Welcome to the twilight zone

LIHUE— Unique life is flourishing in the deeper waters surrounding Hawaii, and much of it is endemic to its twilight zone island environment, according to a new study.

The study published Tuesday in the journal PeerJ and was conducted over 20 years by 16 scientists from NOAA, the University of Hawaii, the Bishop Museum and state entities.

Some of the world’s most extensive coral systems have been documented through the study in Hawaii’s oceanic twilight zone — an environment located from 100 to 500 feet deep, also known as the mesophotic coral ecosystem (MCEs).

“What is unique about this study is how vast and dense the coral cover is,” Richard Pyle, a Bishop Museum research and lead author of the study told The Associated Press.

Off of the southeast coast of Kauai, researchers found nearly 100 percent coral cover of the species Leptoseris at a depth of about 300 feet, which extends for several square miles, according to the study.

The corals are living on undercut limestone ledges with small caves remnants of the ancient shorelines, which is the dominant habitat for coral in the MCEs at the depths of 160 — 190 feet, 260 — 295 feet, and 360 — 390 feet.

In addition to the corals living off the coast of Kauai, scientists discovered a large MCE off the coast of Maui.

“Although there was a bit of a hint that corals could survive down at those depths, these reefs off Maui were far and away much more dramatic both because they were deeper and they had higher coral cover percentage,” Pyle said.

Across the Hawaiian Archipelago, more than 70 species of microalgae were documented in the zone and those “meadows,” as they are named in the study, are home to 259 different fish species.

Of those, 27 percent — or 70 species — are endemic. That’s higher than the 20.5 percent of endemic fishes across all reef and shore fishes reported for the archipelago, according to the study.

It is difficult to explore the ocean at depths beyond 100 feet and because of that, the majority of the information that exists about coral reefs is derived from the shallow water reefs, according to Randall Kosaki, deputy superintendent for the Papahanaumokuakea Marine National Monument.

Scientists on Kauai said they’re fascinated by the study and hope with the discovery of these MCEs will come the desire for their protection.

“Oh my, yes, so much life in the seas,” said Katherine Muzik, who holds a Ph.D. in biological oceanography.

For part of her Ph.D. research, Muzik said she was able to dive to a depth of 1,500 feet in the waters off of Hawaii in a submersible to research coral life at those depths.

“There were all these new corals that were never known to mankind and I could have spent the rest of my life naming them,” Muzik said.

There could be potential to use these twilight zone areas as rehabilitation places for coral species from the shallower reefs that are suffering, the study concludes, but that potential would have to be evaluated for each specific species.

The deep-water species are completely different than their shallow living counterparts, Muzik said. She explained the corals that live in the deeper waters don’t create substrate or build upon themselves.

Hanalei marine scientist Terry Lilley said in his experience as well, the deep-water corals aren’t the same species as the shallow water species, “so I’m not so sure if the deep water healthy reefs would help repair the shallow reefs.”

However, these deep-water corals could be thousands of years old, Muzik said, which is why she chooses to focus on coral conservation and education.

“I have been down there,” Muzik said, “and I’ve seen what’s already been done by dredging and fishing and I chose to come to the surface to say ‘OK, we have to educate.”

That’s because, whether in the shallows or in the twilight zone, humans activities have affected the corals, she said.

Lilley said he, too, acknowledges a need to learn more about the Earth’s seas, as well as focus on the known issues surrounding the corals.

“Whether plastics, sound pollution, herbicides, bacteria and viruses, or biopharmaceuticals, we are relentlessly destroying life that is so much older than human existence,” Muzik said.


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