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  3. Global warming looks like it will be a bigger problem for the world’s fish species than scientists first thought; A new study sh

Global warming looks like it will be a bigger problem for the world’s fish species than scientists first thought; A new study sh

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问题     Global warming looks like it will be a bigger problem for the world’s fish species than scientists first thought; A new study shows that when fish are laying eggs, they are more vulnerable to hotter water. With medium-level human-caused climate change expected by the end of the century, the world’s oceans, rivers and lakes will be too hot for about 40％ of the world’s fish species in the egglaying stage, according to a study. That means they could go extinct or be forced to change how and where they live and reproduce.
    Until now, biologists had just studied adult fish. For adult fish, around 2％ to 3％ of the species would be in the too-hot zone in the year 2100 with similar projected warming. So using this new approach reveals a previously unknown problem for the future of fish, scientists said. In a worst case climate change scenario the figure for species in trouble jumps to 60％. These vulnerable times in the life of a fish make this a "bottleneck" in the future health of species, said Hans-Otto Portner, a marine biologist at the Alfred Wegener Institute in Germany.
    A marine heatwave last year caused large numbers of migrating salmon fish to die throughout Alaska’s rivers. It also killed off cod fish eggs, showing what a warmer future might be like, said Flemming Dahlke, a marine biologist at the institute. "With those fishes most sensitive to warming waters, it means fish populations won’t be able to replace themselves," said Rutgers University ecologist Malin Pinsky. "Without reproduction and offspring, we have no fish, no fishing and no fish on our plates. "
    In studying 694 species, Dahlke and Portner found some of the fish likely to be hardest hit by this phenomenon include Alaska pollock—the biggest fishery in the United States and the source of fast food fish slices—and well-known fish species such as sockeye salmon, brown trout, bonito, barracuda and swordfish. "The more we allow temperature to change, the more we will lose the natural foundation of human life, including food from the sea," Portner said. When it gets too warm for living, the species could still possibly move to someplace cooler or lay at another time, but that’s not easy, Dahlke said. "This could mean a lot of problems to many species.
The underlined word "bottleneck" (Line 5, Para. 2) is closest in meaning to________.
选项 A、intricacy
B、aggravation
C、barrier
D、obscurity
答案C
解析 词义题。根据题干可定位至第二段最后一句These vulnerable times in the life of a fish make this a “bottleneck” in the future health of species. 即“鱼类生命中这些易受伤害的时期，是未来物种健康的‘瓶颈”’，根据上下文可以推知，更热的水不适合鱼类的繁殖，鱼类在繁殖阶段会比较脆弱，因此会影响整个鱼类的未来健康，所以该词的意思是“瓶颈，障碍，阻碍”。C项barrier意为“障碍”，故为正确答案。A项intricacy意为“错综，复杂”；B项aggravation意为“加剧”；D项obscurity意为“朦胧，阴暗”；A、B项D项均不符合题意。
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