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Coral bleaching appears off Maui as ocean heats up

Nina Wu
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State officials said signs of severe and widespread coral bleaching event, as earlier predicted, are already apparent along reefs off of Maui due to higher than average ocean temperatures.
Video courtesy DLNR
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A team from the DLNR Division of Aquatic Resources discovered coral bleaching at Molokini and along Maui’s south shore from Makena to Maalaea last week.

State officials said signs of severe and widespread coral bleaching event, as earlier predicted, are already apparent along reefs off of Maui due to higher than average ocean temperatures.

In August, National Oceanic and Atmospheric Administration officials and scientists had warned of a severe coral bleaching event this month, one that could possibly be worse than the last one in 2015.

Coral bleaching is a change from normal coloration of browns, yellows and greens to a nearly white color. It occurs when corals are exposed to environmental stressors, such as temperature increases, runoff or pollution. When stressed, corals expel a symbiotic algae from within their tissues, causing them to turn white.

>> Click here to see photos of coral bleaching seen along reefs off of Maui.

During a rapid assessment of coral health last week, a team from the state Division of Aquatic Resources found evidence of coral bleaching at Molokini and along the south shore, from Makena to Maalaea.

“Molokini is composed of high percentages of the coral species, Montipora capitata, and we found roughly 50% of this coral already bleached or paling heavily,” said Russell Sparks, a DAR aquatic biologist, in a news release.

In waters off Makena, Wailea, and Kihei, the team found that the percentage of corals showing bleaching were currently at less than 10%. At Olowalu, scientists detected numerous Porities corals that were bleached and overgrown with turf algae during routine monitoring in August.

Sparks said that reefs in dirty water , such as the ones closer to shore at Kalama Park and other areas in North Kihei, are doing better than in similar areas with cleaner water. Ironically, this may be due to the shading effect of dirty water, which possibly reduces some of the stress from direct sunlight.

Ocean temperatures, meanwhile, remain well above average across much of the state, according to Jamison Gove, a NOAA research oceanographer.

“Areas along West Hawaii and Maui Nui are especially warm, as much as 3 to 3.5 degrees Fahrenheit above typical summertime temperatures,” said Gove in a news release. “Warm ocean temperatures are expected to persist in the coming weeks, likely worsening the coral bleaching that has recently been observed across the islands.”

The Arizona State University Center for Global Discovery and Conservation Science (ASU-GDCS) has partnered with NOAA and DAR on coral reef science, conservation and management in Hawaii, and is offering advanced aircraft and satellite monitoring of reefs throughout the main Hawaiian isles.

The public can help by taking six, simple steps to reduce additional stress on corals during the current bleaching event, as outlined in a new coral bleaching alert card. The public is also encouraged to report coral bleaching at a new website, hawaiicoral.org, to help researchers map out the events in real time.

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