Every spring, in regions at high altitudes around the world, one of Earth’s tiniest migrations takes place. The migrants are single-celled green algae (海藻); they are relatives to plants growing in the sea, but instead of living in the sea they live in snow. They spend the winter deep in the snow. In the spring, they wake and swim up through flowing streams of melted snow to the surface, dividing and photosynthesizing (进行光合作用) as they go. Then, at the top, they turn red. This creates what scientists call pink snow.
The color comes from astaxanthin (虾青素), a substance that gives some living things their reddish color. The algae produce astaxanthin as a form of sun protection; it absorbs UV light, thereby warming the organisms and thus melting the surrounding snow. “The melting helps them a lot,” said Roman Dial, a biologist at Alaska Pacific University. “The moment there is liquid water on the snow, the algae start growing.”
Pink snow is a perfectly natural phenomenon, but in an age of disappearing glaciers (冰川), it is also problematic. Last year, scientists discovered that the algae turned the snow surface dark, reducing the amount of sunlight reflected by some glaciers in Scandinavia—and increasing the amount of sunlight absorbed—by 30%. The result, as Dial and his colleagues demonstrated in this month’s issue of Nature Geoscience, is faster melting. As in other parts of the warming planet—particularly the Arctic, where scientists fear that melting permafrost (永冻土层) may lead to further climatic changes. Ice sheets are already being darkened by dust and ash, which makes the process of melting faster and provides nutrients for algae growth. As the organisms multiply, they melt even more snow, which allows them to increase in their population again. “It spreads more rapidly than people realize, once it gets established,” Dial said.
Snow algae need snow; when that’s gone, which seems to be the direction of things, the snow algae will go, too. Before the snow algae disappear, though, and while there’s still some glacier left, it’s entirely possible that the last snow we’ll see on Earth will be pink or even red, a wound on Earth.
【小题1】What causes the color of pink snow?
| A．The migration that involves the algae and other plants. |
| B．The flowing streams that the algae travel through. |
| C．The algae that turn red at the snow’s surface. |
| D．The sunlight that directly reflects on the algae. |
【小题2】How does astaxanthin benefit the algae according to Paragraph 2?
| A．It absorbs UV light to cool down the algae. | B．It prevents the algae from photosynthesizing. |
| C．It colors the algae for the purpose of decoration. | D．It helps protect the algae from the sun. |
【小题3】What is the problem associated with pink snow mentioned in Paragraph 3?
| A．It increases the reflection of sunlight. | B．It speeds up the melting of glaciers. |
| C．It leads to a decrease in algae populations. | D．It reduces the amount of liquid water available. |
【小题4】According to the passage, what concern do scientists have regarding the Arctic region?
| A．The rapid melting of glaciers may lead to an increase in permafrost. |
| B．The darkening of ice sheets may slow down the process of melting. |
| C．The warming climate may result in the extinction of algae in the region. |
| D．Darkening ice sheets and multiplied algae may worsen climate change. |
【小题5】What is the author’s attitude towards pink snow in the passage?
| A．Concerned. | B．Indifferent. | C．Neutral. | D．Optimistic. |
