Volcano kills coral.

Scientists in Israel recently discovered a coral reef nearly smothered to death. The culprit? Mount Pinatubo, a volcano in the Philippines, 9,700 kilometers (6,000 mi) away.

"We were amazed that a volcanic eruption thousands of kilometers away could hurt the coral reef right outside our office," says Amazia Genin, an Israeli marine biologist.

When Mount Pinatubo erupted in 1991, it spewed gases high into the atmosphere, explains Tyler Volk, an earth scientist at New York University. "Like tiny mirrors, droplets of the gas reflected sunlight and kept some of the rays from reaching Earth," he says. As a result, temperatures in the Red Sea--home to many corals--dropped last winter.

When the cool surface water sank, it pushed deep, nutrient-rich water upward, says Genin. On the surface, the nutrients fed huge numbers of plantlike organisms, called algae, which grew to form a thick red algae "carpet" on the sea. The carpet blocked sunlight from reaching the plants that provide nutrients for the corals below.

Within a year, many polyps--the tiny, jellyfishlike animals that make up a coral reef--died. Only the dead coral jellyfishlike skeletons remained.

But now, says Genin, the reef is making a comeback. As the volcanic gases gradually settle out of the atmosphere, more sunlight reaches the sea. The water is warming, surface algae are dying, and the coral is growing back.