“Caulerpa taxifolia is an invasive marine alga that is widely used as a decorative plant in aquaria. A cold-tolerant strain was inadvertently introduced into the Mediterranean Sea in wastewater from the Oceanographic Museum at Monaco, where it has now spread over more than 13,000 hectares of seabed. Caulerpa taxifolia forms dense monocultures that prevent the establishment of native seaweeds and excludes almost all marine life, affecting the livelihoods of local fishermen.”
(NIMPIS 2011, Caulerpa taxifolia general information, National Introduced Marine Pest Information System, viewed 29 January 2011 <http://www.marinepests.gov.au/nimpis>)
See also: Southern California Caulerpa Action Team
Native circum-tropical distribution: Africa, Australia, Bermuda, China, Fiji, India, Japan, Maldives, New Caledonia, Hawaii (USA)
Non-native range: Australia, Croatia, France, Germany, Italy, Monaco, New Zealand, Spain, Tunisia, California (USA)
(Global Invasive Species Database – Caulerpa taxifolia viewed 29 January 2011)
First observed in Mediterranean in 1984 in Monaco from which it spread rapidly (Bourdouresque et al., 1995). Found in Southern California 12 June 2000, where rapid-respone eradication and control measures seem to have been fairly effective (Williams & Grosholz, 2002; Anderson, 2005; SCCAT accessed 1 February 2011).
Substrate: rock, sand, seagrass
Depth: 3 to 35 m, though to 100 m in Mediterranean
(NIMPIS 2011, Caulerpa taxifolia reproduction and habitat, National Introduced Marine Pest Information System, viewed 29 January 2011 <http://www.marinepests.gov.au/nimpis>)
United States Law: It is illegal to import or transport Caulerpa taxifolia aquarium strain across state lines including internet sale (Federal Noxious Weed Act, 1999; and Federal Plant Protection Act, 2000).
California State Law: It is illegal to possess, transport, transfer, release alive, import, or sell Caulerpa taxifolia, Caulerpa sertularioides, Caulerpa mexicana, Caulerpa ashmeadii, Caulerpa scalpelliformis, Caulerpa racemosa (and all varieties of C. racemosa), Caulerpa cupressoides, Caulerpa verticillata, Caulerpa floridana (California Fish and Game Code 2300).
City of San Diego Law: Bans the possession, sale, and transport of all Caulerpa species within city limits (City of San Diego Ordinance 18967).
Caulerpa taxifolia is similar in appearance to C. scalpelliformis, C. mexicana, C. sertularioides, and C. ashmeadii -- all also illegal in California (USA) (California Sea Grant - Caulerpa species identification key - "feather").
“Caulerpa taxifolia is a light green macroalga with upright leaf-like fronds arising from creeping stolons. The fronds are flattened laterally and the small side branchlets are constricted at the base (where they attach to the midrib of each frond), are opposite in their attachment to the midrib (as opposed to alternating) and curve upwards and narrow towards the tip. The invasive aquarium clone is morphologically identical to native populations of the species. Frond diameter is 6-8mm and frond length is usually 3-15cm in the shallows, 40-60cm in deeper situations but can grow up to 2.8m in height.”
(NIMPIS 2011, Caulerpa taxifolia general information, National Introduced Marine Pest Information System, viewed 29 January 2011 <http://www.marinepests.gov.au/nimpis>.)
In its native tropics, it reproduces sexually and vegetatively. In its invasive range in the Mediterranean, all reproduction is believed to be via thallis fragmentation. Though male gametes are produced (synchronously) there are no female gametes, suggesting this population is an all-male clone (Žuljević & Antolić, 2000).
Highly invasive, spreading rapidly and leading to reduced numbers and diversity of other algae, invertebrates, and fish (Bourdouresque et al., 1995; Balata et al., 2004).
Vectors for introduction: ornamental aquaria (public and private), fisheries and aquaculture, natural dispersal from introduced populations, vessels (NIMPIS 2011, Caulerpa taxifolia general information, National Introduced Marine Pest Information System, viewed 29 January 2011 <http://www.marinepests.gov.au/nimpis>).
Photosynthesis. Capable of enhancing N2 fixation, giving it another competitive advantage in nutrient-poor waters.