Caulerpa taxifolia

Stop the spread of invasive seaweed: Putting the cap on Caulerpa.

Why is Caulerpa a problem?

Caulerpa taxifolia is an invasive marine seaweed that has been found in coastal waters of NSW, including Lake Conjola, Burrill Lake, Sydney Harbour, Narrawallee Inlet, Port Hacking, Botany Bay, Pittwater and Lake Macquarie. It is a threat to the environment because it overruns native seagrasses, can dramatically alter marine ecosystems and is difficult to eradicate. Caulerpa threatens coastal ecosystems in NSW and may alter marine habitats and biodiversity.

Caulerpa is introduced from small fragments accidentally transported by boat and other water users. Such fragments can survive for days in damp conditions amongst anchor rope, fishing gear or diving equipment.

How to recognise Caulerpa taxifolia?

Caulerpa taxifolia is a bright green seaweed with 'palm-like' fronds that can be 5–65 cm in length. It typically covers the seabed in dense growth, and will spread fast growing horizontal 'runners' into adjacent areas.

photo of Caulerpa taxifolia next to a diagram labelling the runners as creeping stolon with rhizoid stems anchoring, the fronds have pinnules
Caulerpa taxifolia is a bright green seaweed with 'palm-like' fronds that can be 5–65 cm in length.

What can you do to help control the spread of this marine pest?

  • If possible, avoid boating in shallow weedy areas, and particularly near Caulerpa taxifolia outbreaks. Propellers can cut the plant into small fragments that can drift away and grow into new plants
  • Obey any vessel exclusion zones or fishing closures in your area, and if in doubt seek advice from your local Roads and Maritime Services or Department of Primary Industries (DPI) Office
  • Inspect all equipment, including:
    • Anchors, ropes and chains for pieces of Caulerpa before leaving an area
    • Fishing equipment such as fishing lines, nets and traps before and after use
    • Diving equipment such as wetsuits, bags and other gear before and after use
    • Trailers, propellers and engine intakes when retrieving your vessel from the water
  • Use dedicated 'wash-down' facilities where available, ensuring that your vessel is thoroughly free of all matter before leaving the area
  • Collect any fragments of Caulerpa that you may have accidentally picked up. Seal the pieces in a plastic bag and dispose of them in a bin where they cannot re-enter the waterway
  • Contact your local Roads and Maritime or DPI office if you think you have found Caulerpa taxifolia in a new area.

Are there ways of removing Caulerpa from NSW waterways?

DPI is currently trialling a number of methods to remove localised infestations, and covering the plants with large amounts of salt has shown initial promise. Removal by hand-picking or mechanical means is rarely effective as it is difficult to get all the plant material or avoid releasing fragments.

Where can I get further information or report possible sightings?

Further information can be obtained through the DPI fisheries website. If you suspect a new infestation of Caulerpa taxifolia, contact the NSW Dept of Primary Industries (DPI) Aquatic Biosecurity Unit on (02) 4982 1232 or report it on the 24-hour Pests Reporting Line (02) 4916 3877 or email aquatic.pests@dpi.nsw.gov.au. Alternatively, contact your local NSW DPI Fisheries office or Roads and Maritime operations centre.

Frequently asked questions

  • It is a marine seaweed, known scientifically as Caulerpa taxifolia.
  • It is bright green seaweed with 'palm-like' fronds that can be 5-65 cm in length.
  • In several NSW estuaries including Lake Conjola, Burril Lake, Narrawallee Inlet, Port Hacking, Botany Bay, Pittwater and Lake Macquarie.
  • It overruns native seagrasses, can dramatically alter marine communities and is difficult to eradicate. In the long term, Caulerpa is a serious threat to the State's coastal biodiversity and may ultimately impact on recreational and commercial fisheries.
  • Queensland and Lord Howe Island.
  • Probably by being dumped from home aquariums.
  • No. The Caulerpa taxifolia causing problems in NSW is a cold-adapted strain, apparently able to survive temperatures as low as 10 degrees for lengthy periods.
  • Genetic studies have linked it to a cold-resistant strain developed by public aquariums in Europe.
  • Yes. It has invaded the Mediterranean Sea, infesting thousands of hectares, and has also been reported in California.
  • No, it is illegal to keep Caulerpa taxifolia in your home aquarium without a special permit from DPI.
  • Seek advice from a specialist marine aquarium dealer. Recent advances in aquarium lighting and water management now allow the cultivation of several other commonly available plant varieties.
  • Place any unwanted material, including rocks, gravel coral etc. that may have pieces of Caulerpa attached, in the freezer for 24 hours. Secure the material in a plastic bag and place the lot in a garbage bin. Discard water from an aquarium must not be disposed of anywhere it could wash into waterways, such as down a street drain or gutter.
  • Avoid shallow weedy areas; obey any local vessel exclusion zones or fishing closures; inspect all ropes, anchors, fishing gear etc before and after use; and check your vessel carefully after removal from the water.
  • If you suspect it’s from a new infestation, contact your local Roads and Maritime or DPI office for advice; otherwise seal it in a plastic bag and dispose of it in a bin where it cannot re-enter the waterway.
  • No; it's better not to disturb any Caulerpa that you find. Take a careful note of its position and advise DPI.
  • Roads and Maritime, DPI and local councils are working together to educate waterway users about how to avoid spreading Caulerpa. Exclusion zones, fishing restrictions and warning signs have been placed in appropriate areas. Specific vessel wash-down facilities have been provided around badly infested estuaries to help prevent the transfer of Caulerpa to new areas.
  • DPI is currently trialling a number of methods to remove localised infestations, and covering the plants with large amounts of salt has shown initial promise. Removal by hand-picking or mechanical means is rarely effective as it is difficult to get all the plant material or avoid releasing fragments.
  • On our website (see page on seagrass or from DPI. You can also ring 136 186.
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