Caulerpa taxifolia is a species of seaweed, an alga of the genus
Caulerpa. Native to the Indian Ocean, it is widely used ornamentally
in aquariums, because it is considered attractive and neat in
arrangement, and is easy to establish and care for. The alga has a
stem (rhizome) which spreads horizontally just above the seafloor.
From this stem grow vertical fern-like pinnae, whose blades are flat
like those of the yew (Taxus), hence the species name taxifolia.
It is one of two algae on the list of the world's 100 worst invasive
species compiled by the
IUCN Invasive Species Specialist Group.
2 Introduced species
2.1 Reproduction mechanism
2.2 Other introductions
2.3 Possible natural control method
4 External links
Unlike most aquarium macro algae, C. taxifolia has the appearance of a
vascular plant with "leaves" arranged neatly up stalks, like a fern.
Behind this appearance, the plant is a typical macro alga, without the
vascular system to transmit nutrients and cells that plants originally
evolved on land have.
Caulerpa taxifolia is a single celled organism,
however this is often overlooked because of its complexity and size.
Caulerpa taxifolia has been described as storing in its "leaves" a
single chemical, 'caulerpicin', that is noxious to fish and other
would-be predators, though not toxic to the water around it. This is
in contrast to plants which produce a variety of toxins, but in
reduced amounts. On the other hand, studies have found that there is
reduced pollution and toxicity in waters where it grows invasively, as
around port cities in the Mediterranean. Original concerns about it
decreasing biodiversity of fauna have also been allayed, as species
counts have shown this remains about the same.
In 1980, the staff at the
Wilhelma Zoo in
Stuttgart, Germany found
that a specific strain of this alga thrived in cold aquarium
environments. Selective breeding under exposure to both chemicals and
ultra-violet light produced even hardier
Caulerpa strains. When it
eventually found its way into the Mediterranean, widespread concern
developed that the algae threatened to alter the entire ecosystem by
crowding out native seaweed while being inedible to animals.
It is thought that the seaweed was accidentally released into coastal
waters of the
Mediterranean Sea just below Jacques Cousteau's
Oceanographic Museum of Monaco
Oceanographic Museum of Monaco in 1984. Ten years later, the claim was
Caulerpa had grown to cover 7,400 acres (30 km2),
and was preventing native plants from growing. This concern earned the
algae the dubious nickname "Killer Algae" after the title of a book
written on the subject. Its author, Marine biologist Alexandre
Meinesz first discovered the alga in the 1980s, and requested the help
of the Monaco Oceanographic Museum, which sat right next to the first
known C. taxifolia patch. The director of the museum argued that this
invasion probably happened naturally, the result of ocean currents
carrying a tropical species into the area. The parties bickered
publicly for years over whether the species was natural or invasive,
and whether the museum had released it or not, at the expense of sound
scientific research on the species and its ecological significance.
Beds of the algae typically inhabit polluted, nutrient-rich areas such
as sewage outfalls, explaining its spread among port cities in the
Mediterranean Sea. This actually reduces the pollution in those areas,
as the caulerpa consumes it: In an eight-year study of
in the French Bay of
Menton by the European Oceanographic Observatory
of Monaco (based within the Museum of Monaco), it was found that
the alga reduced pollution and aided in the recovery of native
Despite claims that as many as half of fish species have disappeared
from areas where
Caulerpa grows, scientific studies
have shown that fish diversity and biomass are equal or greater in
Caulerpa meadows than in seagrass beds, that
Caulerpa had no effect
on composition or richness of fish species, and that species
richness and epiphytic plant diversity is greater in
Caulerpa than in
pure sea grass. Thus, in contrast to widely publicized reports to the
contrary, the species appears to have many beneficial ecological
effects on aquatic communities in the
Aquarist Jean Jaubert, director of the aforementioned Oceanographic
Museum of Monaco, has said that the affected areas in the nearby Bay
Menton have been exaggerated 100-fold.
The aquarium strain reproduces asexually, that is, vegetatively: the
viscous, elastic white fluid inside the stem was found under the
microscope to contain only male gametes. Rate of growth can be as fast
as a centimeter per day. If any small part is severed from the rest of
the alga, this small part will regrow into another alga. Anchors of
ships and fishing nets can serve as carriers of Caulerpa. Thus this
alga has been found to jump from the coast of one port city to the
coast of another port city. The natural strain has both male and
female individuals and additionally reproduces sexually. Gametes are
expelled from each sex and meet to form a zygote which then goes
through two larval stages before becoming an adult.
In 2000, the strain was found on the coast of
near San Diego, and also on the coast of New South Wales, Australia.
California colonization was small enough to be considered
controllable: it was covered with tarpaulin which was held down with
sandbags at the edges of the infestation. Then chlorine was poured in
through tubes which fed into certain openings in the tarpaulin: the
interior of the tarpaulin filled up with chlorine and killed living
organisms inside it, not only the unwanted alga but also fish,
invertebrates and other seaweeds. The killing of such other organisms
was not desirable but was deemed preferable to letting the algae grow
The appearance off the
California coast was most probably caused by an
aquarium owner improperly dumping the contents, allowing C. taxifolia
to flow through a storm sewer into the lagoon where the invasion was
California has since passed a law forbidding the
possession, sale or transport of
Caulerpa taxifolia within the state.
There is also a federal law under the Noxious Weed Act forbidding
interstate sale and transport of the aquarium strain Caulerpa.
In July 2006, the alga had been declared eradicated from the two
California locations (Agua Hedionda Lagoon in Carlsbad and
Seagate Lagoon in Huntington Beach).
Possible natural control method
Researchers at the
University of Nice
University of Nice in France have been studying a
tiny aquatic slug which is a natural predator of C. taxifolia.
Called Elysia subornata, it was found off the coast of Florida, in
waters warmer than those in the Mediterranean. This slug is believed
to feed exclusively on C. taxifolia, by sticking its proboscis into
the stem and sucking out the white viscous liquid inside the stem:
this causes the alga to become limp, discolored, and dead. As the slug
does so, it absorbs the alga's poison. The slug has an enzyme which
neutralizes the noxious effect of the poison, and at the same time,
the poison protects the slug from being eaten by fish. However, this
slug cannot survive in the cooler waters of the
therefore, is unable to control the invasive alga there.
^ Guiry, M.D.; Guiry, G.M. (2007). "Genus:
Caulerpa taxonomy browser".
AlgaeBase version 4.2 World-wide electronic publication, National
University of Ireland, Galway. Retrieved 2007-09-23.
^ Pierre Madl; Maricela Yip (2004). "Literature Review of Caulerpa
taxifolia". BUFUS-Info. 19 (31). Retrieved 2007-06-10.
^ Bright, C. 1998. Life out of bounds: Bioinvasion in a borderless
world. W. W. Norton & Company, New York.
^ Meinesz, A. 1999. Killer algae. University of Chicago Press,
^ Frakes, T.A. 2001. Killer algae: Ecological disaster or media
hysteria? Submitted during the hearing in
California concerning the
proposed bill # 1334 available at
^ Meinesz, p. 206
^ Jaubert, J.M., J.R.M. Chisholm, G. Passeron-Seitre, D. Ducrot, H.T.
Ripley, and L. Roy. 1999. No deleterious alterations in
in the Bay of
Menton (France) eight years after
colonization. Journal of Phycology 25:1113-1119.
^ Relini, G., M Relini, and G. Torchia. (1998)
Fish biodiversity in a
Caulerpa taxifolia meadow in the Ligurian Sea. Italian Journal of
Zoology 65 Supplement:465-470.
^ Francour, P., M. Harmelin-Vivien, J. G. Harmelin, and J. Duclerc.
1995. Impact of
Caulerpa taxifolia colonization on the littoral
ichthyofauna of north-western
Mediterranean sea. Hydrobiologia
^ Thibaut, T. 2001. "
Elysia subornata a potential control agent of the
Caulerpa taxifolia in the
Mediterranean Sea" Archived 2005-10-25
at the Wayback Machine., Journal of the Marine Biological Association
of the United Kingdom
Peplow, M. 2005. "Algae create glue to repair cell damage", Nature
"Start-up drills for oil in algae" by Martin LaMonica,
May 20, 2005, retrieved July 13, 2006
Theodoropoulos, David. 2003. Invasion Biology: Critique of a
Pseudoscience. pages 42,159. Avvar Books, Blythe, CA. 237 p.
Wikispecies has information related to
Wikimedia Commons has media related to
Killer Algae BBC Documentary Full on YouTube
Attack of the killer algae - Eric Noel Muñoz on YouTube
In-depth article on invasions of
Caulerpa taxifolia, source as escaped
aquarium plant, etc.
Caulerpa Taxifolia fact sheet
An excerpt from Killer Algae by Alexandre Meinesz
Caulerpa taxifolia at the Center for Invasive Species Research
"Deep Sea Invasion"
Nova (TV series)
Nova (TV series) broadcast April 1, 2003
Species Profile- Caulerpa,
Mediterranean Clone (
National Invasive Species Information Center, United States National
Agricultural Library. Lists general information and resources for