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
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
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)
Caulerpa taxifolia (Vahl) C. Ag.
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 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)
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.:
- 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)
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)
What can you do?
Laws and lists:
Caulerpa taxifolia
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:
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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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