Whenever we hear stories about courageous adventurers overcoming all odds in order to explore the most desolate and unforgiving of places, we sometimes feel depressed because we believe that doing so is no longer possible on Earth. We have visited all the remote islands, penetrated into the deepest jungles, endured the hottest deserts, and even conquered the ruthless Arctic. However, there is one place left to explore: a wet and deadly wasteland permeated by total darkness — the deep sea.
Let’s dive down.
Continental Shelf — 0 to 200 meters below sea level:
We begin our journey in the Continental Shelf, where around 90% of all fish are located. Here, light can still penetrate the water all the way through, which allows for photosynthesis to occur. As a result, phytoplankton, trillions of single-celled algae and bacteria, thrive and make up the base of the ocean’s ecosystems. At this level, the seafloor is similar to the Amazon’s rainforests because it is full of coral reefs, algae, and other sea plants that function as homes to plenty of sea animals. Altogether, the Continental Shelf consists of a pleasant environment where we swim, fish, and sadly, pollute.
Continental Slope — 200 to 4,000 meters below sea level:
As we move further into deeper and more remote waters, we reach the edge of the Continental Shelf and transition into the Continental Slope. Here, with every additional meter of water, light fades exponentially, and as a result, most sea plants aren’t able to survive. Also, we won’t be seeing the ocean floor for a while.
- Sublevel: Twilight Zone (300 to 1,000 meters below sea level)
300 to 600 meters: From 300m onwards, the water pressure rises to deadly levels. For example, if you were to swim at this depth, you would feel 200 cars stacked on top of you. What’s more crazy is that swimming here is actually survivable (with the right equipment of course) as demonstrated by the deepest scuba dive ever — at 332 meters.
Unexpectedly, half of all fish and other sea animals actually spend half of their lives at this depth. During the day, these sea creatures rest and recover in the vast dark waters of the Twilight Zone, where predators are less of a threat. During the night, they travel into shallower waters to feed on the rich and abundant foods of the surface.
600 to 1,000 meters: In the extremely dark waters of this depth, light becomes a powerful device to have since it can greatly help with both mating and hunting. This is why over 90% of the species native to this environment use some sort of bioluminescence to create small amounts of light. On top of this, most species living here have to rely on marine snow as their food source. It consists of shells, dead plant or animal parts, and fecal matter that slowly sinks from the surface to the bottom of the ocean. Without marine snow, life in the deep sea would not be possible.
- Sublevel: Midnight Zone (1,000 to 4,000m below sea level)
The Midnight Zone is a barely explored wasteland covered in utter darkness. Finding food at these depths becomes exceedingly hard, which is why species living here had to adapt and become extremely energy efficient. Additionally, to improve their chances when hunting, deep sea predators evolved several sets of sharp and long teeth, with most having some form of “lantern” on top of their heads. One famous example is the angler fish shown to the right.
3,000 to 4,000 meters: Everything down here hovers motionless or swims extremely slowly to preserve the most energy possible. The only time a creature will move fast is when escaping danger, but, for the most part, life in slow motion at this depth.
Continental Rise & Ocean Basin — 4,000 to 6,000m below sea level:
We finally reach the ocean floor after 3,800 meters of nothing but open waters. All the marine snow that wasn’t consumed while falling is now eaten by animals such as shrimp, sea urchins, and sea cucumbers. In some regions, sponges and corals can actually be seen, especially around deep sea geysers. In these areas, chemotrophs use the geysers’ expulsion of extreme heat and minerals to create nutrients through a process called chemosynthesis (basically the same as photosynthesis, but instead of using the sun, bacteria use heavy elements like methane).
Hadal Zone — 6,000 to 11,000m below sea level:
Surprisingly, we haven’t even explored half of the depth of the ocean! The Hadal Zone is made primarily of long narrow trenches (including the Mariana Trench) where the pressure is 110 times stronger than the pressure on the surface. As a result, only extremophiles are able to survive, and yet again, they feed on left-over marine snow. On top of this, most of the sea creatures living here are arthropods (think shrimp), but they are way larger than their surface counterparts. Sadly, scientists discovered that our pollution has even reached the deepest part of the ocean when they found a plastic bag on the ocean floor.