VOA标准英语2009年-Fish Kills Linked to Water Pollutants

By Zulima Palacio
Washington
19 October 2009

 
Scientists dissect¹ fish from a river near Washington, DC
Since 2002 thousands of fish in the United States have died and continue to die in many rivers, most in the rivers of the southern east coast.   Researchers have found what they call "the feminization of fish" or the presence of immature² eggs in male fish. They have also found different levels of water contamination all related to human activity. The government says twenty percent of male black bass³ in river basins across the country have immature egg cells in their sexual organs.

This is a different way of fishing. With electric shocks delivered in the water, all fish nearby rise to the surface, belly⁴ up. 

Rick Router is with the Virginia Department of Environmental Quality. "We are applaying about 300 volts⁵ to the water at 6 amps. It doesn't kill the fish, it just stuns⁶ them momentarily," he says.

The fish recover in a minute or two. But they don't live much longer, because the scientists test their blood and then dissect them. 

Here on the Potomac River, south of the U.S. capital, fish are being caught for complex analyses. It's part of a joint⁷ study between the states and federal government.

It began seven years ago when thousands of fish were found dead in rivers of the Shenandoah region on the US east coast.

The frequent fish kills are triggering questions - but there are few answers.

Fish pathologist Vicki Blazer, of the U.S. Geological Survey, has been studying both the fishkills and the live fish. She says, so far, there are two major findings: deadly external lesions and another condition called intersex, also known as feminization. Scientists say both findings are related to contaminants in the water. "Intersex as we see it in the smallmouth bass is the presence of immature oocytes (immature eggs) in the testes of the male bass. So far the females look fairly normal although it is not just the males that are dying in the fish kills. The females also die in the fish kills," she says.

Blazer and the scientists on her team are studying smallmouth bass in this region of the Potomac. "This is a blood sample which when we get back to the lab we'll centrifuge and get the plasma⁹," she says.

The plasma is analyzed¹⁰ to determine what is killing¹¹ the fish. Blazer also checks for lesions and other abnormalities that could kill them. On this fish, one eye is abnormal, while this one has defects on its fin⁸. "These are pale discolor areas on the gills that is not normal," she says.

Research biologist Luke Iwanowicz removes some of the vital organs for further study. "This is a male. That's the testy¹². Many of the changes we can't see with the naked eye just looking at the testy itself. We need to fix the tissue and look at the cells under a microscope," he says.

Blazer says a national study also found intersex characteristics and lesions. 

She and other scientists agree the cause is related to water quality. 

Scientists have found contaminants such as herbicides, pesticides¹³, estrogen and birth control chemicals in the river. Higher concentrations were found where farming is intense and human population dense¹⁴. In general, water treatment plants do not remove all chemicals before dumping water back into rivers.
 
So called endocrine disruptors are especially worrisome because they can change sexual behavior. "One of the concerns is if you have a less aggressive male, they may be less able to protect their nest and do what they are supposed to do. We have done some studies to look at the quantity and quality of the sperm¹⁵, and intersex bass did have somewhat lower sperm count as well as less motor sperm," she says.

Environmental biologist Fred Pinkney is with the U.S. Fish and Wildlife Service. He is studying another area -- the Chesapeake Bay. "I think these fish are sort of swimming in a mixture of low level concentrations of pesticides, of hormones¹⁶ that are released either from waste water plants or from failing septic systems," he says.

He believes the problems are related to hormones, whether from human medical treatments or from farms with large numbers of animals. "People excrete hormones, including things like birth control pills, that largely go untreated through the waste water plants and into the rivers," he says.

Pinkney is also concerned about drinking water. He says fish all over the planet could be developing similar problems because of pollution. 

1 dissect   

v.分割；解剖

参考例句：

• In biology class we had to dissect a frog.上生物课时我们得解剖青蛙。
• Not everyone can dissect and digest the public information they receive.不是每个人都可以解析和消化他们得到的公共信息的。

2 immature   

adj.未成熟的，发育未全的，未充分发展的

参考例句：

• Tony seemed very shallow and immature.托尼看起来好像很肤浅，不夠成熟。
• The birds were in immature plumage.这些鸟儿羽翅未全。

3 bass   

n.男低音(歌手)；低音乐器；低音大提琴

参考例句：

• He answered my question in a surprisingly deep bass.他用一种低得出奇的声音回答我的问题。
• The bass was to give a concert in the park.那位男低音歌唱家将在公园中举行音乐会。

4 belly   

n.肚子，腹部；(像肚子一样)鼓起的部分，膛

参考例句：

• The boss has a large belly.老板大腹便便。
• His eyes are bigger than his belly.他眼馋肚饱。

5 volts   

n.（电压单位）伏特( volt的名词复数 )

参考例句：

• The floating potential, Vf is usually only a few volts below ground. 浮置电势Vf通常只低于接地电位几伏。 来自辞典例句
• If gamma particles are present, potential differences of several thousand volts can be generated. 如果存在γ粒子，可能产生几千伏的电位差。 来自辞典例句

6 stuns   

v.击晕( stun的第三人称单数 )；使大吃一惊；给（某人）以深刻印象；使深深感动

参考例句：

• But sometimes, a moment stuns us as it happens. 但总有那么一个瞬间让我们惊喜。 来自互联网
• Shield Stun: Stuns the top of the aggro chart, 3s stun. 盾牌昏迷：最大眩晕，3秒钟晕眩。 来自互联网

7 joint   

adj.联合的，共同的；n.关节，接合处；v.连接，贴合

参考例句：

• I had a bad fall,which put my shoulder out of joint.我重重地摔了一跤，肩膀脫臼了。
• We wrote a letter in joint names.我们联名写了封信。

8 fin   

n.鳍；(飞机的)安定翼

参考例句：

• They swim using a small fin on their back.它们用背上的小鳍游动。
• The aircraft has a long tail fin.那架飞机有一个长长的尾翼。

9 plasma   

n.血浆，细胞质，乳清

参考例句：

• Keep some blood plasma back for the serious cases.留一些血浆给重病号。
• The plasma is the liquid portion of blood that is free of cells .血浆是血液的液体部分，不包含各种细胞。

10 analyzed   

v.分析( analyze的过去式和过去分词 )；分解；解释；对…进行心理分析

参考例句：

• The doctors analyzed the blood sample for anemia. 医生们分析了贫血的血样。 来自《简明英汉词典》
• The young man did not analyze the process of his captivation and enrapturement, for love to him was a mystery and could not be analyzed. 这年轻人没有分析自己蛊惑著迷的过程，因为对他来说，爱是个不可分析的迷。 来自《简明英汉词典》

11 killing   

n.巨额利润；突然赚大钱，发大财

参考例句：

• Investors are set to make a killing from the sell-off.投资者准备清仓以便大赚一笔。
• Last week my brother made a killing on Wall Street.上个周我兄弟在华尔街赚了一大笔。

12 testy   

adj.易怒的；暴躁的

参考例句：

• Ben's getting a little testy in his old age.上了年纪后本变得有点性急了。
• A doctor was called in to see a rather testy aristocrat.一个性格相当暴躁的贵族召来了一位医生为他检查。

13 pesticides   

n.杀虫剂( pesticide的名词复数 )；除害药物

参考例句：

• vegetables grown without the use of pesticides 未用杀虫剂种植的蔬菜
• There is a lot of concern over the amount of herbicides and pesticides used in farming. 人们对农业上灭草剂和杀虫剂的用量非常担忧。 来自《简明英汉词典》

14 dense   

a.密集的，稠密的，浓密的；密度大的

参考例句：

• The general ambushed his troops in the dense woods. 将军把部队埋伏在浓密的树林里。
• The path was completely covered by the dense foliage. 小路被树叶厚厚地盖了一层。

15 sperm   

n.精子，精液

参考例句：

• Only one sperm fertilises an egg.只有一个精子使卵子受精。
• In human reproduction,one female egg is usually fertilized by one sperm.在人体生殖过程中，一个精子使一个卵子受精。

16 hormones   

n. 荷尔蒙，激素 名词hormone的复数形式

参考例句：

• This hormone interacts closely with other hormones in the body. 这种荷尔蒙与体內其他荷尔蒙紧密地相互作用。
• The adrenals produce a large per cent of a man's sex hormones. 肾上腺分泌人体的大部分性激素。