Scientists Study, Map Vast Coral Reefs of Northwest Hawaiian Islands

Stephanie Holzwarth took one look at the swarm of seabirds on the murky water and knew immediately what lurked beneath.

“This place smells like shark soup!” she recalls telling a handful of fellow marine scientists as their Boston Whaler pulled up to Maro Reef in the northwestern Hawaiian Islands.

Holzwarth’s fear was confirmed when half a dozen gray reef sharks began circling the boat just as she and dive partner Matt Dunlap prepared to roll into the water, video cameras in hand.

“The sharks fascinated me,” Holzwarth recounted in an e-mail diary. “I watched them with saucer eyes, glad they were acting curious, not aggressive.”

The Sept. 20 dive, which ended safely, was among hundreds researchers have made in the last month as they complete the most extensive mapping ever of the northwestern Hawaiian Islands’ reefs.

The 10 mostly uninhabited islands and atolls extend over 1,200 miles from the main Hawaiian chain. They total a little more than three square miles, but their waters are home to 70% of the coral reefs in the United States.

Beyond the reach of crowds that flock to Waikiki Beach, the islands are a haven for endangered Hawaiian monk seals, sea turtles, albatrosses and other birds, and species of fish, algae and invertebrates found nowhere else.

Sharks also call these islands home--tigers, Galapagos and a host of reef sharks that divers hope are too sated by their prey to crave humans.

Federal and state agencies will use data from the monthlong expedition to draft plans to protect the reefs and the habitats they support.

“This is one of the most isolated and pristine large-scale coral reef systems left in the world,” said Dave Gulko, a marine biologist with the state Department of Land and Natural Resources and a principal investigator for the Hawaii Coral Reef Initiative Research Program.

The string of tiny islands has captured the attention of President Clinton, who this year directed federal agencies to develop a quick plan for protecting the islands’ underwater ecosystems. The reef expedition, a $1.7-million project, was conceived before the presidential directive but has the same goal, organizers say.

The main Hawaiian Islands account for 15% of U.S. reefs, the Florida Keys another 2%. The rest are mainly off Texas, the Virgin Islands, Puerto Rico and U.S. territories in the Pacific.

But reefs are faring poorly.

“You’re seeing disappearance of coral reefs faster than you’re seeing disappearance of rain forests,” Gulko said. Overfishing, urbanization and pollution are among the reasons, he said.

Although isolation has helped to preserve the northwestern Hawaiian Islands, the islands and their reefs are not immune to human impact.

Marine debris poses a threat to monk seals and turtles, and the occasional grounded fishing boat damages reefs. Environmentalists say commercial fishing for lobsters has taken food from monk seals.

The U.S. military also has left its mark on the islands, best known for the 1942 Battle of Midway that turned the tide against Japan during World War II.

At Tern Island in French Frigate Shoals, animals get caught in steel pilings installed by the military in 1942 to hold in place a 3,000-foot airstrip on a patch of coral pieces dredged from a reef. The federal government has appropriated $8 million to repair the rusted wall next year.

Eco-tourism, meanwhile, has brought diving groups to Midway, near the northwest end of the chain.

Coral grows about an inch a year at lower latitudes, and even more slowly in the cooler and sometimes more turbulent waters northwest of the main Hawaiian Islands, so “any impact is going to take a lot longer to recover from,” Gulko said.

The islands are part of a national wildlife refuge except for Kure Atoll, the most distant, which is host to a state wildlife refuge.

Despite several studies of monk seal, turtle, seabird and reef fish populations, researchers do not have a complete, detailed accounting of the reef system, said Jim Maragos, a U.S. Fish and Wildlife Service marine biologist and chief scientist for the reef project.

Even the islands themselves may be off their positions on existing charts by a mile or more, he said.

About 55 scientists, teachers and support staff are on the Rapture, a 145-foot ship that left Honolulu on Sept. 20 and returned on Oct. 20. Another ship, the 165-foot Townsend Cromwell, left Sept. 8 carrying 11 scientists, including Holzwarth, a marine ecologist with the Fisheries Service in Honolulu.

Scientists from the Townsend Cromwell, operated by the National Oceanic & Atmospheric Administration, have been filming vast stretches of the underwater landscape with a method called tow-boarding. Divers are equipped with digital video cameras attached to “sleds” that enable them to maneuver quickly in the water. The divers are hooked by a 200-foot line to a boat that pulls them at about 2.5 mph, at depths of no more than 60 feet, for 50 minutes at a time.

One camera, facing forward, counts fish and records their length. The other, which faces downward, films coral, rock and sand.

Closer inspections of marine species, underwater chemistries and life on land are being made by scientists aboard the Rapture, a private boat.

Scientists have recorded unusual swarming behavior by large reef fish, and have found two species of table coral never seen before at a French Frigate Shoals lagoon.

At Nihoa Island, the closest to the main Hawaiian chain, Bishop Museum entomologist Gordon Nishida was surprised to find that nonnative insects greatly outnumbered native ones. The 1/4-square-mile island is not believed to have been inhabited since between AD 1000 and 1500, and access to it is strictly controlled by federal wildlife agencies.

Coral reefs at Nihoa and nearby Necker Island struggle to grow as they “suffer from constant scouring from swells and currents that rush against nearly all sides of these tiny islands,” Maragos said.

After several dives through churning, shark-infested waters, Holzwarth and company were rewarded at Pearl and Hermes Atoll.

“Her reefs are beautiful--we dove in clear blue waters (100 feet visibility) this morning over classical spur and groove patterns of coral ridges interlaced with clean white sand,” Holzwarth wrote in one Web posting. “Monk seals swam among us, spinner dolphins leapt around us, an exquisite spotted eagle ray flew out from under me--my mouth hung open in amazement at the beauty of her lacy black and white patterns.”

*

Hawaii Coral Reef Initiative Research Program: https://explorers.bishopmuseum.org/nwhi