Scientific name: Caulerpa taxolia

What Is It?

Caulerpa is native to the Caribbean Sea and the Indian Ocean. It is a bright green, marine alga popular as a saltwater aquarium specimen. Called “killer algae,” it is known as the algae that took over the Mediterranean Sea.

Is It Here Yet?

No, but California recently spent $7 million to eradicate two small infestations in its southern waters. Although scientists consider caulerpa a tropical species, it can survive many moths in cooler waters. Like many invasive species, it is highly adaptable.

Why Should I Care?

In the Mediterranean Sea, caulerpa has infested thousands of acres of seafloor. It created ecological and economic devastation by overgrowing and eliminating native sea grasses, reefs, and other native communities. It has harmed tourism and recreational diving, and had a costly impact on commercial fishing by altering the fishery and entangling fishing nets. Should caulerpa adapt to the cooler waters of Puget Sound, it could have devastating impacts to Washington.

How Can We Stop It?

Do not dump the contents of any aquarium into marine or freshwaters. Do not purchase, plant, or trade this species. Although the federal government lists caulerpa taxifolia on the federal noxious weed list, there are other caulerpa species for sale. Do not purchase caulerpa on the Internet. Please see more information here for aquarium owners or see our “Dont Let it Loose” campaign page.

What Are Its Characteristics?

  • Bright green
  • Long-running stem known as a stolon, which extends out from main patch at multiple locations
  • Rubbery texture that holds its shape out of water
  • Upright fronds of various shapes
  • Secured in ground with fine hairs known as rhizoids

How Do I Distinguish It Form Native Species?

Caulerpa may sometimes be confused with the following:

  • Codium sp. (Deadman’s fingers)
  • Bryopsis sp. (Sea fern)
  • Corallina sp.
  • Enteromorpha sp. (Hollow green weed)
  • Fucus sp. (Bladder wrack)
  • Ulva sp. (Sea lettuce)

Additional Photographs