(CNN) -- A massive molasses spill this week in Honolulu Harbor could lead to an increase in the number of sharks, barracuda and eels, as well as bacteria in the area, the Hawaii Department of Health warned.
"While molasses is not harmful to the public directly, the substance is polluting the water, causing fish to die and could lead to an increase in predator species," the health department said in a statement Wednesday.
"The nutrient-rich liquid could also cause unusual growth in marine algae, stimulate an increase in harmful bacteria and trigger other environmental impacts."
Roger White of Cool Blue Diving shot video of the mess on the ocean floor, where the heavy liquid settled. "I didn't know so many creatures were down there before, but they're all dead, and they're all laying across the bottom -- hundreds and hundreds, thousands," he told CNN affiliate KHNL.
Crews from the health department were collecting marine animal carcasses and water samples to monitor the movement and the impact of the molasses plume.
"This is the worst environmental damage to sea life that I have come across, and it's fair to say that this is a biggie, if not the biggest, that we've had to confront in the state of Hawaii," Deputy Director Gary Gill told KHNL.
Video from CNN affiliate KITV showed the colorful bodies of the wildlife bobbing on the surface of the water as workers scooped them into nets.
"It seemed like they were trying to gasp for air," resident Sachi Uehara told KITV. "There were, I would say, over 50 eels that were up at the surface that we could see."
The health department warned against eating the fish and urged swimmers to stay out of the ocean where the water is brown.
The fish kill began before dawn Monday, when a ship loaded with 1,600 tons of molasses set sail for the West Coast, where its cargo was to be processed.
But a leak in a pipeline to the Matson Navigation ship spewed as many as 1,400 tons -- 233,000 gallons -- of the sticky stuff into the water, the health department said, citing the shipper.
By 8 a.m., the Coast Guard had been notified that Honolulu Harbor's water was discolored; a plume was moving with the tides and currents from the harbor into nearby Keehi Lagoon, where it was expected to dissipate.
In a statement issued Thursday afternoon, Matson spokesman Jeff Hull said the company was working with state and federal agencies to address the spill. Its molasses terminal has been shut down, the damaged pipeline has been temporarily patched and the company was working to repair it permanently.
"We have sent divers into the water to monitor the effect of molasses and are taking aerial shots to monitor the movement of the molasses," Hull said. "Matson is bringing in environmental experts to help provide more resources to help support the response efforts."
But experts said the spill's impact will be long-lasting.
"It's in a bay, so there's not a lot of circulation, so you're not going to have flushing of this water out," biologist David Field told KHON. "So, in this area where the spill occurred, we're going to see the effects probably for a long time."
Field, an assistant professor of marine sciences at Hawaii Pacific University, said the effects of the spill may grow.
"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," he said.
The fish are dying because the molasses displaces the oxygen-rich water, causing them to suffocate, said Mike Torresan, a scientist with the U.S. Geological Survey's Coastal and Marine Science Center in Santa Cruz, California.
"It's poisonous in that they're not going to get enough oxygen," he said.
But Dave Cacchione, a retired oceanographer with the U.S. Geological Survey in Menlo Park, California, said the timing of the spill may help speed the recovery.
The highest tides off Honolulu this month are projected to occur Thursday through Saturday and will result in stronger tidal currents that could speed the dispersal of the molasses, he said.
The difference between low tide and high tide will be about 2 feet during those days. "That's pretty high tide for the middle of an ocean," where there is normally no tide at all, he said.
That phenomenon is familiar to sunbathers on Hawaii because "laying on the beach, you don't have to move your blanket up and down" to accommodate changing tides.
He predicted that the water purity would recover on its own.
Molasses can prove fatal to more than fish. On January 15, 1919, a 50-foot-high tank in north Boston broke apart, unleashing 2.3 million gallons of the stuff on the city, according to the EPA (PDF).
Traveling at an estimated speed of 35 mph over two city blocks, a wave 15 feet high and 160 feet wide wound up killing 21 people and injuring more than 150 others, causing damage estimated at the equivalent in today's currency of more than $100 million.
CNN's Christine Theodorou contributed to this report.