© R. Mickens / AMNH

On the deep sea floor, there is no light for photosynthesis—and thus no plants for sea-floor animals to eat. Their primary food is the constant shower of dead plant and animal particles that rain down from above. But most of this banquet is eaten by other animals before it reaches the sea floor.

So how do animals on the deep sea floor survive?

Feasts From Above
On the deep sea floor, where food is scarce, a fallen whale carcass represents unimaginable wealth. A wide assortment of animals are specially adapted to make use of this rich resource.

Arriving within minutes after a whale carcass falls are swarms of small crustaceans called amphipods, which locate the carcass by smell. Larger scavengers such as crabs, rattail fishes and sleeper sharks also tear into the whale, while eel-like hagfish burrow inside to consume the flesh from within.

In the next few years, a carpet of tiny white snails and other mollusks, worms and bacteria consumes the dissolved nutrients that have leached into the mud around the whale.

Over the next 15 years, furry mats of bacteria grow on the bones. Specially adapted mussels, crabs, snails and clams digest chemical nutrients from the bones, some with the help of symbiotic bacteria similar to those found at hydrothermal vents.

Food is scarce on the sea floor, so many animals conserve energy by remaining rooted in place. This feather star (Florometra serratissima) extends branching arms to collect as much sea snow as possible. © Ken Lucas / Visuals Unlimited

The muddy sediment teems with nematodes, or thread worms - the most abundant multicellular animals on Earth - and polychaete worms, isopods and mollusks. Crabs, snails and starfish wander the surface, while scavenging sea cucumbers suck up mud like vacuum cleaners, digest the nutrients in it and eject the "cleaned" mud from the other end in coiled piles. But the vast majority of sea-floor inhabitants are one-celled organisms too small to see by eye.