This is me.
I'm about to go scuba diving
for the first time ever.
I went in expecting muffled peace and quiet.
I mean, one of the earliest documentaries
on underwater life was literally called “The
Silent World”.
“They roamed deep under the Mediterranean,
the Red Sea, and the Indian Ocean, in a mysterious
realm, a silent world.”
But as soon as I got down a few yards, I couldn't
help but notice sound all around me.
It was hard to tell what direction it was
coming from, or how far away it was.
It was coming from boats above me.
As far as I can tell, the Earth’s water
is not as quiet as I thought.
I’ve been binging this podcast all about
sound, and they've been looking into this too
"From DeFacto Sound, you’re listening to
Twenty Thousand Hertz: The stories behind the
world’s most recognizable and interesting
sounds.
I’m Dallas Taylor."
So Dallas — life underwater can be pretty
loud, right?
It can!
Just listen to these toadfish— they oscillate
their swim bladders to make sounds that are
loud enough to keep houseboat residents in
Sausalito, California up at night.
Or these Barred Grunt fish, that make a grinding
sound with the teeth in their gullet.
Or these snapping shrimp — they produce a sound by creating
tiny popping bubbles with their claws.
It’s been measured at 200 decibels.
That’s louder than a gunshot.
Light doesn’t penetrate very deep in water,
so a lot of ocean life has evolved to use
sound as its primary sense.
Because water particles are more densely packed
together than air, sound travels farther and
faster in water.
That makes it an efficient medium of communication
at any depth or time of day.
“Let's say we had 440, like the middle
key of your piano, or whatever.”
That’s John Hildebrand, he’s a professor
at the Scripps Institution of Oceanography.
He's an expert in the field of underwater
sound and how it’s used by and how it affects
marine mammals.
“If you looked at the wavelength of that
sound in air, that note, the 440 note, would
be a little bit less than a meter long.
In water, it's more like several meters
long.”
What that means is that noise travels about
four times faster and farther in water than
it does in air.
In an experiment in 1991, sound emitted from
Heard Island was picked up at 16 sites in
the Atlantic, Pacific, and Indian Oceans.
It turns out that one of the most common noises
in the entire ocean that can be picked up
almost anywhere these days, sounds like this:
It's the sound of boats.
Noise from ship traffic has doubled every
decade since the 1960s.
“Basically, anywhere you go, the ambient
noise in the ocean is dominated by anthropogenic
sound.”
“Let's say I made a measurement 30 years
ago and now if I went to the same place and
made the same measurement, it would be 10
dBs or more higher sound level than what I
measured when I started my career.
That’s spooky.”
That’s a huge problem for animals that use
sound as their primary sense.
Just listen to this audio of how noise from
a passing boat totally drowns out dolphin
communication.
But arguably the worst culprit of underwater
sound pollution is a process that sounds like this:
This is seismic surveying.
It’s a process that allows companies to
locate spots on the ocean floor where they
can drill for fossil fuels.
Boats with about 30-40 airguns that all go
off at once will move back and forth over large
parts of the ocean.
Bubbles from the horns expand and contract
typically every 10 seconds, creating a huge
amount of acoustic energy that maps geological
structures deep in the ocean floor.
And it’s about as loud as a jet at takeoff.
This can go on for weeks at a time.
A study of seismic survey noise between 1999
and 2009 found that airgun sounds were recorded
almost 2500 miles away from the survey ship
itself.
At some locations, they were recorded on 80
percent of days for over a year.
And that changes how animals behave.
A study by the Institute of Marine Science
at the University of North Carolina found
that reef fish abundance decreased by 78 percent
during seismic surveying.
This is what the reef looked like before seismic
surveying in the area.
And this is what it looked like after.
“Seismic surveying is a constroversial topic at the
coast
and new research is only adding to the conversation.
“One of those impacted is local fisherman
Jack Cox.
He’s seen firsthand the impact seismic
surveying has on fish.”
“It does something, that — we just don’t catch fish.
For animals like whales — who rely on complex
sound communication systems to socialize,
find food, and mate — that poses a huge
problem.
If you watch this heat map from a study of
endangered North Atlantic right whales, you
can see that shipping paths near Boston squeeze
the whales into a tiny space where communication
is possible — it's about a third of what
it was without the ships.
Susan Parks, a biology professor at Syracuse,
recorded right whale sounds throughout the
early 2000s.
And when she compared her audio to some that had
been recorded in 1956, she noticed that the
older sounds were much deeper than her high-pitched
recordings.
It turns out that the whales had started calling
at higher and higher frequencies in order
to hear each other over the hum of ship noise.
Apart from habitat displacement and communication
changes, there’s also evidence that boat
noise simply stresses these whales out.
After the September 11th attacks, researchers
in Canada’s Bay of Fundy compared underwater
noise levels during a period of reduced ship
traffic to the stress-related hormone levels
in the right whale population.
They discovered a 6 decibel noise decrease
in the bay after 9/11, which correlated to
lower baseline levels of stress related hormones.
Effects like this go all the way down the
food chain.
A 2017 study found that there were two to
three times more dead zooplankton after after
a day of blasts from a single airgun.
And the larvae of krill, which whales rely
on for food, were totally destroyed.
In April 2017, Donald Trump signed an executive
order to open offshore drilling in the Atlantic.
It directed the Interior Department to consider
allowing seismic exploration by 5 companies
that had been blocked under the Obama administration.
It’s getting widespread pushback in Congress
— there’s a bipartisan House bill and
Democrat-led Senate bill to ban seismic testing
— but if those authorizations go through,
companies could be conducting seismic testing
in the Atlantic by Fall 2017.
So… is there any good news?
Yes, there is.
In 2014, the International Maritime Organization
adopted guidelines for reducing commercial
ship noise levels with things like noise-muffling
propellers and insulated engines — though
they’re not mandatory yet.
A year later, the US Navy agreed to limit
sonar testing — which has been linked to
whales stranding themselves on beaches in
habitats near Southern California and Hawaii
— following a lawsuit from environmental
groups.
And in June 2016, the National Oceanic and
Atmospheric Administration laid out an Ocean
Noise Strategy Roadmap.
It’s the start of a 10-year plan to assess
the human impact on underwater sound and the
measures required to reduce it.
Seismic surveys can work better, too.
Norway has started multi-client surveys, so
that seismic data from a particular area is
only collected once.
US authorities are considering a similar process.
The ocean is huge.
We’ve explored less than 5 percent of it
so far.
So it’s easy to forget that what we do on
the surface affects everything down below.
But like plastic, chemicals, and waste, noise
pollutes our oceans.
Understanding that is key to doing our part
to protect it.
Thank you so much for watching, we loved doing
this collaboration with Twenty Thousand Hertz.
They create super highly produced podcasts that tell stories all about sound.
If you enjoyed this video, you should absolutely go check out their podcast on the exact same topic.
You can find that and subscribe at applepodcasts.com/20k.
