Caulerpa taxifolia - Invasive Aquatic Plants of the United States

Non-Native Invasive Aquatic Plants in the United States

Center for Aquatic and Invasive Plants, University of Florida
and
Sea Grant

Habit
Habitat
Identification
Might be confused with...
Origin
U.S. distribution
How it got here...
Spread potential
Problems/Effects
Control
What can you do?
Laws and lists
Want to know more?
The Literature
Other web sites
Page author

CAULERPA TAXIFOLIA

pronounced: caul-er-pa tax-i-fol-ee-ah (long/short marks) (audio clip)

from:

"referring to the dark-green and flattened foliage similar to that of the genus Taxus (Yew)"

Synonymy:

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

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- and sesqui-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 7^o C (45^o F), lethal minimum temperature elsewhere is 14^o C (57^o F) (Komatsu et al., 1994); optimum growth temperature is 20-30^o C (68-86^o F):; its lethal maximum temperature is 32^o C (90^o F)
it has a very low light compensation point and can grow in low light levels (Gacia et al., 1994; Komatsu et al., 1994)

Quick ID:

Caulerpa taxifolia:

More complete identification:

Caulerpa taxifolia

Original description:

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 m m²" (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)

Caulerpa taxifolia might easily be confused with other Caulerpa species, several of which, for example, grow in Florida marine waters

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

Distribution in the U.S.:

This distribution map combines
USGS and Kartesz data

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).

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)

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.

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)

Control:

Caulerpa taxifolia

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)

What can you do?

There's plenty

you can do to help.

Laws and lists:

Caulerpa taxifolia

is "state-listed" only by South Carolina
is on the Federal List of Noxious Weeds (USDA/APHIS, 2000)

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 54,000 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:

A Prevention Program for the Mediterranean Strain of Caulerpa taxifolia
U.S. Aquatic Nuisance Species Task Force

http://www.anstaskforce.gov/Caulerpa.htm

http://www.sci.sdsu.edu/CMI/swilliam/swilliam.htm

"Caulerpa"

http://www.unice.fr/

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, the world's largest collection of scientific literature about aquatic, wetland and invasive plants. For this project, Jessica Munsch serves as the library research assistant; Mary Langeland searches the literature; Laura Line is the illustrator; and Ann Murray is the photographer and web image specialist.

Anecdotal information about Caulerpa taxifolia would be appreciated by users of this web site. Please submit anecdotal information, additional reference citations and corrections for this page to CAIP-WEBSITE@ufl.edu