Can the ocean run out of oxygen? - Kate Slabosky

翻译人员: Sabrina Wang 校对人员: Helen Chang

For most of the year, the Gulf of Mexico is teeming with marine life,

在一年的大部分时间里， 墨西哥湾充斥着丰富的海洋生物，

from tiny crustaceans to massive baleen whales.

从微小的甲壳类动物 到巨大的长须鲸。

But every summer, disaster strikes.

但是每年夏天，灾难都会来临。

Around May, animals begin to flee the area.

大约在5月的时候， 海洋动物们开始从那里逃离。

And soon, creatures that can’t swim or can’t swim fast enough

很快，那些不会游泳 或游得不够快的生物

begin to suffocate and die off in massive numbers.

开始窒息，甚至大量死亡。

From late spring to early autumn,

从春末到秋初，

thousands of square kilometers along the coast become a marine dead zone—

沿海数千平方公里的海域 变成了海洋生命的死亡地带 --

unable to support most forms of aquatic life.

大多海洋生物无法生息。

This strange annual curse isn’t unique;

这每年一次的怪异诅咒， 并非独一无二；

dead zones like this one have formed all over the world.

像这样的死亡地带已散布于世界各地。

But to explore what’s creating these lethal conditions,

要想探寻导致这些致命 环境形成的原因，

we first need to understand how a healthy marine ecosystem functions.

我们先要了解一个健康的 海洋生态系统是如何运作的。

In any body of water that receives sufficient sunlight,

在任何阳光照射充足的水体中，

plant-like organisms such as algae and cyanobacteria thrive.

藻类和蓝藻细菌等类似植物的生物体 会生长得很茂盛。

Clouds of algae streak the surface of deep waters,

深水区域的表面，有成群的水藻，

and in shallower regions, large seaweeds and seagrass cover the ground.

在较浅的区域，大型海藻和海草 覆盖着海底的地面。

Not only do these organisms form the foundation of local food chains,

这些生物不仅形成了 当地食物链的基础，

their photosynthesis provides the oxygen necessary for aquatic animals to survive.

它们的光合作用也提供了海洋动物 生存所需的氧气。

Besides sunlight and C02,

除了阳光和二氧化碳，

algae growth also depends on nutrients like phosphorus and nitrogen.

水藻的生长也需要 依赖于营养物质，

例如磷和氮。

While such resources are typically in short supply,

这些资源经常短缺，

sometimes the surrounding watershed can flood coastal waters with these nutrients.

有时周围流域的营养物质 会将沿海的水域淹没。

For example, a large rainstorm might wash nutrient-rich sediment

例如，一场大暴雨可能会把森林中 富含营养物质的沉积物

from a forest into a lake.

冲入湖中。

These additional resources lead to a massive increase in algae growth

这些额外的资源会导致 藻类的生长大量增加，

known as eutrophication.

被称为“富营养化”。

But rather than providing more food and oxygen,

但这种激增不仅 没有提供更多的食物和氧气，

this surge of growth has deadly consequences.

反而造成了致命的后果。

As more algae grows on the surface, it blocks sunlight to the plants below.

随着更多藻类在水面生长， 阻挡了海下植物生长所需的阳光。

These light-deprived plants die off and decompose

这些因失去光照而死亡的植物， 在分解的过程中

in a process which uses up the water’s already depleted oxygen supply.

进一步耗尽了海水中 已经枯竭的氧气供应。

Over time, this can reduce the oxygen content

随着时间的推移，这可能会使氧气含量

to less than 2 milligrams of oxygen per liter,

减少到每升不到2毫克的氧气。

形成一个不适合生息的死亡地带。

creating an uninhabitable dead zone.

There are rare bodies of water that rely on natural eutrophication.

有少数的水体要依赖 天然的“富营养化”。

Regions like the Bay of Bengal are full of bottom-dwelling marine life

像孟加拉湾这样的地区 就满是底栖海洋生物，

that has adapted to low-oxygen conditions.

并已适应低氧条件。

But human activity has made eutrophication a regular and widespread occurrence.

但人类活动已经使“富营养化”

成了一种经常和广泛发生的现象。

Nutrient-rich waste from our sewage systems and industrial processes

污水处理系统和工业生产所致的 富含营养物质的废物，

often end up in lakes, estuaries and coastal waters.

往往最终进入湖泊、河口和沿海水域。

And the Gulf of Mexico is one of the largest dumping zones on earth

而墨西哥湾是地球上 最大的倾倒区之一，

for one particular pollutant: fertilizer.

它特定的污染物就是：化肥。

American agriculture relies heavily on

美国农业严重依赖于

nitrogen and phosphate-based fertilizers.

氮肥和磷肥。

31 states, including America’s top agricultural producers,

美国31个州，包括其顶级 农业生产基地，

are connected to the Mississippi River Basin,

都与密西西比河流域相连，

and all of their runoff drains into the Gulf of Mexico.

它们的所有径流通通 流入墨西哥湾。

Farmers apply most of this fertilizer during the spring planting season,

农民在春季播种季节 大量使用这种肥料，

so the nutrient flood occurs shortly after.

所以在不久之后会出现养分洪流。

In the Gulf,

在墨西哥湾，

decomposing algae sinks into the band of cold saltwater near the seafloor.

分解掉的藻类会沉入 接近海底冰冷的咸水带中。

Since these dense lower waters don’t mix with the warmer freshwater above,

由于这些密集的低层水 不与上面的较温暖的淡水混合，

it can take four months for tropical storms

热带风暴可能需要四个月的时间，

to fully circulate oxygenated water back into the gulf.

才能完全使含氧水彻底 循环到海湾中。

This dead zone currently costs U.S. seafood and tourism industries

目前，这个死亡海域每年 给美国的海产品和旅游业

as much as $82 million a year,

带来高达8200万美元的损失。

and that cost will only increase as the dead zone gets bigger.

而且这个损失只会随着死亡海域的 扩大而增加。

On average the gulf dead zone is roughly 15,000 square kilometers,

平均而言，死亡海域大约为 1万5千平方公里，

but in 2019 it grew to over 22,000 square kilometers—

但在2019年，它增长到 2万2千多平方公里 --

approximately the size of New Jersey.

大约相当于新泽西州的面积。

Human activity is similarly responsible for growing dead zones around the world.

人类活动同样对世界各地 死亡海域的增长负有责任。

So what can be done?

那么，可以做些什么呢？

In the short term, countries can set tighter regulations on industrial run-off,

在短期内，各国可以对工业废水 制定更严格的法规，

and ban the dumping of untreated sewage into ocean waters.

并禁止将未经处理的污水 倾倒在海洋中。

On farms, we can plant buffer zones

在农场，我们可以种植

由树木和灌木组成的缓冲区 来吸收径流。

composed of trees and shrubs to absorb runoff.

However, long term solutions will require radical changes to the way we grow food.

然而，长期的解决方案将需要彻底 改变我们种植食物的方式。

Farmers are currently incentivized to use techniques

目前的农民因被鼓励而使用的技术，

that reduce the health of the soil

会降低土壤健康，

and rely heavily on nitrogen-rich fertilizers.

并严重依赖富含氮气的肥料。

But there would be less need for these chemicals

但是我们未必那么需要这些化肥。

if we restore the soil’s natural nutrients

如果我们种植多样化的作物

by planting diverse crops that manage soil erosion and fertility.

管理好土壤的侵蚀和肥力， 恢复土壤中的天然养分。

Hopefully we can make these fundamental changes soon.

希望我们能尽快做出 这些根本性的改变。

Because if we don’t,

因为如果不这样做，

我们海洋生态系统的未来 可能就会沉沦于水中。

the future of our marine ecosystems may be dead in the water.