A thick orange slime is choking Honolulu Harbor, littering the seabed with dead animals as it coats everything in its path. About 233,000 gallons of the sludge leaked from a pipeline this week, forming a sticky plume that killed thousands of fish in just a few days.

The scene is reminiscent of an oil spill, but this isn't oil. Hawaii's busiest harbor is being suffocated by something with a much less sinister reputation: molasses.

"This is the worst environmental damage to sea life that I have come across," Gary Gill of the state health department tells KHNL-TV. "It's fair to say this is a biggie, if not the biggest that we've had to confront in the state of Hawaii."

"Everything is dead," adds diver Roger White, who filmed an underwater video of the devastation. "We have to start from zero because there's nothing alive."

The spill came to light Monday, when molasses was found escaping from a pipeline that links onshore storage tanks to ships in the harbor. Pipeline operator Matson Navigation says it fixed the leak Tuesday, but can't do anything now to clean up its mess. "Matson truly regrets what has happened," senior vice president Vic Angoco said in a press conference Thursday. "We take pride in being good stewards of the land, of the ocean. In this case, we didn't live up to our standards. We are truly, truly sorry for that."

But why is molasses so destructive? It's a byproduct from the process of refining sugar, and while it may not be the most nutritious food source, it's widely eaten by humans. In fact, Americans ate more molasses than granulated sugar until about 100 years ago.

Honolulu Harbor

Honolulu Harbor at sunset, before the spill. (Photo: Grant Montgomery/Flickr)

A sticky situation

Unlike oil, molasses isn't toxic. But when this much of it surges into the sea, it can boost algae populations that rob the water of oxygen, similar to how nitrogen creates "dead zones" in places like the Gulf of Mexico and Chesapeake Bay. And although oil tends to float on water — allowing some to be scooped up or burned away — Matson's molasses sank to the bottom of Honolulu Harbor, blanketing the ecosystem in a way that defies conventional cleanup while also directly smothering an array of plants and animals.

Molasses may mimic an oil spill's carnage, but raw sewage is a better analogy, says Paul Kemp of Hawaii's Center for Microbial Oceanography. "It's relatively fresh material, it's organic-rich, it's heavy," he tells NBC News. "All of those things would be somewhat comparable." The sugary goo will eventually leave the harbor naturally, but that could take years. Algae will keep depleting oxygen as they digest the molasses, and the harbor's lack of strong ocean currents means the sludge won't be churned out to sea quickly.

"This is in a bay, so there's not a lot of circulation," marine scientist David Field tells KHNL. "So in this area where the spill occurred, we're probably going to see the effects for a long time." And even when the molasses is flushed out, he adds, it could go on to threaten coral reefs farther from the harbor. "As water does leave this bay area and goes out into the neighboring ocean, we can expect the effects in the long term, in days, weeks, months and probably years, to spread out over some of the South Shore reefs."

Dead fish and coral are a nightmare for Hawaii's ocean-centric economy, and the specter of toxic algae blooms doesn't bode well for tourism at Waikiki beaches. State health officials are already warning swimmers and surfers to stay out of waters around Honolulu Harbor, fearing algae as well as sharks, which might be lured by all the dead fish.


Molasses is highly viscous, making cleanup difficult. (Photo: Wikimedia Commons)

Unsafe harbor

The cause of the leak remains unclear, Matson's Vic Angoco said Thursday, but KHNL reports "several investigations" are now underway. The state health department is reportedly mulling whether to take action against Matson, which says it has sealed the pipe, closed all valves and temporarily shut down its Honolulu operation. The company normally makes weekly molasses deliveries from Hawaii to the mainland.

"Matson accepts responsibility for the spill and is working directly with state and federal agencies to respond to this unprecedented event," Gov. Neil Abercrombie said Thursday, pledging to "do everything needed to restore harbor channel waters to the highest quality and take all appropriate action to ensure that such a spill will not reoccur."

While investigations continue and Hawaii waits for the sludge to wash away, it's worth noting there are some similarities between molasses and oil. As TreeHugger's Chris Tackett points out, the saccharine slime behaves a lot like tar sands oil, aka diluted bitumen:

"Because the tar sands are so thick, they are diluted with a cocktail of toxic chemicals, which allows them to flow through a pipeline. However, when a spill occurs, the diluents evaporate into the air, leaving behind the thick, heavy and very sticky bitumen, which sinks to the bottom and is not easily skimmed off the top of the water."
That's what made recent tar-sands spills in Michigan and Arkansas so destructive, requiring complex and expensive cleanups. But if the Hawaii molasses spill doesn't dissolve or wash away quickly enough, state officials may have some options for cleaning it up themselves. The U.S. Coast Guard has tested underwater vaccums, for example, to use when heavy crude oil sinks below the surface. "They're designed to vacuum up the oil, to remove it from the bottom," oil-spill expert Nancy Kinner tells NBC News. "Something like that could be deployed, but you'd need to get it out there and mobilize it."

Hawaii has had molasses spills before, but this week's is widely considered the state's largest and most destructive. And while the full toll may not be known for years, it at least seems unlikely to be the worst molasses spill in U.S. history. That distinction belongs to the 2 million-gallon Boston Molasses Flood of 1919, in which a 30-foot wall of molasses surged through the city at up to 35 mph, eventually killing 21 people.

For more about the Hawaii molasses spill, check out this video from KHNL:

Related Hawaii stories on MNN:

Russell McLendon ( @russmclendon ) writes about humans and other wildlife.

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