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US Scientists Discover Large Die-off of River Mussels

时间:2019-12-28 20:29来源:互联网 提供网友:nan   字体: [ ]
    (单词翻译:双击或拖选)

Scientists are investigating a massive die-off of mussels in a major river in the southeastern United States. They hope to learn the cause.

In 2016, fish and wildlife officials discovered a big drop in the mussel population in the Clinch1 River. The river flows about 480 kilometers through the states of Virginia and Tennessee. It is home to many different kinds of fish and 46 species of mussels.

While freshwater mussels are small, they perform some important activities to keep rivers healthy. Mussels can clean up up to 38 liters of river water each day, removing algae2, metals and other materials. The process can create a better river environment for fish, amphibians4, plants and insects.

For this reason, scientists are working to find the cause of the large drop in mussel populations.

Jordan Richard is a biologist with the U.S. Fish and Wildlife Service. He told The Associated Press that officials have estimated that hundreds of thousands, possibly even millions, of mussels have died in the Clinch River.

The mass die-off in the river of one kind of mussel, called the pheasantshell, has been especially worrisome. Officials say the population of pheasantshells dropped from 94,000 in 2016 to less than 14,000 in 2019. They measured the decrease along a 200-meter stretch of the Clinch River.

Similar die-offs have been reported on at least five U.S. rivers and another in Spain. Richard has studied reports of similar die-offs over the years in rivers around the world. But so far he has not come up with many answers about why they happened.

Speaking about the Clinch, Richard said the river could even be compared to the Amazon because it contains so many different kinds of life. He spoke5 to the AP while examining the river's mussel population in a rural community in Tennessee.

Mussel populations around the world have dropped sharply over the past 100 years. Scientists blame this on pollution, habitat loss and climate change. But they suspect the most recent decreases have another cause.

Richard and his team believe an infectious disease could be responsible. The team is comparing healthy pheasantshell mussels to dying ones in an attempt to narrow down a list of possible diseases.

"All living things are chock-full of microorganisms, and we don't have any sort of map for what is healthy inside a mussel," Richard said.

University of Wisconsin disease specialist Tony Goldberg is helping6 with the investigation7. He specializes in wildlife illnesses of unknown cause. Goldberg told the AP that often disease is the final thing to kill a species that has already been harmed by other environmental conditions.

However, he says he is hopeful that the freshwater mussel team will be able to discover the cause of the massive die-offs and find a way to prevent them. The team includes scientists from the U.S. Geological Survey and a nonprofit conservation group.

"I see it as a race against time, not an impossible task," Goldberg said, adding "...if we lose these mussels, the rivers we all love are never going to be the same."

Words in This Story

species – n. a group of animals or plants that are similar and can produce young animals or plants

algae – n. a plant with no stem or leaves that grows in or near water

amphibian3 – n. a type of animal that can live both on land and in water

habitat – n. the natural living environment for living things

chock-full – n. very full


点击收听单词发音收听单词发音  

1 clinch 4q5zc     
v.敲弯,钉牢;确定;扭住对方 [参]clench
参考例句:
  • Clinch the boards together.用钉子把木板钉牢在一起。
  • We don't accept us dollars,please Swiss francs to clinch a deal business.我方不收美元,请最好用瑞士法郎来成交生意。
2 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。
3 amphibian mwHzx     
n.两栖动物;水陆两用飞机和车辆
参考例句:
  • The frog is an amphibian,which means it can live on land and in water.青蛙属于两栖动物,也就是说它既能生活在陆地上也能生活在水里。
  • Amphibian is an important specie in ecosystem and has profound meaning in the ecotoxicology evaluation.两栖类是生态系统中的重要物种,并且对环境毒理评价有着深远意义。
4 amphibians c4a317a734a700eb6f767bdc511c1588     
两栖动物( amphibian的名词复数 ); 水陆两用车; 水旱两生植物; 水陆两用飞行器
参考例句:
  • The skin of amphibians is permeable to water. 两栖动物的皮肤是透水的。
  • Two amphibians ferry them out over the sands. 两辆水陆两用车把他们渡过沙滩。
5 spoke XryyC     
n.(车轮的)辐条;轮辐;破坏某人的计划;阻挠某人的行动 v.讲,谈(speak的过去式);说;演说;从某种观点来说
参考例句:
  • They sourced the spoke nuts from our company.他们的轮辐螺帽是从我们公司获得的。
  • The spokes of a wheel are the bars that connect the outer ring to the centre.辐条是轮子上连接外圈与中心的条棒。
6 helping 2rGzDc     
n.食物的一份&adj.帮助人的,辅助的
参考例句:
  • The poor children regularly pony up for a second helping of my hamburger. 那些可怜的孩子们总是要求我把我的汉堡包再给他们一份。
  • By doing this, they may at times be helping to restore competition. 这样一来, 他在某些时候,有助于竞争的加强。
7 investigation MRKzq     
n.调查,调查研究
参考例句:
  • In an investigation,a new fact became known, which told against him.在调查中新发现了一件对他不利的事实。
  • He drew the conclusion by building on his own investigation.他根据自己的调查研究作出结论。
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