the dangers, companies would love to get their hands on more of the deep sea’s resources, especially methane hydrates (ice that contains combustible gas) and the rich minerals produced from hydrothermal vents.

Just one cubic meter of methane hydrate can hold 164 cubic meters of natural gas. They’re hard to get to because they lie below the seabed, but there may be as many as 700,000 trillion cubic feet of methane hydrate deposits in the world. And if we could bring them up, we could drastically increase our supply of natural gas, by as much as 100,000 trillion cubic feet. (U.S. shale reserves contain 827 trillion cubic feet.) Mining for methane hydrates, however, could disrupt fish habitat, and drilling could lead to underwater landslides and methane leaks. Not to mention what burning all that natural gas would mean for the climate: Methane hydrates contain more carbon than all other fossil fuels combined, so if we mine and burn them, we have no hope of saving ourselves from climate change catastrophe. 

Photo: Ocean Networks CanadaThe crown of the Godzilla, one of the largest and highest-energy hydrothermal vents, rises 27 meters from the base.

Hydrothermal vents, which are openings on the seafloor that spew fluids from within the earth, could be a mining company’s, well, gold mine. As water seeps below the seabed, magma heats it up to about 750 degrees Fahrenheit. (It doesn’t boil because of the deep sea’s pressure.) This fluid, which becomes hotter and more acidic through chemical reactions, leaches metals like copper, iron, cobalt, and zinc from the surrounding rocks.

Once the fluid reaches the seafloor, it reacts with the cold water. Minerals fall out, creating “chimney” walls (through which the fluids “smoke” out to the surface) and leaving behind valuable metals. Meanwhile, chemicals within the fluid feed organisms that don't need photosynthesis to survive. The metals produced from this process are in high demand because many are used in smartphones and computers. But exploiting them could pollute the water and disrupt life in the lowest reaches of the ocean.

"Deep-sea mining is a lot like strip mining or clear-cutting a forest. It destroys sea life anchored to the ocean floor and spreads suffocating sediments far and wide," says Lisa Speer, director of the international oceans program at NRDC (which publishes Earthwire). "There are serious issues of toxic mine tailings that are dumped back in the water—these can contain heavy metals and poisonous compounds like arsenic."

No Diving

Although the ability to protect deep-sea areas outside of a country's jurisdiction is, according to Speer, "limited at best," there is the United Nations’ International Seabed Authority. It oversees who can mine and where to help ensure that our drive to harvest the deep sea’s resources doesn’t end in ruin. If a company or country wants to explore or mine, it must submit a proposal for two sites. The International Seabed Authority then chooses one and sets the other aside to be protected or to be used later by a country that doesn’t currently have the resources to mine. Although the organization has issued only seven exploratory permits from its inception, in 1994, to 2011, that number is expected to double by the end of the year. So far—thankfully—it hasn’t issued any mining permits. 

Reserves designated by individual nations, like the Pacific Remote Islands Marine National Monument, which President Obama made so much bigger this September, help protect our deepest seas, too. Pew Charitable Trusts is also working with different countries as well as the U.N. to conserve swaths of the ocean that are off-limits to fishing and mining. With new marine reserves and careful evaluation of mining proposals, we can better appreciate what’s down below—and this helps us figure out how to harvest the deep sea's bounty, if at all, without destroying the ecosystem. Let's hope the wrong people don't dive in before that.


onEarth provides reporting and analysis about environmental science, policy, and culture. All opinions expressed are those of the authors and do not necessarily reflect the policies or positions of NRDC. Learn more or follow us on Facebook and Twitter.

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