Formation, characteristics, and creatures of the Hadalpelagic Zone

In 1960, Swiss engineer Jacques Piccard and Navy Lieutenant Don Walsh, took the US Navy bathyscaph Trieste and dove 35,797 feet(10,910 meters) down the Mariana Trench in an area called the challenger deep. This exploration opened a new scientific window to a region in the ocean we considered devoid of life.

Contents

Formation
Characteristics
Creatures
Limitations
Technology for the depths
Conclusion
Bibliography

Former US navy Victor Vescovo is the first person to ever visit the deepest points in every ocean. His expeditions have opened many doors to previously unanswered questions about the hadal zone. In this article I will discuss what the hadal zone is and the creatures that lurk in its silent darkness.

Approximately 20,000-36,000 feet(6,000-11,000 meters) below sea level we arrive at the deepest point of the ocean, known as the hadal zone. Also known as the hadalpelagic zone, the term hadal comes from the Greek word “hades”, the ancient Greek God of the underworld. The hadal zone is the deepest oceanic environment on planet Earth. It is home to some of the most fascinating and unbelievable creatures residing on this planet.

Formation

The hadal zone can be found in trenches worldwide including the Mariana Trench, Kermadec trench, Japan trench, and Peru-Chile trench. These hadal trenches are formed from the movement of plate tectonics, where one ocean plate is forced under another, creating a long narrow trench. These trenches act as funnels that help concentrate a large amount of the organic matter, also known as “marine snow”, that drifts down to be collected in those areas. This allows the creatures living in this region to be able to survive for as long as they have.

Characteristics

Some Characteristics of the hadal zone that make it impossible for most of the creatures of Earth to survive in include:

Pressure: water pressure reaches more than 1,100 times that at higher sea levels.
Darkness: there is not a single ray of light that reaches this zone. It goes deeper than the sunlight, twilight, midnight and abyssal zones. The only light source comes from the few bioluminescent creatures that pass through there. This complete lack of light forces the creatures living there to rely completely on other senses to survive.
Temperature: water temperature in this zone is 1-4°C(34-39°F). This makes it near freezing and extremely hard for most creatures to survive there.
Food: with the complete lack of sunlight, photosynthesis is impossible in this region, causing the creatures residing there to completely rely on organic matter that drifts down from higher sea levels. So the main source of food here is dead organisms.

Creatures

Hadal Snailfish: these sea creatures hold the depth record for vertebrates. Their bodies have adapted specialized proteins that prevent cellular damage even under those extreme pressures. They have reduced bone density and specialized lipids that allow them to be neutrally buoyant.

In the Kuril-Kamchatka trench and the western Aleutian trench a colony with thousands of worms and mollusks has been discovered nearly 10 kilometers deep. These communities have a diverse range of creatures, from bivalves to siboglinid polychaeta.

Amphipods: some of the most abundant creatures found in the hadal zone are the crustacean-like creatures. These creatures are known to grow to enormous sizes as compared to their shallow-water counterparts. An example is the supergiant amphipod Alicella gigantea.

Sea cucumbers: these echinoderms have been found to thrive in dark, high pressure environments. They process the organic matter that comes down to the hadal zone for nutrition.

Polychaete worms: many worms have been able to thrive in dark, high pressure environments such as the hadala seafloor, hydrothermal vents and cold seeps.

Bivalves: clams and mussels are also a part of the wide range of creatures that have been able to survive the harsh environments of the hadal zone.

Foraminifera: some of the most abundant life forms found in the hadal zone sediments are single celled organisms. Some of which are even visible to the naked eye.

Fish: such as Cusk eels, rattails and snailfish are some examples of fish that have been able to survive and thrive in the hadal zone.

Dumbo octopus: have a gelatinous body that allows them to survive the high pressure environment and survive on smaller organisms.

Brittle stars: their upper body contains light sensitive calcium carbonate structures and it has 5 hands that allow it to move along the ocean floor

Black dragon fish: long, thin fishes containing 2 red lights that allow them to see without being seen and attract prey. It contains a long accessory on its chin with illumination at the end.(Briceño, G., V., & Briceño, G., V.)

Limitations

It is clear that the hadal zone is a rich environment with a multitude of creatures living in it. Even with all the creatures in the hadal zone it still doesn’t compare to more favourable environments. There are a few factors that make it hard to find creatures freely living in the hadal zone such as,

Energy limitations: a limited amount of food sources, and the deeper one goes into the ocean even the organic matter that falls from above becomes increasingly scarce.

Extreme conditions: high pressure, low temperature, complete darkness, all of these things contribute to the harsh environment that is the hadal zone.

Isolation: isolation in this case doesn’t allow the creatures living here to have many options for sexual reproduction, that’s if they can even find any at all. This leaves only space for asexual reproduction which greatly limits genetic diversity. It also limits the food sources since everything and everyone is so far apart.

Chemical constraints: the unique chemistry of the ocean depths disallows many creatures to survive there, but there are areas such as hydrothermal vents and cold seeps where chemosynthetic communities are able to grow and thrive.

Technology for the depths

Landers: these are autonomous instruments that freefall to the hadal zone to collect data. They are able to work for days in the dark, high pressure environment.

ROVs(Remotely Operated Vehicles): these are robots that are controlled from ships above, though only a few of them are able to reach the depths where the hadal creatures live.

Full Ocean Depth Submersible: The Limiting Factor and Triton’s ultra-deep submarines are examples of these machines that carry humans to the deepest parts of the ocean.

Baited traps: devices that are made to bait and catch creatures of the hadal zone for studying by scientists.

Conclusion

The hadal zone is still being explored to this day and with every exploration comes a new discovery. Studying the hadal zone allows us to understand the complexity of survival in such extreme environments. It gives us an insight into the lives of the creatures in that environment, how they survive on a day to day basis and how they are adapting to the ever changing environmental factors. It helps us understand and grasp just how life is able to emerge and thrive in such extreme regions on planet Earth.