A federal research ship returned to Honolulu from the Northwestern Hawaiian Islands on Tuesday with evidence of aquatic species never seen before and having made discoveries of fishes never before recorded in those waters.
But scientists also documented some distressing news: a major episode of coral bleaching at remote Lisianski Island, plus moderate bleaching at Midway Atoll National Wildlife Refuge and Pearl and Hermes Atoll.
"Large areas of once vibrant purple coral are now stark white, and some corals were showing signs of mortality," said Courtney Couch, research biologist with the Hawaii Institute of Marine Biology.
Coral bleaching is caused by elevated sea surface temperatures, and prolonged bleaching can end up killing corals, a growing phenomenon scientists say is linked to climate change.
The event marks the third reported bleaching episode in the Northwestern Hawaiian Islands. The northern atolls were severely affected by bleaching and mortality in 2002 and 2004.
On a positive note, scientists said an introduced fish that has dominated the reefs of the main Hawaiian chain — the taape, or blue-lined snapper — has not moved into the deepest parts of the reef in the northwest chain, probably due to the cooler water temperatures.
Those cooler temperatures, they said, help make the deeper reefs in the Northwestern Hawaiian Islands the most pristine marine ecosystem on Earth. About 95 percent of the species within the ecosystem are endemic.
The primary mission of the 25-day expedition was to explore the deeper coral reefs within Papahanaumokuakea Marine National Monument, the massive marine conservation area encompassing 139,797 square miles of Pacific Ocean surrounding the string of islands and atolls stretching to the northwest of the main Hawaiian chain.
Scientists aboard the National Oceanic and Atmospheric Administration ship Hiialakai returned with specimens and photographs of new types of marine life, including sea urchins, sea cucumbers, algae, sponges and reef fish possibly new to science.
It will take several months of lab work to figure out whether in fact they are new species, said chief scientist Randall Kosaki, NOAA’s deputy superintendent of Papahanaumokuakea Marine National Monument.
What’s more, researchers diving at depths of up to 300 feet saw and photographed several fish species not previously seen by divers and known only via observations from submersibles.
Visiting the waters of French Frigate Shoals, Lisianski Island, Pearl and Hermes Atoll and Midway Atoll, scientists used high-tech scuba gear to dive to the largely unexplored deeper reef, which goes down to 400 feet.
"Literally every reef that we dive on is a reef that no human being has ever laid eyes on," Kosaki said.
Kosaki said daylight starts to disappear in the deep reef and that the temperature drops to the low 60s.
"It’s a realm we call the twilight zone," he said. "It’s like going to another world. It’s like going to the moon."
As for the bleaching, it was discovered on NOAA’s August expedition to the northwest islands. Research biologist Couch decided to return for another look.
What she found was moderate bleaching on most of Lisianski’s reefs. But several of the shallow reefs were in trouble, with 90 percent of the corals affected.
Unfortunately, she said, a mass of warm water is predicted to linger there for at least a month, meaning the bleaching could worsen.
When corals are thermally stressed for extended periods, they expel the symbiotic algae they rely on for most of their nutrition, causing the corals to turn white, explained Couch, a UH postdoctoral researcher. While corals that bleach are not necessarily dead and can recover, prolonged bleaching can result in significant coral die-off.
Lisianski, a small island about halfway up the northwest chain and surrounded by a huge and diverse reef, is looking "pretty dire" right now, Couch said, but she will check back next year.
"It’s heartbreaking, but corals do have the ability to bounce back. We’ll have to see what happens next year," she said.
Kosaki added, "We’re working in one of the most protected marine areas on Earth, and yet we’re not immune to human impacts that originate many thousand miles away."
Couch said people can help the situation by cutting down on their carbon footprint, including burning fewer fossil fuels.
Other researchers on the expedition tagged sharks and ulua (jacks), and deployed and recovered underwater acoustic receivers that listen for tagged predators. A scientist from NOAA Fisheries deployed underwater cameras with bait to attract fish. The cameras filmed and measured sharks, jacks and other predators.
ENLARGE PHOTO.
