Deep sea dinner

Oceans cover two-thirds of the earth’s surface. We speak of the deep sea from a depth of 200 meter. The average depth is 4000 meter, but the Mariana Trench sinks to a depth of 11,000 meter. 88% of the surface area of our oceans is considered deep sea. Of this, 318 million km² lie at a depth of 1000 meter. This is 62% of the Earth’s entire surface. It is therefore an enormous, almost unexplored habitat. The deeper, the more unreal and inhospitable the deep sea becomes. It is a barren place shrouded in absolute darkness with strange, creepy-looking creatures. In this absolute darkness, it never gets warmer than 4 C and there is enormous pressure. Depending on the depth, the pressure increases and so it is possible that up to a tonne of pressure weighs on every square centimetre of the body of these ocean dwellers. What an enormous adaptation is required to survive in such places. They are curious creatures with true superpowers.

Due to the lack of photosynthesis, there is a lack of food, the question arises as to how these deep-sea dwellers get their dinner. Of course, this requires skilful strategies. Two-thirds of the survival artists in the deep sea utilise bioluminescence. They use enzymatic reactions to produce their own light and attract their prey. Some deep-sea dwellers have huge mouths and are able to swallow prey larger than themselves.

Glowing lantern fish, glittering helmet jellyfish and schools of shrimps begin their journey to the upper layers of the sea, where they find plenty of plankton and algae. But they have to sink back into the gloom before sunrise, otherwise they become easy prey. The lantern fish is the record holder among night-time diners. It takes 1700 meter and a three-hour ascent to hunt for prey at a depth of around 100 meter. He then has to factor in this distance and time for his return journey into the eternal darkness. He seems to have a “built-in alarm clock” that gives it the internal signal when it is time to start its ascent.

The ocean dwellers that make the effort to ascend and descend supply the entire deep sea with food. For example, the helmet jellyfish that has made the effort to climb up to feed on plankton may itself become prey on its way back to its deep-sea home. However, the hunter of this helmet jellyfish can suffer the same fate a little deeper and end up in the stomach of a hungry deep-sea shark. The motto “eat and be eaten” also applies in the deep sea. Once he has reached the end of its life, he will sink down and provide plenty of food for the creatures that do not embark on this nocturnal feeding journey. Whale carcasses also sink down and are devoured by all kinds of creatures, such as hagfish, amphipods and grenadier fish. The skeleton of these gentle giants provides bacteria with a safe source of food for years. Oxedax worms are known as bone eaters. They use an acid to break down the hard-to-degrade skeleton of a whale. It can take up to ten years for such a giant to be digested.

The hasselhof crab lives in the South Seas and in the Pacific Ocean at a depth of 2000 meter along the Black Smokers. It breeds bacteria in its fur, which it grazes with its claws. It therefore has its own food farm.
Even marine snow provides food for bacteria, which are then reintroduced into the food chain.

Those who remain at the bottom of the deep sea, where there are few nutrients, have to manage their energy well while they wait motionless for their prey. Down there, creatures that could star in a scary film have their kingdom. For example, the viper fish lives there, its teeth reaching right up to its eyes. 

The deep sea frogfish Thaumatichthys (“miracle fish”), like many other deep-sea creatures, uses cells that produce light thanks to bacteria, which in turn attracts other sea creatures in the darkness. With its luminous palate, it guides unsuspecting victims directly into its maw.

Giant squids glide through the dark depths in search of a tasty morsel. But it’s not just deep-sea dwellers that make their nightly journey to the higher regions of the sea, where they hope for a rich dinner. Creatures such as Sperm whales, Cuvier’s beaked whales and Blue sharks also glide into the depths to feast on their prey. Dinner in the deep sea therefore takes place according to the lift principle, from both sides, in a constant up and down. An ingenious cycle in which everything has its place and is well utilised.

One deep-sea inhabitant, the Scabbard fish, is well known in Madeira and is a culinary dinner speciality for tourists and locals alike. So we also benefit from the deep sea.

Image credit GEO Martin Künsting

By Fatima Kutzschbach