Why do deep sea creatures glow

Deep sea: life in the dark

In 1000 meters of water it is pitch black. But even here creatures large and small live. But how? - This is explained by an article and an interactive animation

There is no sunlight and no plants in the deep sea. The realm of eternal darkness begins 200 meters below sea level and extends down almost eleven kilometers at the deepest point, the Mariana Trench in the Pacific. Creepy creatures live here, with glittering eyes, transparent bodies or huge bellies.

Huge load It never gets warmer than four degrees. The pressure of the water masses is so great that many animals can only move very slowly. Up to a ton of weight rests on every square centimeter of living beings in the depths. Just because their wobbly bodies contain a lot of water, they won't be crushed.

Eternal night

On top of that, only faint shreds of light penetrate the water at a depth of 300 meters. It is pitch black deeper than 1000 meters. Without light, however, corals, algae, and plants cannot flourish - and that is why there is little to eat. Surviving in this dreary region is tough. The animals would all starve to death - were it not for a sophisticated system with which nature supplies the deep sea with food.

Nightly meals

She sends the "basement dwellers of the oceans" to where there is something to sniff - up! At night, glittering crown jellyfish, shining silver lantern fish and large schools of shrimp soar into the higher ocean layers, where they find plenty of plankton and algae. Here they eat their fill and then return to the gloom before sunrise. To stay in the light would be too dangerous. There the plankton eater could be caught by the hungry predatory fish that follow them from the depths.

Record diver

The lantern fish with the complicated name Ceratoscopelus warmingii holds the record for the longest journey: it dives for three hours every night from a depth of 1,700 meters to hunt 100 meters below sea level. A kind of built-in alarm clock tells him when to start swimming. Practical, isn't it? Thanks to these excursions, not only the night hikers will be satisfied - they provide the whole deep sea with new food!

Sophisticated food chain

Because animals like the crown jellyfish are something like express couriers for energy. As if on a ladder, the nutrients climb with them from top to bottom. So from the alga on the surface of the sea to the deep sea fish on the bottom. The chain works like this: Fully fed with plankton, the jellyfish plunges into the dark. If she is unlucky, she will be devoured by a robber on the way. That in turn lands a few hundred meters deeper in the stomach of a deep-sea shark. If he dies, his carcass sinks even deeper.

Delicious "sea snow"

In this way, nutrients are "passed down" until finally only a remnant of the original amount reaches the bottom of the sea floor. It is mainly the droppings, remains of dead animals and tiny plant particles that end up there. They trickle down like snowflakes. But even this "sea snow" is food - for bacteria, which are then gobbled up by larger soil dwellers.

Motionless robbers

Because only a few nutrients arrive at the lower end of the ladder, the living beings have to save energy there: They hardly move and lurk motionless for prey. Experts even believe that some can go without food for years! So that the hunters of the deep sea do not miss any tasty chunks, many have creepy-looking mouths: the viper fish has teeth so large that they protrude out of its mouth up to its eyes.

Luminous palate trap

The frogfish Thaumatichthys (that is Greek and means "miracle fish") is particularly cunning: it lures the victims in the darkness with its shining palate and guides them directly into its throat! Like many animals in the deep sea, it has cells in which bacteria produce light.

In search of the giant squid

The deep sea has hardly been explored because it is very difficult to get down there. The researchers estimate that there are at least a million previously undiscovered species in the cold darkness. Many of them are so tiny that you can only see them under a microscope. But one of the largest marine animals still needs to be tracked down: the giant squid, an octopus up to 17 meters long. So far it has only ended up dead in fishing nets or flotsam on the beach.

Read also at GEOlino.de