Layers of the Ocean
The Five Layers of the Ocean – Oceanic Zones
The ocean’s the ocean, right? It’s just one homogeneous mass of water doing its stuff underneath the surface. That’s pretty much what we thought too, until we looked at the subject in more depth and discovered there’s a whole new world of layers of the ocean to be discovered “down under”.
Scientists basically divide the ocean depths into 5 main layers of the ocean (or ocean zones) which extend from the surface to very deep – we’re talking 36,000 feet which is more than a mile deeper than Mount Everest is tall.
Almost all light is absorbed in the first 656 feet (200 m) but small amounts of sunlight can penetrate down to around 3,280 feet (1,000 m). At these lower oceanic zones some weird and wonderful sea life has evolved. There’s a case for a sixth layer of the ocean. According to Marcus Eriksen, Director of Research and Co-founder of the 5 Gyres Institute “The ocean is covered in a thin layer of plastic”.
|Other names||Features / Characteristics||Temperatures||Depth feet (m)||Life||Pressure (atm & Pa)|
(top zone of the ocean)
|The sunlight zone||This ocean layer has the most visible light and warmest temperatures, hence its nickname. It’s the thinnest layer accounting for just 5% of the ocean depth.||The most variable temperatures depending on location and proximity to the ocean surface which allows light, and consequently heat, to penetrate.||0 – 650|
(0 – 200)
|Most of the sea creatures we know live in the epipelagic layer including fish, photosynthesizing microorganisms, sharks, coral etc.||Land pressure = 1 atm (101,326 Pa) to 21 atm (2,127,825 Pa)|
(middle of the ocean)
|The twilight or midwater zone||The mesopelagic zone, sometimes referred to as the twilight zone or midwater zone is the deepest layer that light can penetrate and represents 20% of the average ocean depth.|
Collectively the epipelagic and top of the mesopelagic layers are known as the photic zone, which means light gets to them.
|Consistently cold temperatures.||656 – 3280|
(200 – 1000)
|Many bizarre fishes and some bioluminescent creatures.|
Semi-deep sea creatures including swordfish and wolf eels live in this zone.
|21 atm (2,127,825 Pa) to 101 atm (10,233,825 Pa)|
(from Greek “bathýs” for deep)
|The midnight or dark zone||In this layer the only visible light is that produced by the creatures themselves. Despite the pressure, a surprisingly large number of creatures can be found.||Average temperature around 39 °F (4 °C).||3281 to -13,124|
(1000 – 4000)
|From this level downwards there’s no plant life. Sealife living in this zone feeds off the detritus falling from above. Large whales, frill shark, squid and octopuses can be found here along with viperfish, sponges, brachiopods, sea stars, and echinoids. Most sea creatures found are black or red because of the absense of light.||Up to 398 atm (40,334,330 Pa)|
(from Greek “abyss” for bottomless)
|The abyssal zone or simply the abyss||No light at all. Around 75% of the ocean floor lies at depths within this layer. The deepest fish ever discovered was found in the Puerto Rico Trench at a depth of 27,460 feet (8,372 m).|
Only the hardiest deep-diving submersibles can explore this zone due to the immense pressure.
|Near freezing, around 35-37°F (2-3°C) for most of its mass.||13,124 – 19,686|
(4000 – 6000)
|Sparsely inhabited on account of the huge pressure here. Mostly invertebrates including basket stars, tiny squid and bottom-feeders that feed off the detritus on the ocean floor, black swallower and deep-sea anglerfish.||Up to 750 atm (76,000,000 Pa)|
|The Hadal zone, after Hades the Greek god of the underworld||Largely unexplored deep sea trenches and canyons. The deepest known point lies within the Mariana Trench, near Japan, at 36,072 feet (10,995 m). Despite the tremendous pressure and low temperature we know life is present. To date, the Hadalpelgic layer has only been visited by the manned Deepsea Challenger submarine and the Trieste (bathyscaphe), Kaiko and Nereus remote controlled submersibles.||Just above freezing.||19,686+|
|Mostly invertebrates like starfish and tube worms, but in 2014, at a depth of 27,000 feet (8,200 metres) researchers discovered a previously unknown white-transparent fish belonging to the snailfish family. It looks like an eel and moves slowly above the ocean bottom, which isn’t surprising considering the incredible pressure. It can only survive because of the molecule protein trimethylamine oxide which protects against high pressure.||Up to 1219 atm (123,515,175 Pa)|
Comedian Steven Wright observed: “sponges grow in the ocean. That just kills me. I wonder how much deeper the ocean would be if that didn’t happen.”
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- We strive for accuracy but we’re not oceanologists so if you spot any errors, disagree with anything in our layers of the ocean table or have any questions, please add your comments below…