Kahalu‘u Beach Park in Kailua-Kona will be closed on May 20 and May 21 due to “anticipated coral spawning events,” according to a Hawaii County news release.
Cauliflower coral (Pocillopora meandrina) was once abundant on shallow coral reefs along West Hawaii, including Kahalu‘u Bay. However, environment stressors and high ocean temperatures impacted West Hawaii in 2015 and caused catastrophic bleaching and mortality of more than 90 percent of the regional population of cauliflower coral.
To recover from this loss in the coral population, natural reproduction events are critically important, the release said. For more than a decade, researchers have observed annual broadcast spawning events for cauliflower corals, and can now accurately predict when they will likely occur based on season, solar, tidal and lunar cycles.
During broadcast spawning events, corals emit reproductive cells (“gametes”) into the water column, and these materials are carried by the tides to mix and generate planktonic coral larvae. The high volume of daily visitors to Kahalu‘u Bay may cause harm to larval corals due to physical and chemical disturbances (e.g. 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.
After many years of unsuccessful cauliflower coral larvae settlement within a laboratory setting, the very first successful settlement occurred last year at the Natural Energy Laboratory of Hawaii Authority. Undisturbed by pollutants and human activity, it took as little as 24 hours for coral gametes to find proper colony areas within the tanks.
Minimizing pollutants and physical disturbances within the spawning period in their natural environment will help ensure that corals are able to successfully reproduce and settle properly.
For more information, please contact the Kahalu‘u Bay Education Center at (808) 895-1010.