Hadal zone

The hadal zone is the deepest region of the ocean, extending from approximately 6,000 meters to 11,000 meters below the sea ​​surface . This zone does not extend along the ocean floor, but exists only in the deepest ocean trenches . Because the light does not reach this part of the ocean, it is impossible for plants to be able to grow, but there are still hardy creatures that manage to find their home in these depths. The hadal zone represents the deepest marine habitat on Earth. Much of the knowledge about hadal biology is derived from two sampling expeditions that took place in the 1950s with theDanish Galathea and Vitjaz’s Soviet Expeditions . Far from lacking life as was believed at the beginning of the studies, the observations made have since stimulated the hypothesis that the hadal zone is home to a significant diversity and abundance of fauna with a high degree of endemism. However, as a result of historical factors and severe technical challenges associated with extremes of hydrostatic pressure and distance from the sea surface, the hadal zone continues to be one of the least investigated habitats on Earth.

Characteristics of the hadal area

The most outstanding characteristics of the hadal area are the following:

• The hadal zone does not have any type of sunlight or even reflections because it is too far from the surface, however, there are fauna in it .
• There is convincing evidence that the food supply , which occurs in the form of particulate organic carbon, accumulates along the axes of marine trenches as a result of the characteristic V-shaped topography that causes resources to travel down.
• The hadal zone comprises a series of marine trenches. There are 33 trenches and 13 valleys around the world, 46 individual habitats in all. The mean depth of the trenches is 8,216 km. The total area of ​​the hadal zone is less than 0.2% of the entire seabed , but represents 45% of the total depth range.

Fauna of the hadal area

Many marine organisms are found deep in the hadal, and the most common groups are polychaetes , bivalves , gastropods , amphipods, and holothurians . Although there is no sunlight in the area, it is known that it is inhabited by a type of marine beings known as the hadopelagic or hadal fauna . At the beginning, the only fish that were believed to dwell in this place were called rat fish , but is now known for various types of animals such as a type of star sea called ofiuro , jellyfish , sea cucumbersand some cartilaginous species such as the dumbo octopus, which is capable of surviving even at depths greater than 5,000 meters. Within the fauna we can find the sharp-finned slugs that can inhabit up to 9,000 meters deep. Some species that can be found are:

• The ghost fish is the only organism on Earth that uses mirrors in its eyes instead of lenses. Each eye has two parts, one pointing up and the other pointing down, so they can see prey and predators.
• Fish dragon black are long and slender proportionally animals, but in real life only reach about 40 cm long in the females and 5 cm in males. It has two red lights that allow it to see without being seen and to attract its prey, they use a long and flexible accessory on its chin, the end of which is illuminated . They are tertiary consumers of this part of the sea and eat other fish
• The angler fish is spectacular due to the parasitic relationship between males and females. Most organisms would be in a parasitic relationship with a member of a different species, but the male angler fish actually feeds on and harms the female . Angler fish are black, gray, or brown in color, with large heads and sharp, translucent teeth.
• The eel shark is one of the less well-known species, its body is elongated and flexible , with very bright eyes and long, thin needle-like teeth.

Flora of the hadal area

In the hadal zone there are no plants of any kind . This is because in these areas sunlight cannot reach and for this reason the plants are not able to grow or reproduce .