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 area does not extend along the ocean floor but exists only in the deepest ocean trenches. Because light does not reach this part of the ocean, it is impossible for plants to grow, but there are still resilient creatures that manage to find their home in these depths. The hadal zone represents the deepest marine habitat on Earth. Much of the knowledge of Hadal biology comes from two sampling expeditions in the 1950s with the Danish Galathea and the Soviet expeditions of Vitjaz. Far from being as lifeless as it was believed at the beginning of the studies, the observations made have since stimulated the hypothesis that the hadal area is home to an important 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 area remains one of the least researched habitats on Earth.
The most outstanding features of the hadal area are as follows:
Many marine organisms are found deep in the hadal and the most common groups are polychaetas, 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 life known as hadopelagic or hadal fauna. At first, the only fish believed to inhabit this place were called ratfish, but now we know of several types of animals such as a type of starfish called ofiuro, jellyfish, sea cucumbers and some cartilaginous species such as the octopus Dumbo, which is capable of surviving even at depths greater than 5,000 meters deep. Within the fauna we can find slugs with sharp fins that can inhabit up to 9,000 meters deep. Some species that can be found are:
There are no plants in the hadal area. This is because in these areas, sunlight cannot reach and for this reason, plants are not able to grow or reproduce.
Briceño V., Gabriela. (2019). Hadal zone. Recovered on 27 May, 2021, de Euston96: https://www.euston96.com/en/hadal-zone/