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A study has found that warmer waters off North America's West Coast caused many kinds of sea life to move farther north than ever before.
The study was a project of scientists from the University of California, Davis.The scientists examined waters off the coast of Northern California in the eastern Pacific Ocean.The researchers say they recognized a local of 67 species (物种) between 2014 and 2016, during what was described as a “marine heatwave”．Marine heatwaves were explained in the study as “a period of extreme sea surface temperatures lasting for days to months”．The 2014－2016 heatwave is thought to be the largest ever recorded.The warm water later moved southward toward California.
The warmer waters were partly a product of El Niño conditions during the same period, researchers noted.El Niño develops when winds off the coast of South America weaken.This enables the warm water in the western Pacific to move eastward.El Niño often causes ocean temperatures in the area to rise between 2 to 4 degrees Celsius, the study found.
The researchers reported that 37 of the 67 species they studied had never before been observed so far north as California.These creatures are native to an area hundreds of kilometers to the south, mainly around Baja California in Mexico.A few were even found north of California, off the state of Oregon.The northward travel of so many different sea creatures was considered “unprecedented” (史无前例的) by the researchers.Among the species found in the study were a meateating sea slug that hunts other sea slugs, a sea snail “butterfly” and a purplelined jellyfish.Another unexpected visitor was the pelagic red crab, which researchers said had only been found in areas off the coast of Mexico.
Scientists involved in the study believe the findings can provide valuable information for knowing future sea life reactions to warming oceans.
语篇解读：本文是一篇说明文。文章主要介绍了海洋热浪致美国大量海洋生物异常北迁。
1．What is a marine heatwave according to the passage?
A．An ocean with the rough surface.
B．A wave with low temperatures.
C．A period of warmer ocean surface water.
D．A species living in extreme weather.
解析：选C 细节理解题。由第二段中的Marine heatwaves were explained in the study as “a period of extreme sea surface temperatures lasting for days to months”．可知，海洋热浪是一个海洋表层水变暖的时期。
2．What contributes to El Niño conditions?
A．Warmer waters.
B．Weakened winds off South America.
C．The colder sea surface.
D．Species moving northward.
解析：选B 细节理解题。由第三段中的El Niño develops when winds off the coast of South America weaken.可知，南美洲减弱的风促使了厄尔尼诺现象的产生。
3．Why does the author mention the meateating sea slug in Paragraph 4?
A．To point out that ocean environment becomes worse.
B．To suggest that sea creatures need separate living space.
C．To prove that many kinds of sea life can adapt to warmer waters.
D．To evidence that ocean temperatures along California are higher than before.
解析：选D 推理判断题。由第四段内容可知，所有研究的67个物种中，有37个在加利福尼亚州北部从未被观察，这是因为加利福尼亚州沿岸的海洋温度比以前高。作者在第四段中提到了食肉海蛞蝓就是为了证明加利福尼亚州沿岸的海洋温度比以前高了。
4．What can be inferred from the passage?
A．The heatwaves disturb the life of many sea creatures.
B．The increased temperature benefits many sea creatures.
C．Sea life reactions can be valuable to predict future heatwaves.
D．The heatwaves cause many unexpected visitors to move southward.
解析：选A 推理判断题。通读全文尤其是第一段内容可知，海洋热浪导致美国大量海洋生物异常北迁，这是一种被迫性地迁移。根据海洋生物的被迫迁移可以判断出，热浪扰乱了许多海洋生物的生活。
