A significant fish kill in the Kapoho tide pools this weekend represents yet another worrisome event within a fragile ecosystem that is seemingly under siege from all sides.
Usually teeming with brightly colored fish and diversity of coral reefs, the pools turned a dark, reddish brown Friday and Saturday, and neighbors and visitors discovered dead fish of various species floating and submerged in the water.
Marine scientists with the University of Hawaii at Hilo visited the pools at Waiopae on Monday, collecting water and fish samples in an effort to identify the cause of the die-off. Among the species found dead were sea cucumbers, crabs, various invertebrates and other creatures not as mobile as fish and therefore unable to escape to deep water when the event occurred, said Misaki Takabayashi, an associate professor with the UH-Hilo Marine Science Department.
“Today, we did a little survey down the coast. The Waiopae tide pools are still brown,” she said Monday afternoon. “Something is definitely going on down there. There are lots and lots of crabs and sea cucumbers dead. It apparently started happening Friday night.”
Because Takabayashi did not learn of the event until Monday, many of the dead fish might have been washed out to sea with the change of tides, but many dead creatures remained, she said.
The exact cause of the die-off is yet to be conclusively determined, but it appeared likely to be the result of some kind of substance washing into the water, she said. That could include sewage leaking from cesspools in the area, which have caused problems before, as well as agricultural runoff or a chemical spill.
“From my quick walk around, it (the cause) seems to be water quality. Whatever is happening seems to be pretty extensive,” she said.
Takabayashi expected her team could receive the results of their water testing by Friday.
Deborah L. Ward, spokeswoman for the state Department of Land and Natural Resources, said Monday afternoon her department was awaiting the results of the water testing by UH and the state Department of Health.
“We are also collecting marine specimens for testing,” she said.
The fish kill comes at a particularly delicate time for the tide pools, with researchers noting in the last month the most serious bleaching of coral in the area in recent history, Takabayashi said.
“We have ongoing data of this bleaching, which has been happening over the last month at least,” she said. “And (the health of the coral) might actually be worsened because of this most recent acute event.”
The bleaching is a process by which the live coral lose their symbiotic relationships with algae and thereby lose their ability to generate energy from the sun. While it does not directly kill the coral, the process makes it significantly harder for them to survive.
The bleaching, which has been noted recently in coral reefs throughout Hawaii, is the result of warming ocean temperatures, she said.
“You can blame every one of us who is using too much carbon,” Takabayashi said. “This is definitely an effect of global climate change. And not only is it the temperature of the seawater rising, but the global circulation system is all screwed up.”
The bleaching has hit some species harder than others.
Blue rice coral in the Waiopae area have been almost completely wiped out, while other species have seen as little as 10 percent bleaching.
Marjane Allan, a nearby resident who snorkels at the tide pools on a weekly basis, said she arrived to snorkel at the pools Saturday and was dismayed to see how many fish were dead.
“Hundreds of fish were killed. Crabs, shrimp, moray eels, butterfly fish, starfish, they were strewn all over,” she said. “… Some were collected at the bottom and some were floating.”
Email Colin Stewart at cstewart@hawaiitribune-herald.com.