Thursday, Nov. 30, 2023 |
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LIHUE — Rising ocean temperatures may be part of the answer to a mystery state scientists are trying to uncover: What’s causing a deadly disease to thrive at the expense of Kauai’s coral reefs?
“A weak relationship was found between the abundance of the disease and water temperature,” Christine Runyon, a graduate research assistant at University of Hawaii’s Institute of Marine Biology, said at a news conference Wednesday on Oahu.
It’s a far cry from determining a cause and effect. But the apparent link between our warming ocean and a lethal, rapidly spreading coral disease is a sign of progress in the state’s effort to restore the reef’s health.
Half the coral reef sites surveyed by state scientists in nearshore Kauaian waters in the last year are plagued by disease. This finding is mined from the research of Runyon, who was tapped by the Department of Land and Natural Resources a year ago to research black band coral disease on Kauai and identify treatment options.
All told, 23 of the 47 sites surveyed by Runyon and her team are being killed by black band disease, which derives its name from the black band lesion it forms on three types of Montipora coral, also known as rice coral, living in local waters. This lesion starts small and quickly progresses until the coral colony is dead.
“The one thing that I was able to pull out by looking at environmental data is that there is a trend that when you have warmer water you see a higher prevalence of black band,” Runyon said. “So, in October, water temperatures were at their highest for the year and they were over 85 degrees. The warmth makes the coral susceptible to disease and it stresses it out.”
Forecasters predict ocean temperatures could be even warmer this coming autumn. The culprit is El Nino, an irregularly occurring weather pattern that results in warmer-than-average water temperatures in the Pacific Ocean.
“The models predict it will be at least 2 to 3 degrees warmer this October than last October,” Runyon said.
At Wednesday’s news conference, Runyon recommended the state monitor ocean temperatures in the affected areas and continue its multi-agency response to the coral disease outbreak that has been dubbed an “epidemic” in a recent U.S. Geological Survey report.
There’s no shortage of hypotheses on what’s allowing black band disease to flourish here. Every local marine biologist seems to have one, ranging from chemical runoff and pollution to human waste and climate change. The official word from the state, however, is that a cause hasn’t been determined.
Ask Hanalei biologist Terry Lilley, and he’ll tell you the coral disease is generated by the Navy’s use of sonar and electronic microwaves along the North Shore.
“The entire reef is basically falling apart,” Lilley said in an email. “The corals have lost their resistance and have a compromised immune system. We are in the process of having an entire ‘reef collapse’ that will take hundreds of years to repair.”
Lilley, who first alerted scientists to Kauai’s coral disease outbreak, said it’s old news that the disease is killing the island’s reefs. Environmental officials need to look beyond studying black band disease and instead focus on determining and eliminating its catalyst, he said.
“I am solution oriented,” he said. “I really do not care what is killing the coral. I care what is causing the coral to lose its immune system so disease can eat it up.”
The black band disease was first spotted at low levels on Kauai in 2004, then identified on the North Shore of Kauai in 2012 at 10 times background levels, according to the DLNR. It continues to plague the three Montipora (rice) corals found around the island.
The places most affected by the disease are the reefs surrounding Makua (Tunnels), Anini and Anahola beaches as well as Ahukini Landing, according to Runyon’s research.
Runyon said she has not herself seen the disease on the South Shore. For reasons related to access, she said the Westside is under-investigated.
Scientists have so far found some success in reducing the amount of coral tissue death from the disease by treating afflicted coral with a special putty. But no substantial remedies have been determined.
In March, a Management Response Team charged with finding connections between the disease and environmental factors met and mobilized a multi-year project led by Peter Swarzenski of USGS’s Pacific Coastal and Marine Science Center to investigate the relationship between black band coral disease, groundwater and other oceanographic drivers.
Katherine Muzik, a marine biologist and Kapaa resident, said many forms of pollution contribute to the disease and decay of Kauai’s coral reefs — including cesspools.
There are nearly 14,000 cesspools on Kauai, according to the state Department of Health, and experts say these cesspools release as much as 23,700 pounds of nitrogen and nearly 6,000 pounds of phosphorus into the ground each day. These gases can degrade water quality, stimulate undesirable algae growth and harm coral reefs.
“People act like it’s a big mystery, but I don’t think it’s a mystery at all,” Muzik said. “We’re polluting our oceans and the corals can’t run away like the fish. They’re stuck. So they get sick and die.”
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