- Caulerpa taxifolia is an invasive marine alga that is often referred to as "Killer Algae".
- Fronds are fern-like, bright green, pinnate, and from 2-26 in. (5-65 cm) long that extend upward from horizontal stolons. The stolons can grow to 10 ft. (3 m) long and attach to underwater surfaces such as rocks, mud, or sand via root-like rhizoids.
- Does not flower.
- There is no sexual reproduction; propagation is purely vegetative. 0.5 in. (1.2 cm) long stem and stolon fragments can grow into new algae. These fragments are easily transported by boating and fishing activities.
- Ecological Threat
- The non-invasive form of Caulerpa taxifolia is native to the Caribbean, Indo-Pacific and the Red Sea. A clone of the species was cultured for display at the Stuttgart Aquarium in Germany and provided to aquariums in France and Monaco. It either escaped from or was released from an aquarium into the Mediterranean Sea in 1984 where it spread rapidly, densely blanketing thousands of acres of underwater surfaces. Populations of the invasive Mediterranean aquarium strain were discovered in 2000 in California and threaten native kelp and eelgrass meadows. The invasive clone is genetically distinct from the native (DNA tests are necessary to distinguish them) and it tolerates cooler water, grows more rapidly, and grows at greater depth than the native species. Once established, this alga becomes the dominant species, altering native algal and marine animal communities. Infestations negatively affect tourism, commercial fishing, and recreational activities. The invasive clone was designated in 1999 as a prohibited species under the Federal Noxious Weed Act. Its current distribution includes Croatia, France, Italy, Monaco, Spain (Mediterranean Sea, Adriatic Sea), Australia and the United States.
Makowka, J. 2000. Monterey Bay National Marine Sanctuary Fact Sheet: Caulerpa taxifolia. Report to the Monterey Bay National Marine Sanctuary 
Global Invasive Species Database. 2011. Invasive Species Specialist Group (ISSG) of the IUCN Species Survival Commission 
National Park Service, U.S. Department of the Interior, Natural Resource Stewardship and Science 
University of Florida Center for Aquatic and invasive Plants 
USDA National Invasive Species Information Center 
NSW Department of Primary Industries 
University of Hawaii at Manoa 
USDA NRCS PLANTS 
Images from Bugwood.org