The ocean is a vast place, and not all of it looks the same – with varying temperatures, light, and marine life, scientists have classified the ocean into five main zones: the sunlight zone, the twilight zone, the midnight zone, the abyss, and even farther down, the trenches.
Keep reading for an in-depth look at what these ocean zones are like, and what kind of creatures you’d encounter there!
1. The Sunlight Zone (Euphotic Zone)
The sunlight zone gets its name because this is where most of the visible light is. This zone begins at the surface and ends about 660 feet down, and with all that light comes plenty of heat, which means that a huge variety of marine life make the sunlight zone their home.
The marine life that live in the sunlight zone have no shortage of small fish or phytoplankton to feed off (since they call this zone home too). Some of the most common marine species here include sharks, stingrays, tuna, jellyfish, and even sea turtles!
While the warm water and sunlight do make for ideal living conditions, there aren’t a lot of places to hide (due to all the light) – which works in favor of sharks and sea turtles, but is deadly to their prey.
2. The Twilight Zone (Dysphotic Zone)
Once you go past the 660 foot mark, you’ll enter the twilight zone, which extends down to 3,280 feet. Here, while there can be some faint light towards the start, photosynthesis can no longer occur, so no plants are able to survive in this zone.
As water pressure increases and temperature decreases, the marine life that thrive in the twilight zone have to be able to withstand its tough conditions. These animals may have thinner bodies to hide from potential predators, or darker bodies to better camouflage themselves into the dark surroundings. Octopus, squid, and hatchet fish make this zone their home, and some whales even visit the twilight zone to feed.
You’ll even begin to notice bioluminescence fish, which create their own light in these dark conditions!
3. The Midnight Zone (Aphotic Zone)
From 3,280 feet to about 13,135 feet is the midnight zone, which, hence the name, doesn’t have any sunlight. Any light that IS produced here comes from bioluminescent fish! Water pressure is even greater in this zone, and depending where you’re located, it can be as high as two tons per square inch.
Just like in the twilight zone, photosynthesis does not occur here, which means you won’t see any plans living down here. While the entire area is called the midnight zone, scientists have actually categorized it into two different sections:
- The bathyal zone: The bathyal zone is the first part of the midnight zone, and it covers just about 6,600 feet.
- The abyssal zone: The abyssal zone makes up the remaining part of the midnight zone, all the way down to 13,135 feet, and extends further down into “the abyss.” (We’ll get more into this below!)
Along with sperm whales that venture down here to feed, the midnight zone is home to certain kinds of algae, anglerfish, mussels, vampire squid, and tripod fish.
4. The Abyss (Abyssal Zone)
From 13,135 feet to 19,700 feet, the Abyssal zone (aka “the abyss”) contains zero sunlight and crushing levels of water pressure. The Abyssal zone alone covers around 83% of the total area of the ocean!
Although the abyssal zone is so vast, very few animals can handle the extreme conditions. Those that can withstand the pressure are usually invertebrates, like tiny squid or basket stars (a species of sea star). Food is scarce here, and many of these animals end up eating whatever they can get their hands (or fins) on.
5. The Trenches (Hadal Zone)
The Trenches covers the ocean from around 20,000 feet to the very bottom – which may be close to 36,000 feet. Not only is the temperature this deep, freezing or below in the trenches, but the water pressure is extreme at eight tons per square inch in the Mariana Trench (the deepest ocean trench on earth).
These trenches are steep depressions in the deepest parts of the ocean, which is what this zone is aptly named for. It’s also officially known as the Hadal zone, after Hades, the Greek god of the Underworld.
While the hadal zone may have pretty hostile living conditions, a small percentage of marine life do make their home here. This exclusive club of deep-deep sea dwellers includes grenadiers, pearlfish, cusk-eels, and cutthroat eels.
With five different zones that make up over 35,000 feet, the ocean is mind-blowingly immense. In fact, less than 10% of the the global ocean has been mapped. We have so much more exploring to do!
And while you may never be able to venture into the midnight zone or down into the trenches yourself, you can still support marine life! Check out our newly released Strawberry Squid clasp, 15% of each sale goes right back to the Woods Hole Oceanic Institution!