Caulerpa taxifolia

The aquarium strain of Caulerpa taxifolia is an invasive pest species that has infested Sydney Harbour.

A native strain of Caulerpa taxifolia exists in many tropical and sub-tropical waters around the world, including northern Australia. The pest species is thought to have been selectively bred for use in aquariums and is hence known as "the aquarium strain". Its invasion into oceans probably originated from the discharge of aquarium water close to, or into, the ocean in the early 1980's, and has created problems throughout the world's waters since. It is an especially large problem in the Mediterranean Sea, where well over a thousand hectares are covered by a thick mat of Caulerpa taxifolia.

Looking like bright green feathers, Caulerpa taxifolia has fernlike fronds that extend upwards from a horizontally running stem. The fronds are commonly between 5-14cm high, however in the Mediterranean they have been measured at heights of up to 80cm.


Caulerpa taxifolia has the ability to cover surfaces ranging from rock to sand with a dense carpet of growth at depths anywhere up to 50 metres. It grows rapidly, greatly reduces local biodiversity and is particularly threatening to native seagrass beds. This is a concern since seagrass beds act as a habitat and feeding area for many marine species. Loss of this resource could mean a reduction in the abundance of many species in the area.

Caulerpa taxifolia spreads rapidly and easily as new plants grow from fragments that have been broken off. Experiments have shown that fragments as small as 1mm can grow into new plants. Such small fragments can easily be caught in anchor chains, fishing gear, diving gear, etc, and in certain conditions can even survive out of the water for up to 10 days. This means that separate colonies can be established large distances apart through means of human transport.

Harbourkeepers & CoastKeepers divers are monitoring this invasive weed so that measures can be taken to minimise its impact on our precious harbour environment.

To find out when you can get involved in any of these HarbourHeepers activities, visit our Calendar of Community Events page.

Below are some helpful links for further information on Caulerpa taxifolia:

• NSW Fisheries - great basic scientific information on Caulerpa taxifolia in NSW waters, including the preferred methods of control.
• Literature Review on the aquarium strain of Caulerpa taxifolia - Very detailed, comprehensive scientific information on the worldwide Caulerpa taxifolia problem.
• Underwater Research Group - information on studies on Caulerpa conducted by URG which formed the basis for this HarbourKeepers survey.
• US National Marine Fisheries Service - the background to the Californian infestation and their control methods.
• University of Technology Sydney news release - an easily read document that introduces some concerns for native Australian marine life regarding the Caulerpa taxifolia problem.
• Science News - an excellent article on the huge Mediterranean problem, including some possible paths of controlling the weed.
• Victoria Department of Primary Industries - an informative page that details some of the strategies for controlling the weed in Victorian waters.