Some corals may adapt to warmer seas

Science : Fast-growing coral species in colonies that have been previously bleached by high sea temperatures may be able to adapt or evolve to elevated water temperatures in a single generation. Corals rely on symbiotic algae, called zooxanthellae, to produce nutrients through photosynthesis; when water temperatures exceed a certain threshold, the coral expels the algae, turns white, and if high temperatures persist for too long, dies. James Guest of University of New South Wales Australia and colleagues studied three coral reef sites during a 2010 bleaching episode. At an Indonesian site that had not been subjected to warmer water previously, the higher temperatures brought on the familiar bleaching and die-offs of fast growing species; slow growing species experienced less bleaching. However, the sites in Singapore and Malaysia, where the coral had been bleached in 1998, the fast growing species remained healthy. Slow-growing species still suffered bleaching. It’s uncertain whether the coral itself or the zooxanthellae—or both—that adapted to exhibit bleaching resistance. While this is hopeful news, the global threat to coral reefs from climate change must still be dealt with.