鯨魚被曬傷或爲臭氧層空洞所致

It's not just holidaymakers who need to keep covered up in the sun.

Scientists have discovered that a growing number of whales are suffering from sunburn - and that the hole in the ozone layer could be to blame.

The findings come from a study of 156 blue, fin and sperm whales swimming in the Gulf of California.

Researchers have long known that whales suffer blisters on their backs. However the reason why they have lesions has been a mystery - until now.

After analysing the sores on high resolution photographs and studying whale skin samples in the laboratory, a team of British and Mexican researchers now believe they are caused by acute sunburn.

Dr Laura Martinez–Levasseur, of the Zoological Society of London, said: 'Whales need to come to the surface to breathe air, to socialise and to feed their young, meaning that they are frequently exposed to the full force of the sun.'

Blue whales, who have fairer skin than most whales, suffered more than the darker fin whales, she reports in the journal Proceedings of the Royal Society B.

Sperm whales, which spend more time than other species at the surface, were also vulnerable.

The increase in sunburn appears to be worst for blue whales, the study found. In 2007, just six out of 48 blue whales had sunburn. By 2009, 15 out of 22 whales studied were suffering.

'The increase in skin damage seen in blue whales is a matter of concern, but at this stage it is not clear what is causing this increase,' Dr Martinez-Levasseur said.

'A likely candidate is rising ultraviolet radiation as a result of either ozone depletion, or a change in the level of cloud cover.'

Her co-author Professor Edel O'Toole, from Queen Mary, said: “As we would expect to see in humans, the whale species that spent more ‘time in the sun’ suffered greater sun damage.

'We predict that whales will experience more severe sun damage if ultraviolet radiation continues to increase.”

The researchers are unsure whether the lesions are painful - and whether sunburn increases the risk of skin cancer in whales.

One reason for the rise in sunburn could be the hole in the ozone layer - the protective layer that shields the Earth from the sun's harmful ultraviolet rays.

Since the 1970s, scientists have known that the protective layer is being depleted by manmade gases, in particularly the CFCs once used in aerosols.

Although CFCs have been banned, the ozone layer is still being depleted from gases released many years ago, and holes exist above both poles.

並不是只有外出度假的人才需要防曬。

科學家發現，越來越多的鯨魚被曬傷，而臭氧層空洞則可能是幕後元兇。

這些發現是在對加利福尼亞灣的156只藍鯨、長鬚鯨和抹香鯨進行研究後得出的。

研究者在很久以前就知道鯨魚的後背上會起水皰。但是直到現在，造成這些皮膚傷的原因依然是個謎。

一個由英國和墨西哥研究人員組成的研究團隊對高分辨率照片上的鯨魚水皰進行了分析，並在實驗室裏對鯨魚的皮膚樣本進行了研究，他們現在認爲這些水皰是由嚴重的曬傷導致的。

倫敦動物學會的勞拉•馬丁內斯-勒瓦瑟博士說：“鯨魚需要到水面上來呼吸空氣、進行社交和哺育幼兒，這意味着它們會頻繁地暴露在陽光的強力照射之下。”

她在英國皇家學會生物研究期刊上的報告中寫道，藍鯨的皮膚顏色比大多數鯨魚都淺，因而曬傷也比皮膚顏色深的長鬚鯨更厲害。

抹香鯨待在水面上的時間比其他種類的鯨魚都要長，所以也很容易被曬傷。

研究發現，被曬傷的鯨魚越來越多，而藍鯨在這方面情況似乎是最糟的。2007年，48只藍鯨中只有6只被曬傷。到了2009年，作爲研究對象的22只藍鯨中就有15只被曬傷。

馬丁內斯-勒瓦瑟博士說：“藍鯨皮膚傷的增多令人擔憂，但在目前這個階段還不清楚是什麼原因導致了曬傷的增多。”

“一個可能的原因是臭氧耗竭或雲層高度改變引起紫外線輻射增強。”

和她一起合著這一報告的來自倫敦大學瑪麗皇后學院的艾德爾•奧圖爾說：“正如我們會在人類身上看到的一樣，‘在太陽下的時間’更多的鯨魚也會遭受更嚴重的曬傷。

“如果紫外線輻射繼續加強的話，我們預計鯨魚將遭受更嚴重的曬傷。”

研究人員不確定這些水皰是否會疼痛，也不確定曬傷是否會增加鯨魚患皮膚癌的風險。

曬傷增多的一個原因可能是臭氧層空洞，而臭氧層是保護地球不受太陽紫外線危害的保護層。

自從20世紀70年代以來，科學家就知道這一保護層一直被人造氣體損耗，特別是曾用於噴霧劑的氯氟烴。

儘管氯氟烴已經被禁用，但是由於多年前排出的氣體，臭氧層仍然繼續被損耗，目前在地球兩極上方都有臭氧層空洞。

Vocabulary:

lesion: damage to the skin or part of the body caused by injury or by illness （因傷病導致皮膚或器官的）損傷，損害

Royal Society B: 這裏的B指的是biological sciences

CFC: 全寫爲chlorofluorocarbon，氯氟烴

aerosol: a substance enclosed under pressure and able to be released as a fine spray, typically by means of a propellant gas（噴霧劑）