Native sea urchins are being used to eradicate invasive seaweed destroying the reef in Hawaii’s Kaneohe Bay, the United States’ only barrier reef system. Funding from the military's Port Royal Trust Fund is now being used to continue coral reef restoration, with sea urchins the secret weapon.

"The algae was introduced in the 1970s and it took about 15 to 20 years for us to start seeing a real problem in the bay," said David Cohen of the Department of Land and Natural Resources. For years, the state used a marine vacuum pump to remove the unwanted algae, but environmentalists realized this was merely a band aide solution for a much bigger problem. That’s where the urchins came in.

"We needed something else to follow up after the algae was removed and that's when we started testing these sea urchins. They are native to Hawaii, the Collector sea urchin," said program leader Jonathan Blodgett.

Since 2011, about 2,000 to 5,000 have been placed into the bay almost every other week. The venture is partly funded courtesy of an environmental accident. In 2009, the USS Port Royal ran aground off Honolulu International airport, destroying massive amounts of coral. Some $600,000 from the Port Royal Trust Fund is being utilized to fund the project. The entire process from larvae to mature sea urchins is done in the hatchery at Anuenue Fisheries Research Center in Honolulu. Currently, it is the only such facility in the world producing urchins for restoration purposes.

The hope is to remove enough invasive seaweed and replace it with native urchins and eventually native seaweed to promote a healthy ecosystem. "If we have healthy corals we've got lots of space in among the reef which provides extra habitat for other fish and other organisms to grow," said Cohen.

Collector urchins are found between depths of 2 to 30m in the waters of the Indo-Pacific, Hawaii and the Red Sea.