Coral Reef Cooling

Climate Foundation
Posted on: 10/18/2018 - Updated on: 2/28/2020

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There are very few tools available for Coral Reef managers for counteracting mass coral bleaching, primarily caused by elevated seawater temperatures. Climate Foundation developed a field-based cooling system for reef water to give Coral Reef managers the possibility to act on bleaching warnings to preserve high-value reefs in the face of climate threats. ​

We asked ourselves, can we reverse coral bleaching in the field on a small scale? Can we scale it? Can we provide reef managers with new tools to protect high-value reefs against climate change?

Experimental setup:

In order to test methods of reversing coral bleaching Climate Foundation selected an area     where it is possible to estimate precisely the beginning and the end of an annual coral bleaching process. The Tutuila airport reef was chosen as a perfect exploration ground since it offers all relevant site selection criteria. It was near to shore, it was near a power source,  the coral bleached annually and Doug Finner had systematically logged the temperature and bleaching for years. ​
Photos of coral were calibrated using a CoralWatch coral-health chart to measure color intensity. On this scale, low values of 1-2 correspond to pale, bleached color, while higher values of 3-5 correspond to more intense color (less bleached). Temperature loggers and illumination data loggers recorded temperature to 0.1°C.  Recordings were made for up to two weeks after treatment to observe the prolonged biological response to treatment.
Experiment results:
Color intensity increased 3 to 4 units at test sites in one day on the CoralWatch scale with no increase at reference sites. Color intensity held for over a week before declining by 1 unit a week after cooling stopped. Other reference sites remained bleached. In under 12 hours, the color returned to the coral! The bleaching had stopped.

Based on these results, effective strategies to reverse coral bleaching can be developed. Besides using the NOAA bleaching forecasts to provide warning to reef managers, reef managers can deploy  portable thermal management systems to ensure reef survival through major thermal bleaching events. Therefore regional scaled cooling infrastructure anticipating future bleaching can be designed and procured after testing biological response with a portable cooling system.