The color of the ocean has changed greatly over the last 20 years and human-caused climate change is probably responsible, according to a new study.

More than 56% of the world’s oceans have changed color, and this cannot be explained by natural changes, said a team of researchers. Tropical (热带的) oceans close to the equator especially have become greener in the past two decades, reflecting changes in their ecosystems.

The color of the ocean is derived from the materials found in its upper layers. For example, a deep blue sea will have very little life in it, while a green color means there are ecosystems there. The ecosystems are based on plant-like small living things which include chlorophyll(叶绿素). The living things form the base of a food web which supports larger creatures such as fish, seabirds and some other sea animals.

It’s not clear exactly how these ecosystems are changing, said study author Stephanie Dutkiewicz. Ocean ecosystems are finely balanced and any change in the small living things will influence the food chain. “All changes are causing an imbalance in the natural organization of ecosystems. Such imbalance will only get worse over time if our oceans keep heating,”she said. It will also affect the ocean’s ability to act as a store of carbon(碳), Dutkiewicz said, as different living things take in different amounts of carbon.

The researchers are still working to find out exactly what the changes mean. However, what is clear, they said, is that the changes are being driven by human-caused climate change.

The researchers checked changes in ocean color from space by following how much greenor blue light was reflected from the surface of the sea. They studied the changes in color from 2002 to 2022. And then they used climate change models to see what would happen to the oceans both with additional(额外的) planet-heating pollution and without.

The color changes matched almost exactly what Dutkiewicz said would happen if greenhouse gases were added to the atmosphere — around 50% of our oceans would change color.

【小题1】Which areas of the ocean have shown the greatest color change?

A．Deep-sea areas with little life.	B．Oceans with lower temperatures.
C．Coastal areas close to large cities.	D．Tropical oceans near the equator.

【小题2】What does the underlined “is derived from” in para.3 mean?

A．Is reflected in something.	B．Comes from something.
C．Influences something.	D．Creates something.

【小题3】How can the changes in ecosystems influence oceans?

A．They keep the balance among different living things.

B．They reduce the ocean’s ability to store carbon.

C．They improve the health of large sea animals.

D．They make oceans support more life.

【小题4】What did the researchers use climate change models for?

A．To support space exploration.

B．To find the sources of greenhouse gases.

C．To show future ocean temperature changes.

D．To study the influence of planet-heating pollution.