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Narrator: Listen to part of a lecture in a Marine Biology class.
聽一段海洋生物學課程。
Professor: We've been talking about the decline of coral reefs in tropical areas all over the world...um... how natural and man-made stresses are causing them to degrade, and in some cases, to die.
我們之前提到了世界各地熱帶區域中珊瑚礁的衰落......即自然和人為（造成的）壓力是怎樣造成珊瑚礁退化的，某些情況下，死亡。
So now let's focus on a specific example of a natural predator that can cause a lot of damage to coral reefs—the Crown of Thorns, or CoT starfish.
讓我們注意一下珊瑚礁自然天敵的一個具體例子，這種天敵能對珊瑚礁造成巨大傷害——刺冠海星，或COT海星。
The Cot starfish is found on coral reefs in the tropical Pacific Ocean and it eats coral.
刺冠海星生活在太平洋的熱帶區域中的珊瑚礁里，而且以珊瑚為食。
Now, in small numbers, the starfish don't affect coral reefs dramatically.
數量較小時，海星不會對珊瑚礁產生重大影響。
But periodically, starfish population explodes.
但海星數量有周期性地暴增。
And when that happens, the reefs can become badly damaged or even destroyed, something we are trying very hard to prevent.
當這種事情發生的時候，珊瑚礁會嚴重受損，甚至毀于一旦，而這正是我們費盡心力要避免的。
For example, during the 1960s, there was an outbreak of CoT starfish in the Great Barrier Reef, off the east coast of Australia.
例如，在20世紀60年代，在澳大利亞東海岸的大堡礁，刺冠海星數量暴增。
Luckily, the CoT starfish population gradually declined on its own and the reefs recovered.
幸運的是，刺冠海星的數量漸漸地自發減少了，珊瑚礁恢復了。
But we were left wondering—what cause the population to increase so suddenly?
但我們感到不解——是什么造成了刺冠海星數量突然暴增？
Well, over the years, we've come up with a few hypotheses, all still hotly debated.
這些年來，我們都提出了好幾種假說，人們仍然爭論不休。
One hypothesis is that it's a natural phenomenon, that the starfish naturally undergo population fluctuations following particularly good spawning years.
一種假說認為，這是自然現象，在特別適合產卵的那幾年，刺冠海星自然會經歷種群數量的波動。
There are also several hypotheses that suggest some sort of human activities are partly responsible, like fishing.
還有一些假說認為，一些人類活動也要負一定責任，比如釣魚。
There are fish and snails that eat starfish, particularly the giant triton snail, which is the main predator of the starfish.
有魚和蝸牛以海星為食，特別是巨型法螺蝸牛，是海星的主要天敵。
These fish and snails have themselves experienced a decline in population because of overfishing by humans.
由于人類過度捕撈，這些魚和蝸牛的種群數量隨之減少。
So with a decline in starfish predators, the starfish population can increase.
所以，海星天敵數量減少，海星數量就會增加。
