Three Layers of the Ocean
The three primary ocean layers include the epipelagic zone, the mesopelagic zone, and the bathypelagic zone.
Our oceans cover approximately 70 percent of the Earth’s surface and are huge. The Pacific Ocean, for example, stretches for about 165 million square kilometers. It might not be a surprise then that humans have only discovered 5 percent of these vast stretches of water; who knows what more ocean secrets will be uncovered as scientific advances allow us to push further into the unknown.
What we do know is that our oceans are deep. The deepest part can be found in the Pacific Ocean at Challenger Deep, reaching over 11,000 meters. Oceanographers have split the ocean’s depths into different zones from the surface down to the ocean bed.
Here’s a rundown of the three main layers of the ocean and a few others you may not have heard of.
Epipelagic Zone (0-200m)
The Epipelagic Zone is known as the Sunlight Zone. You’ll find most organisms living here because, as the name suggests, you’ll find the most sunlight! Animals that enjoy hanging out at these depths are seals, dolphins, various species of fish, coral, jellyfish, and lots more. As sunlight can penetrate the waters, photosynthesis can occur so plants can grow.
We humans can reach up to 40-50 meters with diving equipment, and the pressure is the same as a 1kg weight on your fingernail.
Mesopelagic Zone (200-1000m)
Deeper down, we enter the Mesopelagic Zone, also known as the Twilight Zone. Animals such as whales, swordfish, shrimps, and octopuses live in these depths. The absence of sunlight means no plants can grow, as photosynthesis can’t occur. The pressure at these depths has now increased to equal a 29-88 kg weight on your fingernail!
You may bump into a few sea sponges at these depths, a unique marine animal around 600 million years old. Many people think that sea sponges are plants, but they’re, in fact, animals – sessile (non-moving) animals, to be specific.
Bathypelagic Zone (1000-4000m)
Also known as the Midnight Zone, at this depth, the sunlight cannot penetrate at all, which means that the animals at this depth will need to generate their light. To put it into perspective, the Titanic, a doomed ocean liner that sank in 1912, rests at 3,800 meters! Humans cannot reach these depths without the help of some pretty advanced equipment. The pressure in the Midnight Zone is the same as a 100kg-393 kg weight on your fingernail!
We mentioned animals producing their light earlier. Well, here’s an example: the Anglerfish. These scary-looking creatures are notable for their bioluminescent lure hanging over their gaping mouths, attracting prey – a biological feature only found in females. There are around 200 species of Anglerfish in the world.
Abyssopelagic Zone (4000-6000m)
Also known as the Lower Midnight Zone, temperatures at this depth are freezing; just like the Midnight Zone above, it’s pitch black. By now, we’ve reached the ocean floor, home to more weird and wonderful creatures like the Vampire Squid and the Dumbo Octopus. The Lower Midnight Zone is the most extensive environment on the planet. The pressure at these depths has increased to 400-590 kg on your fingernail!
Fear not, the Vampire Squid only feels at home in deep-sea conditions and looks like a cross between an octopus and a squid; despite their scary-looking appearance, they’re the opposite, spending their time combing the depths for plankton.
Hadopelagic Zone (Lower than 6000m)
Believe it or not, we don’t stop there. The Hadopelagic Zone, also known as The Trenches, can stretch more than 6000 meters deep. The Challenger Deep is the deepest known point in our ocean, reaching over 11,000 meters. The pressure at these depths is the same as resting a 600-100 kg weight on your fingernail!
You’ll find the rat-tailed fish at these depths, a species of deep-sea fish that swims along the bottom of the ocean. As it’s blind, it relies on its other senses to catch food; its nose is tuned in to the smell of animal carcasses, and it has small barbels to attract other tasty morsels such as crustaceans and worms.
