Friday, February 7, 2020

Life in the ocean depths, minerals too

Wil S. Hylton, History's Largest Mining Operation Is About to Begin, The Atlantic, January/February 2020. As the title indicates, the article is primarily about mining the ocean depths, but this passage struck me:
Until recently, marine biologists paid little attention to the deep sea. They believed its craggy knolls and bluffs were essentially barren. The traditional model of life on Earth relies on photosynthesis: plants on land and in shallow water harness sunlight to grow biomass, which is devoured by creatures small and large, up the food chain to Sunday dinner. By this account, every animal on the planet would depend on plants to capture solar energy. Since plants disappear a few hundred feet below sea level, and everything goes dark a little farther down, there was no reason to expect a thriving ecosystem in the deep. Maybe a light snow of organic debris would trickle from the surface, but it would be enough to sustain only a few wayward aquatic drifters.

That theory capsized in 1977, when a pair of oceanographers began poking around the Pacific in a submersible vehicle. While exploring a range of underwater mountains near the Galápagos Islands, they spotted a hydrothermal vent about 8,000 feet deep. No one had ever seen an underwater hot spring before, though geologists suspected they might exist. As the oceanographers drew close to the vent, they made an even more startling discovery: A large congregation of animals was camped around the vent opening. These were not the feeble scavengers that one expected so far down. They were giant clams, purple octopuses, white crabs, and 10-foot tube worms, whose food chain began not with plants but with organic chemicals floating in the warm vent water.

For biologists, this was more than curious. It shook the foundation of their field. If a complex ecosystem could emerge in a landscape devoid of plants, evolution must be more than a heliological affair. Life could appear in perfect darkness, in blistering heat and a broth of noxious compounds—an environment that would extinguish every known creature on Earth. “That was the discovery event,” an evolutionary biologist named Timothy Shank told me. “It changed our view about the boundaries of life. Now we know that the methane lakes on one of Jupiter’s moons are probably laden with species, and there is no doubt life on other planetary bodies.”
As for mining:
Deepwater plains are also home to the polymetallic nodules that explorers first discovered a century and a half ago. Mineral companies believe that nodules will be easier to mine than other seabed deposits. To remove the metal from a hydrothermal vent or an underwater mountain, they will have to shatter rock in a manner similar to land-based extraction. Nodules are isolated chunks of rocks on the seabed that typically range from the size of a golf ball to that of a grapefruit, so they can be lifted from the sediment with relative ease. Nodules also contain a distinct combination of minerals. While vents and ridges are flecked with precious metal, such as silver and gold, the primary metals in nodules are copper, manganese, nickel, and cobalt—crucial materials in modern batteries. As iPhones and laptops and electric vehicles spike demand for those metals, many people believe that nodules are the best way to migrate from fossil fuels to battery power.

The ISA has issued more mining licenses for nodules than for any other seabed deposit. Most of these licenses authorize contractors to exploit a single deepwater plain. Known as the Clarion-Clipperton Zone, or CCZ, it extends across 1.7 million square miles between Hawaii and Mexico—wider than the continental United States. When the Mining Code is approved, more than a dozen companies will accelerate their explorations in the CCZ to industrial-scale extraction. Their ships and robots will use vacuum hoses to suck nodules and sediment from the seafloor, extracting the metal and dumping the rest into the water. How many ecosystems will be covered by that sediment is impossible to predict. Ocean currents fluctuate regularly in speed and direction, so identical plumes of slurry will travel different distances, in different directions, on different days. The impact of a sediment plume also depends on how it is released. Slurry that is dumped near the surface will drift farther than slurry pumped back to the bottom. The circulating draft of the Mining Code does not specify a depth of discharge. The ISA has adopted an estimate that sediment dumped near the surface will travel no more than 62 miles from the point of release, but many experts believe the slurry could travel farther. A recent survey of academic research compiled by Greenpeace concluded that mining waste “could travel hundreds or even thousands of kilometers.

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