A study by University of Guam researchers has found that shade can mitigate the effects of heat stress on corals. The study, which was funded by the university’s National Science Foundation was published in February in the peer-reviewed Marine Biology Research journal.
“We wanted to see what role light has in coral bleaching,” said UOG Assistant Professor Bastian Bentlage, the supervisor and co-author of the study. “Usually, people talk about temperature as a cause for bleaching, but we show that both light and temperature work together.”
Previous UOG research found that more than one-third of all coral reefs in Guam were killed from 2013 to 2017 over the course of multiple bleaching events. Coral bleaching is the process in which corals stressed by environmental changes expel the essential symbiotic algae that live in their tissues, causing them to turn white and often die.
This latest study examined the resilience of staghorn corals in heightened seawater temperatures. This species of coral is one of Guam’s dominant reef-builders, and its habitats experience temperatures up to 97 degrees Fahrenheit during the hottest months of the year, leaving it vulnerable to bleaching episodes and population decline.
The researchers found that the corals took three weeks to recover from a week-long heat stress event. The experiment was then replicated to see how the corals would react if they were given shade while subjected to warmer temperatures.
Lead author Justin T. Berg, a UOG graduate student studying biology said
“We found that when we put the shading over coral with increased seawater temperatures, it greatly increased photosynthetic yield of the symbiotic algae. Shade made a huge difference for coral health when you have high temperatures,” Berg said.
