Ninety percent of our ocean has never been explored. We know very little about what secrets lurk in its deepest, darkest corners. Yet it's within these deepest zones where some of the ocean's most bizarre and fascinating creatures survive... 

Please note that the Midnight Zone has been replaced with the Cave Dwellers exhibit - but we're leaving this info up here because we know there is a desire to learn about the deepest parts of our ocean.

You can now discover the wonders of the abyss at Two Oceans Aquarium's new, interactive Midnight Zone!

What is the "midnight zone"?

The ocean's midnight zone is a region between one and four kilometres deep, where no sunlight at all penetrates the frigid water. With no light, there is no growth of plants or phytoplankton - all animals are thus predators or scavengers.

The few bathypelagic (a term for fish and other organisms that nhabit the deep sea, between about 1 000 and 3 000m down) species that survive at this depth have all made evolutionary sacrifices for survival. Because there is no light, few have large eyes. Because animals are blind, they have no camouflage or bright colours. Because there is so little food, they have slow metabolisms, small muscles and grow very slowly.

Occupying the so-called bathyal zone, characteristic fish species include the deep-sea anglerfish, which uses a tiny bioluminescent lure to attract prey. The giant oarfish swims upright, surveying the overlying waters and waiting for the occasional small fish or shrimp to stray too close. Ocean-wandering species, like the colossal squid, frequent the midnight zone, both for shelter in the darkness and for food.

On the sea floor, in the benthic zone, food is still scarce and animals have adapted to take advantage of a wide variety of food. The gulper eel has tiny teeth which it uses to feed on small crustaceans, but it also has a huge mouth and stomach, which can expand to eat a fish a quarter of the size of its own body - handy for consuming a sinking carcass or a passing octopus!

Image courtesy of FactZoo.

Why don't we keep actual midnight zone fish?

Because fish that live in the midnight zone have adapted to complete darkness, cold waters and high pressures, it is difficult to create an environment on the surface that could support their needs ethically (and even more difficult to create one where visitors could see the animals). It is so difficult to create these conditions on the surface, that few aquariums attempt it except for research purposes.

One of the only aquariums to ever have attempted such an exhibit is the Océanopolis in France. Their 600kg "Abyss Box" is only big enough for 16 litres of water - nowhere near big enough for any of the species that we've listed in this article. The aquarium in France, according to this detailled article by Wired magazine, is only hosting small crustaceans. 

All this machinery only keeps a few litres under 2km of ocean pressue. Image courtesy of Wired.

Furthermore, it would be very difficult for these animals to be collected without injuring them. According to the Wired article, "most creatures of the deep can survive only a few hours at sea level (the drop in pressure messes up cell-to-cell communication and causes paralysis), and any decompression can be fatal." The deepest scuba dive ever was 332m - and that took four years of preparation. By comparison, modern military submarines cannot survive depths greater than 750m. Mini-submarines and deep-submergence vehicles (DSVs) are sometimes able to reach these depths (some going as deep as 14km), but they are rare, expensive and dangerous machines, and do not provide any way to bring animals to the surface safely.

Mini submarines, like this Johnson Sea Link, although often shown diving deep in movies, actually cannot get near 1km depth. To go beyond that needs an even more specialized DSV. Image courtesy of Chip Baumberger/ScienceBlogs.

So for now we'll all have to just make do with the glowing Midnight Zone at the Two Oceans Aquarium...  

Other interactive experiences at the Aquarium

We believe that the best way to have a lasting experience is to learn something new - and what better way to do that than an engaging, interactive activity. Here are just a few on offer:

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