Green alga

Caulerpa taxifolia -- Center for Aquatic and Invasive Plants

Caulerpa taxifolia

Non-Native to Florida

This species appears on the following legally prohibited plant lists

CAULERPA TAXIFOLIA (Vahl) C. Ag.
Green alga
Chlorophyta: Ulvophycees

pronounced: caul-er-pa tax-i-fol-ee-ah
from: caulis (L.): stalk of a plant
taxi : Yew-like
folia (L.): leaves
"referring to the dark-green and flattened foliage similar to that of the genus Taxus(Yew)"

Caulerpa taxifolia is a marine, green alga, a certain strain of which is invading sectors of the western coasts of the Mediterranean Sea where it grows much more robustly than it does in its native range. In the Mediterranean it has spread into thousands of hectares where it fills the water column with hundreds of tons of plant biomass per hectare. It is protected from sea urchins, fish and other herbivores by its toxicity. Caulerpa taxifolia is native to the Caribbean and other tropical seas where it grows in small patches and does not present problems. However, it was reported in 2000 that the Mediterranean Sea strain of the alga was discovered in California waters, where it is not native, and where it may spread as it has in the Mediterranean.

Habit

  • Caulerpa taxifolia is a marine green alga believed to have been accidentally introduced into the Meditteranean Sea
  • it forms continuous meadows from the surface to more than 30 m deep; has been found in water to 100 m deep (Boudouresque et al, 1995)
  • meadows of Caulerpa taxifolia in the Mediterranean can attain exceptional densities, while in its native tropical seas the plant is usually isolated (Meinesz and Hesse, 1991)
  • reproduces by fragmentation; sexual reproduction has not been observed
  • at 10 m depth, reported biomass rates up to 700 g (dry weight) m2 (375 tons of wet biomass per acre) (Meinesz et al, 1994)
  • Caulerpa taxifolia protects itself by producing substances that are toxic to the Mediterranean's two main macro-herbivores, sea urchins and their eggs (as well as to hamsters and mice) (Lemee et al., 1993), and the fish Sarpa salpa
  • toxicity is highly seasonal: highest in July-November, lowest in March-April

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Habitat

  • the Mediterranean plants grow on many kinds of substrates including rocks, sand, mud and dead rhizomes of seagrasses
  • "its high growth rate, its total substrate occupation, its improved light access, the increased sedimentation rates it creates, and the synthesis of toxic secondary metabolites (mono-andsesqui-terpenes)" are reasons why Caulerpa taxifolia outcompetes native seaweeds and seagrasses
  • new colonies usually appear between 2 and 10 meters depth (Meinesz et al., 1993)
  • growth is highest in summer and fall
  • C. taxifolia is able to withstand severe nutrient limitation (Delgado et al., 1996), which probably partly explains its growth ability
  • temperature tolerance: its lethal minimum temperature in the Mediterranean is 7o C (45o F), lethal minimum temperature elsewhere is 14o C (57o F) (Komatsu et al., 1994); optimum growth temperature is 20-30o C (68-86o F):; its lethal maximum temperature is 32o C (90o F)
  • it has a very low light compensation point and can grow in low light levels (Gacia et al., 1994; Komatsu et al., 1994)

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Identification

  • Caulerpa taxifolia is a siphonalean alga
  • the Mediterranean strain of Caulerpa taxifolia is somewhat different, chiefly in size, length, growth rate and temperature tolerance from samples collected in tropical areas (Boudouresque et al, 1995)
  • fronds are feather-like "leaf blades" each of which has a relatively wide central axis (rachis), from which grow many pinnules
  • primary fronds grow directly on the stolons at regularly spaced intervals; fronds may be quite short or even absent in shallower water (leaving only the stolons), becoming longer in deeper water in low light conditions; primary fronds are 2-15 cm (1-6 in) in the tropical version of the alga, while primary fronds of the Mediterranean strain range from 5 cm in shallower water, to 40 cm at depths of 15 m, and even to 60-80 cm long (24 in to 38 in) at greater depths (Meinesz, 1995); branching fronds grow from the primary fronds
  • pinnules are up to 1 cm long; number 4 to 7 per cm along each side of the frond axis; are usually upcurved, tapering at the ends; some pinnules are split in two at the ends (bifurcate); pinnule spacing and length depend on light availability (Meinesz, 1995)
  • primary frond cover density may range from 5,100 (September) to 14,000 (April) fronds per m2 (Meinesz et al., 1995)
  • stolons (stems) bear the fronds and the rhizoids; stolon length averages 1 to 1.5 m in autumn (Meinesz, 1995); new stolons arise from old stolons that have survived the winter; cumulative stolon length "tends to stabilise around an equilibrium value of 220 mm2" (Meinesz, 1995)
  • unlike vascular plants, there are no "roots" on algae; however in C. taxifolia, regularly spaced "rhizoid pillars" descend from the stolons, tapering at the ends, having many extremely thin filamentous "rhizoids"; the rhizoids mimic roots by attaching to rocks and other substrata and taking up and translocating inorganic and organic nutrients from the substrate; "on rock, the lacework of these rhizoids, trapping grains of sand or mud, may form a felt, completely covering the substrate" (Meinesz, 1995; Chisholm et al., 1996)

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Origin

  • the marine alga, Caulerpa taxifolia, is native to the tropical oceans and seas of the world, including Australia, Brazil, Ceylon, Indonesia, Philippines, Tanzania and Vietnam
  • in the early 1980s it was used for decoration in aquaria
  • it was first observed in the Mediterranean Sea in 1984

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Distribution in the U.S.

  • Caulerpa taxifolia is reported from the tropical waters in the Caribbean south of Florida where it is native and does not present problems (yellow in map above).
  • The Mediterranean strain was reported in 2000 to be found in California waters (green in map above).

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How it got here

  • long distance spread of Caulerpa taxifolia can be the result of cleaning anchors and fishing nets (Meinesz, 1992; Sant et al, 1994), or emptying aquarium contents
  • short distance spread is from fragments transported by currents
  • newly colonized sites are often harbors, marinas and other places where boats anchor (Boudouresque et al 1995)

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Potential to spread elsewhere in U.S.

  • DNA testing confirmed the 2000 discovery of the Mediterranean strain of Caulerpa taxifolia in Carlsbad and Huntington Harbour, California. Because this alga can easily spread from these infested areas to other U.S. waters, there has been a call for "rapid eradication". (Jousson et al., 2000)
  • Can we stop "killer algae" from invading Florida?, by C. Jacoby & L. Walters is a 2 page illustrated fax sheet describing Caulerpa, what it is, what it looks like, why it is invasive, and how people can help prevent an invasion of this noxious aquatic weed.

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Problems/Effects

  • in the Mediterranean, Caulerpa taxifolia occupied 1 m2 in 1984; 30 ha by 1991; 1000-2000 ha by the end of 1993
  • in the Mediterranean, the alga is causing a "major ecological event" (Boudouresque et al., 1995)
  • in the Mediterranean, Caulerpa taxifolia invades the dominant seagrass, Posidonia oceanica, and in invaded areas able to kill up to 45% of Posidonia shoots in one year (Villele and Verlaque, 1994)
  • where it is found in the Mediterranean, other native seaweeds are being more or less totally replaced
  • the numbers of individuals of Mollusca, Amphipoda and Polychaeta in Caulerpa taxifolia meadows is greatly reduced (Bellan-Santini et al, 1996)
  • Caulerpa taxifolia is toxic to herbivores such as sea urchins and fish; where the plant is the sole food source, then these herbivores are eliminated
  • caulerpenyne extract inhibits or delays the proliferation of several phytoplanktons of the marine food chain (Lemee et al., 1997)

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Caulerpa taxifolia is difficult to control

  • for the California infestations, managers covered the plants with a tarp and injected liquid chlorine underneath; the chlorine will kill the algae as well as other plants and animals that live there; as of February, 2001, managers felt that the treatment was being effective, and they will follow up with more treatments, and will monitor the site (Clark, 2001)
  • unsuccessful methods tested include suction pumps, dry ice, hot water, ultrasound and electrolysis with copper
  • manual methods seems most appropriate to eradicate small and isolated patches (Riera et al, 1994)

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What can you do?

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Laws and lists

Caulerpa taxifolia

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Want to know more?

The information contained on this wep page was extracted from published scientific literature and agency reports. It is important to know that plant research, like most areas of scientific research, is still relatively young and incomplete--much may have been published about the physiology of one plant but not about its management; much may have been published about how to culture and grow another plant but not about its natural ecology. Thousands of research articles may have been published about one invasive plant, but perhaps only a dozen about another.

If you want to read the research yourself, perhaps to clarify or expand an area of information contained here, or to help determine your own line of research, you are welcome to query the world's largest collection of international scientific literature about aquatic, wetland and invasive plants, the APIRS bibliographic database, which contains more than 65,000 citations and their content keywords. Or you might want to ask us to do it for you and mail or e-mail the search results to you.

This is the literature about Caulerpa taxifolia that was used to develop this web page. More research items about this plant may be found at APIRS:

  • Bellan-Santini D, Arnaud PM, Bellan G, Verlaque M. 1996. The influence of the introduced tropical alga Caulerpa taxifolia, on the biodiversity of the Mediterranean marine biota. J. Marine Biological Association of the United Kingdom 76(1):235-237
  • Boudouresque CF, Meinesz A, Ribera MA, Ballesteros E. 1995. Spread of the green alga Caulerpa taxifolia (Caulerpales, Chlorophyta) in the Mediterranean: Possible consequences of a majro ecological event. Scientia Marina 59(Dec)Suppl. 1:21-29
  • Boudouresque CF, Meinesz A, Verlaque M, Knoepffler-Pegue M. 1992. The expansion of the tropical alga Caulerpa taxifolia (Chlorophyta) in the Mediterranean. Cryptogamie-Algologie 13(2):144-145
  • Boudouresque CF, Bellan-Santini D, Belsher T, Duclerc J. 1992. The introduction of the green alga Caulerpa taxifolia into the Mediterranean: The repercussions for the indigenous communities. Communication Presentee Au 6th European Ecological Congress, 7-12 Sept 1992, 52:88-89 (Abstract)
  • Ceccherelli G, Cinelli F. 1999. Effects of Posidonia oceanica canopy on Caulerpa taxifolia size in a northwestern Mediterranean bay. J. Experimental Marine Biology and Ecology 240(1):19-36
  • Chisholm JRM, Joubert JM, Giaccone G. 1995. Caulerpa taxifolia in the northwest Meditteranean: Introduced species or migrant from the Red Sea?. Comptes Rendus de L'Academie des Sciences 318(12:1219-1226
  • Chisholm JRM, Dauga C, Ageron E, Grimont PAD. 1996. Roots' in mixotrophic algae. Nature 381:382
  • Clark R. 2001. More information on "Algae invades California". Interview with B. Hoffman, National Marine Fisheries. www.Scientificsonline.com
  • Delgado O, Rodriguez Prieto C, Gacia E, Ballesteros E. 1996. Lack of severe nutrient limitation in Caulerpa taxifolia (Vahl) C Agardh, an introduced seaweed spreading over the oligotrophic northwestern Meditteranean. Botanica Marina 39(1):61-67
  • Jousson I, Pawlowski J, Zaninetti L, Zechman FW, Dini F, Di Guiseppe G, Woodfield R, Millar A, Meinesz A. 2000. Invasive alga reaches California. Nature 408:9 November 2000
  • Lemee R, Pesando D, Issanchou C, Amade P. 1997. Microalgae: a model to investigate the ecotoxicity of the green alga Caulerpa taxifolia from the Mediterranean Sea. Marine Environmental Research 44(1):13-25
  • Lemee R, Pesando D, Durand-Clement M., Dubreuil A. 1993. Preliminary survey of toxicity of the green alga Caulerpa taxifolia introduced into the Mediterranean. J. Applied Phycology 5:485-493
  • Meinesz A. 1999. Killer Algae: A True Tale of Biological Invasion. Univ. Chicago Press. 360 pp.
  • Meinesz A, Benichou L, Blachier J, Komatsu T, et al. 1995. Variations in the structure, morphology and biomass of Caulerpa taxifolia in the Mediterranean Sea. Botanica Marina 38:499-508
  • Meinesz A, de Vaugelas J, Hesse B, Mari X. 1993. Spread of the introduced tropical green alga Caulerpa taxifolia in northern Mediterranean waters. J. Applied Phycology 5:141-147
  • Ribera MA, Ballesteros E, Boudouresque CF, Gomez A, Gravez V, editors. 1996. Second Internationl Workshop on Caulerpa taxifolia, Barcelona, 15-17 December 1994. University of Barcelona. 457 pp.

Other web sites that treat Caulerpa taxifolia:

 


 

Sea Grant

This web page was authored in June, 2001, by Victor Ramey (Center for Aquatic and Invasive Plants, University of Florida), with significant contribution from Barbara Peichel (Sea Grant, University of Minnesota). The information contained herein is based on the literature found in the APIRS database.

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