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500 miles from the coast
of Antarctica,
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the icebreaker Polarstern
has forced her way
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deep into the ice pack
surrounding the continent.
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Now a team of scientists is
leaving the safety of the ship
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to venture out onto the ice.
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They're in search of a tiny
shrimp-like creature...
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Seemingly insignificant...
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But with a vital role
in the food chain.
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The penguins eat them,
the fish eat them,
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the seals eat them.
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But all this is under threat.
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We have a decrease of over 50%.
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Krill have declined
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in some areas by 90%.
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Because something unknown is
decimating the krill population.
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That means the system
is changing dramatically,
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and we have to understand why...
why that is.
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The answer may lie
hidden under the ice.
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Finding it means
a dangerous dive
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into a dark and unexplored
world,
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with no guarantee
that they can solve
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the "Mystery Beneath the Ice."
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Right now, on NOVA.
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This is the Antarctic ice pack
proin the dead of winter...
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Conditions here are so harsh
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that few ships
would dare to enter.
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But this icebreaker is taking
a group of scientists
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on a mission.
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Something unknown threatens the
most extensive natural ecosystem
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on Earth...
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The food web that
sustains all life
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around the vast continent
of Antarctica...
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A place as remote
as it is beautiful.
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The early explorers
called Antarctica
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"the Land of the Gods."
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And the first time
you come down here
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that's pretty much how you feel.
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It's giant mountain ranges
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that descend directly down
into the ocean.
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You have it carved up
by glaciers.
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You have icebergs all around.
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It's just a spectacular,
stunning place.
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And the waters here
teem with life.
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If we look at the seas around
the Antarctic Peninsula,
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we have the most
fantastic wildlife.
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Massive diversity,
iconic animals.
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Antarctica is home to tens
of millions of penguins,
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millions of seals,
hundreds of thousands of whales.
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But all these creatures depend,
to a greater or lesser extent,
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on a single species:
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Antarctic krill.
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The Antarctic krill,
euphausia superba,
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is a shrimp-like organism about
the size of your little finger.
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And it's the key link
in the Antarctic food chain.
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The whales eat them,
the penguins eat them,
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the fish eat them,
the seals eat them.
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There are thought to be perhaps
500 trillion krill
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in the waters around Antarctica.
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Just as well; one whale can
consume a million
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in a single meal.
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Krill essentially support all
this life we see around us.
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But there's a threat to life
in Antarctica.
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Evidence suggests that
the population of krill
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has been in decline.
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Still the most effective way
to do a krill census
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is to drag a net through the
ocean and physically count them.
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If you compile
all those records,
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the general trend suggests
that they are declining.
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In some areas by 90%.
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So, yeah,
it's pretty significant.
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And it's a potential disaster
for wildlife.
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Many of the penguins come back
to the same location
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and breed year after year,
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so if the krill disappear
in that location,
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those penguins are toast.
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Already, some penguin
populations
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on the Antarctic Peninsula
have declined
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by as much as 85%.
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Wildlife populations
on the peninsula,
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an important breeding ground
for many animals,
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are intensively monitored
by scientists,
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such as those based at the
British Antarctic Survey Station
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at Rothera Point
on Adelaide Island.
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Rothera is a phenomenal place
to come and work.
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All stations, all stations,
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Victor Bravo Bravo on final,
runway three six.
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And it's phenomenal because
what you see in the life here
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you don't see anywhere else.
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If we look at the seas around
the Antarctic Peninsula,
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where we are now,
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then the areas on this part
of the Antarctic,
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along the peninsula,
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are probably the biggest
breeding ground
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for Antarctic krill.
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That's why we have the most
fantastic wildlife
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in this part of the world.
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Krill are a key link
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that connects top predators
such as penguins and seals
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with the base of the food chain.
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Here, as everywhere
in the oceans,
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that consists of algae and other
microscopic floating plants,
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called phytoplankton.
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In the summertime here
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we have very, very intense
phytoplankton blooms.
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And they're so intense
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that the visibility for divers
is very poor.
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The sea at the moment
is like green soup.
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That green soup is absolutely
the bottom of the food chain
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that provides the energy
for everything else
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up in the levels
of the food chain.
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Like plants on land,
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phytoplankton harness the sun's
energy to make living tissue
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from carbon dioxide
dissolved in the water.
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They're then eaten by krill and
other small marine animals,
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and the krill then become
a key food source
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for the top predators.
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We've seen krill swarms going
through, in massive clouds,
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all feeding on that massive
density of phytoplankton.
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And the reason these waters are
so productive in the summer
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is that the days are so long.
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In mid-December
below the Antarctic Circle,
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the sun never sets,
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and phytoplankton can grow
24 hours a day.
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But as summer turns to winter,
the days rapidly shorten until,
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by April, starved of sunlight,
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virtually all the phytoplankton
in the water column
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have died off.
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In the wintertime
the phytoplankton,
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the bottom of the food chain,
just about disappears.
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You might have visibility
like a 100 meters maybe.
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It's like flying through the air
or it's like diving in gin,
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because it's so clear.
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So the differences
between seasons here
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are greater than anywhere else
on Earth,
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and as a scuba diver they
absolutely hit you in the face.
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Most krill are spawned
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when the seas are still full
of phytoplankton.
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But to reach maturity they will
have to make it through
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their first winter, a period
when there will be
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little or no phytoplankton
for the young krill,
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called larvae, to feed on.
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This is the most vulnerable part
of a krill's life cycle,
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and researchers suspect it is
the most important factor
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determining krill population.
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But to test their ideas,
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they need to make observations
in Antarctic seas
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in the depths of winter,
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and that's cold, difficult,
and even dangerous.
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It's August.
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At a port on the tip
of South America,
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50 scientists embark
for Antarctica.
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These are some of the world's
leading experts on krill
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and the Southern Ocean.
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Their mission is to try to find
krill larvae,
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observe their winter behavior,
and so shed light
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on why their population
has declined so drastically.
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Is it science,
or is it adventure?
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I would say it's both,
to be totally honest.
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I don't think that many people
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have the opportunity
to make a winter cruise.
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These cruises
are extremely rare.
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The big challenge for krill
larvae is surviving
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the Antarctic winter.
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But the question is,
how do they do it?
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And if we understand how they
can do it,
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we can understand how changes
in the planet
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might affect their ability
to do it.
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Leading the expedition is
chief scientist Bettina Meyer
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from Germany's Alfred Wegener
Institute.
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I am pretty sure that we will
find krill.
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The question is how much krill
we will find.
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But I think you always have
to be optimistic,
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and I am an optimistic person.
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The scientists are aboard
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the German research vessel
Polarstern.
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She's a scientific icebreaker,
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specially adapted for work
at high latitudes.
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The first leg of her nine-week
voyage will take her east
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across the Southern Ocean.
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During this part
of the expedition,
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the scientists plan to deploy
a specialized fishing net
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called a rectangular
midwater trawl.
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The goal is to gather data on
how many krill are to be found
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in these waters in winter.
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It has multiple nets... three
big ones and three small ones,
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so it's pretty complicated
to string it all together.
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The big nets are working well.
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And we still have a small
problem with the small nets.
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Well, it's never easy
to find krill.
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Because you'll come along
on one voyage
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and you'll sail through
a sea of red...
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You know, you can have super
swarms of krill
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100 kilometers long...
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And then you can sail through
another 100 or, you know,
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500 kilometers of ocean
with nothing.
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Krill are a schooling animal,
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there's no two ways
to look at it.
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The krill in a school
is dazzling:
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one krill by itself wouldn't
last, you know, two seconds
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00:12:44,563 --> 00:12:45,497
in the Southern Ocean.
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The krill itself is basically
a feeding machine in the middle,
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an optical machine at the front
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for detecting where other krill
and predators are
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with the big eyes,
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and then at the back end
is the propulsion system,
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00:13:01,113 --> 00:13:03,148
which is five swimming legs,
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00:13:03,249 --> 00:13:05,016
and they're just constantly
pushing the krill
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00:13:05,117 --> 00:13:06,684
through the water.
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00:13:09,855 --> 00:13:13,158
Krill have a very fine feeding
basket at the front.
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They have six pairs of
thoracic legs, if you like...
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00:13:15,895 --> 00:13:17,028
They're the front legs...
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00:13:17,129 --> 00:13:20,398
And they form what's called
a filtering basket.
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00:13:20,499 --> 00:13:22,634
And that allows them
to sieve out, you know,
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00:13:22,735 --> 00:13:26,437
almost the smallest
phytoplankton in the sea.
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00:13:26,539 --> 00:13:29,507
It's almost like humans
being able to feed on dust.
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00:13:29,608 --> 00:13:31,609
If we could sieve dust out
of the air,
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00:13:31,710 --> 00:13:33,611
we'd be doing what
krill can do in the ocean.
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Be careful.
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00:13:41,086 --> 00:13:43,588
On deck, they're finally
getting the trawl
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00:13:43,689 --> 00:13:47,125
into the water.
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00:13:47,226 --> 00:13:50,428
Trawling is the best way
to directly survey life
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00:13:50,529 --> 00:13:51,796
below the surface.
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00:13:55,534 --> 00:13:57,335
So biological oceanographers
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00:13:57,436 --> 00:14:00,738
like Brian Hunt
and Evgeny Pakhomov
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00:14:00,840 --> 00:14:04,008
never lose an opportunity
to sample the waters.
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00:14:04,109 --> 00:14:09,380
But a single trawl on its
own won't tell them much.
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00:14:09,481 --> 00:14:12,116
It was only by
combining the results
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00:14:12,218 --> 00:14:13,852
from thousands of trawls
like this,
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00:14:13,953 --> 00:14:16,287
taken on hundreds
of different cruises,
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00:14:16,388 --> 00:14:19,657
that scientists realized there
was something strange
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happening to the krill
population
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00:14:21,961 --> 00:14:23,428
in the Southern Ocean.
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00:14:26,799 --> 00:14:28,666
The man who led the project
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00:14:28,767 --> 00:14:32,570
was British oceanographer
Angus Atkinson.
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00:14:32,671 --> 00:14:37,075
He found records dating
all the way back to the 1920s.
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00:14:37,176 --> 00:14:39,978
We realized there was a lot
of data lying around
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00:14:40,079 --> 00:14:44,048
in various old notebooks
and in data archives
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00:14:44,149 --> 00:14:45,717
that hadn't ever been
put together.
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00:14:50,422 --> 00:14:54,459
I was involved in Nature paper
led by Angus Atkinson,
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00:14:54,560 --> 00:14:58,062
which allowed us for the first
time to estimate distribution
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00:14:58,163 --> 00:15:01,299
of the krill around
Antarctic continent.
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00:15:01,400 --> 00:15:05,236
We had about a dozen countries'
data that we compiled
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00:15:05,337 --> 00:15:07,972
into this central database
that we call KRILLBASE.
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00:15:08,073 --> 00:15:12,977
The combined data from
nearly 12,000 net hauls
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00:15:13,078 --> 00:15:15,914
revealed patterns that were not
immediately apparent
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00:15:16,015 --> 00:15:19,417
from the individual results.
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00:15:19,518 --> 00:15:22,854
We were able to reconstruct
the changes
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00:15:22,955 --> 00:15:26,758
of the density of the krill
over past about 25, 30 years,
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00:15:26,859 --> 00:15:28,393
since about mid '70s.
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Strikingly, they found that the
krill population varies a lot,
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00:15:33,332 --> 00:15:36,267
shrinking and growing
from year to year.
252
00:15:36,368 --> 00:15:39,570
Krill abundance varies tenfold
from one year to the next,
253
00:15:39,672 --> 00:15:42,807
so obviously we need to know
what is causing that.
254
00:15:42,908 --> 00:15:47,745
But the combined data also
revealed a long-term trend
255
00:15:47,846 --> 00:15:51,916
superimposed
on the annual variations.
256
00:15:52,017 --> 00:15:53,351
Remarkably, what we found
257
00:15:53,452 --> 00:15:57,055
is a significant decrease
in the krill density.
258
00:15:59,191 --> 00:16:03,428
It's about an 80% decline
over 30 years.
259
00:16:03,529 --> 00:16:08,566
So that's a significant decline
in the abundance of krill.
260
00:16:08,667 --> 00:16:12,437
In the ten years since Angus
Atkinson published his findings,
261
00:16:12,538 --> 00:16:15,907
most krill scientists have come
to accept that krill numbers
262
00:16:16,008 --> 00:16:19,310
have indeed declined
dramatically.
263
00:16:19,411 --> 00:16:21,145
But why?
264
00:16:23,349 --> 00:16:29,787
There's an important clue hidden
in Angus's data...
265
00:16:29,888 --> 00:16:35,460
A clue that now takes Polarstern
due south, towards the ice.
266
00:16:48,774 --> 00:16:52,443
As she approaches Antarctica
and the temperature drops,
267
00:16:52,544 --> 00:16:55,146
the sea begins to freeze.
268
00:16:55,247 --> 00:16:57,115
I mean you spend a long time
269
00:16:57,216 --> 00:16:58,496
sort of bouncing
around the ocean
270
00:16:58,584 --> 00:17:02,820
on a voyage to, you know,
to the sea ice to do work,
271
00:17:02,921 --> 00:17:05,089
and you can't help but get
a little bit excited
272
00:17:05,190 --> 00:17:06,491
when you start to get in there.
273
00:17:18,370 --> 00:17:21,339
This is the marginal ice zone...
274
00:17:21,440 --> 00:17:25,643
A wide region where
dangerous icebergs lurk,
275
00:17:25,744 --> 00:17:28,179
disguised by the ocean swell.
276
00:17:55,507 --> 00:17:57,141
♪ ♪
277
00:18:17,463 --> 00:18:19,697
People wouldn't understand
how much there is to know
278
00:18:19,798 --> 00:18:20,798
about sea ice.
279
00:18:20,899 --> 00:18:24,435
They'd just say,
"Ice, it's ice."
280
00:18:24,536 --> 00:18:25,770
Well, it's not.
281
00:18:25,871 --> 00:18:27,839
And it really is quite
extraordinary
282
00:18:27,940 --> 00:18:30,641
what there is to learn about it.
283
00:18:30,742 --> 00:18:32,477
Because it is the structure
284
00:18:32,578 --> 00:18:34,212
which this ecosystem
is built on.
285
00:18:41,186 --> 00:18:43,621
Each winter the Southern Ocean
freezes over.
286
00:18:46,592 --> 00:18:50,161
And the whole ocean environment
changes dramatically.
287
00:18:50,262 --> 00:18:53,564
This animation of satellite data
288
00:18:53,665 --> 00:18:56,634
shows how the ice grew out
day by day
289
00:18:56,735 --> 00:18:59,370
in the years 2009 and 2010.
290
00:19:02,641 --> 00:19:06,644
The sea ice extent goes from
four million square kilometers
291
00:19:06,745 --> 00:19:08,479
in the summertime
292
00:19:08,580 --> 00:19:10,715
to 20 million square kilometers
in the wintertime.
293
00:19:10,816 --> 00:19:12,350
So it's absolutely massive.
294
00:19:15,487 --> 00:19:18,990
So over a period of six months,
the size of Antarctica,
295
00:19:19,091 --> 00:19:22,193
if you like, you know,
more than doubles.
296
00:19:22,294 --> 00:19:24,534
So it's, you know, an enormous
change to the environment.
297
00:19:26,365 --> 00:19:30,635
How far the sea ice extends
varies from year to year
298
00:19:30,736 --> 00:19:35,706
and, analyzing their data, Angus
Atkinson and Evgeny Pakhomov
299
00:19:35,807 --> 00:19:38,809
found a link between
these annual variations
300
00:19:38,911 --> 00:19:42,346
and krill population.
301
00:19:42,447 --> 00:19:44,649
In the Nature paper
302
00:19:44,750 --> 00:19:48,452
we tried to find some
mechanistic explanation
303
00:19:48,554 --> 00:19:51,255
for the decline
in the krill abundance.
304
00:19:51,356 --> 00:19:56,027
The best correlation has been
found with density of krill
305
00:19:56,128 --> 00:19:59,897
and with the ice coverage.
306
00:19:59,998 --> 00:20:05,203
When there was a large increase
in the population size of krill
307
00:20:05,304 --> 00:20:10,074
in a particular year, we found
that six months before that,
308
00:20:10,175 --> 00:20:11,442
the previous winter,
309
00:20:11,543 --> 00:20:14,579
there was a heavy sea ice
coverage in that sector.
310
00:20:17,416 --> 00:20:20,418
It looked as if the size
of the krill population
311
00:20:20,519 --> 00:20:23,554
depended on the extent
of the ice.
312
00:20:23,655 --> 00:20:27,225
But it wasn't clear
exactly how it depended on ice.
313
00:20:27,326 --> 00:20:29,493
Is it providing the krill
with shelter,
314
00:20:29,595 --> 00:20:33,097
to hide away from predators,
for example?
315
00:20:33,198 --> 00:20:35,333
Is it providing a food source?
316
00:20:35,434 --> 00:20:38,970
Is it just certain types
of ice that are useful?
317
00:20:39,071 --> 00:20:41,505
Is all ice the same?
318
00:20:41,607 --> 00:20:43,975
And that means actually
going into the ice,
319
00:20:44,076 --> 00:20:47,011
looking at the actual effects,
320
00:20:47,112 --> 00:20:50,581
how ice affects the survival
of these krill.
321
00:20:58,423 --> 00:21:01,525
After 24 hours
of careful steaming
322
00:21:01,627 --> 00:21:06,797
through the marginal ice zone,
Polarstern enters the pack ice.
323
00:21:19,711 --> 00:21:24,282
The icebreaker has a double hull
and a sharply sloping prow
324
00:21:24,383 --> 00:21:27,918
designed not to slice
through the icepack,
325
00:21:28,020 --> 00:21:31,822
but to ride up over it and crack
the ice open with her weight.
326
00:21:37,462 --> 00:21:40,931
Even after 80 years
of krill science,
327
00:21:41,033 --> 00:21:44,635
it is quite unclear
where krill is in wintertime.
328
00:21:44,736 --> 00:21:49,006
And I guess that is
one of the main topics
329
00:21:49,107 --> 00:21:52,176
of this voyage of Polarstern
in the Antarctic winter,
330
00:21:52,277 --> 00:21:55,179
to just look under the ice.
331
00:21:55,280 --> 00:21:57,148
And that means
a diving operation.
332
00:21:58,617 --> 00:22:02,520
The plan is to dive
beneath the ice
333
00:22:02,621 --> 00:22:07,291
to search for krill
and film their behavior.
334
00:22:07,392 --> 00:22:10,594
But to make sure they are
observing undisturbed animals,
335
00:22:10,696 --> 00:22:14,765
they'll have to venture at least
half a mile from Polarstern
336
00:22:14,866 --> 00:22:18,202
and the noise of its engines.
337
00:22:18,303 --> 00:22:22,106
So they need to find an ice floe
thick and stable enough
338
00:22:22,207 --> 00:22:25,776
to support a dive camp away
from the safety of the ship.
339
00:22:32,851 --> 00:22:35,186
To help them find
the right floe,
340
00:22:35,287 --> 00:22:37,722
they will scout the area ahead
341
00:22:37,823 --> 00:22:40,291
with a flying instrument
called the EM Bird.
342
00:22:50,802 --> 00:22:53,637
The Bird carries two precision
instruments:
343
00:22:53,739 --> 00:22:56,607
a laser that measures
the distance to the surface
344
00:22:56,708 --> 00:22:57,842
of the ice floe,
345
00:22:57,943 --> 00:23:00,511
and another instrument
which measures the distance
346
00:23:00,612 --> 00:23:04,148
to the seawater beneath the ice.
347
00:23:04,249 --> 00:23:06,617
The difference is basically
the ice thickness.
348
00:23:06,718 --> 00:23:10,821
So, for us, ice thickness
means ice plus the snow on top.
349
00:23:24,736 --> 00:23:29,106
The Bird reveals a strange world
of floes of varying thickness,
350
00:23:29,207 --> 00:23:31,575
divided by ribbons
of open water,
351
00:23:31,676 --> 00:23:34,678
which look almost like
rivers on land.
352
00:23:54,433 --> 00:23:58,135
Thanks to the Bird, team members
identify thicker floes
353
00:23:58,236 --> 00:24:01,639
to the south,
and by the 31st of August...
354
00:24:01,740 --> 00:24:04,575
Two and a half weeks
into the expedition...
355
00:24:04,676 --> 00:24:11,015
The ship is stationed next to a
floe they believe will be safe.
356
00:24:11,116 --> 00:24:14,452
Now it's time to find out
for sure.
357
00:24:46,151 --> 00:24:48,552
When we first stepped
on the first ice floe,
358
00:24:48,653 --> 00:24:49,720
yeah, it was...
359
00:24:49,821 --> 00:24:51,989
a feeling maybe a little bit
like, you know,
360
00:24:52,090 --> 00:24:53,791
the first men on the moon had,
you know?
361
00:24:57,462 --> 00:24:58,996
You make the first step on a...
362
00:24:59,097 --> 00:25:03,133
on a very new piece of land
or something.
363
00:25:03,235 --> 00:25:04,735
It was exciting.
364
00:25:11,576 --> 00:25:14,245
You have to keep in mind every
day that you are walking
365
00:25:14,346 --> 00:25:16,213
basically on ocean surface.
366
00:25:16,314 --> 00:25:20,584
You have 4,000 meters of water
under you.
367
00:25:20,685 --> 00:25:23,921
It's absolutely astonishing.
368
00:25:26,224 --> 00:25:28,626
But it's not the surface
of the ice
369
00:25:28,727 --> 00:25:32,630
that interests the scientists...
It's what lies below.
370
00:25:32,731 --> 00:25:35,533
And that means venturing
beneath the ice,
371
00:25:35,634 --> 00:25:38,369
in winter, in Antarctica.
372
00:25:48,647 --> 00:25:52,783
You have an environment
which is super icy
373
00:25:52,884 --> 00:25:58,923
and has temperatures about
10, 20, -30 degrees.
374
00:25:59,024 --> 00:26:03,193
We have to have a big,
big dome tent
375
00:26:03,295 --> 00:26:06,030
where the divers can operate
sheltered away from the wind
376
00:26:06,131 --> 00:26:08,766
and from the quite fast-changing
environment.
377
00:26:11,303 --> 00:26:14,371
Only Ulli, the dive leader,
has any experience at all
378
00:26:14,472 --> 00:26:18,776
of diving beneath sea ice,
and an operation on this scale
379
00:26:18,877 --> 00:26:21,211
in the middle
of the shifting ice pack
380
00:26:21,313 --> 00:26:23,414
has never been attempted before.
381
00:26:35,827 --> 00:26:38,228
As the drill breaks
through the ice,
382
00:26:38,330 --> 00:26:41,565
a momentary silence
comes over the team.
383
00:26:41,666 --> 00:26:44,301
All of us sort of looked
at this entry hole
384
00:26:44,402 --> 00:26:46,370
with sort of mixed emotions.
385
00:26:50,342 --> 00:26:51,542
How will I react?
386
00:26:51,643 --> 00:26:54,778
Will I be able to do my work
down there?
387
00:26:57,115 --> 00:26:58,649
Will I be able to function?
388
00:27:02,454 --> 00:27:04,121
Outside the dive tent,
389
00:27:04,222 --> 00:27:07,858
wind chill makes it -58.
390
00:27:09,828 --> 00:27:12,863
Inside, the divers prepare
to enter the water
391
00:27:12,964 --> 00:27:14,164
for the first time.
392
00:27:14,265 --> 00:27:17,635
To get prepared for a dive
needs a lot of time.
393
00:27:19,604 --> 00:27:21,705
You have a mixture of feeling.
394
00:27:21,806 --> 00:27:24,475
You don't know what is under
the ice, you know?
395
00:27:24,576 --> 00:27:29,113
It was not very secure,
you need to secure yourself.
396
00:27:29,214 --> 00:27:32,149
Some claustrophobic feelings
were always present.
397
00:27:34,653 --> 00:27:37,254
Ulli has recruited a team
of scientist-divers
398
00:27:37,355 --> 00:27:39,890
experienced in marine ecology,
399
00:27:39,991 --> 00:27:43,160
which usually means surveying
the life on the sea floor
400
00:27:43,261 --> 00:27:45,963
in relatively shallow seas.
401
00:27:46,064 --> 00:27:49,767
I have never dived
in the ocean before...
402
00:27:49,868 --> 00:27:53,671
Not in the ice,
not in the ocean.
403
00:27:53,772 --> 00:27:55,372
I mean, it's not just the ice,
404
00:27:55,473 --> 00:27:59,209
it's also more than 4,000 meters
deep where you dive.
405
00:27:59,310 --> 00:28:02,179
So it is... different.
406
00:28:05,583 --> 00:28:07,885
Of course I was nervous.
407
00:28:07,986 --> 00:28:12,156
Because it is a new thing
and there's a lot of effort
408
00:28:12,257 --> 00:28:13,390
being made around you
409
00:28:13,491 --> 00:28:15,459
and you don't want
to disappoint anybody.
410
00:28:15,560 --> 00:28:20,497
So I think it was excitement
and also nervousness.
411
00:28:21,700 --> 00:28:24,735
But I guess you have
to be nervous
412
00:28:24,836 --> 00:28:28,539
when something new
like that comes around.
413
00:28:34,412 --> 00:28:38,682
It is quite hard in the first
stage to find the way
414
00:28:38,783 --> 00:28:43,087
to jump in and to feel happy.
415
00:28:43,188 --> 00:28:46,490
It is quite a hard psychological
moment in the first dives
416
00:28:46,591 --> 00:28:47,958
to come over this point.
417
00:28:49,761 --> 00:28:52,162
What you see is a black hole,
418
00:28:52,263 --> 00:28:54,031
which looks really
a little bit like
419
00:28:54,132 --> 00:28:55,599
the entry in the underworld.
420
00:29:18,056 --> 00:29:19,790
And then you dive down.
421
00:29:19,891 --> 00:29:22,126
You need one meter to go down
and then you see...
422
00:29:22,227 --> 00:29:23,927
then you just see the white
of the ice.
423
00:29:26,164 --> 00:29:29,800
But then you come under this,
and then your eyes are looking
424
00:29:29,901 --> 00:29:34,104
in the distance and you have
the idea that you can look
425
00:29:34,205 --> 00:29:37,708
more or less in all directions
without limits.
426
00:29:37,809 --> 00:29:40,244
It's stunning.
427
00:30:00,799 --> 00:30:05,869
The first surprise is how varied
the under-ice landscape is.
428
00:30:15,079 --> 00:30:18,916
The under-ice landscape is full
of colors, full of light,
429
00:30:19,017 --> 00:30:21,718
full of life.
430
00:30:21,820 --> 00:30:23,754
It's like you step
into a forest.
431
00:30:23,855 --> 00:30:26,290
It's very diverse,
and it's beautiful.
432
00:30:28,526 --> 00:30:30,928
On the surface,
a thick layer of snow
433
00:30:31,029 --> 00:30:33,831
makes the floe
look fairly uniform.
434
00:30:33,932 --> 00:30:37,968
But underneath, the scientists
can see that the floe
435
00:30:38,069 --> 00:30:42,005
is really a collage of hundreds
of pieces of ice
436
00:30:42,106 --> 00:30:47,611
of different sizes, shapes,
thicknesses, and ages.
437
00:30:47,712 --> 00:30:49,980
In some areas it's very smooth,
438
00:30:50,081 --> 00:30:53,283
and other areas there's
over-rafted pieces of ice
439
00:30:53,384 --> 00:30:54,751
sticking out.
440
00:30:54,853 --> 00:30:57,387
It's very variable and different
441
00:30:57,488 --> 00:30:58,968
and something new
every time you look.
442
00:31:01,459 --> 00:31:04,628
And, of course, the light is
quite nice because it changes
443
00:31:04,729 --> 00:31:07,998
with the thickness of the ice
in intensity and color.
444
00:31:11,970 --> 00:31:14,238
It's almost like
an out-of-body experience.
445
00:31:16,975 --> 00:31:19,676
Down there under
this cathedral of ice
446
00:31:19,777 --> 00:31:22,880
with all its different colors,
447
00:31:22,981 --> 00:31:25,315
and it's almost
like psychedelic.
448
00:31:26,784 --> 00:31:28,752
Even though it is expected,
449
00:31:28,853 --> 00:31:32,456
they are struck by just
how clear the water is.
450
00:31:32,557 --> 00:31:34,992
It shows that there's
very little phytoplankton
451
00:31:35,093 --> 00:31:36,526
in the water column.
452
00:31:38,630 --> 00:31:42,399
But there are a few krill
in the water,
453
00:31:42,500 --> 00:31:46,203
though they're hard to see.
454
00:31:46,304 --> 00:31:49,840
So the question is,
what are they feeding on?
455
00:32:05,023 --> 00:32:08,892
Larvae are being spawned,
if you like, at the summer
456
00:32:08,993 --> 00:32:11,561
and end of summer, and
so as all the primary production
457
00:32:11,663 --> 00:32:14,331
of phytoplankton is finishing up
in the Antarctic,
458
00:32:14,432 --> 00:32:15,799
that's when they are coming up
459
00:32:15,900 --> 00:32:18,201
and looking for their
first lunch, if you like.
460
00:32:18,303 --> 00:32:20,470
At that time
they have to eat something.
461
00:32:20,571 --> 00:32:23,640
If they don't feed, don't eat
within 15 days, they die.
462
00:32:25,343 --> 00:32:27,911
So I'm really intrigued
to have a good look
463
00:32:28,012 --> 00:32:29,279
at some of the behavior,
464
00:32:29,380 --> 00:32:31,815
the things that we can't
normally see from a dead sample,
465
00:32:31,916 --> 00:32:34,351
to try and understand
a bit more about this puzzle
466
00:32:34,452 --> 00:32:37,354
of larval feeding and how they
get through this period
467
00:32:37,455 --> 00:32:38,622
of food scarcity.
468
00:32:47,432 --> 00:32:50,334
The second day
of diving operations.
469
00:32:50,435 --> 00:32:52,402
But even before the divers
get into the water,
470
00:32:52,503 --> 00:32:55,806
they spot something
quite remarkable.
471
00:32:55,907 --> 00:32:58,942
Thin ice has formed
over the dive hole,
472
00:32:59,043 --> 00:33:02,579
and it gives them a completely
unexpected view of krill
473
00:33:02,680 --> 00:33:05,082
on the underside of the ice.
474
00:33:07,485 --> 00:33:10,187
When I saw the first larvae
under the ice
475
00:33:10,288 --> 00:33:15,392
and how they behaved,
I was really amazed
476
00:33:15,493 --> 00:33:17,594
because you start
to understand the system,
477
00:33:17,695 --> 00:33:19,563
how it works, so why...
478
00:33:19,664 --> 00:33:21,698
why sea ice might be important
for the larvae.
479
00:33:23,568 --> 00:33:25,268
They are actively feeding.
480
00:33:25,370 --> 00:33:27,610
They're scooping something
from the surface of the ice...
481
00:33:27,672 --> 00:33:31,174
It could be bacteria, or it
could be microzooplankton.
482
00:33:31,275 --> 00:33:35,912
The krill appear to be grazing
on an invisible film
483
00:33:36,014 --> 00:33:41,551
of microscopic living material
on the underside of the ice.
484
00:33:41,652 --> 00:33:45,322
We've seen a very thin layer
of ice over the dive hole
485
00:33:45,423 --> 00:33:47,758
and the larvae orientate
themselves upside down to it,
486
00:33:47,859 --> 00:33:51,128
working their way across it,
scraping that biofilm off.
487
00:33:51,229 --> 00:33:54,431
I mean, it's an incredibly
tedious way to feed
488
00:33:54,532 --> 00:33:56,533
but if there's something there
and nothing anywhere else
489
00:33:56,634 --> 00:33:58,802
and you're gonna die if you
don't do it, you go for it.
490
00:33:58,903 --> 00:34:03,707
But how well are the larvae
doing on this meager diet?
491
00:34:03,808 --> 00:34:06,276
To find out,
they need to catch some.
492
00:34:06,377 --> 00:34:09,346
I saw these larvae,
and it was, "Wow!"
493
00:34:09,447 --> 00:34:10,847
And we took samples, of course.
494
00:34:10,948 --> 00:34:13,817
We had a MASMA pump, which
allows us to suck in the larvae
495
00:34:13,918 --> 00:34:16,520
in a very smooth way that they
just, whoosh, get sucked in
496
00:34:16,621 --> 00:34:18,555
and are in perfect
physiological conditions
497
00:34:18,656 --> 00:34:20,590
for further experiments
on board.
498
00:34:23,061 --> 00:34:26,997
This is the first time
that the diver catch the krill.
499
00:34:27,098 --> 00:34:28,832
Oh, komme hier!
500
00:34:28,933 --> 00:34:31,468
Oooh.
501
00:34:31,569 --> 00:34:34,771
And now we were really surprised
that they were there,
502
00:34:34,872 --> 00:34:39,843
and so everybody
was very excited and, yeah,
503
00:34:39,944 --> 00:34:42,112
started with the hunting.
504
00:34:47,418 --> 00:34:49,719
It's quickly apparent
that the behavior they saw
505
00:34:49,821 --> 00:34:53,223
under the dive hole
is not unique.
506
00:34:53,324 --> 00:34:57,127
In every direction the divers
find swarms of krill
507
00:34:57,228 --> 00:34:59,429
doing the same thing.
508
00:34:59,530 --> 00:35:03,400
For me as a krill biologist,
it was absolutely awesome
509
00:35:03,501 --> 00:35:09,106
to see, actually,
how krill larvae really live,
510
00:35:09,207 --> 00:35:11,808
how they live
in their environment...
511
00:35:11,909 --> 00:35:14,377
How they hide during the day
in these little caves
512
00:35:14,479 --> 00:35:16,847
and how they feed
from the ice surface.
513
00:35:16,948 --> 00:35:18,215
It was absolutely beautiful.
514
00:35:21,085 --> 00:35:27,324
That was the first time where I
really saw a big swarm of krill
515
00:35:27,425 --> 00:35:29,559
hanging under the ice.
516
00:35:29,660 --> 00:35:35,298
There were just so many of them,
all closely attached to the ice.
517
00:35:37,335 --> 00:35:39,836
I was really overwhelmed.
518
00:35:39,937 --> 00:35:42,405
When you see the animal
you work with
519
00:35:42,507 --> 00:35:45,575
in their natural environment,
with their natural behavior,
520
00:35:45,676 --> 00:35:48,278
and this is breathtaking.
521
00:35:52,183 --> 00:35:55,018
There are millions of square
kilometers of sea ice
522
00:35:55,119 --> 00:35:56,753
around Antarctica.
523
00:35:56,854 --> 00:35:59,623
If this floe
is in any way typical,
524
00:35:59,724 --> 00:36:03,059
there must be trillions
upon trillions of krill larvae
525
00:36:03,161 --> 00:36:05,896
feeding on the underside
of the ice.
526
00:36:08,733 --> 00:36:11,368
And experiments with the larvae
they've caught
527
00:36:11,469 --> 00:36:14,304
prove the krill are not just
surviving;
528
00:36:14,405 --> 00:36:17,274
they're actually growing.
529
00:36:25,316 --> 00:36:27,918
As krill grow, they molt,
530
00:36:28,019 --> 00:36:30,854
throwing off their old skin
like a snake.
531
00:36:33,758 --> 00:36:35,992
By comparing a molt
with the individual
532
00:36:36,093 --> 00:36:37,694
that has just discarded it,
533
00:36:37,795 --> 00:36:40,897
Rob King can determine
the rate of growth.
534
00:36:42,633 --> 00:36:44,801
What we've found
for this ice station
535
00:36:44,902 --> 00:36:47,671
is that the krill are growing
at about five percent per molt.
536
00:36:50,208 --> 00:36:52,442
So if they're molting
every sort of 20 to 30 days,
537
00:36:52,543 --> 00:36:55,979
that's doing all right for a
krill, considering it's winter.
538
00:36:56,080 --> 00:36:58,748
Typically in summer you can find
them growing
539
00:36:58,849 --> 00:37:00,784
around seven or eight percent,
540
00:37:00,885 --> 00:37:03,453
so these krill that we've got
here were doing very well
541
00:37:03,554 --> 00:37:04,788
until we got them.
542
00:37:06,657 --> 00:37:10,393
But what exactly
are the krill eating?
543
00:37:13,431 --> 00:37:14,898
Scientists have known
for some time
544
00:37:14,999 --> 00:37:18,501
that there's more to sea ice
than just frozen water.
545
00:37:19,971 --> 00:37:23,039
As the Polarstern fights its way
through thick floes
546
00:37:23,140 --> 00:37:25,108
to a second dive location,
547
00:37:25,209 --> 00:37:29,279
what's hidden within the ice
becomes clearly visible.
548
00:37:29,380 --> 00:37:31,081
The floes crack open and turn up
549
00:37:31,182 --> 00:37:33,550
and you can see
down the section.
550
00:37:33,651 --> 00:37:36,152
Some of them are just rich
green-brown colored.
551
00:37:39,290 --> 00:37:43,193
That color is the color
of life...
552
00:37:43,294 --> 00:37:46,730
Phytoplankton in the form
of algae.
553
00:37:46,831 --> 00:37:49,099
I get always excited
when I see this colored ice
554
00:37:49,200 --> 00:37:51,534
because sometimes you have
ice algae biomass
555
00:37:51,636 --> 00:37:55,238
in such high concentration that
actually the ice turns brownish.
556
00:37:56,741 --> 00:37:59,309
These are the pigments
of the algae.
557
00:37:59,410 --> 00:38:02,379
These algae, frozen
into the ice when it formed
558
00:38:02,480 --> 00:38:06,116
at the end of summer,
will play a vital role
559
00:38:06,217 --> 00:38:07,984
in restocking the ocean
with phytoplankton
560
00:38:08,085 --> 00:38:09,419
when the sun returns.
561
00:38:11,489 --> 00:38:13,757
So when that ice melts in summer
562
00:38:13,858 --> 00:38:15,859
and the phytoplankton drop
into the ocean,
563
00:38:15,960 --> 00:38:18,395
the nutrients are there
and off they go... boom!
564
00:38:18,496 --> 00:38:19,863
Off goes the ecosystem.
565
00:38:23,768 --> 00:38:27,237
So the ice actually preserves
the base of the food chain
566
00:38:27,338 --> 00:38:29,873
through the long
Antarctic winter,
567
00:38:29,974 --> 00:38:33,443
ready to bloom again
when summer returns.
568
00:38:36,247 --> 00:38:39,983
This gigantic phytoplankton
Popsicle also helps
569
00:38:40,084 --> 00:38:44,120
to keep krill larvae alive
through the winter,
570
00:38:44,221 --> 00:38:49,159
and that may be why krill
are struggling.
571
00:38:53,631 --> 00:38:56,733
For in their most important
spawning ground,
572
00:38:56,834 --> 00:38:58,201
the Antarctic Peninsula,
573
00:38:58,302 --> 00:39:00,603
the Popsicle is changing.
574
00:39:14,418 --> 00:39:16,586
So we've traveled six
or maybe seven miles
575
00:39:16,687 --> 00:39:19,589
from the British Antarctic
Survey Station at Rothera Point
576
00:39:19,690 --> 00:39:22,359
on the Antarctic Peninsula,
577
00:39:22,460 --> 00:39:25,862
through fields and fields of sea
ice, and we've arrived here.
578
00:39:25,963 --> 00:39:29,099
And this is the Sheldon Glacier.
579
00:39:29,200 --> 00:39:31,167
When I first came here
20 years ago,
580
00:39:31,268 --> 00:39:34,838
the ice that we now see as
this Sheldon Glacier behind us
581
00:39:34,939 --> 00:39:37,307
stretched more than two miles
in that direction.
582
00:39:37,408 --> 00:39:40,543
So not this headland
but the one beyond it
583
00:39:40,644 --> 00:39:43,680
and all the way across the bay
was under ice,
584
00:39:43,781 --> 00:39:45,315
under a glacier.
585
00:39:45,416 --> 00:39:48,051
Maybe 500 feet of ice was here.
586
00:39:48,152 --> 00:39:51,688
So somewhere in the region
of trillions of tons of ice
587
00:39:51,789 --> 00:39:54,190
have disappeared from this bay
588
00:39:54,291 --> 00:39:55,959
and we're now sitting
in open water
589
00:39:58,496 --> 00:40:02,699
And it's absolutely astonishing
to be doing that in the time
590
00:40:02,800 --> 00:40:04,401
that I've been coming
to this station.
591
00:40:04,502 --> 00:40:07,904
It's an absolutely stark
reminder of the change
592
00:40:08,005 --> 00:40:10,540
that we're getting along
the Antarctic Peninsula
593
00:40:10,641 --> 00:40:12,241
following this warming
that we're getting
594
00:40:12,309 --> 00:40:14,110
from climate change.
595
00:40:31,028 --> 00:40:34,431
This area, in about the last
50 years, has warmed up
596
00:40:34,532 --> 00:40:36,065
by seven degrees Celsius.
597
00:40:36,167 --> 00:40:38,868
So that's 11 or 12 degrees
Fahrenheit.
598
00:40:38,969 --> 00:40:40,970
And it's about five times
599
00:40:41,071 --> 00:40:43,606
the global average
temperature change.
600
00:40:43,707 --> 00:40:47,210
And this area is so poised
around the freezing point
601
00:40:47,311 --> 00:40:50,280
that that much change is just
a really profound,
602
00:40:50,381 --> 00:40:52,849
fundamental change
in this system.
603
00:40:54,718 --> 00:40:58,488
The biggest change is not
how far the ice extends.
604
00:40:58,589 --> 00:41:01,925
In fact, the total area of
the Southern Ocean that freezes
605
00:41:02,026 --> 00:41:05,528
in winter has increased slightly
in recent years.
606
00:41:05,629 --> 00:41:08,398
Instead, what's changing
on the peninsula
607
00:41:08,499 --> 00:41:13,970
is how long the ice lasts
and when it forms.
608
00:41:14,071 --> 00:41:19,042
Every year it's freezing later
and melting earlier.
609
00:41:19,143 --> 00:41:22,345
Over the last 30 years since
we've had satellite technology,
610
00:41:22,446 --> 00:41:25,315
what we've seen is the winter
sea ice season,
611
00:41:25,416 --> 00:41:28,218
when it grows out,
is 90 days shorter.
612
00:41:28,319 --> 00:41:31,120
And again if you think of that
from your own perspective
613
00:41:31,222 --> 00:41:33,356
when you're sitting at home
in wintertime
614
00:41:33,457 --> 00:41:34,791
and someone is saying,
615
00:41:34,892 --> 00:41:40,063
"We're going to change winter by
90 days," that's a huge effect.
616
00:41:42,399 --> 00:41:47,537
One effect is on the content
of the sea ice.
617
00:41:47,638 --> 00:41:50,540
If the sea starts to freeze
in late summer,
618
00:41:50,641 --> 00:41:54,911
the ice will incorporate
lots of phytoplankton.
619
00:41:56,514 --> 00:42:00,483
But ice that forms later,
when the days become short
620
00:42:00,584 --> 00:42:02,519
and the phytoplankton has
started to die,
621
00:42:02,620 --> 00:42:04,921
will be different.
622
00:42:05,022 --> 00:42:07,991
It will lack the biomass
that krill larvae need
623
00:42:08,092 --> 00:42:09,692
to survive to adulthood
624
00:42:09,793 --> 00:42:13,796
and complete krill's
reproductive cycle.
625
00:42:13,898 --> 00:42:16,232
The krill need the ice to breed,
626
00:42:16,333 --> 00:42:19,435
and so if you shut it down
you essentially remove
627
00:42:19,537 --> 00:42:21,337
that breeding location.
628
00:42:21,438 --> 00:42:22,772
And then that has an impact
629
00:42:22,873 --> 00:42:24,474
through the rest
of the food web.
630
00:42:26,677 --> 00:42:29,212
So what does the future hold
for krill
631
00:42:29,313 --> 00:42:33,483
and all the other animals
that depend on them?
632
00:42:33,584 --> 00:42:37,887
The answer will lie in how well
krill can adapt
633
00:42:37,988 --> 00:42:40,123
to the shifting ice season.
634
00:42:40,224 --> 00:42:43,560
Will their life cycle and
behavior evolve fast enough
635
00:42:43,661 --> 00:42:45,895
to track a changing climate?
636
00:42:52,169 --> 00:42:54,804
It's six weeks into the voyage,
637
00:42:54,905 --> 00:42:57,040
and the Polarstern scientists
are continuing
638
00:42:57,141 --> 00:43:01,110
their investigation of krill
at a second dive location
639
00:43:01,211 --> 00:43:04,847
700 miles further east
in the Weddell Sea.
640
00:43:08,185 --> 00:43:10,653
They're intrigued
by a fascinating contrast
641
00:43:10,754 --> 00:43:13,790
in krill's daytime
and nighttime behavior.
642
00:43:17,695 --> 00:43:20,396
It was first spotted
by Rob King.
643
00:43:23,901 --> 00:43:26,769
Aboard the ship
Rob and his colleagues
644
00:43:26,870 --> 00:43:28,838
have been experimenting
with a different way
645
00:43:28,939 --> 00:43:29,939
of collecting krill.
646
00:43:34,044 --> 00:43:36,679
They are using
an adapted fish pump,
647
00:43:36,780 --> 00:43:38,214
normally used in fish farming,
648
00:43:38,315 --> 00:43:40,984
to suck krill
directly out of the water
649
00:43:41,085 --> 00:43:45,989
beneath the ship's keel,
at a depth of about 20 feet.
650
00:43:46,090 --> 00:43:49,726
And Rob has noticed
a very surprising pattern
651
00:43:49,827 --> 00:43:52,629
in when he catches krill.
652
00:43:52,730 --> 00:43:54,764
Yes, so we're doing
this around the clock
653
00:43:54,865 --> 00:43:58,001
and we're finding that there's
nothing turning up
654
00:43:58,102 --> 00:44:00,536
for much of the day,
and then at this specific time,
655
00:44:00,638 --> 00:44:04,007
and it was within two minutes
of the same time as last night,
656
00:44:04,108 --> 00:44:06,776
out comes this flood of larvae.
657
00:44:06,877 --> 00:44:09,112
I just wanted to show
that this is the situation
658
00:44:09,213 --> 00:44:10,880
that we found yesterday.
659
00:44:10,981 --> 00:44:15,018
So very exactly at 7:22,
660
00:44:15,119 --> 00:44:17,453
the larvae appeared here
in the fish pump.
661
00:44:17,554 --> 00:44:21,257
And it's a pretty clear signal
exactly at sunset.
662
00:44:21,358 --> 00:44:25,061
And then with sunrise
the signal went off,
663
00:44:25,162 --> 00:44:28,698
so no larvae appeared anymore.
664
00:44:28,799 --> 00:44:31,567
At sunset we have a peak
in catch rate,
665
00:44:31,669 --> 00:44:34,637
and then it falls off
to a sort of one-third level.
666
00:44:34,738 --> 00:44:37,840
And then just before sunrise
we see another peak,
667
00:44:37,941 --> 00:44:39,008
that's the other peak.
668
00:44:39,109 --> 00:44:40,343
And then it drops right off
669
00:44:40,444 --> 00:44:43,279
to maybe only catching one
or no larvae an hour,
670
00:44:43,380 --> 00:44:44,914
compared to the high points,
671
00:44:45,015 --> 00:44:46,683
which are like a hundred
larvae an hour.
672
00:44:46,784 --> 00:44:48,518
So these are big differences.
673
00:44:48,619 --> 00:44:52,288
So what's going on?
674
00:44:54,491 --> 00:44:58,528
Out on the ice,
the divers suggest an answer.
675
00:45:01,331 --> 00:45:05,101
Krill only seem to be associated
with the ice during daylight,
676
00:45:05,202 --> 00:45:09,672
and it seems that once
it starts to get dark,
677
00:45:09,773 --> 00:45:12,675
then they start to pack
their bags
678
00:45:12,776 --> 00:45:14,477
and go back into
the water column.
679
00:45:14,578 --> 00:45:18,381
The divers see signs
of a daily migration
680
00:45:18,482 --> 00:45:20,817
into and out
of the water column,
681
00:45:20,918 --> 00:45:24,787
and hence the reach
of the fish pump.
682
00:45:24,888 --> 00:45:27,557
Having observed that,
we wanted to quantify that
683
00:45:27,658 --> 00:45:28,891
with these transects.
684
00:45:28,992 --> 00:45:31,127
And, therefore,
we dived during the day
685
00:45:31,228 --> 00:45:34,897
and also during the night
doing the exact same transects,
686
00:45:34,998 --> 00:45:36,232
where we follow a line
687
00:45:36,333 --> 00:45:38,968
that has been mounted
under the ice beforehand.
688
00:45:50,514 --> 00:45:53,549
You can see the
different footages.
689
00:45:53,650 --> 00:45:58,221
During midday the krill are
really sitting on the ice
690
00:45:58,322 --> 00:46:00,623
and the little larvae
feeding on the ice.
691
00:46:02,459 --> 00:46:05,962
And then later during the day
between 4:00 and 5:00,
692
00:46:06,063 --> 00:46:11,334
towards sunset,
they start sort of dispersing.
693
00:46:11,435 --> 00:46:15,638
And in all our night dives
we have never seen krill
694
00:46:15,739 --> 00:46:19,342
on the ice... in none of the
areas, none of the dives.
695
00:46:20,878 --> 00:46:23,679
So that's a pretty
straightforward result.
696
00:46:32,623 --> 00:46:36,092
In the daytime hours they are
probably sticking very close
697
00:46:36,193 --> 00:46:39,128
to the ice and not moving away
from it very much
698
00:46:39,229 --> 00:46:41,497
so that they can't be taken
by predators very easily.
699
00:46:41,598 --> 00:46:45,134
And then at nighttime they can
come out of those areas,
700
00:46:45,235 --> 00:46:47,336
because it's harder for
predators to see them,
701
00:46:47,437 --> 00:46:49,338
and they can feed in the open
water as well.
702
00:46:53,744 --> 00:46:57,213
Under the ice,
light levels vary a lot,
703
00:46:57,314 --> 00:46:59,315
depending not just
on the time of day,
704
00:46:59,416 --> 00:47:02,285
but on the thickness of the ice
and even the weather.
705
00:47:05,422 --> 00:47:09,225
But the daily migration of krill
from the ice to the water column
706
00:47:09,326 --> 00:47:12,328
is strikingly punctual.
707
00:47:12,429 --> 00:47:14,497
The numbers we get each night
are different,
708
00:47:14,598 --> 00:47:17,733
but we see this clear start.
709
00:47:17,835 --> 00:47:19,735
And the question
we're interested in is,
710
00:47:19,837 --> 00:47:22,171
is there a clock
running in these animals?
711
00:47:26,810 --> 00:47:29,779
The circadian clock is
the clock that controls
712
00:47:29,880 --> 00:47:31,314
sleeping and waking
713
00:47:31,415 --> 00:47:33,950
and those really sort of basic
behaviors in humans.
714
00:47:34,051 --> 00:47:36,552
But it also works
in other animals as well.
715
00:47:36,653 --> 00:47:40,656
It looks as if kri's daily
feeding patterns are controlled
716
00:47:40,757 --> 00:47:43,726
by an internal circadian clock
717
00:47:43,827 --> 00:47:46,562
that is regulated
by exposure to light.
718
00:47:49,800 --> 00:47:52,468
But everywhere on Earth,
except near the equator,
719
00:47:52,569 --> 00:47:56,138
the length of the day
varies with the seasons.
720
00:47:56,240 --> 00:47:59,675
So in many species the circadian
clock has a second,
721
00:47:59,776 --> 00:48:06,048
equally vital function:
it controls seasonal behavior.
722
00:48:06,149 --> 00:48:07,683
Because if you see
723
00:48:07,784 --> 00:48:09,919
what the circadian clock
basically is doing,
724
00:48:10,020 --> 00:48:11,921
it's measuring day length.
725
00:48:12,022 --> 00:48:15,424
So if over the season
day length is changing,
726
00:48:15,525 --> 00:48:19,262
the circadian clock can perceive
that, can measure that.
727
00:48:23,467 --> 00:48:26,235
But obviously day length is
not something that's affected
728
00:48:26,336 --> 00:48:29,238
by climate change.
729
00:48:29,339 --> 00:48:32,074
So if krill's seasonal breeding
behavior is controlled
730
00:48:32,175 --> 00:48:35,044
by day length,
rather than a climatic variable
731
00:48:35,145 --> 00:48:38,214
like temperature, that could
make it much more difficult
732
00:48:38,315 --> 00:48:40,416
for them to track
the shifting ice season.
733
00:48:45,989 --> 00:48:50,459
All the organisms in this
ecosystem have their life cycles
734
00:48:50,560 --> 00:48:53,162
synchronized and attuned
and adapted
735
00:48:53,263 --> 00:48:55,431
to the rhythm of the sea ice.
736
00:48:55,532 --> 00:48:57,800
And what's happening now
with climate change
737
00:48:57,901 --> 00:48:59,735
is that that's changing...
738
00:48:59,836 --> 00:49:03,105
The duration of sea ice
is getting less over time.
739
00:49:03,206 --> 00:49:06,108
So it advances later
and it retreats earlier,
740
00:49:06,209 --> 00:49:09,111
and, of course, the organisms
are pretty hardwired
741
00:49:09,212 --> 00:49:11,113
to that original timing.
742
00:49:12,783 --> 00:49:15,051
And so as the sea ice changes,
743
00:49:15,152 --> 00:49:17,853
literally the habitat of
the krill and other organisms
744
00:49:17,955 --> 00:49:20,156
is melting away.
745
00:49:31,902 --> 00:49:35,604
Polarster and her scientists
have spent six weeks
746
00:49:35,706 --> 00:49:37,273
in the winter pack ice.
747
00:49:37,374 --> 00:49:40,409
It's time to head north again.
748
00:49:43,847 --> 00:49:47,183
There's one last series
of dives,
749
00:49:47,284 --> 00:49:49,552
to observe krill
in the marginal ice zone.
750
00:49:59,196 --> 00:50:02,098
The scientists have learned
a lot about the importance
751
00:50:02,199 --> 00:50:03,799
of sea ice to krill
752
00:50:03,900 --> 00:50:07,269
and how that has made them
vulnerable to the climate change
753
00:50:07,371 --> 00:50:10,439
caused mainly by our burning
of fossil fuels.
754
00:50:13,210 --> 00:50:16,712
It took the Earth tens of
millions of years to make oil,
755
00:50:16,813 --> 00:50:21,417
and humans will have burned it
in a few hundred years.
756
00:50:21,518 --> 00:50:23,352
That experiment has happened,
757
00:50:23,453 --> 00:50:27,456
and now we're going to see where
that experiment's gonna take us.
758
00:50:29,159 --> 00:50:32,228
Krill will find it hard
to change their behavior.
759
00:50:34,798 --> 00:50:39,135
So the question is,
can we change ours?
760
00:50:44,408 --> 00:50:47,743
I think the really important
thing to get hold of
761
00:50:47,844 --> 00:50:52,615
is that we are at a point now
where we can understand
762
00:50:52,716 --> 00:50:56,118
our ecosystem like we've never
understood it before,
763
00:50:56,219 --> 00:50:58,354
and we really need
to pay attention
764
00:50:58,455 --> 00:51:00,122
to what we're learning from it.
765
00:51:02,426 --> 00:51:04,260
That was stunning.
766
00:51:04,361 --> 00:51:09,632
Hundreds of millions of larvae
hanging around under the ice,
767
00:51:09,733 --> 00:51:13,169
all in caves
and sheltered areas.
768
00:51:13,270 --> 00:51:16,739
Swarms and swarms full of larvae
sheltered away.
769
00:51:16,840 --> 00:51:19,708
Super, super cool dive.
770
00:51:19,810 --> 00:51:23,179
Really one of the best I did.
771
00:51:23,280 --> 00:51:24,847
Just stunning.
772
00:52:06,423 --> 00:52:08,224
On NOVA...
773
00:52:22,839 --> 00:52:25,608
This NOVA program
is available on DVD.
774
00:52:25,709 --> 00:52:31,147
To order, visit shopPBS.org,
or call 1-800-PLAY-PBS.
775
00:52:31,248 --> 00:52:33,849
NOVA is also available
for download on iTunes.