1 covers the sea like a blanket. For the past
six months, the sun hasn't shone in Antarctica.
Now, in early October, the sun hangs low in the
sky. In the light, this place looks lifeless. It's not.
Fish, sea stars, plankton, and more live
hidden just below the sea ice. Most living
things would die instantly in this cold, dark
place. The creatures here thrive, though.
They have found ways to maintain
homeostasis. That's a perfect balance of such
things as temperature, oxygen, and energy
needed to survive. They may live in an extreme
habitat. Yet on the inside, they are just fine.
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How? wonders oceanographer Stacy Kim.
She decides to dive in to find out. First, she
needs to make sure she can survive in their
world. She straps on a tank of oxygen so she
can breathe underwater. She grabs a fl ashlight
to help her see in the dark.
Lastly, she zips up her diving suit. The water
here is _2° Celsius (28.4° Fahrenheit). That's
cold enough to kill an unprotected diver in
minutes. The suit keeps her dry and a little
warm. Even so, she knows she can only survive
about an hour under the ice before she gets
life under the ice sounds tough, check out
this cave in Mexico. Like the sea ice habitat,
some places in the cave are always dark. There's
a more extreme problem with this place,
though. The air and water are full of toxic gases.
Welcome to Cueva de Villa Luz. It's also
called Mexico's poisonous cave. The air here
can kill a human in minutes.
Yet insects, fish, bats, and other organisms
make this deadly cave their home. In fact,
some of them need the poison gases to survive.
Biologist Diana Northup wants to know more
about these odd adaptations.
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Outside the cave, Northup notices a stream
trickling by. The gases have turned its water a
milky color. She sniffs the air. It smells funny,
like rotten eggs. The smell comes from gases
deep inside the cave. Just a small whiff and she
Northup takes no risks. She straps a gas
mask over her nose and mouth. It will block
bad air, yet let oxygen in.
Northup also brings a tool to monitor the
air. If the air gets too poisonous, even the mask
won't save her. That's when the tool beeps a
warning. It tells her it's time to get out.
underwater caves, the problem isn't little
food, little light, or toxic gases. It's all three.
That doesn't stop National Geographic Explorer
Kenny Broad. He dives into some of the most
dangerous underwater caves in the world. They
are the saltwater blue holes in the Bahamas.
Like a caver, he must avoid toxic gases. Like
a diver, he must bring his own oxygen. Like
both, he needs to bring his own light. Then
there is the worst danger of all-getting lost.
These caves are like a maze. Getting lost
could be fatal. He can only survive underwater
as long as he has oxygen in his air tanks.
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That's why Broad's guideline may be his
most important tool. It is a rope attached
to the entrance of the cave. He holds onto it
throughout his dive. If Broad takes a wrong
turn, the line is his only way out.
Broad and his team hike through a forest to
reach a blue hole. It looks like a pond. Broad
knows better. It's an entrance to a huge, hidden
world. Before diving in, he checks his gear
twice, and then again. Extra air tanks? Check.
Extra face mask? Check. Extra flashlights?
Check. He must be ready for any problem.
Finally, he drops into the dark water.