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Commercial whaling was really bad for whales, especially sperm whales.

People killed so many of them in the 19th and 20th centuries that even 10 years after hunting was stopped,

there were less than a third as many sperm whales as there were before. 

And their populations are still recovering today.

But not only did whaling land sperm whales on the endangered species list,

it may have caused some major problems for us too, by making climate change worse.

And that's because all those whales were helping cool the planet by doing a lot of

what every animal does best: pooping. 

While the blue whale is the largest whale in the ocean, sperm whales aren't exactly tiny.

They grow to be up to 18 meters long and weigh around 35 thousand kilograms! 

And, no surprise here, they need to eat a lot to reach such massive proportions.

Each whale consumes around 200 tons of food a year.

Yes, I said each whale.  

Luckily, they are excellent divers, so they can feast on the buffet of creatures,

like squid and octopus, that live thousands of meters down.

These yummy critters are full of nutrients, including iron, something not always easy

to come by in the ocean.

They have tons of it because it gets bound up in the dark pigment in their ink.

And I promise that's not just a fun fact, it will become important in a moment.

Now, while sperm whales eat most of their food in the dark depths, they do all their other business at the surface.

That's because, when they're diving, their bodies shut down all non-essential functions to conserve oxygen.

And that includes expelling waste.

Also, it just so happens their poop is super loose and runny.  Which is a lovely visual!

Point is, because of its consistency, it floats around at the top of the water, instead of sinking.

And these floating, watery feces are packed full of iron because the whales don't need

all the stuff they get from those deep sea noms.

About 90 percent of it gets pooped out. You know what does need iron? Plants.

It's an essential nutrient for photosynthesis.

So all the tiny photosynthesizers that live in the ocean — collectively known as phytoplankton, love iron.

They don't care if it's from runny whale poop.

In fact, in some spots in the ocean, these tiny plants literally can't get enough of the stuff.

The dissolved iron in the water is so low that it keeps their populations from growing. 

That's because they require a specific form of iron called iron 2 that can easily dissolve in water.

And most iron 2 makes its way to the ocean via dust.

So places far from dusty lands, like the Southern Ocean that surrounds Antarctica, are extremely low in dissolved iron.

But whales can help with that!

Whales that live in low iron waters are like giant ocean crop dusters, fertilizing the water with their iron-rich poop.

When a bunch of iron becomes available, the phytoplankton reproduce like it's going out of style. 

They can double their numbers in a single day, creating swirls of green visible from space! 

We call this a bloom. These blooms do a bunch of photosynthesizing, so they build tons of sugar out of carbon dioxide and water. 

That means they suck up lots of dissolved carbon dioxide, carbon dioxide that went into the water from the air. 

These blooms end up feeding all sorts of ocean creatures, from microscopic animals to filter-feeding whales.

Eventually, though, all that yummy iron gets used up, and any phytoplankton that aren't eaten die.

At this point, the carbon in their bodies could get broken down by microbes and return to the atmosphere as CO2. 

But most of it sinks too quickly for that, so it ends up on the bottom of the ocean instead. 

And once it's down there, it stays down there.

That carbon gets trapped for a really long time, like, thousands of years or more.

So, the ultimate effect of whales pooping is less carbon dioxide in our atmosphere!

But it couldn't be that much, right?

Well, in 2010, researchers actually crunched the numbers to figure out just how much carbon

the 12,000 sperm whales living in the Southern Ocean were helping store.

They found that while these whales breathe out around 160,000 tons of carbon per year,

their poop fertilizes 400,000 tons of carbon storage.

That's a net storage of 240,000 tons a year!

Now, this is a drop in the bucket compared to the billions of tons of carbon humans pump into the air every year. 

So Southern Ocean sperm whales aren't making much of a dent in our climate problem all by themselves.

But they aren't the only whales in the Southern Ocean, and researchers believe that other

species found there may be doing the same thing. 

Also, there used to be over one million sperm whales worldwide before commercial whaling.

Just imagine the carbon storage potential if their populations rebounded to that level!

And we're working on that. 

Sperm whales are currently protected in the US under the Endangered Species Act and the Marine Mammal Protection Act,

and listed under the Convention on International Trade in Endangered Species of Wild Fauna and Flora.

And conservation groups continue to push for legislation to protect the animals, as well as

encourage companies to adopt whale-safe fishing gear and shipping practices and reduce ocean noise pollution.

So, the whales are already doing their part to combat climate change.

Now, thanks to science, we know that by helping them bounce back, we can do ours. 

And that's not the only reason this kind of research is important! 

It also helps us understand how ocean ecosystems function as a whole, and how quickly that

delicate balance can be disrupted. 

And that's just plain old important science right there!

Thanks for watching this episode of SciShow!

And thanks especially, to today's sponsor, Brilliant. 

Brilliant strives to make learning fun, they also offer dozens of interactive STEM courses through their website and app.

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how scientists make decisions with limited data.

Statistics is one of the most important things in the world to understand!

But they've also got an entire library of math courses!

So you can learn how to best determine things like how much poop 12,000 whales make without

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