Ecology
Siren smell
誘人的氣味
Why turtles eat plastic rubbish
海龜為何會食用塑料垃圾
Foul smells fair
垃圾也芬芳
19英語W 陳靜 翻譯
葉靜老師 推薦
Turtles have an unfortunate habit of devouring plastic objects floating in the sea. These then get snared in their alimentary canals, cannot be broken down by the animals』 digestive enzymes and may ultimately kill them. It is widely assumed that this penchant for plastics is a matter of mistaken identity. Drifting plastic bags, for instance, look similar to jellyfish, which many types of turtles love to eat. Yet lots of plastic objects that end up inside turtles have no resemblance to jellyfish. Joseph Pfaller of the University of Florida therefore suspects that something more complicated is going on. As he writes in Current Biology, he thinks that the odour of marine micro-organisms which colonise floating plastic objects induces turtles to feed.
海龜有個壞習慣，它們會吞食漂浮在海面上的塑料物品。這些物品隨後進入它們的消化道，無法由消化酶分解，最終可能會導致死亡。人們普遍認為海龜喜歡食用塑料是因為誤把塑料當成了海洋生物。以漂浮著的垃圾袋為例，它們形似許多海龜愛吃的食物——水母。然而最後進入海龜體內的很多塑料與水母卻沒有一絲相像之處。因此，佛羅裡達大學的約瑟夫·普萊瑟認為背後還有更複雜的原因。正如他在《當代生物學》所寫的那樣，他認為那些大量繁殖於塑料漂浮物中的海洋微生物的氣味是引誘海龜食用的一大原因。
The idea that the smell of plastic flotsam might lure animals to their doom first emerged in 2016. Researchers at the University of California, Davis, noticed that certain chemicals, notably dimethyl sulphide, which are released into the air by micro-organism-colonised plastics, are those which many seabirds sniff to track down food. These chemicals mark good places to hunt because they indicate an abundance of the algae and bacteria that lie at the bottom of marine food chains. The researchers also found that birds which pursue their food in this way are five or six times more likely to eat plastic than those which do not.
「海洋漂浮物的氣味會吸引海龜捕食並最終致命」這一觀點首次出現於2016年。加州大學戴維斯分校的研究者們注意到，許多海鳥靠著某些化學物的氣味來追蹤食物，如最典型的二甲基硫化物，微生物大量繁殖的塑料就會發出這種味道。這些化學物質的出現標誌了此處是捕獵的絕佳之處，因為這裡有大量處於海洋食物鏈最底端的藻類和細菌。研究者們還發現，以此種方式尋覓食物的鳥類，食用塑料品的可能性是其他鳥類的五或六倍。
Since turtles are known to break the surface periodically and sniff the air when navigating towards their feeding areas, Dr Pfaller theorised that they are following these same chemicals, and are likewise fooled into thinking that floating plastic objects are edible.
由於海龜們會定期地探出水面通過聞氣味來尋找捕食區，約瑟夫·普萊瑟便提出了該理論——海龜們追隨著這些相同的化學物質，同樣也為之欺騙而誤認為那些塑料漂浮物是可食用的。
To test that idea, he and his colleagues set up an experiment involving loggerhead turtles, a species frequently killed by plastic. They arranged for 15 of the animals, each around five months old, to be exposed, in random order, to four odours delivered through a pipe to the air above an experimental arena. The odours were: the vapour from deionised water; the smell of turtle-feeding pellets made of shrimp and fish meal; the smell of a clean plastic bottle chopped up into ten pieces; and the smell of a similarly chopped bottle that had been kept in the ocean for five weeks to allow algae and bacteria to grow on it.
為了驗證該理論，約瑟夫·普萊瑟和他的同事便開展了一項實驗，對象為赤蠵龜，它們經常死於食用塑料物品。他們準備了15隻赤蠵龜，年齡都在5個月左右，然後隨機安排去嗅四種氣味，這些氣味會通過管道輸送到實驗區上方的空氣中。這四種氣味分別來源於去離子水蒸汽，小蝦和魚粉製成的龜糧，切成十小塊的乾淨塑料瓶，以及一個同樣砍碎但已放置於海中五個星期以便藻類和細菌依附生長的塑料瓶。
Two of the smells proved far more attractive to the animals than the others. When sniffing both the odour of food pellets and that of five-week-old bottles turtles kept their nostrils out of the water more than three times as long, and took twice as many breaths as they did when what was on offer was the smell of fresh bottle-plastic or deionised-water vapour. On the face of it, then, the turtles were responding to the smell of old bottles as if it were the smell of food.
實驗證明，其中兩種氣味對動物的吸引力要遠遠高於其他氣味。當聞到龜糧和由海水浸泡了五個星期的瓶子散發出的氣味時，海龜們探出水面的時長是以往的三倍多，呼吸的次數也多了一倍。從表面可以看出，海龜們會受到舊塑料瓶氣味的吸引，就好似聞到了食物的氣味一般。
Though they have not yet tested whether dimethyl sulphide is the culprit, Dr Pfaller and his colleagues think it is the most likely candidate. In an unpolluted ocean, pretty well anything which had this smell would be edible—or, at least, harmless. Unfortunately, five-week-old plastic bottles and their like are not.
儘管約瑟夫·普萊瑟和他的同事還未證實是否二甲基硫化物是誤導海龜食用塑料物品的罪魁禍首，但他們認為這是「頭號嫌疑犯」。
在未受到汙染的海域，任何帶有這種氣味東西都是可以食用的，最起碼它們沒有任何危害。
然而不幸的是，在海洋中存放了5個星期的塑料瓶以及類似的物品並非如此。
原文選自 The Economist 2020.03.14
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