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By HECTOR BECERRA, Times Staff Writer
Scientists donned scuba gear and dived into a murky Huntington
Beach lagoon Monday in a high-stakes effort to kill Caulerpa
taxifolia, an exotic seaweed that could create an ecological nightmare
in Orange County coastal waters if it is not contained.
Just weeks ago, hundreds of patches of the tropical algae were
found in a three-acre pond off Huntington Harbour, one of two
known as the Seagate Lagoons.
Monday's dive marked the beginning of a painstaking $300,000
effort to eradicate the stubborn organism.
"This is the defensive lineman of seaweed," said Mark Doalson,
an environmental specialist for the Santa Ana Regional Water Quality
Control Board, a state agency. The algae can grow up to 9 feet long,
with up to 200 fronds, making it one of the largest single-cell
organisms in the world. It can survive 10 days out of the water, and
leaving even one millimeter of the algae behind could cause another
outbreak.
"If this ever gets to Huntington Harbour, things could get pretty
ugly," said Rachel Woodfield, a marine biologist with Merkel &
Associates, a San Diego-based biological consulting firm.
In 1984, the exotic seaweed was accidentally released into the
Mediterranean Sea, probably from an aquarium. There, it quickly
bloomed into watery forests. The seaweed has harmed tourism and
destroyed recreational diving across a large area by killing vegetation,
and driving sea life away. The seaweed is so pervasive in the
Mediterranean now, it is unlikely ever to be eradicated, said Andrew
Cohen, a biologist for the San Francisco Estuary Institute.
The algae found in three infestations--from the Mediterranean
Sea to Southern California--are all males, meaning they have cloned
after a parent was broken into pieces.
The discovery in the lagoon off Huntington Harbour marked only
the second time that the bright-green seaweed has been found on the
west coasts of North and South America. In July, officials announced
the first occurrence of Caulerpa taxifolia in Carlsbad's Agua
Hedionda--or "filthy water"--lagoon 35 miles north of San Diego. In
1998, thousands of scientists banded together to get Caulerpa taxifolia
listed as a noxious weed, making it illegal to import it to the United
States, Cohen said.
But the algae still makes its way into the country. The major
infestations probably started with something that seemed harmless:
someone dumping strands of the seaweed from their aquarium into a
saltwater environment, Cohen said.
On Monday, Woodfield and colleague Robert Mooney swam
carefully in dark waters. They used two techniques to kill the
seaweed. Where individual strands existed, they pulled them out,
taking care to remove at least 10 centimeters of material below the
root-like rhizoids.
The scientists planted yellow flags wherever they pulled up a
strand so they could monitor the location.
In the second method, whole patches were covered with plastic
tarps and sealed in with a chlorine "puck." The chlorine should poison
the seaweed, Woodfield said.
The scientists labored in a gloomy, sticky environment. The
foul-smelling pond has poor visibility. Flapping stingrays kick up
sediment. Numerous fish--like smoothhound sharks, bass, goby and
yellowfin tuna--have somehow made their way into the artificial
pond.
There's also guano everywhere, from a variety of seabirds.
The stakes are high. Screens were placed over pipes so that any
pieces of seaweed accidentally sheared off could not travel to a
nearby lagoon, which connects to Huntington Harbour.
The work could cost the state more than $300,000, Doalson said.
The scientists all agree: It's a good thing only male Caulerpa taxifolia
has been found where it doesn't belong.
"If someone introduced a female [and it survived as well as the
male strain], that would be very bad," Woodfield said. "There would
be spores floating out there. . . . There's no way we could stop it."
* * *
Poisoning Seaweed
County officials are trying to kill an invasive seaweed, Caulerpa
taxifolia, found growing off Huntington Harbor. The weed can't be
cut down because it fragments, and each piece can regenerate into a
new plant. Divers will either remove plants by hand or use chlorine to
try and poison plant beds.
CAULERPA TAXIFOLIA FACTS:
* Grows to more that nine feet long, with up to 200 fronds per stem.
* Spreads vegetatively, through fragmentation.
* Can survive up to ten days out of the water.
* Spread in Mediterranean by fishing nets and boat anchors.
ON LARGE PATCHES OF CAULERPA TAXIFOLIA
1. Divers place a heavy plastic tarp over the seaweed patch.
2. A chlorine "puck' is placed underneath tarp, then tarp is weighted down, enveloping the seaweed bed.
3. The tarp is sealed along all the edges and the top is fitted with a
vent, to allow release of gas produced during photosynthesis. Without
the vent, the tarp might stretch and inflate from the gas--possibly
uncovering the seaweed patch.
4. The chlorine poisons the seaweed under the tarp.
Source: Rachel Woodfield, Merkel & Associates
Graphics reporting by HECTOR BECERRA / Los Angeles
Times
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