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Warm waters likely to trigger coral bleaching

Hawaii reefs face a major bleaching event coming soon

The Maui News

Warmer than normal ocean temperatures in Hawaiian waters “are likely to cause corals . . . to bleach and even die” in a repeat of 2014 and 2015, the state Department of Land and Natural Resources said Friday.

Data from the National Oceanic and Atmospheric Administration’s Coral Reef Watch program indicates Hawaii’s coral reefs are entering a major bleaching event within the next two months, if not sooner, DLNR said.

“Ocean temperatures are extremely warm right now across Hawaii,” about 3 degrees higher than a typical mid-August, said NOAA scientist Jamison Gove.

Division of Aquatic Resources Administrator Brian Neilson said that the bleaching is “probably going to be worse than the ones we experienced four and five years ago.” Maui shorelines experienced mortality of 20 to 30 percent; West Hawaii recorded a 50 percent mortality rate.

Leeward Maui reefs were among the hardest hit, ocean experts said.

Beaching already is being observed in corals off West Hawaii, said Nikki Sanderlin, acting aquatic biologist for the Division of Aquatic Resources West Hawaii district office.

Coral bleaching is a change from normal coloration of browns, yellows and greens to a nearly white color, the DLNR news release said. This change occurs when corals are stressed by environmental changes, especially temperature increases. Although corals can recover from moderate levels of heat, prolonged warming will kill them.

Scientists say that reducing secondary stress on corals during these bleaching events can improve the chances of coral survival, with which the public can help by:

• Avoiding touching corals or coral reefs while diving, snorkeling or swimming.

• Not standing or resting on corals.

• Using reef-safe sunscreens.

• Having boaters use mooring buoys or anchor only in sand areas.

• Keeping anchor chains off the reef.

• Having fishers reduce or stop their take of herbivores, such as parrotfish (uhu), surgeonfish and sea urchins. Herbivores clear reefs of algae, which overgrow and kill corals during bleaching events.

• Taking extra precaution to prevent other potential contaminants from getting to the ocean, such as dirt from poorly managed commercial and private earthwork; chemical pollution from fertilizers, soaps, detergents used in outdoor watering and car washing; and other contaminants like oil from poor containment practices.

“These are actually things we should be doing all the time, but it’s especially important now,” Neilson said. “We’d also like swimmers, snorkelers and divers to report when and where they see both bleaching and healthy corals. Those healthy corals may provide valuable information about how some corals are better able to survive these types of events.”

DLNR and NOAA are using new technology to better understand the real-time extent of predicted bleaching events. Arizona State University, which created and is maintaining the Hawaii coral website, is providing weekly satellite imagery, which helps identify bleaching areas. The website is hawaiicoral.org.