Until recently we thought that the deep ocean was lifeless; too
dark and cold to support life. We were wrong! Although there is no
sunlight in the depths of the ocean, life still exists. How?!
Deep under the ocean there are hydrothermal vents: cracks in the
sea floor from which superheated water erupts. The water gushes out
of these vents at temperatures of 464 degrees Celsius. As the
pressure down at the bottom of the ocean is so high, water is still
a liquid at these temperatures; on Earth it would have boiled into
a gas. To make conditions even more extreme, the water is also
acidic. No humans could survive down here.
Life on the surface of the Earth depends on sunlight. Plants
photosynthesise to turn energy from the sun into starch. Animals
then feed on plants and gain energy from the starch that the plants
have stored. At the bottom of the ocean life has had to find a
different method of creating energy, as sunlight can't reach to
these depths. Here, baceria use chemosynthesis: they turn chemicals
in the water pouring from hydrothermal vents, mostly hydrogen
sulphide, into food. These bacteria are known as extremophiles.
This means that they thrive in conditions that are too hostile for
most other species.
What else is down there?
It's not just bacteria at the bottom of the ocean. Weird and
wonderful animals feed on the bacteria, and on each other! Tube
worms, found surrounding hydrothermal vents, let the extremophile
bacteria live inside them. These bacteria provide nutrients for the
tube worm and the tube worm provides hydrogen sulphide for the
bacteria. It's a good example of symbiosis: a relationship between
two organisms where both of them benefit.
You can see a great video of tube worms here: BBC
Loads more species have been discovered in the deep ocean since
these hydrothermal vents were found. These include crabs, eyeless
shrimp and even an Eel City:
Or view the video in YouTube.
So, life at the bottom of the ocean is far from boring. I wonder
what we'll find there next!