Adapted to the Deep
A deep-sea fish at the edge of a mussel bed on the Blake Ridge. Photo © NOAA.
DB: This is Earth and Sky, on how some sea creatures have adapted to life thousands of meters below the ocean surface.
JB: One challenge of deep ocean life is that there’s not much to eat. Since no light penetrates, no plants or algae can grow?
DB: Some deep ocean creatures survive on the steady “rain” of plankton and other particles coming down from surface waters.
JB: Others get their food from below. Geysers of hot water and nutrients called hydrothermal vents erupt from spots on the sea floor. These hydrothermal vents feed bacteria. The bacteria in turn feed tubeworms and other creatures.
DB: And sometimes a large object – say, a dead whale – makes it to the sea floor. Deep ocean fishes have an excellent sense of smell, so they can find the food bonanza. They’re also equipped to seize living prey that can be few and far between.
JB: For example, the gulper eel is mostly mouth and teeth, and it has an expandable stomach, so it can swallow creatures its own size. Most deep-sea fish and squid have organs that generate light through a chemical reaction. In the darkness, flashing lights help attract mates, or scare off predators. But most often, the lights are used to attract food. The “black dragon” fish, for example, has chin whiskers – really dangling chin barbs – that act as glow-in-the dark fishing lures.
DB: For links to pictures of some deep-sea creatures, come to earthsky.org. We’re Block and Byrd for Earth and Sky.
To see some images of deep-sea creatures, visit:
Monterey Bay Aquarium – Living Species List – Deep Sea
NOVA – Into the Abyss – Deep Sea Bestiary
Creatures of the Deep (Images of Viper fish, Fangtooth fish and Gulper Eel) – Extreme Science Adventures
Creatures of the Deep (Image of Giant Tube Worms) – Extreme Science Adventures
Creatures of the Deep (Illustration of Giant Squid) – Extreme Science Adventures
Creatures of the Deep (Image of Sea Pig) – Extreme Science Adventures
Creatures of the Deep (Image of Rattail or Grenadier fish) – Extreme Science Adventures
Other Resources:
DEEP-SEA Pages College)
Monterey Canyon and the Deep Sea (The web site for the Monterey Bay Aquarium’s “Mysteries of the Deep” exhibit)
Sea and Sky: Monsters of the Deep
Author’s notes:
The pressure on the ocean floor can be hundreds of times greater than at the surface. Deep-sea creatures handle this crushing pressure thanks to a compound called trimethylamine oxide. It helps critical metabolic enzymes keep working under pressure.
Some deep-sea dwellers get their meals by migrating. At night, they swim toward the surface, till they reach shallower water where food is more plentiful.
More on photophores:
Many deep-ocean fish and squid have rows of photophores on their bellies. These rows of lights act like cloaking devices. To understand how that works imagine you’re a deep-sea predator, swimming below a school of fish. When you look up, you see the dark bellies silhouetted against the faint light coming down from the surface. But if you are looking at fish with photophores on their abdomens, the fish will look light, not dark, so they will able to blend in with their backgrounds.
Hydrothermal vent communities:
Hydrothermal vents are cracks along the ridges formed on the ocean floor where plates of the earth’s crust are slowly spreading apart. Seawater that has been heated by the magma below the sea floor shoots out of the vents. The water is rich in hydrogen sulfide and other chemical compounds.
Recently, scientists discovered some unique life forms living around hydrothermal vents. They are bacteria that produce energy, not through photosynthesis, but through a process called chemosynthesis. Instead of using sunlight to make energy, these bacteria use the hydrogen sulfide.
Other strange deep-sea creatures are found only around the vents, including giant clams, pink sea urchins, and blood-red “tube worms,” ten feet long, that have no mouth or guts. These worms get all their nourishment from the chemosynthetic bacteria that live packed inside their bodies.
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