The discoveries awaiting us in the oceans twilight zone Heidi M. Sosik
I bet all of you are familiar
with this view of the ocean,
but the thing is,
most of the ocean looks nothing like this.
Below the sunlit surface waters,
there’s an otherworldly realm
known as the twilight zone.
At 200 to 1,000 meters below the surface,
sunlight is barely a glimmer.
Tiny particles swirl down
through the darkness
while flashes of bioluminescence
give us a clue that
these waters teem with life:
microbes, plankton, fish.
Everything that lives here
has amazing adaptations
for the challenges
of such an extreme environment.
These animals help support
top predators such as whales, tuna,
swordfish and sharks.
There could be 10 times
more fish biomass here
than previously thought.
In fact, maybe more
than all the rest of the ocean combined.
There are countless
undiscovered species in deep waters,
and life in the twilight zone
is intertwined with earth’s climate.
Yet the twilight zone
is virtually unexplored.
There are so many things
we still don’t know about it.
I think we can change that.
I was drawn to oceanography
by just this kind of challenge.
To me it represents
the perfect intersection
of science, technology and the unknown,
the spark for so many breakthrough
discoveries about life on our planet.
As a college student,
I went on an expedition
across the Atlantic
with a team of scientists
using a high-powered laser
to measure microscopic algae.
The wild thing that happened on that trip
is that we discovered what everyone
who looked before had completely missed:
photosynthetic cells
smaller than anyone thought possible.
We now know those tiny cells
are the most abundant
photosynthetic organisms on earth.
This amazing discovery happened
because we used new technology
to see life in the ocean in a new way.
I am convinced that the discoveries
awaiting us in the twilight zone
will be just as breathtaking.
We know so little about the twilight zone
because it’s difficult to study.
It’s exceedingly large,
spanning from the Arctic
to the Southern Ocean
and around the globe.
It’s different from place to place.
It changes quickly
as the water and animals move.
And it’s deep and dark and cold,
and the pressures there are enormous.
What we do know is fascinating.
You may be imagining
huge monsters lurking in the deep sea,
but most of the animals are very small,
like this lantern fish.
And this fierce-looking fish
is called a bristlemouth.
Believe it or not, these are the most
abundant vertebrates on earth
and many are so small
that a dozen could fit in this one tube.
It gets even more interesting,
because small size does not stop them
from being powerful through sheer number.
Deep, penetrating sonar shows us
that the animals form dense layers.
You can see what I mean
by the red and yellow colors
around 400 meters in these data.
So much sound bounces off this layer,
it’s been mistaken for the ocean bottom.
But if we look, it can’t be,
because the layer is deep during the day,
it rises up at night
and the pattern repeats day after day.
This is actually the largest
animal migration on earth.
It happens around the globe every day,
sweeping through the world’s oceans
in a massive living wave
as twilight zone inhabitants
travel hundreds of meters
to surface waters to feed at night
and return to the relative safety
of deeper, darker waters during the day.
These animals and their movements
help connect the surface and deep ocean
in important ways.
The animals feed near the surface,
they bring carbon in their food
into the deep waters,
where some of that carbon can stay behind
and remain isolated from the atmosphere
for hundreds or even thousands of years.
In this way, the migration
may help keep carbon dioxide
out of our atmosphere
and limit the effects
of global warming on our climate.
But we still have many questions.
We don’t know which species are migrating,
what they’re finding to eat,
who is trying to eat them
or how much carbon
they are able to transport.
So I’m a scientist
who studies life in the ocean.
For me, curiosity about these things
is a powerful driver,
but there’s more to the motivation here.
We need to answer these questions
and answer them quickly,
because the twilight zone is under threat.
Factory ships in the open ocean
have been vacuuming up
hundreds of thousands of tons of small,
shrimp-like animals called krill.
The animals are ground into fish meal
to support increasing demands
for aquaculture
and for nutraceuticals such as krill oil.
Industry is on the brink
of deepening fisheries such as these
into the mid-water
in what could start
a kind of twilight zone gold rush
operating outside the reach
of national fishing regulations.
This could have irreversible
global-scale impacts
on marine life and food webs.
We need to get out
ahead of fishing impacts
and work to understand
this critical part of the ocean.
At Woods Hole Oceanographic Institution,
I’m really fortunate to be surrounded
by colleagues who share this passion.
Together, we are ready
to launch a large-scale exploration
of the twilight zone.
We have a plan to begin right away
with expeditions in the North Atlantic,
where we’ll tackle the big challenges
of observing and studying
the twilight zone’s remarkable diversity.
This kind of multiscale,
multidimensional exploration
means we need to integrate
new technologies.
Let me show you a recent example
that has changed our thinking.
Satellite tracking devices
on animals such as sharks
are now showing us that many top predators
regularly dive deep
into the twilight zone to feed.
And when we map their swimming patterns
and compare them to satellite data,
we find that their feeding hot spots
are linked to ocean currents
and other features.
We used to think these animals
found all of their food in surface waters.
We now believe they depend
on the twilight zone.
But we still need to figure out
how they find the best areas to feed,
what they’re eating there
and how much their diets depend
on twilight zone species.
We will also need new technologies
to explore the links with climate.
Remember these particles?
Some of them are produced
by gelatinous animals called salps.
Salps are like superefficient
vacuum cleaners,
slurping up plankton and producing
fast-sinking pellets of poop –
try saying that 10 times fast –
pellets of poop that carry carbon
deep into the ocean.
We sometimes find salps
in enormous swarms.
We need to know where
and when and why and whether
this kind of carbon sink
has a big impact on earth’s climate.
To meet these challenges, we will need
to push the limits of technology.
We will deploy cameras
and samplers on smart robots
to patrol the depths and help us track
the secret lives of animals like salps.
We will use advanced sonar
to figure out how many fish
and other animals are down there.
We will sequence DNA from the environment
in a kind of forensic analysis
to figure out which species are there
and what they are eating.
With so much that’s still
unknown about the twilight zone,
there’s an almost unlimited
opportunity for new discovery.
Just look at these beautiful,
fascinating creatures.
We barely know them.
And imagine how many more
are just down there waiting
for our new technologies to see them.
The excitement level about this
could not be higher on our team
of ocean scientists,
engineers and communicators.
There is also a deep sense of urgency.
We can’t turn back the clock
on decades of overfishing
in countless regions of the ocean
that once seemed inexhaustible.
How amazing would it be
to take a different path this time?
The twilight zone
is truly a global commons.
We need to first know and understand it
before we can be responsible stewards
and hope to fish it sustainably.
This is not just a journey for scientists,
it is for all of us,
because the decisions we collectively make
over the next decade
will affect what the ocean looks like
for centuries to come.
Thank you.
(Applause)