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Water Pollution

Can the world's coral be saved?

Can the world's coral be saved?

Two Steps is a perfect snorkeling spot on the Big Island of Hawaii. Black lava rocks step down twice into the clear waters of a small bay where, on a good day, you're guaranteed to see brightly colored fish and green sea turtles shoaling through myriad forms of coral in shades of brown, green, yellow, pink and purple.

But if you happened to visit last month, you would have found about 30% of the corals bleached wedding-cake white.

It's a sure sign that the ocean is heating up. Overly warm water causes living coral polyps to expel the photosynthetic algae, called zooxanthellae, that give them their varied colors and about 70% of their nutrients. If the bleaching lasts too long,...