Hawaii County officials are closing Kahaluu Beach Park in Kailua-Kona on May 20 and 21 to protect the reef during coral spawning events.

Last year, according to Cindi Punihaole, director of Kahalu‘u Bay Education Center, the bay was only closed for a half-day for two days, but scientists have recently concluded it would be beneficial to close the bay for two, full days of rest during critically important reproduction events, which they can now accurately predict.

Cauliflower coral (Pocillopora meandrina) was once abundant on shallow coral reefs along West Hawaii, including Kahaluu Bay, according to state officials from the state Division of Aquatic Resource and Eyes of the Reef, a community reporting network for coral disease. In 2015, environmental stressors and very high ocean temperatures due to El Nino caused catastrophic bleaching and the mortality of more than 90% of the regional population of cauliflower coral.

For more than a decade, researchers have observed annual “broadcast spawning events” for cauliflower corals. During these events, corals emit reproductive cells (“gametes”) into the water column, which are carried by the tides to mix and generate planktonic coral larvae.

Scientists can predict when spawning events will likely occur based on season, solar, tidal and lunar cycles. Last year was also the first year scientists were able to “settle the gametes.”

After years of trying, the first case of successful cauliflower coral larvae settlement within a laboratory setting took place at the Natural Energy Laboratory of Hawaii Authority (NELHA). Without disturbance, it took as little as 24 hours for coral gametes to find proper colony areas within the tanks.

The high volume of daily visitors to Kahaluu Bay may cause harm to larval corals due to physical and chemical disturbances, said Punihaole, including residue from sunscreens and other personal care items in surface waters of the bay. In recent studies, oxybenzone chemicals in sunscreens were shown to cause damage to larval corals and prevent successful settlement on the reef.

“In the long-run, this is going to be for our future, and our children’s future,” said Punihaole.

Contact the Kahalu’u Bay Education Center at 895-1010 for more information.