Quick Facts

Quick facts

• Aquarium Caulerpa (Caulerpa taxifolia) is a green seaweed with horizontal stems and upright, flattened, fern-like branches.
• It is introduced and invasive in New South Wales and South Australia.
• The invasive strain is difficult to distinguish from the widespread, non-invasive strain without genetic testing.
• Aquarium Caulerpa is spread by poor aquarium maintenance and dumping of aquarium water and materials. Once established it may spread by hull-fouling. It impacts on native species by competing for space.
• It can be controlled by mechanical removal, poisoning with chlorine, or application of salt.

What Does It Look Like?

What is it?

Aquarium Caulerpa (Caulerpa taxifolia) is a green seaweed (marine algae). It has creeping stems (stolons) that meander across the sea bottom, from which upright fronds arise. Stems of the upright fronds are unbranched or sparsely branched, compressed, and to approximately 20-60 cm in height. They produce small lateral branchlets that are 5-9 mm long and arise in one plane. The branchlets are slightly flattened, unbranched, sickle-shaped, straight or upwardly curved. There is a slight constriction at the base of the branchlets and a small gap between adjacent branchlets (Hewitt et al. 2002).

For further information and assistance with identification of Aquarium Caulerpa, contact the herbarium in your state or territory.

Flower colour

No flower

Growth form (weed type/habit)

Aquatic

Where it currently grows? Preferred habitat

Aquarium Caulerpa is a marine alga that grows on a range of substrates, including rock, sand, mud and seagrasses. Its usual depth range is from 3 to 35 m, but in the Mediterranean it has been recorded from 100 m depth. It can grow successfully in a variety of conditions and water qualities (Hewitt et al. 2002).

Are there similar species?

Aquarium Caulerpa is similar in appearance to a number of other species in the genus, particularly Caulerpa mexicana, Caulerpa sertularioides and Caulerpa scalpelliformis. C. mexicana has a flat midrib, whereas that of C. taxifolia is compressed; C. sertularioides has cylindrical lateral branchlets (those of C. taxifolia are flat), and C. scalpelliformis has branchlets that arise in an alternate (i.e., offset) pattern, whereas those of C. taxifolia are opposite. As noted, the invasive form (Aquarium Caulerpa) can only be discriminated from native populations of Caulerpa taxifolia by genetic testing (Murphy & Schaffelke 2003).

Why Is It A Weed?

What are its impacts?

Native ecosystems: Aquarium Caulerpa can be extremely invasive, smothering other algal species, seagrasses and sessile invertebrate communities (Wright et al. 2007). These impacts are due to the alga either out-competing these species in capturing nutrients and light or through the toxic effects of secreted caulerpenyne compounds. Its large monospecific (single species) meadows can impact native species diversity and fish habitats (Hewitt et al. 2002).

How does it spread?

Aquarium Caulerpa is dispersed by aquarium trade and potentially by hull fouling (transported from infected areas to new areas by attaching to the hulls of ships). Local distribution is by vegetative growth or by the dispersal of small fragments that develop into new plants (Creese et al. 2004).

What is its history in Australia?

The first Australian record of an incursion of Aquarium Caulerpa outside of its native range was in 2000 in New South Wales. It was discovered in South Australia in March 2002 in West Lakes and the upper Port River, Adelaide. Likely vectors for its introduction and potential spread in these areas are through an escaped aquarium specimens or the transport of infected recreational equipment. It is unknown if the New South Wales incursion was due to range extension or accidental introduction, but the former is thought to be unlikely given the large distances between populations (Creese et al. 2004). However, there is a closer relationship between the Queensland and New South Wales populations than with the Mediterranean population, suggesting the New South Wales introduction might have been from the Queensland source (Murphy & Schaffelke 2003).

How To Manage It?

Best practice management

Aquarium Caulerpa can be controlled by mechanical removal, poisoning with chlorine, or application of salt.

Chemical control: In NSW, the application of coarse sea salt was found to be an effective method of control as it rapidly killed the seaweed. The effectiveness varied between sites (Glasby et al. 2004). Small infestations in California were covered with black plastic tarpaulins and poisoned with chlorine, which resulted in successful eradication (Anderson 2002; SCCAT Undated).

Non-chemical control: Mechanical control: Mechanical removal and poisoning with chlorine are only possible with small outbreaks (Williams & Schroeder 2004).

Please see the Australia Pesticides and Veterinary Medicine Authority for chemical information http://www.apvma.gov.au 

Does it have a biological control agent?

NO

When does it grow? (lifecycle/growth calendar)

Sexual reproduction in Aquarium Caulerpa is thought not to occur, but the species spreads rapidly by horizontal growth of the stolons (Hewitt et al. 2002). New plants can regenerate from small fragments (Creese et al. 2004). Growth is fastest during the summer months and slowest in winter (NSW DPI Undated A). It has been suggested that this species has an annual cycle, where no single part of the alga persists for more than a year, but the individual persists by means of indefinite vegetative growth (Meinesz et al. 1995).

Where Is It Found?

Which states and territories is it found?

NSW, QLD, SA

What areas within states and territories is it found?

The distribution of Aquarium Caulerpa (i.e., the invasive strain of Caulerpa taxifolia) is difficult to assess as it cannot be differentiated from the non-invasive strain without genetic testing. This can be problematic in tropical areas, where the non-invasive strain naturally occurs. Vigorously growing populations in colder waters, however, will almost certainly be the invasive strain. Outbreaks of what is clearly the invasive strain (based on molecular analyses and cold-tolerance) have occurred in New South Wales and South Australia. Aquarium Caulerpa is thought to be native to southern Queensland. Non-invasive Caulerpa taxifolia is widespread in tropical seas (Hewitt et al. 2002).

Where does it originate?

The origin and natural distribution of Aquarium Caulerpa is difficult to assess, as it is morphologically similar to a widespread, non-invasive strain. Positive identification can only be made by genetic markers. It is likely that the invasive strain originated in Queensland, from where it was distributed worldwide via the aquarium trade. Escapees were first noted in the Mediterranean near Monaco, and outbreaks have also occurred in California (Murphy & Schaffelke 2003).

National And State Weed Listings

Is it a Weed of National Significance (WONS)?

NO

Where is it a declared weed?

VIC, WA

Government weed strategies and lists – Weeds Australia

Is it on the National Alert List for Environmental Weeds?

NO

Government weed strategies and lists – Weeds Australia

Is it on the Agricultural Sleeper List?

NO

Government weed strategies and lists – Weeds Australia

Names And Taxonomy

Main scientific name

Caulerpa taxifolia

Other scientific names (synonyms)?

• Fucus taxifolius Vahl
• Caulerpa falcifolia Harv.& Bailey
• Caulerpa taxifolia var. falcifolia (Harv.&Bailey) W.R.Taylor
• Caulerpa mexicana Sond. ex Kütz. (misapplied by A. B. Cribb and J. W. Cribb, ‘Pl. life Great Barrier Reef and adjacent shores’, p. 17, fig. same page (1985); J. M. Huisman, in F. E. Wells (Ed.), ‘The marine flora and fauna of the Houtman Abrolhos Islands, Western Australia’, p. 181 (1997); P. Saenger, Proc. Roy. Soc. Queensland 90: 53 (1979); J. M. Huisman, ‘Mar. pl. Australia’, p. 253, fig. same page (2000); J. M. Huisman and M. A. Borowitzka, in F. E. Wells, D. I. Walker, D. S. Jones (Eds), ‘The marine flora and fauna of Dampier, Western Australia,’ vol. 2, p. 300 (2003)).
• Caulerpa selago (Turn.) C.Agardh (misapplied by C. Montagne, ‘Voy. Pôle Sud, Botanique, Plantes cellulaires’, p. 20 (1845); O. W. Sonder, Abh. Naturwiss. Naturwiss. Verein Hamburg 5 (2): 66 (1871)

Does it have other known common name(s)?

Caulerpa, Green Macroalga