NOAA Wraps Up Coral Reef Restoration Off Hawaii

NOAA and its partners have completed the work of restoring the damaged reef, after the cargo ship M/T VogeTrader ran aground and was later removed from the waters of Kalaeloa/Barber’s Point Harbor.

Divers remove the thick layer of coral rubble from the seafloor using a vacuum hose attached to a boat. We needed to clear away the corals broken from the ship grounding so that they wouldn’t get swept up and damage intact corals.

While a few young corals have begun to repopulate this area in the time since the grounding, even fast-growing corals grow less than half an inch per year. The ones there now are mostly smaller than a golf ball and the seafloor was still covered in crushed and dislodged corals. These broken corals could be swept up and knocked around by strong currents or waves, potentially causing further injury to the recovering reef. This risk was why NOAA pursued emergency restoration activities for the reef.

Once NOAA’s team transported the donor corals to the restoration site a few hundred yards away, they scraped the seafloor, at first by hand and then with a power washer, to prepare it for reattaching the corals. Using a cement mixer on a 70-foot-long boat, they mixed enough cement to secure 643 corals to the seafloor.

NOAA Wraps Up Coral Reef Restoration Off Hawaii
The 734-foot bulk carrier M/V VogeTrader after it ran aground near Oahu, on February 5, 2010. The milky color in the water beneath the ship is the pulverized coral.

While originally planning to reattach 1,200 coral colonies, the storm-blown corals were so large (and therefore so much more valuable to the recovering habitat) that the divers ran out of space to reattach the corals. In the end, they didn’t replace these colonies in the exact same area that they removed the coral rubble. When the ship hit the reef, it displaced about three feet of reef, exposing a fragmented, crumbly surface below. They left this area open for young corals to repopulate but traveled a little higher up on the reef shelf to reattach the larger corals on a more secure surface, one only lightly scraped by the ship.

The results so far are encouraging. Very few corals were lost during the moving and cementing process, and the diversity of coral species in the reattachment area closely reflects what is seen in unaffected reefs nearby.

NOAA Wraps Up Coral Reef Restoration Off Hawaii
The corals NOAA used to reattach to the seafloor were so large and healthy, NOAA ran out of room to place them in the area cleared.

These include the common coral species of the genus Montipora (rice coral), Porites lobata (lobe coral), and Pocillopora meandrina (cauliflower coral). As soon as the divers finished cleaning and cementing the corals to the ocean floor, reef fish started moving in, apparently pleased with the state of their new home.

But NOAA’s work isn’t done yet. They will be keeping an eye on these corals as they recover, with plans to return for monitoring dives in six months and one year.

NOAA, June 04, 2014; Image: NOAA

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