Our earliest ancestor was a microorganism – likely at a deep sea hydrothermal vent, where some long-ago chemical reaction somehow forged a spark of life.
Today, microorganisms live among us, hiding in not-so-plain sight. Earth’s bacteria alone outweigh all Earth’s humans by a magnitude of more than 1,000. Microorganisms are everywhere: even in the planet’s crust far below the bottom of the sea, they live in what scientists call the “deep biosphere.” We have more microbes than cells inside our bodies. They keep us alive.
So microbes are essential to life on Earth. They were here first, and they’ve made themselves indispensable. They form the bottoms of food chains. They break organic waste down, keeping the planet clean. They produce a fifth of the oxygen we breathe.
The microbial life of the deep sea is still being discovered. But, like microbial life elsewhere, we know it plays a crucial role in supporting ecosystems. What we don’t yet know is exactly how removing the microbes – a likely side effect of deep sea mining – would disrupt ocean life. (Disrupting ocean life on too big a scale, of course, would start to disrupt our own lives.)
Scientists returning to a mining test site 26 years later found that the mined area still hadn’t recovered its microbial activity. The impacts of commercial-scale mining would probably be even more significant. More research is still needed to understand how this could impact the larger ecosystem.
Slightly-bigger tiny organisms face mining’s threats, too. A marine biologist doing PhD research recently found that different hydrothermal vents housed different species of copepods: little shrimp-like creatures. The isolation between vents may help each develop a unique population. Mining hydrothermal vents, which are built of minerals, means removing species that may live nowhere else.
Coral Diaz-Recio Lorenzo, the marine biologist, also looked at polymetallic nodules in a section of the Pacific, where deep sea miners hope to start as soon as 2025. She found copepods on the nodules too, as well as other animals, like nematodes (a type of worm). Most nodules held 10 to 15 individuals. A few held over 200.
In addition to adults, she even found eggs on the nodules, suggesting that this is essential habitat for some creatures’ entire lifespans. The seafloor sediment around the nodules didn’t contain the same life. Her findings suggest that some animals live here, and only here, on the mineral-rich nodules.
We’re currently in a fantastic era of deep sea photography and videography, which has sparked popular interest in deep sea life. It’s easy to see the cool-looking megafauna, like sponges, attached to polymetallic nodules or living on hydrothermal vents. It’s harder to remember the tiny things we can’t see in the pictures.
But without those tiny animals – microfauna and the slightly-larger meiofauna – life in the deep couldn’t exist. Protecting the sea’s smallest lifeforms is part of protecting the big, pretty things we love to look at. In the grand scheme of things, it’s probably part of protecting ourselves, too.