Five days after a faulty pipe leaked about 233,000 gallons of molasses into Honolulu Harbor, all of the coral beds below the spill site and the harbor’s west end are already dead, University of Hawaii researchers say.

More coral approaching Keehi Lagoon, in the direction where the molasses plume is drifting, will be dead in a matter of days, they added.

“I was surprised. I didn’t think it was going to be that bad, that quickly,” Robert Richmond, a research professor and director of UH’s Kewalo Marine Laboratory, said Friday.

“We expect it to get worse,” he added. Richmond and other scientists said it would take years for new coral to grow once the molasses is cleared from the harbor and waters around Keehi Lagoon.

Matson Inc. has accepted responsibility for Monday’s spill during its molasses export operation, in which the syrupy liquid is hauled into the harbor from Maui by barge and then exported by ship to the mainland. The company is assisting cleanup efforts and has expressed regret for the damage, but it has offered few details so far on exactly what caused the massive pipe leak.

As of Friday morning, cleanup crews contracted by the state Department of Health pulled roughly 4,000 dead fish from the affected area, according to DOH Deputy Director for Environmental Health Gary Gill.

UH officials plan to meet Monday with the state and federal agencies responding to the spill, including the U.S. Environmental Protection Agency and the Coast Guard, to discuss possible ways to protect the threatened coral that remains, Richmond said.

The EPA has dispatched two coordinators to assist the state in its response to the disaster, and the agency might recommend a technique known as “air curtains” to act as underwater buffers and protect particularly sensitive areas, officials say.

Approaches typically used in an oil spill, such as floating booms and skimming the surface, wouldn’t stop the molasses spread — it’s a heavy liquid that’s denser than water and sinks below the surface, they added.

The university is assisting the state Department of Land and Natural Resources to assess the damage of the disaster.

On Thursday, UH researchers James Murphy and Luc Rougee spent two hours surveying the harbor floor around the spill site.

Photos and videos of their dive provided by Richmond showed scores of dead rice and lace coral — instead of a healthy tan or chocolate color, they had bleached to a ghostly white. Richmond said the hundreds of dead coral heads they encountered appeared to have perished in the past three to five days.

“Where they were, they said everything was dead,” he said. However, the marine life on the harbor’s east end appeared to be doing OK, Rougee said in an email.

The surprising speed of the fish die-off leads Richmond to consider whether at least some of the creatures died from a process called “osmotic pressure,” in which cells in their gills collapsed as they breathed in the molasses-tinged water so they were unable to breathe further. Many fish are also believed to have suffocated when bacteria breaking up the molasses sucked up the oxygen in the harbor.

Researchers plan to do necropsies on dead fish collected from the harbor to determine exactly how they died.

Meanwhile, DLNR closed Keehi Lagoon to commercial and recreational activities Friday. State officials have advised the public not to swim in those waters ever since the spill, concerned the dead fish could attract sharks and other predators. They’re also concerned about potential health effects from bacteria.

Alan Friedlander, an adjunct associate professor with UH’s Fisheries Ecology Research Lab, said he’s mostly concerned about the molasses disaster’s damage to Keehi Lagoon.

Friedlander described the lagoon as the “most substantial” nursery remaining on Oahu’s south shore to spawn new fish — he said it’s a critical area to propagate local fish species such as oio (bonefish), unicorn fish, weke (goatfish) and others. 

Earlier fish nurseries in regions such as Waikiki, Maunalua Bay and Pearl Harbor disappeared after hotels and buildings were developed and the waters were dredged and altered for boat traffic, Friedlander said. However, Keehi Lagoon has remained relatively unscathed by nearby human development.

Even with storm water and pollution runoff there, “the environment is pretty resilient,” Friedlander said Friday. “The importance of the place is unparalleled.”

Friedlander said he was hopeful the Keehi Lagoon ecology would eventually recover, but that without the coral networks the fish nursery there would not be as strong as before the spill.