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Vol. 17, no. 2
April / May 2014


The Little Urchins That Could 

Story by Tiffany Hill
Photos by Kyle Rothenborg

Andrew Purves is making it rain urchins. Outfitted in a hooded wetsuit and long-blade fins, he gently tilts a white plastic tray underwater. Spiny red urchins the size of marbles drift down onto Kane‘ohe bay’s reef No. 29 like cherry blossoms floating down toward a city sidewalk. Purves scoops out the stragglers clinging to the tray’s bottom with a gloved hand, making sure to spread the juvenile urchins onto the coral at a density of about two per square meter. Purves, a diver with the state Department of Land and Natural Resources, then swims back to the motorboat where reef restoration supervisor Jono Blodgett hands him another tray. It’s not long before the reef is dotted with six thousand new pompon-shaped hawa‘e maoli, or Hawaiian collector sea urchins. Their mission: to eat.

The hungry hawa‘e maoli are the second stage of a two-part restoration effort taking place in Kane‘ohe bay in Windward O‘ahu. The island’s largest bay was at one time home to dozens of loko i‘a, or ancient fishponds. The bay was one of the most abundant fisheries on O‘ahu and boasted a healthy, vibrant reef ecosystem. Like most of O‘ahu’s reefs, it fell victim to pollution and overfishing throughout the twentieth century. Then in the 1970s a University of Hawai‘i aquaculture experiment went horribly awry: Researchers introduced three species of alien seaweed—Kappaphycus alvarezii, Kappaphycus striatum and Eucheuma denticulatum—to develop a commercial industry for carrageenan, a gelatinous substance used as an emulsifier in yogurt, ice cream and more. The seaweed didn’t grow fast enough to create a viable market — as it does in Indonesia and the Philippines — and so the project was abandoned. But it did grow fast enough to damage Kane‘ohe bay’s fringing reef and fifty-four patch reefs. To make matters worse, nothing would eat the stuff, allowing the seaweeds to further proliferate, choking out native corals and destroying habitat for native species. Many of the once vibrant reefs of Kane‘ohe had become algaeinfested wastelands; the prognosis was poor for the reefs that remained.

But now science, a little ingenuity and a lot of teamwork are slowly rehabilitating the reefs. The first step to ridding the bay of the smothering seaweed is a large vacuum dubbed the “Supersucker.” It was developed in 2005 through a partnership among DLNR, UH and The Nature Conservancy, but the state maintains it. “The Supersucker guys”—Blodgett, Purves and a few others — operate the vacuum, which hoovers about a thousand pounds of algae every hour from the reef. Coral colonies once struggling under dense algae forests began to recover, developing a few spindly branches. In 2013 the Supersucker guys uprooted almost 95,000 pounds of algae. To date they’ve vacuumed five patch reefs and part of the fringing reef, totaling more than 125,000 square meters. The crew donates the algae to six Windward farms, where it’s used as fertilizer. “It’s great because something bad in the ocean is something good on land,” says Blodgett, who grew up and still resides in Kailua. The work is “tedious,” adds Purves, “but it’s also rewarding to go underwater and see the difference we’re making.”

But this is only half the battle. Once sucked, the algae will grow back—unless something eats them first. That’s where the urchins come in. Hawa‘e maoli are ideal for the job: They’re native to Hawai‘i, they don’t eat coral like other urchin species do, they stay put (unlike transplanted herbivorous fish) and they have few natural predators. Most important, they like to eat the invasive seaweed and can squeeze into coral crevices to get every bite.

Hawa‘e maoli, it soon became clear, were a natural part of the solution. The only problem? There were no hawa‘e maoli in Kane‘ohe bay.