一些端足目动物会在北极繁育
文章来源:未知 文章作者:enread 发布时间:2013-12-19 08:04 字体: [ ]  进入论坛
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Biologists from the Alfred Wegener Institute, Helmholtz Centre for Polar and Marine1 Research (AWI) have for the first time shown that amphipods(端足目) from the warmer Atlantic are now reproducing in Arctic waters to the west of Spitsbergen. This surprising discovery indicates a possible shift of the Arctic zooplankton(浮游动物) community, scientists report in the journal Marine Ecology Progress Series. The primary victims of this "Atlantification" are likely to be marine birds, fish and whales. The reason is that the migrating amphipods measure around one centimetre, and so are smaller than the respective Arctic species; this makes them less nutritious3 prey4. Amphipods have a preference which made it easy for AWI biologists to recognise these changes. This is because the sea dwellers5, which are classed as zooplankton, would appear to like hiding. "Their favourite hiding places apparently6 include our sediment7 traps which have been suspended for 13 years in HAUSGARTEN, the AWI long-term observatory8 in the Fram Strait. We had originally anchored our funnel-shaped traps at a depth of some 300 metres there in the West Spitsbergen Current in order to catch downward floating material such as algae9 or excrement10 from zooplankton. However, from the start we also found several amphipods in the traps. The sample containers are full to the brim, especially in summer months. We therefore believe that the animals are actively11 swimming into the traps," states AWI plankton2 specialist Dr. Eva-Maria Nöthig.
 
The by-catch rapidly proved to be a valuable sample set, because over years changes were not only seen in the number of amphipods caught, but also in the species composition. "In the first four years our catches consisted exclusively of the Arctic and sub-Arctic individuals Themisto libellula and Themisto abyssorum. We found examples of the smaller species Themisto compressa, which is native to the Atlantic Ocean, in our sediment traps in July 2004 for the first time. They had apparently come that far north during a warm phase of the West Spitsbergen Current," the scientist reports.
 
A one-off discovery? By no means! During subsequent years what had begun as an exception turned into a seasonally12 recurrent rule. From this time scientists documented ever more examples of the Atlantic species Themisto compressa, especially in summer months. Despite this, scientists at that time believed water in the West Spitsbergen Current, with its average temperature of 3 to 3.5 degrees Celsius13, to be too cold to permit the animals from the southern part of the North Atlantic, which have a greater sensitivity to cold, to reproduce there.
 
New findings contradicted this assumption: "The catches in the months of August and September 2011 contained ovigerous females and recently hatched juveniles14 of the Atlantic species for the first time. Moreover in following months we were able to provide evidence of the migrating amphipod in all stages of development, despite the fact that the warm phase of the West Spitsbergen Current had already subsided," says Eva-Maria Nöthig.
 
The scientists began to calculate: the water masses of the West Spitsbergen Current running northwards require approximately 150 days to get from the North Atlantic to the Arctic Ocean. Too long to transport females already bearing eggs from their native habitat at 60 degrees north latitude15 in time for their larvae16 to hatch near the west coast of Spitsbergen. "In view of these facts, we believe that the Atlantic amphipods are reproducing in the waters of the eastern Fram Strait. This means the animals reach sexual maturity17 here and also have their offspring here," Eva-Maria Nöthig says.


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1 marine 77Izo     
adj.海的;海生的;航海的;海事的;n.水兵
参考例句:
  • Marine creatures are those which live in the sea. 海洋生物是生存在海里的生物。
  • When the war broke out,he volunteered for the Marine Corps.战争爆发时,他自愿参加了海军陆战队。
2 plankton B2IzA     
n.浮游生物
参考例句:
  • Plankton is at the bottom of the marine food chain.浮游生物处于海洋食物链的最底层。
  • The plankton in the sea feeds many kinds of animals. 海的浮游生物成为很多种动物的食物。
3 nutritious xHzxO     
adj.有营养的,营养价值高的
参考例句:
  • Fresh vegetables are very nutritious.新鲜蔬菜富于营养。
  • Hummingbirds have discovered that nectar and pollen are very nutritious.蜂鸟发现花蜜和花粉是很有营养的。
4 prey g1czH     
n.被掠食者,牺牲者,掠食;v.捕食,掠夺,折磨
参考例句:
  • Stronger animals prey on weaker ones.弱肉强食。
  • The lion was hunting for its prey.狮子在寻找猎物。
5 dwellers e3f4717dcbd471afe8dae6a3121a3602     
n.居民,居住者( dweller的名词复数 )
参考例句:
  • City dwellers think country folk have provincial attitudes. 城里人以为乡下人思想迂腐。 来自《简明英汉词典》
  • They have transformed themselves into permanent city dwellers. 他们已成为永久的城市居民。 来自《简明英汉词典》
6 apparently tMmyQ     
adv.显然地;表面上,似乎
参考例句:
  • An apparently blind alley leads suddenly into an open space.山穷水尽,豁然开朗。
  • He was apparently much surprised at the news.他对那个消息显然感到十分惊异。
7 sediment IsByK     
n.沉淀,沉渣,沉积(物)
参考例句:
  • The sediment settled and the water was clear.杂质沉淀后,水变清了。
  • Sediment begins to choke the channel's opening.沉积物开始淤塞河道口。
8 observatory hRgzP     
n.天文台,气象台,瞭望台,观测台
参考例句:
  • Guy's house was close to the observatory.盖伊的房子离天文台很近。
  • Officials from Greenwich Observatory have the clock checked twice a day.格林威治天文台的职员们每天对大钟检查两次。
9 algae tK6yW     
n.水藻,海藻
参考例句:
  • Most algae live in water.多数藻类生长在水中。
  • Algae grow and spread quickly in the lake.湖中水藻滋蔓。
10 excrement IhLzw     
n.排泄物,粪便
参考例句:
  • The cage smelled of excrement.笼子里粪臭熏人。
  • Clothing can also become contaminated with dust,feathers,and excrement.衣着则会受到微尘、羽毛和粪便的污染。
11 actively lzezni     
adv.积极地,勤奋地
参考例句:
  • During this period all the students were actively participating.在这节课中所有的学生都积极参加。
  • We are actively intervening to settle a quarrel.我们正在积极调解争执。
12 seasonally ljbzVh     
参考例句:
  • The price of vegetables fluctuates seasonally. 蔬菜的价格随季节变动。 来自《简明英汉词典》
  • They moved seasonally among various vegetation types to feed on plants that were flourishing. 它们还随着季节的变化而在各种类型植物之间迁移,以便吃那些茂盛的植物。 来自辞典例句
13 Celsius AXRzl     
adj.摄氏温度计的,摄氏的
参考例句:
  • The temperature tonight will fall to seven degrees Celsius.今晚气温将下降到七摄氏度。
  • The maximum temperature in July may be 36 degrees Celsius.七月份最高温度可能达到36摄氏度。
14 juveniles 257c9101f917ec8748aa5fc520c6a9e3     
n.青少年( juvenile的名词复数 );扮演少年角色的演员;未成年人
参考例句:
  • Do you think that punishment for violent crimes should be the same for juveniles and adults? 你对暴力犯罪的惩罚对于青少年和成人应一样吗? 来自生活英语口语25天快训
  • Juveniles Should we not exactly in need of such strength and conviction? 少年的我们难道不正是需要这种力量和信念吗? 来自互联网
15 latitude i23xV     
n.纬度,行动或言论的自由(范围),(pl.)地区
参考例句:
  • The latitude of the island is 20 degrees south.该岛的纬度是南纬20度。
  • The two cities are at approximately the same latitude.这两个城市差不多位于同一纬度上。
16 larvae w2CxP     
n.幼虫
参考例句:
  • Larvae are parasitic on sheep.幼虫寄生在绵羊的身上。
  • The larvae prey upon small aphids.这种幼虫以小蚜虫为食。
17 maturity 47nzh     
n.成熟;完成;(支票、债券等)到期
参考例句:
  • These plants ought to reach maturity after five years.这些植物五年后就该长成了。
  • This is the period at which the body attains maturity.这是身体发育成熟的时期。
TAG标签: Arctic traps amphipods
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