Contrary to popular belief, the ocean is not one big homogenous blob of water. Rather, it’s a complex column of water made up of five distinct zones. Each has its own unique temperatures, challenges, and inhabitants. From the sunlit surface to the deepest depths, let’s discover the five different deep-sea zones and which remarkable creatures call these zones ‘home’.
1. Epipelagic Zone (Sunlight Zone)
Dip below the waves to discover the first zone of the ocean: the epipelagic zone, also known as the sunlight zone. This is the surface layer of the ocean that extends to 200 meters or 656 feet. As the name suggests, this is the part of the ocean that receives plenty of sunlight – and the heat that comes with it.
Because of the favorable living conditions in this zone, a plethora of life exists within it. Importantly, this is the only zone where plant life can grow, and so it is home to an incredible number of creatures. This is where you’ll find dolphins, stingrays, sharks, jellyfish, and the majority of other classic sea creatures.
2. Mesopelagic Zone (Twilight Zone)
After the epipelagic zone comes the mesopelagic zone, also known as the twilight zone. This is the point of the ocean that is just out of the sun’s reach, and very little light penetrates here. The twilight zone is found 200 meters or 656 feet to 1,000 meters or 3,281 feet below the ocean’s surface.
A lingering amount of light is present in this zone, but not enough for photosynthesis to occur. There are no plants from this point on, but there are twinkles of bioluminescence in the distance. Despite the lack of plants and light, the twilight zone is home to an array of interesting deep sea creatures. Surprisingly, around 700 species of animals are thought to live here.
Here you will find creatures including lantern sharks, lanternfish, bristlemouth, dragonfish, deep-sea anglerfish, octopus, jellyfish, hatchet fish, certain crabs, some shrimp, and the infamous Coelacanth.
3. Bathypelagic Zone (Midnight Zone)
Next comes the bathypelagic zone, also known as the midnight zone, which extends from 1,000 meters or 3,281 feet to 4,000 meters or 13,124 feet. The only light that exists here is created by the creatures that inhabit this large stretch of ocean. This zone accounts for 70% of all seawater. It’s also where water pressure becomes immense, temperatures very cold, and life scarce – at least at first glance.
Octopuses, deep sea angler fish, tripod fish, gulper sharks, vampire squid, eels, jellyfish, the adorable Dumbo octopus, the iconic giant oarfish, and the legendary long-living Greenland shark are animals that live here. Though they don’t live down in the depths, the sperm whale sometimes visits the midnight zone in search of its favorite food – deep-dwelling squid.
4. Abyssopelagic Zone (Abyssal Zone)
Then we have the abyssopelagic zone, also known as the abyssal zone or simply the abyss. This zone is located 4,000 meters or 13,124 feet to 6,000 meters or 19,686 feet. It’s cold, dark, and desert-like. Due to the near-freezing temperature and immense pressure found this deep, very few creatures can survive in the abyss.
But just because life is incredibly difficult in the abyssal zone doesn’t mean it is impossible. There are a select few remarkable (and remarkably strange-looking) creatures that have adaptations that allow them to survive here. In the abyss, you will find Atolla jellyfish, sea pigs, the megamouth shark, the Fangtooth fish, cusk eel, tripod fish, tubeworms, chemosynthetic bacteria, sea spiders, sea stars, shrimp, and squid.
Incredibly adaptable and fascinating sea creatures aside, it’s worth mentioning that the abyssal seafloor itself is also remarkable. Minerals including nickel, cobalt, manganese, aluminum, and even gold are found in the abyssal seafloor. Deep-sea mining is controversial, but understanding the abyssal seafloor could be the key to solving many problems above the water.
5. Hadalpelagic Zone (Hadal Zone or Trenches)
Lastly, the hadalpelagic zone, also known as the hadal zone or simply the trenches. Trenches are long, narrow, canyon-like, chasms in the abyss. In some areas of the world, the ocean extends itself beyond the abyssopelagic zone into deep-sea trenches that are up to 11,000 meters or 36,000 feet. The Hadalpelagic zone is named after Hades, the Greek God of the Underworld – which says a lot about the type of environment this is.
Down here, life is all but non-existent. Complete darkness, astounding pressure levels, and temperatures that are only just above freezing make it difficult to survive down here, let alone thrive. But somehow, the Grenadier fish, and the Hadal snailfish – which is the deepest-dwelling fish on the planet that has been found at depths of up to 8,200 meters or 26,902 feet – manage to live happily (if hungrily) down here.
It's important to note that this zone is not a continuous stretch of ocean and is instead split across 33 deep sea trenches and 13 oceanic troughs. The four most well-known trenches are the Mariana Trench, the Puerto Rico Trench, the South Sandwich Trench, and the Java Trench.