Corals upgrade algae to beat the heat

By Catherine Brahic

In oceans around the world, heat-resistant algae are offering the prospect of a colourful future for corals. The reef-forming animals are upgrading their symbiotic algae so that they can survive the bleaching that occurs in waters warming under climate change.

"The most exciting thing was discovering live, healthy corals on reefs already as hot as the ocean is likely to get 100 years from now," says Stephen Palumbi of Stanford University.

Corals have a symbiotic relationship with tiny algae called zooxanthellae. The corals give the algae a home and, in exchange, the algae provide the corals with food. When water temperatures get too hot, the corals expel the algae. This is what is known as coral bleaching and it is expected to kill coral reefs around the world as global temperatures rise.

In the past few years, biologists have discovered that some zooxanthellae can live at warmer temperatures than others, making the corals that host them naturally heat-resistant. What's more, during a heatwave on the Great Barrier Reef in 2006, an Australian team found that many corals that survived the hot period had swapped their algae for more heat-resistant ones. …

Corals upgrade algae to beat the heat

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