Eating Away at the Algae Problem in Hawai’i’s Coral Reefs


Sea urchins are all the rage as an exotic ingredient in sushi and even pizza—but they are also helping Hawai’i’s coral reefs. In Kane’ohe Bay,coral reefs are suffering from an overgrowth of invasive algae. With support from NOAA, the state of Hawai’i and The Nature Conservancy are using sea urchins to help remove the algae and help the coral thrive. 

Cleaning up the algae is a two-step process. First, we use anunderwater vacuum called the Super Sucker to remove algae from the coral. Farmers then take the algae and compost it for fertilizer. But, without constant vigilance, the algae will return. 

That’s where the sea urchins come in: we place them over the cleared reefs and the urchins eat the algae. We’ve found that where the urchins are placed, algae are kept in check (less than 5 percent return). With NOAA support, the state and TNC have removed more than 350,000 pounds of algae from the reefs, and placed more than 200,000 urchins to keep the algae from returning.

Corals are a valuable resource: they provide recreation and tourism opportunities, protect coasts from storms, and are habitat for many fish and wildlife species. In fact, Hawai’i’s coral reefs are valued at $34 billion annually. But they face many threats, including invasive algae, and excess nutrients and other pollutants flowing into the bay, which smother the coral.

This project is one of several ongoing coral restoration projects NOAA is supporting in Hawai’i, part of a comprehensive effort to protect and restore these important ecosystems.


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