Arthur Grossman and Dimitri Tolleter of Carnegie Institution with John Pringle and Steve Palumbi of Stanford University published the first documented evidence that coral bleaching occurs in the dark in the Sept. 5, 2013, edition of the journal Current Biology.
The scientists grew coral under laboratory condition in the dark with high temperature water and the coral still bleached. Photosynthesis does not occur in the dark.
This result is inconsistent with the prevailing understanding of the symbiotic relationship between coral and algae and contravenes present plans to reduce the damage to coral from climate change.
Previous thought indicated that the algae provide essential nutrients to coral from photosynthesis and that high temperature water and excessive sun light damaged the relationship or may inhibit the ability of the algae to perform photosynthesis.
The new evidence suggests that more complex relationships may be involved.
Coral may eject algae in the dark or at night to prevent the build up of accumulation of high oxygen content photosynthetic products that could damage coral. The loss of color may be a natural protective mechanism.
The researchers suggest the monitoring of algae and their photosynthetic products as a more reliable means of determining the extent of damage that high water temperature from climate change may cause. They also suggest that the scheme to shade coral to prevent sun damage would only produce more bleached coral because coral become bleached in the dark according to the scientist’s new discovery.