文档介绍：Over the past two or three decades, scientists have noticed that vast stretches of coastal waters are turning into dead zones — patches of seabed so low of oxygen that few creatures can survive there. In 2004, the United Nations Environment Program (UNEP) took stock of估量,观察 the phenomenon — which is caused in large part by agricultural runoff — and pronounced it one of the biggest environmental problems of the 21st century. Two years later it noted that the number of identified dead zones, some of which cover thousands of square miles, had climbed from 150 to 200. Robert Diaz, an ecologist at the College of William and Mary in Virginia who helped UNEP with its numbers,claims that today there are more than 400 known dead zones along coastlines around the world, covering roughly 95,000 sq. mi. of seabed.
That's bad news for fish — and for the people who eat them. Much of the world's fish supply is already troubled due to overfishing, dying reefs and the disappearance of marshland, mangrove forests(红树林) and other coastal environments that serve as breeding grounds and nurseries for many valuable species. Biologists haven't been able to figure out how much oxygen depletion (减少)alone contributes to the decline of teetering(摇摇欲坠) fisheries — the question is hotly debated in marine-science circles these days — but few experts would disagree that an increase in dead zones can only be a detriment(损害).
科学家注意到,在过去的二三十年里,大片的沿海水域变成了海洋死区——一大片的海底因为海水中的氧气缺乏,几乎很少有生物能够在那生存。2004年,联合国环境署对这一现象做出评估,认为海洋死区主要是由于农业排放的污染物所致,并宣称海洋死区是21世纪最严重的环境问题。两年后,联合国环境署注意到被认定的死区数量已经从150块上升到了200块,其中一些死区面积达数千平方英里。罗伯特·达艾斯是弗吉尼亚州的威廉及玛丽学院的生态学家,曾经协助联合国环境署调查过海洋死区的数目,认为现在全球海岸线有400多块已知死区,海底面积大约有95000平方英里。
这无论对于鱼类还是吃鱼的人类来说都不是好消息。由于过度捕捞、珊瑚礁的死亡以及沼泽地、红树林和其他为许多珍稀物种提供繁殖温床的海岸环境的消失,全球的鱼类供应都出现了问题。生物学家还不能确定氧气的耗尽对摇摇欲坠的渔业生产的下滑有多大影响——这个问题现在是海洋科学领域一个热门争论的话题——但是很少有专家否认死区的增加仅仅是个对渔业的损害问题。
Indeed, severe hypoxia:[hai‘pɔksiə]低氧, as scientists refer to the phenomenon, has been linked to the collapse of fisheries and a lobster fishe