Calls to the U.S. Coast Guard and the state Department of Land and Natural Resources caused a stir earlier this week when people claimed to have seen a sewage spill in waters off Ahukini Landing and other areas of the East Side.
The golden brown band of foam floating on the ocean’s surface was a plankton bloom, a natural result of high ocean temperatures and ocean currents, said aquatic biologist Don Heacock, of the DLNR’s Division of Aquatic Resources.
“These blooms occur fairly often but this seems bigger than anything I’ve ever seen,” Heacock said.
The brownish stuff started washing ashore at beaches in Kealia and Wailua earlier this week, and the plankton is expected to be dissipated by next week.
On Tuesday Heacock said he went out by boat to take samples. Through initial analysis, he said he found mainly phytoplankton and zooplankton.
The zooplankton found included small marine shrimp and other crusteceans that had molted out of their shells. Phytoplankton, or algae, are single-celled organisms that grow at the bottom of the ocean.
“I stood at the south end of Kealia Beach, and I could see it about 3-4 miles in every direction,” Heacock said.
Heacock said that by the time they took samples, many of the organisms were being washed away from the mass by ocean currents.
If conditions were windy, no one would have ever seen the bloom because the organisms would have been mixed into the ocean fairly quickly, he said.
But because of glassy water and kona conditions (winds coming from the south) they remained in a massive band on East Side waters.
Jerry Kaneholani, a local fisherman, said that he went down to Kealia Beach Wednesday, and saw what looked like shrimp shells all over the beach.
“We went out about five miles outside of Kealia… It was unusual, gross. I never seen anything like that before,” he said.
Large plankton blooms have been noted on other islands in the past, but not with the intensity of this particular occurrence, said Gary Ueunten, State Department of Health, Clean Water Branch.
Uenten said he received a call on Monday about 4 p.m. that a brownish substance was seen in waters off Anahola.
A helicopter tour company reported seeing the bloom from Ahukini to Kealia; and two people who flew in to Lihue Airport said they saw the plankton bloom as they landed.
Uenten said he didn’t know how long the plankton would remain or if there were health risks associated with it.
Most phytoplankton are not harmful and serve as food for other ocean animals like fish and
Some phytoplankton, when they bloom, release a reddish substance that seems to dye the water red. Along many beaches along the coasts of the United States, “red tides” or harmful algae blooms, can cause medical emergencies for people who enter the water during the algae blooms. Neurotoxins that are produced by some algae travel up the food chain, poisoning zooplankton, fish and humans.
Even entering the water during a red tide can cause shortness of breath, digestive problems and even nerve damage.
In Hawai’i, some phytoplankton cause ciguatera poisoning of fish, which causes nerve and digestive damage, but these organisms in the plankton bloom are not related to ciguatera.