Things that go BUMP in the Dark

Rita Steyn

Are you afraid of the dark? Read on to discover what living in near or total darkness means for marine life and organisms...

In the United States alone, about 11 percent of the adult population is spooked by darkness. In the United Kingdom, 40 percent of adults surveyed in 2012 said they did not like to walk around their own house in the dark! How do you compare? Do you feel worse when it is dark, because you can’t actually see anything, or do you feel better when it is dark, because you can’t actually see anything?

The light begins to fade as you descend into the ocean depths. Blue light travels the furthest. Photo: @ritasteyn

The light begins to fade as you descend into the ocean depths. Blue light travels the furthest. Photo: @ritasteyn

Darkness in the Ocean

Once you go beyond 200 m (656 ft.) in the ocean, light basically falls away. Not enough sunlight penetrates the ocean beyond that depth for photosynthesis to occur, and there is no light in the ‘midnight’ zone stretching from 1000 m (3280 ft.) to the ocean floor below.

Living in near or total darkness usually means that an organism has to have some kind of adaptive ability. These adaptations allow them to live and reproduce, so they must be able to eat, not be eaten, and find a mate, all in the dark.


My, what big eyes you have!

One way to adapt to a dark environment is by having very large eyes in order to capture as much light as possible. Blue light travels the furthest in water, and blue-green is also the colour most emitted in the deep ocean by other creatures, so most deep sea fish have eyes that are sensitive to blue light. The record for the largest eye in the world is held by the giant squid (Architeuthis), and research from 2012 indicated that they can see movement at 120 m (394 ft.) even in the deep ocean!

You'll need big eyes, big teeth, and a big mouth to survive in the deep! Photo: FreeImage.com/GavinMills

You'll need big eyes, big teeth, and a big mouth to survive in the deep! Photo: FreeImage.com/GavinMills

Let your little light shine

If there is no light in your environment, you might have to make your own. The chemical process that produces light in the cells and body of an organism is called bioluminescence. Animals (and other organisms) produce light in order to attract food, like the angler fish, or they produce light in order to prevent themselves from becoming food, like this deep sea shrimp, that emits a glowing cloud of puke in order to avoid predation. Light is also used to attract mates, like the well-lit moustache of the male Caribbean ostracod, another type of crustacean.

It’s a big world out there – you never know who you’ll bump in to

Technically, the deep ocean is anything that lies below 200 m, but 75 percent of that is below 1000 m. There is roughly about 300 times more area in the ocean to support life, than on land. We live, after all, on planet mostly-water, which we decided to call Earth. Scientists now believe that there may be more species in the deep sea than anywhere else, making it the largest unexplored region on our planet – and home to potentially 100 MILLION species. Sometimes, organisms from the surface travel down to the deep sea – for example, beaked whales can dive to a record breaking 2992 m on one breath! You never know just who you’ll bump into in the deep sea, and with 99 percent of the sea floor remaining UN-explored, we still have a lot of ocean to visit.

There's a lot of ocean out there left to explore! Photo: @ritasteyn

There's a lot of ocean out there left to explore! Photo: @ritasteyn


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