Caulerpa taxifolia

An extremely invasive marine algae reported for the first time in the Western Hemisphere.

IDENTITY
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Name: Caulerpa taxifolia
Taxonomic Position:
Plantae*: Chlorophyta:
Common Names: "killer algae"

Significance:
This invasive marine algae has devastated thousands of hectares in the shallows of the Mediterranean Coast, and its expansion is steadily increasing. It was recently found in a coastal lagoon of San Diego, CA, signifying the first documentation of this seaweed in the new world.

Issues of Concern: Caulerpa taxifolia is a tropical seaweed that was bred as a popular aquarium plant. The variety infesting the Mediterranean differs from tropical populations in that it is larger, grows more vigorously, does not rely on sexual reproduction, and is resistant to low temperatures. This clone is able to spread through fragmentation, and is able to readily blanket native ecosystems in a carpet of "astroturf". Evidence suggests that the Mediterranean infestation results from a single escaped or released clone from a saltwater aquarium, which attests to the rapid and persistant growth exhibited by this seaweed.

It has been established that the California variety is identical to the Mediterranean strain, and therefore presents a serious threat to North American coastal areas.

Distribution:
Mediterranean Coast of Monaco, France and Spain; near Sydney, Australia; California, U.S.A.

Quarantines: Caulerpa taxifolia has been designated a U.S. Federal Noxious Weed and currently prohibited in the U.S., but continues to be found in the aquarium trade.

Detection Strategies
There is still an active aquarium trade in this seaweed. The current infestation in California is thought to result from release from an aquarium. Fragments may be transported on boats (propellers, rudders, motors, anchors, anchor lines), on fishing gear and nets, and on marine sporting equipment.

In the marine environment, a seasonal "die-back" has been observed in California, where algal mats tend to lie down and are more difficult to detect.

Comments:
The clone found in California should be considered the same as that infesting the Mediterranean, and therefore threatens the eelgrass beds and coastal resources in the area.

The San Diego infestations are restricted to 2 areas, the Agua Hedionda Lagoon (AHL) and Huntington Harbor (HH). Eradication efforts are underway at both locations. In October 2003, C. taxifolia was declared to be eradicated from AHL.

A new bill, AB 1334 (Chapter 3.5, Section 2300 of the F&G Code), has been introduced for comment in California. This bill would prohibit the sale, possession, and transport of C. taxifolia.

*Placed in Protista by some workers

OTHER INFORMATION:
References:
O. Jousson, J. Pawlowske, L. Zaninetti, A. Meinesz and C. Boudouresque (1998) Molecular Evidence for the Aquarium Origin of the Green Alga Caulerpa taxifolia Introduced to the Mediterranean Sea. Mar. Ecol. Prog. Ser., 172:275-280.

Useful Links:
Diving Information Website Alert
National Marine Fisheries Service Website
California Water Quality Control Board, Region 9 Website
Universite de Nice Website
San Diego Regional Water Control Board Factsheet (March 20, 2001)


Phytosanitary Alert System
Pest Alert www.pestalert.org
Prepared on: 10/20/2003