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Thanks to Brilliant for supporting this episode of SciShow.
感谢Brilliant对本期节目的支持。
Go to Brilliant.org/SciShow to learn how you can take your chemistry skills to the next level this year!
登录Brilliant.org/SciShow学习如何让你的化学知识在今年更上一层楼！
Fish-eating trees sound like they're straight out of science fiction.
吃鱼的树，听起来像是科幻小说里的走出来的。
But they're a real thing—one that exists right here on Earth.
但是它们确实存在——就存在于地球。
In many forests on the west coast of North America, the trees eat salmon.
在北美西海岸的许多森林里，树以鲑鱼为食。
And they show just how interconnected life on this planet is.
它们展示了这个星球上的生命是如何相互联系的。
Now, when we say they "eat" fish, we don't mean they've developed a mouth full of pointy teeth
说它们‘吃’鱼，并不是指它们长出了满嘴尖牙
or razor-sharp claws to pluck a swimming salmon from the water.
或能够水中捕捞鲑鱼的锋利爪子。
What we mean is that the trees obtain a large portion of their nutrients from fish.
我们的意思是，这些树从鱼身上获取大量的营养。
And they can do that because bears that do have pointy teeth and sharp claws catch the fish for them!
它们可以这样做，是因为熊有尖尖的牙齿和锋利的爪子为它们抓鱼！
When salmon are ready to spawn, they make a one-way trip from the ocean up into streams to lay their eggs.
鲑鱼准备产卵时，它们会从海洋出发，一路游到溪流产卵。
This is an all you can eat buffet for bears that feast on the salmon to get ready for their long winter hibernation. But bears are messy eaters.
这些是熊的自助餐，它们以鲑鱼为大餐，为漫长的冬季冬眠做准备。但熊是邋遢的食客。
For example, in two months, on a single stream, they left over 5000 kg of salmon scraps along the river banks and up into the trees!
例如，在两个月的时间里，仅在一条小溪中，它们就在河岸上和树上留下了超过5000公斤的鲑鱼碎屑！
And those scraps have a lot of something trees need desperately: nitrogen.
这些碎屑中有很多树木急需的东西：氮。
Like any living thing, plants need a bunch of different nutrients to grow.
和很多有生命的事物一样，植物生长需要大量不同的营养物质。
But whichever one is in short supply in a given area is deemed the limiting nutrient.
但在特定区域内，任何一种短缺的营养物质都被认为是限制营养素。
And along the northwest coast of North America, the limiting nutrient is often nitrogen.
而在北美的西北海岸，限制营养素通常是氮。
Since fish carcasses have lots of nitrogen in them, scientists studying these ecosystems suspected
因为鱼的尸体含有大量的氮，研究这些生态系统的科学家怀疑
the trees were "eating" the bears' leftovers, once the salmon decomposed and their nutrients sank into the soil.
一旦鲑鱼腐烂，它们的营养物质渗入土壤，树木就开始“吃”熊的残食。
But to prove it, they needed to follow the nitrogen! See, not all nitrogen is the same.
但为了证实这一点，他们需要注意所有氮气！并不是所有的氮都是一样的。
Some nitrogen atoms have more neutrons than others.
一些氮原子比其他原子有更多的中子。
And it turns out nitrogen atoms can have either seven or eight neutrons and remain stable—
结果证明氮原子可以有7到8个中子并且保持稳定——
so nitrogen has what chemists call two stable isotopes.
所以化学家称氮有两个稳定的同位素。
Over 99% of the nitrogen on Earth is the lighter kind: nitrogen-14.
地球上超过99%的氮都是较轻的那一种：氮-14。
But salmon have a weirdly high amount of nitrogen-15, when compared with land-dwelling species.
但和与陆地生物相比，鲑鱼中氮-15含量非常高。
That's partly because most salmon spend nearly all of their adult life in the ocean,
部分原因是因为大部分鲑鱼成年后几乎都生活在海洋里，
and it just so happens that the chemical and biological processes that occur in seawater make more nitrogen-15 available there than on land.
海水中发生的化学和生物过程恰好能比陆地上的产生更多的氮-15。
On top of that, though you may not think of salmon as fierce predators, they're actually pretty high up the food chain.
最重要的是，尽管你可能认为鲑鱼是并不是凶猛的捕食者，但实际上它们在食物链中处于相当高的位置。
And animals use each nitrogen isotope slightly differently.
动物对每种氮同位素的使用略有不同。
Because of quirks of biochemistry we don't fully understand, nitrogen-14 tends to be excreted more than nitrogen-15.
由于我们不完全了解的生物化学的特性，氮-14比氮-15更容易被排出体外。
And since this happens at every level of the food chain, the higher up animals are,
由于这发生在食物链的每一层，因此动物的地位越高，
the more nitrogen-15 they have in their diet — and therefore, in their bodies.
它们饮食中的所需氮-15就越多——因此，它们体内就越多。
Starting in the late 1990s, research revealed that trees near salmon streams in Alaska have impressively high levels of nitrogen-15.
从20世纪90年代末开始，研究发现阿拉斯加鲑鱼溪流附近的树木含有大量的氮-15。
So the obvious conclusion: they get a lot of their nutrients from salmon! That wasn't all.
所以结论很明显：它们从鲑鱼中获取了大量营养。不仅如此。
By looking at nitrogen in individual tree rings—those yearly layers you can see if you cut a tree in half —
通过观察单个树木年轮中的氮含量——如果你把一棵树砍成两半，你就能看到年轮中的氮含量——
the researchers were able to show how important salmon are to the trees.
研究人员能够证明鲑鱼对树木的重要性。
During and after years when more fish came upstream to spawn, the trees grew bigger rings with more nitrogen.
当更多的鱼游到上游产卵时，树木就会长出更大的带更多氮的年轮。
And overall, trees that received nutrients from salmon grew 19% bigger than those that didn't!
总的来说，从鲑鱼中获得营养的树木比那些没有从鲑鱼中获得营养的树木大19%。
So, if you're a tree who wants to grow nice and tall, you'd better not skip out on the sushi.
如果你是一棵想长得又美又大的树，你最好不要错过这些寿司。
And if you're a human who's been inspired by this episode to dive deeper into biochemistry,
如果你受这一集启发，想深入研究生物化学，
well, that's something today's sponsor—Brilliant.org—can help with.
那么Brilliant.org可以帮助你。
For example, you could take their course on chemical reactions and learn about molecules and how they interact.
例如，你可以学习他们的化学反应课程，学习分子和它们的化学反应。
And it's just one of the fun, interactive courses you can take with a Premium subscription.
会员订阅后，你可学习更多有趣的交互课程。
If that sounds your cup of tea, I've got some good news for you,
如果它们的课程适合你，我再告诉大家一个好消息，
the first 200 people to sign up at Brilliant.org/SciShow will get 20% off the annual Premium subscription.
前200名注册Brilliant.org/SciShow的观众将获得年会员8折优惠。
So head over there, check it out and see if it's right for you.
大家可以去看看这些课程是否适合你。
