2001–2002 - California Sea Grant - UC San Diego

Sea Grant Responds to Invasive Seaweed Caulerpa taxifolia
Caulerpa Be Gone…
According to the most recent
survey of the Agua Hedionda
Lagoon in Carlsbad, the Caulerpa
infestation has shrunk from a peak
of about 11,000 square feet to
about 4 square feet. This is a
dramatic reduction but not the end
goal of total eradication.
“It is like a house on fire,” said
Carlsbad senior planner Eric
Muñoz, the city’s liaison to the
Southern California Caulerpa
Action Team, a multi-agency group
that is leading the eradication
effort. “The flames are gone, but
the house is still smouldering.
Likewise, the eradication is not
done.”
In terms of Sea Grant’s role in
the Caulerpa eradication effort,
Muñoz said: “I see Sea Grant as a
credible interface between the
world of science and the resource
agencies. Sea Grant is a vital part
of explaining the problem, communicating
the solution and
keeping stakeholders updated.”
C
aulerpa taxifolia is a bright green, feathery seaweed, infamous
for destroying huge tracts of habitat on the bottom of the
Mediterranean Sea. The seaweed grows quickly, is hearty and attractive—traits
that make it both an ideal plant for aquaria and an extremely difficult
one to eradicate once established in the wild. The first documented patch of
Caulerpa in the Mediterranean was identified around 1984. Tests later showed
the plants were clones of ones cultured for display at the Stuttgart Aquarium in
Germany and shared with aquaria in France and Monaco. That initial patch,
about one-square meter in size, spread faster and farther than anyone could have
then imagined, covering everything—sand,
gravel and boulders—in a feathery green
monoculture, comparable to a living carpet of
Astroturf.
Today, more than 32,000 acres of the
seabed from Tunisia to Croatia are covered in
a vast Caulerpa monoculture, a rolling
meadow of one foreign toxic plant, providing
neither habitat nor food for native marine life.
Fishing, recreational diving, tourism and
marine life have all suffered. Eradication is no
longer a discussed possibility. Scientists speak
of trying only to control the seaweed’s steady
march. Caulerpa, along with species such as
zebra mussels, are held up as case-in-point
reasons for gathering international support for
preventing the further introduction and
spread of nonindigenous species.
In June of 2000, much to the dismay of
biologists, Caulerpa was found in North
America for the first time, in two lagoons in
Southern California, at the Agua Hedionda
Lagoon in Carlsbad and in Huntington
Harbour in Orange County. Recognizing the
An aerial view of the Agua Hedionda Lagoon in
Carlsbad, California. Caulerpa has infested two sites
in North America, both in Southern California. The
infestation at the lagoon is of particular concern
because the waterway is connected to the open
ocean. Photo: City of Carlsbad
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