VOA慢速英语2014 深海岩中的微生物“吃”甲烷

 

Small Organisms in Deep Sea Rocks Eat Methane¹ 深海岩中的微生物“吃”甲烷

The gas methane has been linked to rising temperatures on Earth. But methane does not stay in the atmosphere as long as another “greenhouse gas” -- carbon dioxide. Scientists say both gases trap heat from the sun. They prevent heat from escaping into outer space.

Methane can come from wetlands, as a byproduct of raising farm animals, and from human activities, such as leakage² from natural gas systems. Methane is also plentiful³ in the ocean. It can be found in ice, but also rises from deep within the earth through small cracks, or holes, in the ocean floor.

Little of that methane reaches the atmosphere, thanks to methane-eating organisms that live in sea bed sediments⁵ – materials that sink to the sea floor. Now, an American scientist says other deep sea microorganisms are also attacking the gas. These organisms live in an unlikely place – inside rock on the ocean floor!

Victoria Orphan⁶ is with the California Institute of Technology. She studies microorganisms that live in sediment⁴ near methane vents⁷ in the ocean. These vents release methane trapped inside the earth. Ms. Orphan says the organisms have changed to survive in this extreme environment.

“These organisms would be able to extract energy from methane using sulfate found in sea water rather than oxygen. And as an end product, they would produce hydrogen sulfide, sort of that rotten egg smell. And also as another by-product⁸, these organisms would produce carbonate, sort of like the pavement you see on the sidewalk.”

Over time, that calcium⁹ carbonate forms tall, rocky seamounts around the methane vents. Victoria Orphan suspected that these rocky areas served as a shelter for sea life. So she found a submersible -- a small vehicle like a submarine -- and went down 800 meters to the sea floor to prove it.               

Ms. Orphan made four such trips between 2006 and 2011. As part of her studies, she collected sediments and seamount particles from the near-freezing water. She says the rocks she collected confirmed her theory.

“These are not just simply end products of methane oxidation, but they actually maintain a viable¹⁰ community of microorganisms living inside the pore spaces of the rock that turns out are still capable of consuming methane.”

However, her research showed the seamount microbes attacked the gas at a slower rate than the methane-eating organisms in the sediment. That is because not as much methane reaches the small holes in the rock.

“But considering that the volume of rock that’s available to colonize¹¹ down in these deep-sea environments, it still can be a significant potential source of methane consumption. So instead of just considering this a process that is going on in sediments, we now have this whole other expansive habitat to look at as a sink for methane over time.”

The journal Nature Communications published her findings. She says the large number of small organisms – both in the sediment and in rock – explains how the microbes can limit the amount of methane in the world’s oceans. As a result, the gas has trouble reaching the atmosphere. And she notes that the worms, crabs¹² and other creatures living around the rocks eating the microbes may show evidence of an ecosystem¹³ formerly¹⁴ unknown to scientists.

Words in this Story 

gas – n. any substance that is not solid or liquid

byproduct – n. a secondary product made in the manufacture of something else

atmosphere – n. the gases surrounding any star or planet

trap – v. to catch or be caught by being tricked; to be unable to move or escape

deep – adj. going far down; a long way from top to bottom

1 methane   

n.甲烷，沼气

参考例句：

• The blast was caused by pockets of methane gas that ignited.爆炸是由数袋甲烷气体着火引起的。
• Methane may have extraterrestrial significance.甲烷具有星际意义。

2 leakage   

n.漏，泄漏；泄漏物；漏出量

参考例句：

• Large areas of land have been contaminated by the leakage from the nuclear reactor.大片地区都被核反应堆的泄漏物污染了。
• The continuing leakage is the result of the long crack in the pipe.这根管子上的那一条裂缝致使渗漏不断。

3 plentiful   

adj.富裕的，丰富的

参考例句：

• Their family has a plentiful harvest this year.他们家今年又丰收了。
• Rainfall is plentiful in the area.这个地区雨量充足。

4 sediment   

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。

5 sediments   

沉淀物( sediment的名词复数 )； 沉积物

参考例句：

• When deposited, 70-80% of the volume of muddy sediments may be water. 泥质沉积物沉积后，体积的70-80％是水。
• Oligocene erosion had truncated the sediments draped over the dome. 覆盖于穹丘上的沉积岩为渐新世侵蚀所截削。

6 orphan   

n.孤儿；adj.无父母的

参考例句：

• He brought up the orphan and passed onto him his knowledge of medicine.他把一个孤儿养大，并且把自己的医术传给了他。
• The orphan had been reared in a convent by some good sisters.这个孤儿在一所修道院里被几个好心的修女带大。

7 vents   

（气体、液体等进出的）孔、口( vent的名词复数 )； （鸟、鱼、爬行动物或小哺乳动物的）肛门； 大衣等的)衩口； 开衩

参考例句：

• He always vents his anger on the dog. 他总是拿狗出气。
• The Dandelion Patch is the least developed of the four active vents. “蒲公英区”在这四个活裂口中是发育最差的一个。

8 by-product   

n.副产品，附带产生的结果

参考例句：

• Freedom is the by-product of economic surplus.自由是经济盈余的副产品。
• The raw material for the tyre is a by-product of petrol refining.制造轮胎的原材料是提炼汽油时产生的一种副产品。

9 calcium   

n.钙(化学符号Ca)

参考例句：

• We need calcium to make bones.我们需要钙来壮骨。
• Calcium is found most abundantly in milk.奶含钙最丰富。

10 viable   

adj.可行的，切实可行的，能活下去的

参考例句：

• The scheme is economically viable.这个计划从经济效益来看是可行的。
• The economy of the country is not viable.这个国家经济是难以维持的。

11 colonize   

v.建立殖民地，拓殖；定居，居于

参考例句：

• Around 700 Arabs began to colonize East Africa.公元700年阿拉伯人开始把东非变为殖民地。
• Japan used to colonize many countries in Asia.日本曾经殖民过许多亚洲国家。

12 crabs   

n.蟹( crab的名词复数 )；阴虱寄生病；蟹肉v.捕蟹( crab的第三人称单数 )

参考例句：

• As we walked along the seashore we saw lots of tiny crabs. 我们在海岸上散步时看到很多小蟹。 来自《简明英汉词典》
• The fish and crabs scavenge for decaying tissue. 鱼和蟹搜寻腐烂的组织为食。 来自《简明英汉词典》

13 ecosystem   

n.生态系统

参考例句：

• This destroyed the ecosystem of the island.这样破坏了岛上的生态系统。
• We all have an interest in maintaining the integrity of the ecosystem.维持生态系统的完整是我们共同的利益。

14 formerly   

adv.从前，以前

参考例句：

• We now enjoy these comforts of which formerly we had only heard.我们现在享受到了过去只是听说过的那些舒适条件。
• This boat was formerly used on the rivers of China.这船从前航行在中国内河里。