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  • [♪ INTRO]

  • Once you've smelled the ocean, you can't un-smell it.

  • That sort of sharp, sometimes eggy odor is just that distinctive.

  • And it also plays a big role in ecology and maybe even in the climate!

  • Because sure, there's salt and that whiff of dead fish, but the key ingredient

  • in this smell is something you probably wouldn't expect: exploding plankton.

  • Collectively, the tiny plant-like organisms floating in the

  • sunlit layer of the ocean are called phytoplankton.

  • And they, as well as certain bacteria,

  • make a chemical compound called DMSP.

  • Among other reasons, phytoplankton make DMSP

  • to help protect themselves from too much UV radiation,

  • balance the water content in their cells, and even deter predators.

  • But sometimes, no amount of this compound

  • will prevent them from being a tasty snack.

  • And that's where the fun begins.

  • When something like a hungry predator comes along

  • and breaks open a phytoplankton cell,

  • the DMSP is released from the cell into the water.

  • And there, it becomes an important food source to microbes.

  • As the microbes graze on the DSMP, they ultimately break it down into

  • smaller molecules such as dimethyl sulfide, or DMS.

  • Thesulfidepart means it contains the element sulfur,

  • and that's what gives the ocean its unmistakable odor.

  • It's a bunch of microbes breaking down their food!

  • Now, in some places, this sea smell can be really pungent,

  • leaning towards the rotten eggs end of the spectrum

  • while in other locations, you might barely catch a whiff.

  • The difference depends on how many phytoplankton live in the area.

  • Specifically, it takes a group of actively-growing phytoplankton,

  • called a bloom, to ultimately make a strong odor.

  • The larger the bloom, the more DMSP there is for microbes to break down,

  • and the stronger the sulfur smell.

  • And it's not just humans that notice it.

  • Animals from seabirds to seals to whale sharks

  • will follow the scent to track down their next meal.

  • That's because their prey, such as fish and zooplankton,

  • can often be found chowing down on the phytoplankton that make up a bloom.

  • But there's actually another story here, toobecause DMS in particular

  • also plays another, more surprising role on Earth: helping to form clouds.

  • DMS is the largest source of biologically-produced sulfur on our planet, and,

  • since it's a gas, it quickly makes its way into the atmosphere.

  • On the way there, it goes through chemical reactions

  • to become a variety of sulfur compounds.

  • Then, these compounds act as condensation nuclei in the atmosphere,

  • which means they're something water vapor can collect on to form a cloud.

  • And clouds can have a surprisingly large effect on the climate!

  • Like, fluffy white clouds reflect sunlight back to space,

  • which helps keep the planet cool.

  • At the same time, through the process of photosynthesis,

  • phytoplankton are also removing carbon dioxide from the atmosphere.

  • So, in a way, these tiny creatures are some of the Earth's

  • most important climate regulators.

  • And the process is self-reinforcing: absorbing more CO2 means more energy

  • for bigger phytoplankton blooms, which then produce more DMS

  • and more cloudsas a result.

  • Unfortunately, like other important climate processes,

  • things are starting to get a little out of balance.

  • As the oceans absorb more of the carbon dioxide we're emitting,

  • they're becoming increasingly acidic.

  • And that's not good for phytoplankton growth or the production of DMS.

  • So, ultimately, scientists have a lot left to learn about the complex interplay

  • between the ocean, life, and our atmosphere, and how it will change in the future.

  • One thing is for certain, though: the smell of the sea is unforgettable.

  • If you like learning about things like this,

  • you might also want to try today's Daily Challenges from Brilliant!

  • They release multiple new ones every day

  • to help you freshen up your math and science skills.

  • But if it's been a while since your last STEM class, don't worry

  • they also give you all the context you need to solve the problem.

  • And if you're super into it, each Daily Challenge also has

  • a related Brilliant course that explains the same concept in more detail.

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  • [♪ OUTRO]

Thanks to Brilliant for supporting this episode of SciShow.


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B2 中高級 美國腔

Why Does the Ocean Smell Like That?

  • 5 0
    Miho Ishii 發佈於 2021 年 01 月 27 日