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Why global warming bleaches coral in Hawaii

As temperatures continue to rise in ocean waters surrounding Hawaii, stressed-out coral reefs are losing color and their health. 

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In this August, 2015 photo, a bleached coral is shown in Kaneohe Bay off the east coast of Oahu, Hawaii. Abnormally warm water caused by a powerful El Nino pattern is heating up the Pacific Ocean to the point that coral reefs in the waters off Hawaii have already begun to show signs of coral bleaching. The Seaview Survey team and a crew of scientists were in Kaneohe Bay Thursday to photograph coral as it begins to bleach, hoping to provide a baseline image of the reef before more serious bleaching occurs.

(XL Catlin Seaview Survey via AP)

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Warmer-than-normal ocean temperatures around Hawaii could create the worst year ever for coral bleaching, experts say.

Corals have a symbiotic relationship with the microscopic algae called zooxanthellae that live in their tissues, explains the National Oceanic and Atmospheric Administration (NOAA). But when the coral becomes stressed due to warmer water, algae leaves the coral, taking with it the coral’s color and immunity.

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“Coral bleaching is the result of a loss of algae living within the coral’s tissue that provide them with energy and give them their colors,” explained aquatic biologist Brian Neilson from the Hawaii Department of Land and Natural Resources to UPI. “This loss results in the pale or white ‘bleached’ appearance of the impacted corals. When corals bleach, they lose a supply of energy and become particularly vulnerable to additional environmental stress.”

Coral have been known to recover from a singular bleaching episode. But if the algae loss is prolonged and the stress continues, the coral will eventually die, warns NOAA.

The islands survived a mass bleaching event in 1996, and another in 2014. However, Chris Brenchley, a meteorologist for the US National Weather Service in Honolulu says this year’s temperature increase of three to six degrees Fahrenheit will cause unprecedented conditions.

“You can’t stress an individual, an organism, once and then hit it again very, very quickly and hope they will recover as quickly,” said Ruth Gates, the director of the Hawaii Institute of Marine Biology.

But the reefs might not be the only ones to feel the heat.

“There is a concern about corals dying from bleaching because degraded reefs diminish shoreline protection and the availability of habitat for fish and other marine species, which negatively impacts ocean-related businesses and tourism, availability of fish, as well as quality of life for humans,” notes the state Department of Land and Natural Resources in a press release last week.

“If we fail to protect [coral reefs] and lose them, it could have tremendously negative impacts not only on the overall ocean ecosystem but on Hawaii’s economy,” warned Suzanne Case, the chair of the Department of Land and Natural Resources.

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In a report produced by NOAA, the average annual value of the coral reef ecosystem in Hawaii amounts to $364 million, with 85 percent of that value coming from tourism and a majority of the remaining from property value.

“These high numbers certainly indicate that it is worthwhile, both from an ecological and an economic perspective to take care of this valuable resource,” concludes the report.

And although the public can’t immediately reverse the high oceanic temperatures, Neilson asks people not to add to the coral’s problems. This means avoiding fertilizing lawns where the chemicals could flow into the ocean and not walking on the reefs. Using pono fishing practices – based on traditional conservation methods – could also be helpful to coral reef health.

The state encourages people to report coral bleaching to the volunteer organization Eyes of the Reef Network so experts can help coral reef ecosystems during this time of high stress.