Caulerpa Laws Difficult to Enforce Illegal Sales Continue

August 3, 2006

Contact: Christina S. Johnson, csjohnson@ucsd.edu, 858-822-5334

Although the invasive seaweed Caulerpa taxifolia recently was eradicated from Southern California, NOAA Sea Grant biologists worry that continued sales of the decorative aquarium plant make the region vulnerable to future invasions.

“None of us on the scientific side think we’ve seen the last of the Caulerpa invasion,” said Sea Grant biologist Steve Murray, dean of the college of Natural Sciences and Mathematics at California State University, Fullerton. “We will probably see another infestation.”

“Caulerpa species are widely available in shops and on eBay,” said Sea Grant biologist Susan Williams, director of Bodega Marine Lab at UC Davis. “We are going to see it again until we cut down on the sources of Caulerpa and educate the public about the dangers of invasives.”

Caulerpa meadow in the Mediterranean Sea. [Photo credit: University of Nice, France]

Caulerpa refers to a genus of mostly warm-water seaweeds, the most infamous of which is an aggressive Mediterranean strain, Caulerpa taxifolia, dubbed the “killer alga” by European media. This strain, bred and then cloned for the aquarium trade, has proven to be almost impossible to eradicate once it takes hold in the wild. For one, it grows rapidly. It also spreads rapidly. Even tiny fragments can sprout into whole plants.

In 2000, this same strain was found in North America for the first time – in Agua Hedionda Lagoon in northern San Diego County and Huntington Harbour in Orange County. Groups working under the auspices of the Southern California Caulerpa Action Team (SCCAT) spent nearly six years and $7 million to remove all traces of the noxious aquarium renegade. In July, SCCAT held a ceremony in San Diego, celebrating the Caulerpa eradication – the first time a group has successfully eradicated established populations.

Most scientists believe that Caulerpa was spread to Southern California by people who dumped the contents of home salt-water aquariums into local waterways – hence the emphasis on restricting the sale of Caulpera species for aquariums.

To prevent a repeat, the City of San Diego in 2001 banned the possession and sale of all Caulerpa species. The state passed a less stringent law, which bans nine Caulerpa species, including Caulerpa taxifolia, look-alikes from the Caribbean Sea and other species known to be invasive. It does not ban look-alikes from the Pacific and Indian oceans, explained Williams, who wrote the scientific justification for California Assembly Bill 1334 and testified before the California House Finance Committee on its necessity. California Sea Grant funded Williams’ Caulerpa taxifolia research.

CALIFORNIA FISH AND GAME CODE 2300. (a) No person shall sell, possess, import, transport, transfer, release alive in the state, or give away without consideration the salt water algae of the Caulerpa species: taxifolia, cupressoides, mexicana, sertulariodes, floridana, ashmeadii, racemosa, verticillata, and scapelliformis. (b) Notwithstanding subdivision (a), a person may possess, for bona fide scientific research, as determined by the department, upon authorization by the department, the salt water algae of the Caulerpa species: taxifolia, cupressoides, mexicana, sertulariodes, floridana, ashmeadii, racemosa, verticillata, and scapelliformis. (c) In addition to any other penalty provided by law, any person who violates this section is subject to a civil penalty of not less than five hundred dollars ($500) and not more than ten thousand dollars ($10,000) for each violation.

“Based on the available scientific information, I recommended we should ban all Caulerpa species unless there was good evidence an individual species is not invasive,” Williams said. The aquarium trade industry opposed this recommendation. Most home aquarists will not have the expertise to accurately distinguish legal or illegal products, but even more worrisome is that inspectors, importers and distributors may also lack this expertise.

Linda Walters of the University of Central Florida recently published a paper in the journal, Frontiers in Ecology and the Environment, documenting the dispersal of invasive seaweeds via Internet sales. She and colleagues purchased Caulerpa species from 30 Internet retailers and 60 Internet auction sites from 25 states and Great Britain. Only 10.6 percent of sellers provided the correct genus and species names with their shipments.

Walters and co-authors recommended that both eBay and the USDA “maximize regulation of Caulerpa.”

Part of USC's anti-Caulerpa public education brochure.

It is also unclear whether owners of retail aquarium shops understand or are aware of the laws.

In 2001, California Sea Grant funded Murray and Susan Frisch Zaleski, then a graduate student, to document the availability of Caulerpa species in aquarium stores in Southern California. This survey showed that about 58 percent of stores were selling Caulerpa species; 14 percent were selling C. taxifolia. The findings were used to back anti-Caulerpa legislation.

Zaleski, now the USC Sea Grant Coastal Resources Specialist, recently led a re-survey of stores that were selling Caulerpa species prior to the ban. This second survey shows that 63 percent of these stores are still selling Caulerpa species. The most common retail species were C. sertulariodes (25 percent of stores) and C. racemosa (21 percent). Both species are illegal under California law. Caulerpa taxifolia was still being sold at 8 percent of stores.

In San Diego, where there has been focused public education about Caulerpa and where the anti-Caulerpa law is more stringent, only one of the four stores that previously sold Caulerpa species is still selling them. “The take-home lesson is that the ban and outreach in San Diego made Caulerpa less available,” Zaleski said. “Outreach to a community can make a difference.”

Zaleski currently has support from U.S. Fish and Wildlife Service and USC Sea Grant to educate aquarium hobbyists, retailers and aquarium shipment inspectors about Caulerpa and other invasive seaweeds.

This effort includes a “Don't Release” campaign that lists safe ways to discard of aquarium species [http://www.usc.edu/org/seagrant/AquatNuisance.html]. One safe option is to freeze seaweeds for at least 24 hours before disposing of them in the trash. Another is to give unwanted aquarium organisms to a local aquarium store or to a responsible aquarium hobbyist.

Florida is suffering from its own Caulerpa infestations of C. verticillata and C. brachypus. Zaleski and Walters are collaborating on public education projects, including a plan to create an “alternative seaweeds key” – a photographic listing of non-invasive alternatives to Caulerpa species suitable for home aquariums.

They are also producing Caulerpa species keys that will help inspectors, retailers and others differentiate between legal and illegal species. They plan to hold training sessions for aquarium shipment inspectors as well.