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  • [♪ INTRO]

  • Life in the ocean is a little  different than it is up here.

  • For one thing, water holds onto heat a lot  better than air, so temperatures tend to

  • stay the same from day to day rather  than fluctuating with the sun.

  • But this doesn't mean that ocean-dwelling  organisms are less susceptible to rising

  • temperatures brought about by the climate crisis.

  • In fact, most marine critters  are adapted to live at a

  • very narrow temperature range, so even  a tiny change can quickly spell trouble.

  • And we might not have  understood just how much trouble

  • without the help of an unassuming little snail.

  • The threeline mud snail is a smallspiral-shelled snail commonly found

  • crawling around beneath the waves  on the North Atlantic seafloor.

  • While the adults spend their  lives on the bottom of the ocean,

  • their larvae start out life  swimming around up in the water.

  • These babies are so small that they are at the

  • mercy of the waves and ocean currents.

  • This snail species typically spawns  in the summer, when the water

  • temperatures warm up enough to signal to  their bodies that it's baby-making time.

  • And the summertime ocean currents in the  North Atlantic gently tow the freshly

  • hatched larvae out to cooler, deeper  waters found at the edge of the continental

  • shelf, where the babies can then feed, grow and

  • eventually settle onto the  seafloor as adult snails.

  • However, in a 2020 study, researchers  from Rutgers University uncovered

  • a disturbing trend happening with  the threeline mudsnail, along with

  • potentially dozens of other bottom-dwelling  species living in the North Atlantic.

  • They found that this little snail  was missing from the deeper,

  • colder waters of the North Atlantic outer shelf.

  • They expected to see increasing  populations of these creatures

  • in the deeper waters because the  deep waters are places of refuge.

  • They're cooler than the shallow waters,

  • whose temperatures have risen  dramatically in recent years.

  • Instead, the researchers  found higher populations of

  • these snails in the warmer waters close to shore.

  • Which is not good, because remember, most marine

  • creatures are adapted to survive  at narrow temperature ranges.

  • And the baby mud snails are particularly fragile.

  • They're less likely to make it to adulthood  in warm waters than colder waters.

  • The researchers believe that  this shift in habitat is an

  • unexpected consequence of climate change.

  • But this is not something  the snail is choosing to do.

  • See, in response to changing temperatures,

  • some organisms choose to travel north or south

  • toward the poles to seek refuge in cooler waters.

  • But these snails are too small to travel that far.

  • Instead, the snail's physiology makes  them easily influenced by changes in the

  • ocean's physics, and it's making them  migrate in the completely wrong direction.

  • First, their spawning behavior is  temperature dependent, so when the ocean

  • waters warm earlier in the year, they  trigger an earlier spawning event.

  • This means those little baby snails  are floating around in the water in

  • the springtime instead of in the summer.

  • And the currents in the North Atlantic vary  throughout the year, changing directions

  • depending on the prevailing winds,

  • as well as the amount of water running  into the ocean from the rivers on land.

  • Which leads to the second issue:

  • the baby snails are being pushed  around by springtime ocean currents,

  • which are different from summertime currents.

  • The spring currents funnel  these babies towards the shore

  • instead of away from it, as they do in the summer.

  • And the waters closer to  shore are shallower and warmer

  • than the deeper edge of the shelf waters.

  • That means fewer babies will survive to adulthood,

  • and the survivors will spend the rest of  their lives at those higher temperatures.

  • Which means that those adults will  spawn even earlier in the year than past

  • generations, trapping the threeline  mud snail in a feedback loop

  • that they cannot escape from.

  • This unfortunate circumstance could  spell the beginning of the end for

  • the threeline mud snail, and  potentially several other

  • bottom-dwelling North Atlantic species.

  • That's because other seafloor-dwellerslike sea stars, clams, and worms,

  • have similar spawning and larval  behavior to the threeline mud snail.

  • In fact, researchers have  found that since the 1960's,

  • around 80% of bottom-dwelling  species have disappeared from

  • the deep waters of North Atlantic,

  • potentially all unwilling victims of  this wrong-way migration phenomenon.

  • And it may not be justNorth Atlantic occurrence.

  • This could be happening in other  locations around the world.

  • Through no fault or choice of  their own, bottom-dwelling species

  • are being pushed to the limits of their  survival, thanks to the climate crisis.

  • But at least this is helping us to understand  the many unexpected ways the climate

  • crisis can affect the creatures  who share the planet with us.

  • And maybe help us understand how to help them.

  • If you like learning more about the

  • surprising things the world  around us has to offer,

  • you might enjoy a course from Brilliant.

  • They're overhauling some of their classic  courses to be even more interactive.

  • Like Algorithm Fundamentals, which  requires no prior coding experience.

  • They make it easy to learn  how to make your computer

  • do what you want with  rearrangeable blocks of code.

  • If you're interested, you can get started at

  • brilliant.org/scishow to get 20%  off an annual Premium subscription.

  • And checking them out helps us too, so thank you.

  • [♪ OUTRO]

Thanks to Brilliant for supporting  this episode of SciShow.

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B2 中高級 美國腔

由氣候變化引起的錯誤移民的故事(A Story of Wrong-Way Migration, Caused By Climate Change)

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    rebecca 發佈於 2021 年 09 月 21 日
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