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A. New Insight into Coral Reef Death

Narrator: This is Science Today. The health of coral reefs has been known to be at risk due to direct stressors such as water pollution, climate change and over-fishing, all of which can cause an overgrowth of algae that smothers the corals. Now, a team of scientists has discovered for the first time, an indirect microbial process in which bacteria and algae are combining to kill corals. Marine ecologist, Stuart Sandin of the University of California, San Diego 's Scripps Institution of Oceanography, was part of the study.

Sandin: So, this study was an effort to try to look at some of these indirect effects between the some of the relationships between algae and corals. In regions where there was more sugar in the water, the coral dies more.

Narrator: The researchers discovered that the sugars that algae release, feed bacterial communities living on the coral, causing them to flourish and kill the corals by cutting off their oxygen supply. This frees up more space for algae and the decline continues.

Sandin: We know that in many regions, we're increasing the growth rates of algae on coral reefs. If we want to keep it around, we've got to start doing something for it.

Narrator: For Science Today, I'm Larissa Branin.