Far beneath the ocean surface, the hadal zone is one of the least well-known areas of the globe. Light is virtually absent here. Occasionally brief flashes of circus-like neon sometimes penetrate the darkness, the bioluminescence of whatever strange creatures populate these depths. Warning lights and predatory lures.
Life endures, even here. Particulates known as marine snow drift down from the higher reaches. This biological detritus contains enough nutrients to sustain entire ecosystems. Sometimes food descends in the form of a whale fall. The gigantic corpse of a dead whale can sustain benthic scavengers for years and many of the species seen are found nowhere else in the ocean.
Other communities live here too, existing off non-surface nutrients. The famous Alvin submersible, which found the wreck of the Titanic, was among the first to document the existence of black smokers, underwater geysers that spew super-heated water from deep within the crust. The water is rich in dissolved minerals, especially sulfur, which microbes like bacteria and archaea can process into energy. These, in turn, form the basis of a vast food web. Blind white crabs, brilliant red tube worms, and wriggling polychaetes crawl over chimneys belching black smoke like Victorian factories in what must be one of the most imagination-capturing images of modern science.
On the other hand, far away from the manic volcanism of sea ridges, colder, quieter communities exist. Mussel beds extend as far as the eye can see, covering the sea floor. Like at the hot vents, these creatures live off nutrients not from the surface, but deep within the earth. Methane, captured in ancient times, bubbles out of the sea floor or forms crystalline hydrates. The inestimable Sir David Attenborough introduces one below:
It is famously said that we know more about the moon than the sea floor. Within the last four decades our knowledge of it’s ecosystems has expanded from virtually nil to a rich menagerie of seemingly impossible, alien life. As we continue to explore, as we continue to improve, it seems doubtless that more examples of life enduring beyond belief will appear.
Also, James Cameron just hit the bottom of the Mariana Trench, which is amazing.