Posted on: Monday, July 1, 2002

Mud impeding coral reef's recovery

By Jan TenBruggencate
Advertiser Science Writer

A coral reef expert is recommending possible coral transplants as a way to begin restoring a northeast Kaua'i reef severely damaged by mud flows.

But no restoration can begin until the flow of mud is stopped.

University of Hawai'i biologist Paul Jokiel, who dove on the reef at Pila'a June 6, said sediment flows from the neighboring development have severely damaged the coral reef fronting its white sand beach.

A massive mud flow on Nov. 26 dumped tons of mud into the nearshore waters, and continuing muddy water flow has kept the pressure on the shallow reef flats.

A great deal of the coral has been killed. Algae grow where the coral once did, on beds of mud, which raise clouds of silty water when you wave a hand over the surface, Jokiel said.

In deeper water, large coral heads are dead.

"These corals took decades — maybe even centuries — to develop. These corals are all dead or dying," he said.

Jokiel, as a researcher with the Hawai'i Coral Reef Assessment and Monitoring Program, prepared a report on the Pila'a reef situation for the state Department of Land and Natural Resources.

He compared the Kaua'i reef to the one at Hanauma Bay on O'ahu.

"The Pila'a reef system is a strikingly beautiful area with extensive sandy beaches. The shallow reef area is an excellent site for swimming and skin diving except in times of high surf. This area is excellent fish habitat," he said.

The mud flows have changed that, and as long as rain continues to wash mud into the water, the reef is unlikely to come back, he said. And even when vegetation is restored and the muddy runoff stops, restoration of the reef is a slow process.

"In a system like this, if the system gets overwhelmed, which is the case in this case, the prognosis is not very good," Jokiel said.

Over time, surf will kick up the mud and help sweep it off the reef into deep water. But even then, the mechanism for restoring corals my be missing. On a normal reef, new corals can be found. Not at Pila'a.

"There's no new coral colonies anywhere here. That's striking," he said.

Jokiel is recommending that once the sediment runoff is controlled, there be detailed monitoring of the damaged area to determine whether the reef is recovering, and at what rate. New coral colonization may be inhibited by the thick carpet of new seaweeds, whose growth has been enriched by the mud.

"Coral recruitment by larvae may be a very slow process due to the extensive algal mat," he said.

One option, which has been experimentally employed elsewhere in the Islands, is to actually transplant corals from healthy reef areas into the damaged region, he said.

"We know that the area with many dead coral heads was formerly a good coral environment," he said.