The earth's oceans are mysterious places where creatures have been forced to adapt to extreme
environments. Think there's not too much of interest down in the depths? Think again:
From ecosystems built on corpses to scores of life forms that never see the light,
it's a weird place.
Considering the extreme conditions at the bottom of the ocean,
it's not surprising that more than 80% of it is still unexplored. Scientists and engineers are
developing new ways to explore even the deepest parts of the sea, and they've come a long way.
"You're a pilgrim to the deeps. And remember, God lies in all realms."
As described by Smithsonian Ocean, one option is autonomous water vehicles, or AUVs. These are
robot explorers, programmed to travel to specific areas of the deep sea and bring back information.
There are also remotely operated vehicles, or ROVs. These robots are attached to a ship on the
surface, where human operators can control their movements and watch what happens on monitors.
Sometimes, though, humans still go on these deep sea exploration missions. Human occupied vehicles
are able to travel to the deep ocean and keep the people inside safe without cracking from
the extreme pressure. Some even have "arms" that the explorers inside can use to collect specimens.
NASA, known for its space missions, is also exploring earth's oceans.
As stated by the BBC, it is hoped that by learning more about our own ocean and developing technology
that can explore it, humans can learn more about what it's like on other planets.
One of the biggest difficulties in exploring the ocean's depths is the pressure:
The deeper the water gets, the more difficult it is to exist there.
Below the surface, water presses in on all sides. This is known as hydrostatic pressure. As noted
by The Woods Hole Oceanographic Institution, the average amount of pressure felt when at the
surface or the shore — the amount most people are used to — is referred to as 1 atmosphere.
The deeper into the water one goes, the more hydrostatic pressure there is.
It increases quickly: At just 33 feet below the surface,
the amount of pressure is double the amount at the surface.
Every 33 feet down is the equivalent of another entire atmosphere pressing in from all sides,
so the pressure gets pretty high when you start talking in terms of miles beneath the surface.
In order to explore these depths, special vehicles and robots have to be designed to
withstand enormous amounts of pressure — between 380 and 1,100 atmospheres — without cracking.
Sunlight is the source of heat, light, and energy for most of the planet,
but in the deepest layers of the ocean, there is no sun at all.
As described by the National Weather Service, the zone closest to the surface is known
as the sunlight zone, because the sunlight illuminates and warms the water of this layer.
Around the world, temperatures in the sunlight zone range from 28° to 97° Fahrenheit.
The region below this is called the twilight zone
because while it is very dark, some sunlight still reaches these depths.
Then, at about 3,300 feet below the surface the midnight zone begins.
This zone is completely dark at all times, and it stays at approximately 39° Fahrenheit.
Next comes the layer of the ocean known as the terrifyingly-named abyssal zone.
It is just as dark as the midnight zone and always near freezing.
For most of the sea, this is as deep as it can get.
However, some of the deepest sea trenches have another name:
the hadal zone, starting at 19,700 feet below the surface and stretching as deep as the ocean goes.
In order for life to survive without sunlight, creatures in these deepest parts of the sea
must find other sources of energy. And as for light? They provide their own.
Despite the crushing pressure and the darkness, the deep sea is earth's largest habitat. Still,
studies estimate that more than 90% of the ocean's creatures have yet to be discovered
and classified. The animals that have evolved in this environment may look
other-worldly — but each adaptation allows them to survive at the bottom of the ocean.
NASA researchers have investigated how deep sea creatures like snailfish
can endure the pressure from water crushing in on all sides.
It is believed that they have developed an enzyme that counteracts the weight
pressing down on them by causing proteins in their cells to take up more space.
As seen in BBC Earth's "Blue Planet," many of the creatures that live in the sunless parts
of the oceans are bioluminescent, giving off their own ghostly glow,
but that's just one adaptation researchers have identified.
There's a lot more. Take the strawberry squid: The creature's massive eye is adept at seeking out
bioluminescence in the pitch black water. Then, there's the feather star, which resembles a flower
blooming on the sea floor until its "petals" begin to ungulate and it zooms away into the darkness.
The deep sea is a very, very cool place, and we haven't even scratched the surface.
"Wow…"
"Oh my goodness…."
The deepest part of the ocean is in the Mariana Trench. It is massive,
almost 35 miles across and seven miles deep. To put that in perspective,
if Mount Everest was at the bottom of the Mariana Trench, its peak wouldn't break the surface.
The very deepest point is known as "Challenger Deep," a smaller trench in the bottom of the
enormous Mariana Trench, which is approximately 35,800 feet from the ocean's surface.
And National Geographic says that even at the deepest point of the ocean, life exists.
A kind of crustacean called amphipods that manage to grow to two inches long — more than
twice the length of those found in shallow waters — were discovered in Challenger Deep.
These creatures are believed to swarm below 30,000 feet.
Nothing grows and there is little to eat at these incredible depths,
but these creatures are able to eat wood that sinks from the surface.
It is believed that some of their diet comes from shipwrecks.
While lakes might intrinsically seem like something that could only exist on land,
they can also be found at the bottom of the ocean.
As impossible as it might seem, brine lakes on the ocean floor appear to have a surface
like they would on land. They even have their own waves that don't extend to the sea around them.
As explained by Smithsonian Ocean, these lakes are separate from the oceans around
them because their water is much denser and saltier than the rest of the sea. This
causes the lakes to sit on the ocean floor rather than flow with the rest of the water.
It is believed that these lakes originated in an ancient ocean,
dating all the way back to the Jurassic.
"No immediate danger. Cold-blooded and slow." Scientific American reports that the water in
these "lakes" is so dense that submarines have been able to land on their surface.
The brine in these lakes is full of methane, which would kill most animals that might wander
into the lake. There are, however, forms of bacteria and other single-celled organisms
that can breathe methane that live in the brine lakes. Sometimes daredevil mussels
are attracted to these bacteria, so they may be found near the edges of the brine lakes.
Around 70% of the seafloor is located in the utterly dark abyssal zone — between 9,800 and
19,685 feet below the surface — and the extremely vast and flat seafloor is known as the abyssal
plain. Some portions are rocky, while others have soft substrate. While these plains may appear
uninhabited compared to the populous sunlight zone, this area is home to a variety of creatures.
As stated by Blue Habitats, these ecosystems are some of the least observed in the world,
and there are many things about life in the abyssal plain that are still a mystery.
The seafloor this deep is very cold, and provides little opportunity for sea creatures to feed.
As explained by Smithsonian Ocean, less than 5% of potential food from the surface makes it
to the abyssal plain. Debris from the sunlight zone drifts deeper, but the majority of it is
eaten by the creatures that live above before it can reach the seafloor thousands of feet below.
Despite this, some creatures have evolved to live in these harsh habitats.
Squat lobsters and prawns live there, along with sea cucumbers, mollusks,
worms, and spiny invertebrates like starfish and sea urchins.
It is believed that there are also creatures that live in the soft sediment,
but the only evidence that has been discovered so far are the burrows and trails they leave behind.
Not all of the ocean is as flat, and according to Smithsonian Ocean, there are deep undersea canyons
that stretch for hundreds of miles. As on land, this landscape creates a wide variety of habitats,
not only at the bottom of the canyon but in its rocky walls.
These deep canyons are often full of life, providing the creatures who live there with
a relatively rich food source. Part of this is due to water currents created by the canyon's shape,
and debris from the surface is carried down into the narrowing canyon.
The sides of the canyon provide an ideal home for corals and sponges, while fish hide in the
ledges. The bottom of the canyon is often soft and muddy, which lets mollusks and worms burrow.
Algae grows in the water nearer to the surface, which supports populations of fish,
which in turn attract larger creatures like squids and crabs. Sharks are attracted to
the canyons to feed, and even whales have been discovered in Mid-Atlantic canyons.
It is also believed that the geography of individual canyons impacts the entire ocean.
Canyons can influence the temperature of the sea around them, create strong currents,
and affect the migration of all kinds of fish, from tuna to sharks.
Canyons are not the only enormous geographical feature under the sea.
Underwater mountains, called seamounts, rise up from the seafloor.
Like canyons, seamounts have an impact on ocean currents.
The National Oceanic and Atmospheric Administration says that some seamounts are
incredibly old: For example, Bear Seamount, which can be found in the Atlantic Ocean,
is estimated to be 100 million years old.
There are also a lot of them, numbering in the tens of thousands. The tallest mountain
on earth is a seamount called Mauna Kea — it stands more than 30,000 feet tall,
approximately 1,000 feet taller than Mount Everest — when measured from that underwater base. Like
most seamounts, Mauna Kea is a dormant volcano: So many are, because they tend to be located
at the edges of the earth's tectonic plates, where magma comes up through the earth's crust.
Seamounts create many habitats for various forms
of sea life that would not be able to survive anywhere else.
Their peaks interrupt currents, driving plankton and other sources of food down their slopes.
Deep-sea corals live on their slopes. Although there is no energy from the sun for these corals,
they are able to survive by filtering organic debris that drifts down from the surface.
These communities of corals can exist for hundreds or even thousands of years,
providing shelter for many sea creatures, some of which only live under these specific conditions.
While the majority of the deep sea is frigid, there are a few places where the water is
scalding hot. These are known as hydrothermal vents, and they are teeming with life.
These are places where columns of billowing smoke jet up from the seafloor,
and as described by the National Oceanic and Atmospheric Administration,
volcanically active areas create the vents that support these unlikely ecosystems.
Sea water flows through cracks in the earth's crust, and the water that comes
back into the sea has been heated up to around 700° Fahrenheit by the magma below.
The only reason the water doesn't boil is because of the enormous pressure at the bottom of the sea.
That water is also infused with minerals, formed when the hot hydrothermal fluid
meets the chilling seawater. As the water cools, the minerals solidify, creating vents.
Some are black with iron sulfide, called "black smokers," while others,
"white smokers," come from barium, calcium, and silicon.
Smithsonian Ocean says that organisms are able to live without the sun's
light because of bacteria which use the minerals from the vents instead.
This has allowed for creatures and communities unlike any other.
Take the yeti crab, animals that live over 7,000 feet below the surface,
around the hydrothermal vents near Easter Island. They have been observed holding their
hairy claws over the water surging out of the vents. Colonies of bacteria live in this hair,
and it is believed they may be collecting them intentionally, as a food source.
Food on the ocean floor is scarce, since very little actually makes it down that far.
When a whale dies, however, it is so massive that it supports an entire ecosystem.
As explained by Smithsonian Ocean, whales generally die in shallower, sunlit waters.
Slowly, they sink to the ocean floor, where they become the basis for a community that can support
millions of creatures. These sites are called "whale falls," and they can have
the highest animal density of anywhere in the sea.
No part of the whale is wasted, as animals of every kind flock to the body of the whale.
It doesn't take long. Within hours, it attracts all kinds of
sharks, fish, and crustaceans to the feast.
As they feed, smaller particles are scattered, providing food for nearby anemones, mollusks,
and worms on the seafloor. Some animals have even adapted to be able to eat the bone,
guaranteeing that nothing is wasted. Whale falls are also havens for
bacteria – almost 200 different kinds have been discovered on a single whale fall.
In 2019, explorer Victor Vescovo took a submersible deep into the Mariana Trench,
breaking the record for the deepest ever dive. He stayed in its depths for hours, exploring
the never-before-seen waters. Alongside numerous deep sea creatures, Vescovo found a plastic bag.
It's common knowledge that millions of tons of garbage end up in the ocean every year,
but Vescovo finding a man-made object in a place in the ocean that no human had ever seen before
has become a symbol of mankind's influence on the sea. As explained by The New Yorker, the
deep sea is at risk from not only plastic waste, but all types of pollution, ocean acidification,
and climate change as a whole. How much damage has been done already is not entirely known.
"Life is fragile enough, without the harm done by humans."
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