by Isabella Grabski
figures by Abagail Burrus

Your next smartphone might be made of materials from an unlikely source: the deep sea. Our current manufacturing practices are depleting terrestrial deposits of important metals like copper, aluminum, and manganese, but the demand for these materials shows no sign of slowing down. They’re not only useful for emails and Instagram – these metals also play a key role in many green technologies, including wind turbines, solar panels, and electric storage batteries. With this rising demand but diminishing supply, companies are starting to look to the deep sea to get what they need. 

Deep-sea mining poses great technological challenges, since the materials of interest are typically located anywhere from 800 to 6,500 meters deep. That’s over four miles below the surface! Nevertheless, mining technology has made large advances over the years, and as of 2019, 29 exploration licenses have been issued over a total ocean area five times the size of the United Kingdom. 

Just because the mining technology has improved, however, doesn’t mean that we should be diving in right away. The deep sea comprises 95% of the world’s habitable space, yet remains one of the most poorly understood regions of our planet. There has only been limited research into life in the deep sea, as well as into the potential long-term impacts of any human action in this environment. As deep-sea mining threatens to become less science fiction and more industrial reality, many environmentalists are growing more vocal with their concerns. Are we willing to take the plunge, or are the consequences too risky?

What’s in the deep sea?

When most people think of the deep sea, they might imagine a flat expanse of ocean floor under darkness with very little movement or life. At an average depth of over 3,000 meters, there is essentially no natural light that makes it through. But despite the darkness, crushing pressure, and near-freezing temperatures, the idea of a flat and lifeless floor couldn’t be farther from the truth. 

The geography of the deep sea is as complex as what we see on the land around us. These underwater features include trenches, plains, volcanoes, geysers, and even the longest mountain chain on Earth. Deep-sea life is similarly as varied, with a quantity of organisms comparable to that of a typical tropical rainforest. Although we are still in the early days of learning about these organisms in the deep sea, most have been found to be concentrated around three types of geographic features: flat areas known as abyssal plains, isolated mountains known as seamounts, and sulfuric geysers known as hydrothermal vents (Figure 1). 

Figure 1: Geographic features in the deep sea. A) represents an abyssal plain, which is a mostly flat expanse of seafloor. B) represents seamounts, which are mountains located underwater. C) represents hydrothermal vents, which are geysers shooting out hot water.

Taken all together, these three types of features are home to a vast variety of species, ranging from starfish and sea cucumbers to shrimp and lobsters. In fact, in the hydrothermal vents alone, a new species has been discovered an average of every 10 days since 1977. Because these environments have such unusually harsh conditions, the organisms living there are unique to the deep sea and have adapted to their surroundings unlike any other life on earth. For example, the deep sea contains the only life that is capable of existing entirely independently of sunlight. Instead, these lifeforms derive energy from hydrogen sulfide (the same gas associated with rotting eggs). 

What are miners looking for? 

These same geographic features brimming with life are also the sites of valuable materials. Abyssal plains are spotted with rocks made primarily of manganese and iron, in addition to platinum, copper, and rare earth metals. These nodules are about the size and shape of potatoes, but they take millions of years to form. The materials in them are desirable to a number of industries; for example, the platinum and tellurium they contain are important for solar panels.

Seamounts also feature slow-growing metal deposits, but in the form of crusts rather than nodules. Over millions of years, metal from the water solidifies along the flanks of these mountains to form thick crusts containing manganese, iron, and many other trace metals. These materials are particularly useful for applications like jet aircraft engines and batteries. 

But it’s hydrothermal vents that produce some of the most valuable metals. As hot, mineral-rich water shoots out of these vents, which are primarily at depths of 2000 to 3000 meters, it comes into contact with the near-freezing ocean water. This causes metals to solidify and get dispersed by the currents, resulting in large deposits along the floor known as seafloor massive sulfides (SMS). SMS deposits are, as the name suggests, high in sulfur content, but most notably, they also contain expensive metals like gold and silver.

What could the consequences of mining be?

As eager as companies might be to mine these precious metals, the potential effects on the ecosystem could be devastating. Numerous research efforts suggest that any efforts to mine could harm the organisms living there. 

Because the materials of interest are located on the same geographic features that are hotbeds for life, any form of mining will disrupt active habitats. A number of studies have been done in an attempt to understand exactly what the consequences would be, based on simulated experiments in the ocean. Although these types of investigations are limited in scope compared to the scale of a full industrial mining operation, they all generally suggest that disturbances to the seabed could take decades or more to recover from. For example, scientists found lingering physical evidence of mining even 26 years after nodules were actually removed from an abyssal plain, and the nematode worm population still hasn’t returned to normal.

The physical disturbance isn’t the only concern. Mining will also introduce noise and light in an environment that has operated in relative silence and darkness for billions of years (Figure 2). Some species rely on sound for communication as well as food detection, which could be disrupted by the introduction of new noises. Similarly, these organisms have evolved to thrive in darkness, and they are not equipped to handle light. The lights from vehicles around hydrothermal vents have already been shown to permanently damage shrimp retinas.

Figure 2: Deep Sea Mining. One scheme for deep sea mining involves vehicles going down to hydrothermal vents. These vehicles are tethered and operated remotely, and they gather materials by breaking rock apart.

Destruction of deep sea habitats could mean the loss of species both known and not yet discovered. Because seamounts and hydrothermal vents are so isolated, many species that exist near them are not present elsewhere in the ocean. That means even mining a single seamount could make a large impact on species diversity. 

Even setting these environmental and ecological concerns aside, wiping out life before we even have a chance to learn about it could end up harming us. For instance, these organisms represent an untapped resource for pharmaceuticals. Some deep-sea bacteria have already shown promise in killing pathogenic bugs, which is especially important in the context of antibiotic-resistant superbugs. 

Deep sea mining could help enable both important consumer technologies and green energy systems. At the same time, we know relatively very little about what’s in the deep sea and how impactful mining disturbances could be. Although the International Seabed Authority has begun developing regulations, some environmental organizations have already found these to be insufficient. As intensive deep-sea mining looms closer and closer in our future, it is increasingly important for more research to be done, and for policy-makers to leverage this research to balance commercial interests with environmental protections.

Isabella Grabski is a second-year PhD student in Biostatistics at Harvard University.

Abagail Burrus is a fourth-year Organismic and Evolutionary Biology PhD candidate who studies elaiophore development at Harvard University.

For More Information:

  • See this scientific review article about the impacts of deep-sea mining 
  • Here is an issues brief from the International Union for Conservation of Nature

This article is part of our special edition on water. To read more, check out our special edition homepage

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