After the worst coral bleaching event ever recorded in Hawaiʻi, University of Hawaiʻi scientists and researchers with the Hawaiʻi Institute of Marine Biology are diligently monitoring and testing affected coral reefs in Kāneʻohe Bay, along with other areas on O‘ahu, and in parts of the Northwestern Hawaiian Islands.
“A bleached coral can either recover or it will die,” said Ruth Gates, a researcher in HIMB, part of the UH Mānoa School of Ocean and Earth Science and Technology. “It is as simple as that and we really don’t know what that outcome is until months after that event.”
Fifty to 75 percent of the coral on some reefs in Kāneʻohe Bay are affected by a coral bleaching event earlier this year. HIMB is based on Coconut Island in Kāneʻohe Bay, an area hit hard by the event. UH researchers there are now paying close attention to which species and reefs recover, and which ones fail to survive.
“What is driving the physiology, the biology of that response, is going to be critical for determining the long term implications of this event,” HIMB researcher Courtney Couch said.
Coral bleaching is typically caused by a rise in water temperature. It has already affected an estimated 30 percent of the world’s reefs over the last 20 years. Coral turn white (bleach) when micro algae living in its tissue — that give coral its brown color — leave during stressful environmental conditions. The coral will begin to deteriorate if unfavorable conditions persist or are too extreme and it is unable to bounce back.
“The coral itself, the live animal dies, and gradually the skeleton that is the structure of the reef, starts to dissolve and be flattened,” Gates said.
This can seriously impact a coastal area. As the foundation for reefs, coral play a critical role by providing protection from coastal erosion and are a habitat for food fish and other sea life, while generating millions in tourism dollars in places like Hawaiʻi.
“The bleaching events that we are seeing, there’s evidence that suggests that they are becoming more frequent and severe,” Couch said.
Smaller coral bleaching events have been recorded in Hawaiʻi before. This event was first reported in the Northwestern Hawaiian Islands in mid August and then on Oʻahu in late September as the same body of warmer water moved into the main Hawaiian Islands. That’s when the water temperature in Kāneʻohe Bay spiked three degrees to 90 degrees over a period of nearly four weeks.
“It was a time when the trade winds dropped and so there was no mixing of the water and it was very, very sunny,” Gates said.
UH researchers and scientists are now trying to determine what can be done to minimize the effects of future coral bleaching events, but emphasize that the time to act is now.
“We want to reduce sediment loads, we want to reduce pollutants, we want to do everything we can to protect our near coastal environments so when an event like this comes along, the corals are as healthy as possible to face that event,” Gates said.