Too Much of a Good Thing Can Be Bad for Corals

Pew Marine Fellow Andrew C. Baker (2008) and his doctoral student at the University of Miami's Rosenstiel School of Marine and Atmospheric Science, Ross Cunning, made some surprising discoveries in their research on coral reef resilience in rising ocean temperatures. Their paper, recently published in Nature Climate Change, found that corals may be more severely affected by climate warming when they contain too many symbiotic microalgae. In other words, too much of a good thing can be bad for corals in warmer environments.

Corals have a close relationship (called symbiosis) with microscopic algae that live inside them, which is mutually beneficial. In fact, these microalgae help to give them their color. When water gets excessively warm, corals expel microalgae, causing “bleaching” episodes that often result in coral death. Before this study, scientists had assumed that corals with more symbiotic microalgae would be less likely to bleach severely. With this finding, however, scientists now theorize that corals may be less resilient in areas where they tend to have high levels of beneficial microalgae. And because wastewater and polluted runoff in coastal waters promote the growth of these microalgae in coral tissues, Dr. Baker points out that reducing pollution and improving water quality might be a way that local action could directly help safeguard corals in warming oceans.

Read the paper, Excess Algal Symbionts Increase the Susceptibility of Reef Corals to Bleaching, on the Nature Climate Change website.

Read the press release, Too Much of a Good Thing Can Be Bad for Corals, on the University of Miami website.