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The Honolulu Advertiser
Posted on: Sunday, August 25, 2002

Waikiki volunteers skim invasive limu

 •  Growing algae blooms raise fear of ocean change

By James Gonser
Advertiser Urban Honolulu Writer

Volunteer scuba divers and snorkelers scoured the ocean off Waikiki yesterday, removing hundreds of pounds of an alien species of seaweed that is spreading quickly over the coastal reef and threatening native wildlife.

UH research assistant Thomas Sauvage, center left, and botany professor Celia Smith help sort seaweed found off Waikiki, separating the undesirable Gracilaria salicornia from limu that sustains the ecosystem.

Cory Lum • The Honolulu Advertiser

The divers collected the foreign limu — Gracilaria salicornia — as it floated by.

Bags of the seaweed were then passed to waiting snorkelers who carried the material ashore to be weighed and placed in a dumpster for possible use as mulch.

The seaweed grows into a thick mat that covers the reef, blocking sunlight that coral and reef plants need to survive.

Gracilaria salicornia has spread from Diamond Head to Ala Moana Beach Park. Floating clumps have been seen as far away as Hawai'i Kai. The aggressive species is also a problem in Kane'ohe Bay, said University of Hawai'i botany professor Celia Smith.

"Although it has been here for about 25 years, this is an effort for the first time to focus on removal management and this is hopefully part of a long-term effort to begin a thorough program of managing these alien species," said Smith.

The seaweed was introduced here by researchers in 1974 to foster commercial development of the alga for medical research. That industry never materialized, but the seaweed is pushing out corals and native algae that Hawai'i's marine communities depend on for food and shelter.

Left unchecked, Gracilaria salicornia could come to dominate the Waikiki eco-system, including the Diamond Head shoreline. Invasive seaweeds have also been a problem off Maui, in California and in the Medi-terranean Sea.

The cleanup in Waikiki is a joint project of the state Department of Land and Natural Resources' Division of Aquatic Resources, UH, the Hawai'i Coral Reef Initiative, The Nature Conservancy, Reef Check and the Waikiki Aquarium.

"This is an opportunity for organizations within the state to work together to deal with the alien algae problem," said Bill Devick, Aquatic Resources administrator. "We have to act proactively before the problem develops into something that is beyond our capability to deal with. By removing the algae and discovering information about its life cycle, we can potentially learn new ways to protect our reef."

Smith said this was an initial cleanup geared to controlling invasive alien seaweeds around Hawai'i's reefs.

"The next more difficult task is removal from the reef itself," Smith said.

Reach James Gonser at jgonser@honoluluadvertiser.com or 535-2431.