A deadly disease described as "an Ebola for corals" is laying siege to Kaneohe Bay, leaving vulnerable roughly half the colonies that live in Hawaii’s largest sheltered body of water.
Two weeks after scientists announced that coral colonies in the bay were showing signs of recovery from the fall’s warm-water bleaching event, a new threat has emerged: acute Montipora white syndrome.
"We’re concerned because this disease can move very quickly," Anne Rosinski of the state Division of Aquatic Resources said Thursday.
Scientists with the state Department of Land and Natural Resources, the University of Hawaii and the U.S. Geological Survey have joined forces in hopes of trying to figure out what’s going on in the bay, where more than 50 colonies are being attacked by the disease.
State aquatic officials, meeting Thursday at Heeia Kea Small Boat Harbor in Kaneohe, described a fast-moving disease that eats away at coral tissue, leaving a skeleton engulfed by algae. They said it’s capable of killing a small coral colony within one week.
Fenny Cox, associate professor of biology with UH’s Hawaii Institute of Marine Biology, compared the outbreak to the Ebola virus.
"This coral disease spreads like wildfire, just like Ebola. And it kills really quickly, just like Ebola," Cox said. "We don’t have any vaccine or treatment for it. We don’t even really understand (what’s causing it). If you get it, your chance of survival is very low."
Evidence of the disease was found on patch reefs in the center of the bay only within the past few weeks.
On some patch reefs, officials said, they observed up to 90 percent of rice corals afflicted and the majority of those likely to die.
However, they added, the percentages vary, and not all of the reefs show elevated levels of the disease.
"We’ve seen mortality, but we’re going to do the best we can to quantify that in the coming weeks," state aquatic biologist Stacy Bierwagen said.
The vulnerable species is Montipora capitata, or rice coral, which is one of the main corals thriving in Kaneohe Bay and represents about 50 percent of the corals found there.
At this point scientists don’t know what’s driving the outbreak, although they’re working on a number of hypotheses, including an influx of organic carbon, which probably means some source from the land, such as runoff, that can stimulate an algae bloom.
This is not the first time this disease has been found in the bay. It was first detected in 2010 and again in 2012. Officials said the 2010 outbreak, which was confined to the southern part of the bay, was relatively minor compared with the 2012 outbreak.
"This one right now is looking like it’s going to be worse than 2012 because of the number of corals being affected in the central bay," Cox said.
The outbreak follows last fall’s bleaching event, the worst on record in the Hawaiian Islands. Sea temperatures spiked at 86 degrees, and warm-water bleaching was seen in mostly shallow water from Kauai to Hawaii island.
But the worst of it occurred off Windward Oahu, where 80 percent of the dominant corals experienced bleaching, officials said.
Aquatic officials last month warned that the bleaching might weaken the coral reefs, making them susceptible to disease.
"Coral diseases are just like human diseases," Cox said. "We’re all exposed to different types of pathogens. Some of us get sick, some of us don’t. Often what determines if you get sick is whether you’ve been stressed by something else."
Officials also warned that developing El Nino conditions might cause water temperatures to become dangerously warm for corals again in 2015.
"We were concerned about what was going to happen with temperatures rising, but I would say we’re even more concerned now," Rosinski said.
The Division of Aquatic Resources’ Rapid Response assessment team, along with UH and USGS researchers, has been in the bay over the past week and a half trying to document the extent of this disease.
In addition to surveys, USGS researchers will put coral tissues under a microscope to determine whether infectious agents are associated with the disease.
Scientists with the Hawaii Institute of Marine Biology will be checking ailing reefs as well as continuing experiments on disease pathology and possible environmental drivers of the disease.
The Rapid Response assessment team will be back in the water soon conducting a second round of photographic surveys to further quantify how much coral has been killed.
Bierwagen said the team is also trying to figure out how to prevent the disease from spreading to other parts of the bay as well as to other parts of Oahu, where it has yet to be seen.
Cox said she’s especially concerned because if the rice coral were to disappear from the bay, the teardrop butterflyfish and a host of other organisms might go, too. Cox said the teardrop butterflyfish relies on the rice coral for 90 percent of its diet, and many other aquatic creatures wholely rely on that coral species.
