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By May, spring has reached the coasts of Scotland. Underwater, it arrived rather earlier.
春天在五月降临苏格兰的海岸。她更提前来到海底世界。
During March, the seas had warmed enough to trigger a magical transformation.
三月时水温已回暖，神奇的转变同时展开。
These are phytoplankton, tiny floating algae, each much smaller than a pinhead.
这些是浮游植物群落，微小的漂浮藻类小过针头。
And they multiply with amazing speed to produce more annual growth than all the plants on land put together -- 6 billion tonnes of it.
它们迅速的繁殖量远超过陆上植物每年产量总和。60亿吨。
This immense bloom spreads across the face of the ocean, and within a couple of months turns vast areas of it a dense green.
这庞大的繁殖量在数月内扩散地球表面海域，将广大区域染成浓密的绿。
Animal life reacts to the blooming sea.
动物的生活反应这盛产的海洋。
Although these polyps look like small anemones, they're about to change into something else.
虽然这些珊瑚虫看来像海葵，但它们正要改变型态。
As they separate, they reveal themselves to be tiny, common jellyfish.
当它们分离时，泄露出它们原是渺小平常的水母。
They are less than 3 millimetres across. Within a few months, they will have assembled into vast swarms.
它们体宽不到3公厘。几周内，它们会组成庞大的族群。
Minute copepods are part of their staple diet.
桡足类是它们固定的食物之一。
These appear every spring in vast numbers and graze on the Phytoplankton bloom.
它们在每年春天大量出现，并仰赖浮游植物维生。
Their beating legs create currents that sweep the little algae into the basket-like filters around their mouths.
它们蠕动的脚造成水流，将海藻堆积到嘴边篮状的滤网。
On this microscopic scale, water is so viscous that the phytoplankton can't swim against the current.
渺小的分子下，水变得黏稠，使浮游植物无法逆水流而行。
Whilst feeding, sensors on the copepod's antennae give warning of dangers ahead.
觅食时，桡足类触须上的感应器会发出危机伺伏的警讯。
Lighting by lasers reveals that feeding copepods leave wakes behind them, rather like jet trails in the sky.
激光照射显示，桡足类会在身后留下足迹，像是空中喷射机的烟雾。
Slightly larger floating predators are able to use these trails to find their prey.
稍大的浮游掠食者能利用这些痕迹找到它们的食物。
A close call -- but some predators are simply too large to avoid. Jellyfish!
差一点点--但有些掠食者实在大到无法躲避。水母！
They may appear to be delicate as well as beautiful, but they are deadly hunters.
它们也许看来脆弱又美丽，它们却是致命的杀手。
With every pulse of the delicate bells, plankton-rich water is drawn into their lacy throats and pushed out again, leaving behind copepods stuck to the membranes.
铃铛状身体每一次柔弱的舞动，都将充满浮游生物的水吸进它们蕾丝般的嘴里，再将水推出，留下黏在薄膜上的桡足类。
A single sea-nettle jellyfish only a few centimetres across can collect thousands of copepods in a day.
一只几公分宽的荀麻水母能在一天内收集成千的桡足类。
So the killing power of giants like these is hard to estimate.
因此这种庞然大物的杀伤力是无法预测的。
Each of these jellyfish weighs up to 30 kilos and has tentacles stretching over 8 metres.
这种水母重约30公斤，触须可伸展到8公尺长。
But there are even greater dangers awaiting the copepods.
但桡足类还面临着更大的危险。
By the late spring, the baby common jellyfish are fully grown.
小水母在晚春时完全成熟。
They gather in millions, forming immense swarms hundreds of metres long, which filter out all the small planktonic animals in their path.
它们以数百万群集，形成数百公尺长的大族群，过滤所有通过它们的浮游生物。
Nevertheless, there are such astronomic numbers of copepods that enough will survive to form swarms of their own.
然而，桡足类的数量是天文数字，足够多的桡足类存活下来形成自己的种群。
