When we imagine the ocean, we might find ourselves thinking mostly about the intertidal zone - the part of the ocean where water meets land - and the epipelagic zone - the uppermost part of the ocean with the most sunlight. Hospitable biomes like these host an abundance of incredibly diverse organisms because of readily available sunlight for photosynthesis. However, most marine environments are, for the most part, cold, deep, and completely pitch-black.
We know almost nothing about these “gray areas” below the ocean’s surface, which scientists call the hadal, abyssal, and twilight zones. More people have been to outer space than the deepest parts of the ocean, even though the deep sea constitutes 95% of the Earth’s total living space.
Until recently, the deep sea was inaccessible, but recent advances have allowed scientists to send down underwater drones with sophisticated imaging technology to capture and uncover its mysteries.
Over time, we discovered that the ocean can be a scary place. 650 feet underwater, most light is gone and the weight of the water becomes too great for any human being. Yet, 36,000 feet deep, life thrives. In this area, all light has completely vanished, so animals have adapted to the darkness with big eyes and bioluminescent, or light-producing, bodies.
Interestingly enough, the tiny rays of sunlight that travel here can give away the location of prey to predators, so most prey species are coated with internally produced lights to blend in. For instance, the underside of a hatchetfish has organs that produce bioluminescence to disguise themselves from incoming light.
Bioluminescence is used in a variety of other ways as well. Predators like the dragonfish hunt using “flashlights” emitted by their skin, and some deep sea creatures can communicate with light to signal danger or attract a mate.
This is just a brief glimpse into all that the deep sea has to offer! Scientists haven’t even scratched the surface of what lies underneath, so it’s anybody’s guess what else there is left to discover in these strange, alien-like habitats.
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