科学美国人60秒 SSS 墨西哥湾“死区”对虾业的影响（在线收听）

Every spring, the Mississippi River dumps tens of thousands of tons of nutrient runoff into the Gulf of Mexico. Add temperature, current and wind to that pollution, and you have the Western Hemisphere's largest stretch of oxygen-poor waters—a so-called "dead zone."

有超过数亿磅富含氮的肥料来自密西西比河盆地的流入墨西哥湾。这种污染，在加之温度、水流以及风的影响，造成了西半球最大的缺氧区——“死区”。

That dead zone hits the Gulf's famed—and financially important—brown shrimp fisheries. And it does two things: first, the low oxygen slows down the shrimps’ growth.

“死区”使得墨西哥湾世界闻名——同时具有重要的经济地位——对于布朗虾渔业。主要有两方面的原因：第一，低氧降低了虾的生长速度。

"The other thing that occurs is what I like to call the burning building effect." Martin Smith, an environmental economist at Duke University. "The shrimp try to avoid the low oxygen so they swim out of these areas of depleted oxygen. As a result they end up kind of aggregating on the edges.

“另外一种现象我称之为燃楼效应”马丁·史密斯是杜克大学的生态学家。虾想要摆脱低氧环境，就会游离这些氧气枯竭的地方。最终它们都会聚集到边缘地区。

They kind of line up outside the deoxygenated waters. And that's why I call it the burning building effect. If you're in a burning building you're running to get out of the fire, you don't keep running when you get outside, you stop and you take a breath."

这些虾就排列在缺氧区的外沿。这就是我为何称之为“燃楼效应”。如果深处一个燃烧的建筑物中，你就会逃离火海，但是当到达建筑物之外以后，你就会停止奔跑，停下来喘口气。

Fishermen flock to where those shrimp "take a breath." And shrimp get caught earlier in the season. So combine these two effects—slower growth and earlier catches—and the result is a haul of more small shrimp, and fewer large and jumbo shrimp. Meaning the price on big shrimp temporarily goes up. Supply and demand, right?

渔民门就涌向虾“换气”的地方。所以，这时的捕虾期提前。结果综合这两种影响——虾的生长速度比较慢，同时较早被捕捉——导致收获的多为小虾，而大型虾和巨型虾的数量较少。这就意味着大虾的价格会短暂上涨。供给和需求，对吗?

Smith and his team studied that link—between the dead zone and a spike in large shrimp prices—using 20 years of shrimp pricing data. Their analysis is in the Proceedings of the National Academy of Sciences.

史密斯和他的团队研究了此间的关系——死区和大虾价格飙升——他们利用了20年的大虾价格的数据。该研究结果发表在《美国国家科学院院刊》。

The brown shrimp fishery in the Gulf was once the most valuable in the U.S. Now, Smith says, we can measure the true cost of that nutrient runoff. "We can start to ask questions like, how much does the shrimp industry lose as a result of this problem, and how does that compare to what it would cost to control nutrient flows coming from food prediction upstream in the Mississippi watershed?" In other words—whether there might be some net economic benefit to keeping the water environmentally protected.

曾经墨西哥湾的布朗虾渔业在美国最具价值。 现在，史密斯表示，我们可以衡量营养流失的真正成本。“我们可以问，由于这样的问题虾渔业损失多少?那么与控制密西西比河上游的营养物质流失相比呢?”换而言之——保护水环境是否会有净经济效益呢?