Caulerpa taxifolia Killer Algae
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Facts about Caulerpa taxifolia

The problem: The aquarium strain of Caulerpa taxifolia is an extremely invasive seaweed that is currently infesting tens of thousands of acres in the Mediterranean Sea and has now been found in two coastal water bodies in southern California.

Aquarium use: Due to its fast-growing, hardy nature and attractive appearance, C. taxifolia is used as a decorative saltwater aquarium plant. The variety of this species cultured for use in aquaria, known as the “aquarium strain,” tolerates colder water and grows more rapidly than the native strain. The native strain is not known to be invasive, and is genetically distinct from the aquarium strain. It is now illegal to possess, sell, or transport C. taxifolia in California.

Description: C. taxifolia is bright green, with feathery, fern-like fronds that extend upward from a main stem.

Distribution: C. taxifolia is native to tropical waters, including the Caribbean, Indo-Pacific, and Red Sea. Infestations of the aquarium strain have been found in the Mediterranean Sea, Australia, and California. Growth: The aquarium strain of C. taxifolia has the ability to form a dense carpet on any surface including rock, sand, and mud. It is capable of extremely rapid growth; up to one half inch per day (1 cm/day).

Depth: C. taxifolia can grow in shallow coastal lagoons as well as in deeper ocean waters, possibly to depths of greater than 150 feet (nearly 50 meters). Ecological risks: Plant and animal diversity and abundance are reduced where C. taxifolia has invaded. The aquarium strain of C. taxifolia has been documented to displace native vegetation, particularly seagrass beds, and become the dominant plant life. Human health threat: There are no human health risks associated with Caulerpa taxifolia.

Natural control: Outside of the tropics where Caulerpa occurs naturally, there is no known marine life that eats C. taxifolia in any significant quantities. C. taxifolia contains toxins that are distasteful to species that might feed on it.

Source and spread: Genetic evidence indicates that the most likely source of infestations in areas where C. taxifolia is not native is through release from aquaria. Once introduced, C. taxifolia spreads by fragmentation, and even a small, broken-off fragment can form a new plant. Distances between colonies can be great due to transport on boat anchors and fishing gear. C. taxifolia does not float, has never been observed to grow on boat hulls, and is unlikely to be transported in ballast water. Sexual reproduction has not been observed in the aquarium strain of C. taxifolia.

Mediterranean infestation: The aquarium strain of C. taxifolia was first found in the Mediterranean Sea off Monaco, adjacent to the Oceanographic Museum of Monaco, around 1984. Since then, C. taxifolia has spread along the Mediterranean coast and dramatically altered and displaced native plant and animal communities. Early eradication was not attempted in the Mediterranean, and the infestation is now considered beyond control. As of 2001, it was estimated that C. taxifolia had infested over 30,000 acres of seafloor in Spain, France, Italy, Croatia and Tunisia. C. taxifolia infestations have negatively impacted tourism, commercial and recreational fishing, and recreational activities such as SCUBA diving.

Australian infestation: The invasive aquarium strain of C. taxifolia has been reported in South Australia and New South Wales and is invading in a pattern similar to the Mediterranean infestation. Efforts are being made to control its spread.

Southern California infestations: C. taxifolia was first identified in June 2000 in Agua Hedionda Lagoon, a coastal marine lagoon located in Carlsbad in San Diego County. Its growth pattern was similar to that observed in the Mediterranean Sea, having spread to many areas and displaced the native seagrass. In July 2000, another infestation of C. taxifolia was reported in a portion of Huntington Harbour in Orange County. Test results indicate that the C. taxifolia in both Huntington Harbour and Agua Hedionda is genetically identical to the aquarium strain. Releases from aquaria, either directly into the water body, or indirectly through a storm drain, are the most likely sources of both southern California infestations of C. taxifolia.

Legislation and regulations: Assembly Bill 1334 (Harman), signed into law by the Governor in September 2001, prohibits the possession, sale, and transport of C. taxifolia throughout California. This bill also establishes the same restrictions on several other species of the genus Caulerpa that are similar in appearance to C. taxifolia and that are believed to have the ability to become invasive. Earlier in 2001, the City of San Diego adopted an ordinance banning the possession, sale, and transport of the entire genus of Caulerpa within city limits. Furthermore, the importation, interstate sale (including Internet sale), and transport of the Mediterranean strain (i.e., aquarium strain) of C. taxifolia is prohibited under the federal Noxious Weed Act (1999) and the federal Plant Protection Act (2000).

Eradication effort: The Southern California Caulerpa Action Team, SCCAT, is a committee established to respond quickly and effectively to the discovery of C. taxifolia in southern California. The group consists of representatives from local, state, and federal governmental entities, as well as private organizations. The goal of SCCAT is to completely eradicate all C. taxifolia infestations and to prevent new infestations. As part of the eradication effort, divers periodically conduct surveys in Agua Hedionda and Huntington Harbour. Wherever C. taxifolia is found, it is contained and treated with chlorine. Longterm monitoring will be necessary to assure complete eradication.

Prevention of new infestations: Aquarium water and other contents should never be emptied into or near any gutter, storm drain, creek, lagoon, bay, harbor, or the ocean. Aquarium water should be disposed of only in a sink or toilet. Rock and other solid material from an aquarium should be disposed of in a trash can. C. taxifolia from an aquarium (and anything it is attached to), should be placed in a plastic bag, put in a freezer for at least 24 hours, and then disposed of in a trash can. If any seaweed suspected to be C. taxifolia is found on fishing gear, anchoring gear, or vessels, it should be removed, carefully bagged (since even a small fragment has the potential to regenerate into a new plant), and reported. In order to prevent new infestations and comply with the law, Caulerpa taxifolia should not be purchased, sold, or distributed.

Contact information: Any sightings of Caulerpa taxifolia should be immediately reported to the California Department of Fish and Game at (858) 467-4218 (wpaznokas@dfg.ca.gov) or National Marine Fisheries Service at (562) 980-4043 (bob.hoffman@noaa.gov). For further information, please visit www.caulerpa.cjb.net and www.sccat.net.
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Caulerpa taxifolia

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Caulerpa taxifolia
Scientific classification
Kingdom: Plantae
Division: Chlorophyta
Class: Bryopsidophyceae
Order: Bryopsidales
Family: Caulerpaceae
Genus: Caulerpa
Species: C. taxifolia
Binomial name
Caulerpa taxifolia[1]
(M. Vahl) C. Agardh, 1817

Caulerpa taxifolia is a species of seaweed, an alga of the genus Caulerpa. Native to the Indian Ocean, it has been widely used ornamentally in aquariums. The alga has a stem which spreads horizontally just above the seafloor, and from this stem grow vertical fern-like pinnae, whose blades are flat like yew, hence the species name "taxifolia" (the genus of yew is "Taxus"). The alga produces a large amount of a single chemical that is toxic to fish and other would-be predators. This is in contrast to other plants which produce a variety of toxins, but in reduced amounts.

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.

Contents

[edit] Invasive species

A specific strain of this alga was found to thrive in cold aquarium environments by the staff at the Wilhelma Zoo in Stuttgart, Germany in 1980. Selective breeding under exposure to chemicals and ultra-violet light made the Caulerpa even hardier,[2] and when it eventually found its way into the Mediterranean, it created widespread concern as it 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 the Oceanographic Museum of Monaco in 1984. Ten years later, Caulerpa had grown to cover 7,400 acres (30 km2),[3] preventing native plants from growing and leading to the nickname "Killer Algae". Caulerpa overgrows the seabed and disrupts the food cycle dependent on the native plant life. The plant began to spread between ports along the Mediterranean coast. C. taxifolia has been discovered off the coasts of Australia and the United States, though none of these encroachments have been anywhere near the scale of what is happening in the Mediterranean.

For several years, the origin of the species was unclear. Marine biologist Alexandre Meinesz first discovered the plant in the 1980s, and requested the help of the Monaco Oceanographic Museum, which sat right next to the first known C. taxifolia patch. However, the director of the museum argued that this invasion probably happened naturally, the result of ocean currents carrying a tropical species into the area. Bickering over whether the species was natural or invasive, and whether the museum had released it or not, contributed to a delay that allowed the plant to spread beyond control.[4] The museum continued to deny releasing the plant, although former director Jacques-Yves Cousteau eventually expressed the belief that it was the only reasonable explanation.

It is reported that as many as half of fish species have disappeared from areas where Caulerpa grows. However, scientific studies have shown that fish diversity and biomass are equal or greater in Caulerpa meadows than in seagrass beds,[5] that Caulerpa had no effect on composition or richness of fish species,[6] and that epiphytic plant richness is greater in Caulerpa than in sea grass. A study in 2001 concluded that claims of huge areas smothered by this alga have been exaggerated 100-fold.[7]

[edit] Reproduction mechanism

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 reproduces sexually and has both male and female individuals. Gametes are expelled from each sex and meet to form a zygote which then goes through two larval stages before becoming an adult.

[edit] Other infestations

In 2000, the strain was found on the coast of California (U.S.A.), near San Diego, and also on the coast of New South Wales, Australia. The California invasion 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 fills up with chlorine and kills living organisms inside it, including the killer alga but also fish and plants. The killing of such other organisms was not desirable but was deemed preferable to letting the weed grow unchecked, which would in the end yield greater havoc on these same creatures.

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 discovered. 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 Southern California locations (Agua Hedionda Lagoon in Carlsbad and Seagate Lagoon in Huntington).

[edit] Possible natural control method

Researchers at the University of Nice in France have been studying a tiny aquatic slug which is known to be a natural predator of C. taxifolia.[8] 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. This slug cannot survive in the cooler waters of the Mediterranean, however, and so is unable to check the growth of the killer weed.

[edit] References

  1. ^ Guiry, M.D. & Guiry, G.M. (2007). "Genus: Caulerpa taxonomy browser". AlgaeBase version 4.2 World-wide electronic publication, National University of Ireland, Galway. http://www.algaebase.org/browse/taxonomy/?id=8295. Retrieved 2007-09-23. 
  2. ^ Pierre Madl & Maricela Yip (2004). "Literature Review of Caulerpa taxifolia". BUFUS-Info 19 (31). http://www.sbg.ac.at/ipk/avstudio/pierofun/ct/caulerpa.htm. Retrieved 2007-06-10. 
  3. ^ Bright, C. 1998. Life out of bounds: Bioinvasion in a borderless world. W. W. Norton & Company, New York.
  4. ^ Alda, Alan. "GREEN INVADER", Scientific American Frontiers, Show #1204 "Alien Invasion" Premiered November 6, 2001.
  5. ^ 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.
  6. ^ 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 300-301:345-353.
  7. ^ Frakes, T. A. (2001) "Killer algae: Ecological disaster or Media hysteria?" Submitted during the hearing in California concerning the proposed bill # 1334
  8. ^ Thibaut, T. 2001. "Elysia subornata a potential control agent of the alga Caulerpa taxifolia in the Mediterranean Sea", Journal of the Marine Biological Association of the United Kingdom
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[edit] External links

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Bred for its beauty, fast growth, and tolerance for cold, the "aquarium strain" of Caulerpa taxifolia, a bright green seaweed with fernlike fronds that is used to decorate saltwater aquariums, "escaped" from human control in the 1980s and has spread like a cancer through the Mediterranean, overwhelming native species and habitats. In this time line, written by Alexandre Meinesz, the marine biologist who has fought for years to warn authorities in France and elsewhere of this growing menace, follow the disquieting trajectory of this "killer alga" as it colonizes new waters around the world. Unless otherwise noted, "the alga" and "C. taxifolia" refer to the aquarium strain.



- - - 1980 - - -

A clone of Caulerpa taxifolia that is resistant to cold is observed in the tropical aquarium at the Wilhelmina Zoo in Stuttgart, Germany. It is distributed to the public aquarium in Nancy, France, as well as to aquariums at the Oceanographic Museum of Monaco and the Oceanographic Institute of Paris.

- - - 1984 - - -

A square yard of C. taxifolia grows in the Mediterranean beneath the Oceanographic Museum of Monaco.

- - - 1989 - - -

The acclimatization of the alga to the Mediterranean is discovered by Alexandre Meinesz, who expresses his concerns to the Monacan and French authorities.

Two and a half acres of C. taxifolia now grows in front of the Oceanographic Museum of Monaco.

- - - 1990 - - -

July—The alga turns up in France at Cap Martin, three miles east of Monaco. An initial newspaper article appears, and Meinesz sends his first letters of concern to the French authorities. In the press, the directorate of the Oceanographic Museum of Monaco minimizes the threat.

September—The alga is found near Toulon, 93 miles west of Monaco. Off Monaco and at Cap Martin, the alga covers over seven acres.

- - - 1991 - - -

January—Fishermen of Alpes-Maritimes, the French district that surrounds Monaco, drag up C. taxifolia in nets set more than 330 feet deep.

February—The journal Oceanologica Acta accepts an article by Meinesz and his colleague Bruno Hesse describing the risks associated with the invasion of the introduced alga. The article is published a few months later(1).

April—Meinesz submits to the French Ministry of the Environment and the Secretariat of State for the Sea a file listing studies to be urgently undertaken. The director of the Oceanographic Museum of Monaco turns to the press to deny the Monacan origin of the alga and to proclaim its benefits.

May—Meinesz makes his initial contact with IFREMER, the French Research Institute for Exploitation of the Sea, resulting in no action.

July—IFREMER and the directorate of the Oceanographic Museum downplay the problem.

Autumn—The alga spreads at Monaco and Cap Martin (74 acres in total). It is found at Agay Bay, halfway between Monaco and Toulon, and at Le Lavandou, about 25 miles east of Toulon.

December—C. taxifolia appears at Saint-Cyprien (Pyrénées-Orientales), over 200 miles west of Monaco. Scientists from the Universities of Nice, Marseilles, Pisa, and Trent organize a round table, at which they call for eradication of the alga.

- - - 1992 - - -

January—The alga is discovered at Saint-Cyr-les-Lecques (Var), 125 miles west of Monaco between Toulon and Marseilles.

February to October—Four commissions are created, and four French government ministers come to the Côte d'Azur. But no decision is made to control the algal spread.

June—The alga has reached Imperia, Italy, 25 miles east of Monaco.

September—The alga appears in the Balearic Islands of Spain.

December—The European Union finances the first research ever conducted into the C. taxifolia problem, funding 125 researchers in 25 laboratories.

Late 1992—The alga has invaded at least 28 sites between Menton (near the French border with Italy) and Toulon. More than 1,000 acres are more or less infested.

- - - 1993 - - -

The alga spreads in Italy, including off Liguria, Leghorn, Elba, and as far south as Sicily.

- - - 1994 - - -

The alga is discovered in Port-Cros National Park, on islands off the coast of southern France 62 miles west of Monaco.

December—The scientists assigned to study the problem issue the "Barcelona Appeal," which argues that the spread of C. taxifolia constitutes a major threat to Mediterranean ecosystems.

Late 1994—By this time, at least 38 sites have been invaded, with 3,700 acres infested. The alga is spotted at two sites in Croatia, more than 600 miles east of Monaco in the Adriatic Sea.

- - - 1995 - - -

Late 1995—Monacan researchers publish an article in a journal of the French Academy of Sciences trying to prove that the alga came from the Red Sea and is innocuous(2).

- - - 1996 - - -

July—Meinesz and marine biologist Charles-François Boudouresque publish a counter-article in the Academy of Sciences journal, arguing that certain results of the Monacan researchers are incorrect(3).

September—The European Community finances a second research program.

Late 1996—By this time, at least 68 sites have been invaded and 12,350 acres infested.

- - - 1997 - - -

March—Workshop of the French Academy of Sciences with 50 specialists. Ambiguous conclusions are drawn concerning the origin and danger presented by the alga, but strong recommendations are made to attempt to prevent dissemination and to control the spread.

March—Meinesz publishes the first edition(4) of his book, which is published two years later in the U.S. as Killer Algae: The True Tale of a Biological Invasion (University of Chicago Press, 1999).

September—At the Third International Workshop on C. taxifolia at Marseilles, researchers ask French Prime Minister Lionel Jospin to establish a strategy for prevention and control.

- - - 1998 - - -

March—At the United Nations Environmental Program's "Workshop on the Caulerpa Species Invasive in the Mediterranean," held at Heraklion, Crete, representatives unanimously conclude that the alga constitutes a major threat to Mediterranean ecosystems and recommend that all affected countries establish a strategy to prevent dissemination and curb the invasion.

October—The first published study of C. taxifolia genetics reports that all aquarium strains and colonies from the Mediterranean are genetically the same(5).

- - - 1999 - - -

January—Motion introduced to French Chamber of Deputies calling for inquiry into the polemic surrounding C. taxifolia and the slow response of the national government to the spread of the alga.

April—The U.S. Department of Agriculture adds the aquarium clone of C. taxifolia to the Federal noxious weed list.

- - - 2000 - - -

January—The alga is found for the first time in the southern Mediterranean, in the seas near Sousse, Tunisia.

June—The alga is identified in California waters off San Diego and Los Angeles. Researchers monitor 11,300 square feet of the alga in San Diego's Agua Hedionda lagoon.

November—The scientific journal Nature publishes an article on the genetics of a large collection of C. taxifolia from around the world(6). The C. taxifolia identified in California is genetically the same as the strains from the Stuttgart aquarium and from the Mediterranean. Researchers discover that the aquarium strain is genetically close to a native strain of C. taxifolia that occurs off the Australian coast at Moreton Bay, which appears to be the original source of the alga that was cloned to form the aquarium strain.

- - - 2001 - - -

January—Divers discover the invasive strain of C. taxifolia near Sydney, Australia, hundreds of miles from the native strain at Moreton Bay.

September—The Governor of California prohibits the sale, possession, and transport of C. taxifolia throughout California.

December—An article by Meinesz et al examining the spread of C. taxifolia in the Mediterranean shows that the alga has invaded 50 square miles of seabed along nearly 120 miles of coast(7). Researchers and others have now identified over 100 independent colonies in the sea.

- - - 2002 - - -

January—An international meeting on C. taxifolia is held at San Diego, where the eradication of the alga is well under way under the auspices of the Southern California Caulerpa Action Team.

Spring—C. taxifolia turns up near Adelaide, hundreds of miles to the west of Sydney in southern Australia.

September—C. taxifolia arrives in Sardinia, the largest island in the Mediterranean Sea.

Autumn—A survey of San Diego's lagoon reveals no C. taxifolia.

- - - 2003 - - -

February—A preliminary report on the situation of C. taxifolia along the coasts of southern France shows a rapid expansion, with 40 new colonized areas since December 2000 and more large, concentrated areas resulting from the fusion of numerous smaller zones.




Footnotes

1. Meinesz, A. and B. Hesse. 1991. "Introduction and Invasion of the Tropical Alga Caulerpa taxifolia in the Northwest Mediterranean." Oceanologica Acta, Vol. 14, No. 4: 415-26.

2. Chisholm, J., J. Jaubert, and G. Giaccone. 1995. "Caulerpa taxifolia in the Western Mediterranean: Accidental Introduction or Migration from the Red Sea." Comptes Rendus de l'Académie des Sciences (III, Sciences de la Vie), Vol. 318: 1219-26.

3. Meinesz, A. and C.-F. Boudouresque. 1996. "On the Origin of Caulerpa taxifolia." Comptes Rendus de l'Académie des Sciences (III, Sciences de la Vie), Vol. 319: 603-13.

4. Meinesz, A. Le Roman Noir de l'Algae "Teuse": Caulerpa taxifolia Contre la Méditerranée, ©Éditions Belin, 1997.

5. Jousson, O., et al. 1998. "Molecular Evidence for the Aquariologic Origin of the Green Alga Caulerpa taxifolia Invading the Mediterranean Sea." Marine Ecology Progress Series, Vol. 172: 275-80.

6. Jousson, O. et al. 2000. "Invasive Alga Reaches California." Nature, Vol. 408: 157.

7. Meinesz, A., et al. 2001. "The Introduced Green Alga Caulerpa taxifolia Continues to Spread in the Mediterranean. Biological Invasion, Vol. 3: 201-210.


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