Caulerpa taxifolia, a green seaweed, has invaded southern California, south-eastern Australia, and the Mediterranean Sea. In 2004, the alga covered over 200 kilometers of coastline in the Mediterranean. Dubbed the "killer alga" because of its major ecosystem and economic impacts to tourism and fisheries, Mediterranean populations rapidly became too widespread to eradicate. In California and southern Australia, millions of dollars are being spent to eradicate this weed and monitor for new outbreaks.
All three invasions are believed to be the result of releases of Caulerpa taxifolia from salt-water aquaria. If the unwanted C. taxifolia had been disposed of properly, these invasions would have been prevented!
Typical of invasive species, Caulerpa taxifolia grows quickly, can tolerate a wide range of conditions, and has effective methods of dispersing to new areas. These factors allow it to outcompete native plants and animals. In invaded sites, a lack of natural predators and diseases make it difficult to halt its spread. This map displays the locations of native and invasive populations of Caulerpa taxifolia (yellow squares = native range, orange circles = invasive populations of Caulerpa taxifolia).