Even small concentrations of molasses can threaten coral, local researchers say
Researchers at the Kewalo Marine Laboratory are currently testing the same type of molasses that spilled into Honolulu Harbor last week, resulting in the death of at least 26,000 fish and the rapid bleaching of coral colonies.
Lab Director Dr. Bob Richmond has mixed the molasses with seawater at varying concentrations to see how coral reacts, especially lace coral, which appears to have suffered the most damage because of the massive spill.
"The highest one is 10 parts per thousand, which is the really dark color, and we know initially by the spill this is what the animals were exposed to," Richmond told KITV4.
However, even at five parts per thousand, the molasses has a negative impact on coral colonies. Underwater video shot days after molasses entered harbor waters on the morning of Sept. 9 showed coral dying at an alarming rate.
"They're basically extruding filaments from the mouth, they're called mesenterial filaments, and this is often a defense and a stress response," explained Richmond. "With the presence of the molasses, it's chemical stimulus to them and they're put in a defensive response immediately."
Testing at the marine lab has already produced some bleaching of coral samples and the sloughing of tissue, a precursor to death. However, testing will continue over the next several days to help determine molasses thresholds, as well as conditions that could sustain coral recovery.
"This will help us determine the kinds of approaches we may use for efforts to rehabilitate and restore the area around the spill," said Richmond.
Still, Richmond says a true test of whether harbor waters have returned to normal will involve the placement of coral transplants on the ocean bottom. The transplants, which are grown on small discs, will act like a canary in a coal mine for the harbor.
"If the corals are doing fine, if they're growing properly, then we know the conditions would be acceptable to moving some other corals in," said Richmond.
Matson Navigation Co. has taken responsibility for the release of 233,000 gallons of molasses into the harbor, but has not committed to paying for any coral restoration effort. Such a program could cost millions, mostly due to the man hours that would be involved.
"You would basically cost it out based on diver time, the equipment, the materials, the boats, the gasoline and things of that nature," said Richmond.
Meanwhile, the lab is also using a YSI water quality sampler to determine dissolved oxygen levels in and around the harbor. Water samples taken Wednesday produced such startling results, researchers called the manufacturer to double-check the machine's settings.
"Normally, the dissolved oxygen is about five or six milligrams per liter, and we're seeing results around three, sometimes a little less than that," said Lauren Wetzell, an education specialist at Kewalo Marine Laboratory. "The clarity of the water was very clear, so we were quite surprised to see that."
On Friday, state officials said dissolved oxygen levels at six remaining test locations in Honolulu Harbor and Keehi Lagoon had returned to normal. They said the lagoon would be reopened to recreational users Saturday.
When asked about the inconsistency between test results issued by the state and those revealed by the lab, the state Health Department told KITV4 it would cross reference all water testing equipment to make sure there are no discrepancies.
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