International Caulerpa taxifolia Conference
January 31-February 1, 2002
, San Diego, California (USA)

Conference summary:

To meet the growing information needs of the Caulerpa eradication effort in the U.S. the "International Caulerpa taxifolia Conference" was hosted January 31 - February 1, 2002 in San Diego, CA by Ted Grosholz and Erin Williams of the Department of Environmental Science and Policy of the University of California, Davis. The workshop was made possible with financial support from California Sea Grant College Program, California Department of Fish and Game, the U.S. Fish and Wildlife Service, and the Division of Agriculture and Natural Resources of the University of California.

More than 100 participants with a range of backgrounds attended the conference including internationally known scientists, city planners, water board representatives, county and state regulators, local water sport operators, dive operators, port representatives, national representatives of the aquarium and pet industries, tribal representatives, landowners, and others took part in the two-day event. Key local and regional legislators also attended the conference including two that provided introductions for both days, San Diego City Councilmember Scott Peters and San Diego County Supervisor Pam Slater.

The talks presented at the conference included a range of studies examining various aspects of the biology of Caulerpa and related species. Alex Meinesz, University of Nice (France) outlined the course of the expanding European invasion and the effects it has had in the northwest Mediterranean region. Together with Thierry Thibault, University of Nice (France), they discussed new modeling methods for predicting the spread of Caulerpa in this region. Meinesz and his group are also investigating the use of a sea slug that would eat the Caulerpa as a biological control option.

Research presented by Paul Silva, University of California, Berkeley (USA), showed the range of variation in the shape of many species of Caulerpa including taxifolia and other closely related species. This work suggests that Caulerpa management that depends on distinguishing different species of Caulerpa, especially with immature plants, may be difficult if not impossible. Similar conclusions were reached by Jeanine Olsen, University of Groeningen (Netherlands), using molecular techniques, who found there may be two strains of invasive Caulerpa taxifolia in Australia and in the Mediterranean. Her work using newly developed molecular methods demonstrated that the Mediterranean strain that invaded California and the Mediterranean, originated from Brisbane, Australia, but that the Brisbane invasion may have originated from strains in the tropical seas of northern Australia.

Valerie Paul, University of Guam (USA), discussed some of the unique chemistry of the Caulerpa genus and provided a cautionary note about optimistic attempts to use herbivores as biological control agents, especially among temperate generalist herbivores. Cynthia Trowbridge, Oregon State University (USA), in her studies of the invasive alga Codium, a taxon ecologically similar to Caulerpa, also found little support for using marine slugs, or biological control agents that would effectively control Caulerpa. Ligia Collado-Vides, National University of Mexico, discussed plant chemistry as well as growth form and other features that may make Caulerpa a successful invader. Giulia Ceccherelli, University of Sassari (Italy), discussed mechanisms by which Caulerpa growth is influenced by native sea grasses and the potential impact of Caulerpa on native sea grass habitats.

Closer to home, Susan Williams, Bodega Marine Laboratory and the University of California, Davis (USA) outlined the need for more scientific review of the invasive species management process. In particular, she noted the absence of scientific peer review of the U.S. eradication process, the need for a review of the effectiveness of current methods, and the importance integrating scientific investigation with the ongoing eradication.

Steve Murray and Susan Frisch, California State Fullerton (USA), documented the widespread sales of Caulerpa species including C. taxifolia in aquarium stores throughout southern California. Lars Anderson, U.S. Department of Agriculture (USA), discussed sediment core samples that showed the tarp and chlorine techniques used in the U.S. invasion have resulted in elimination of Caulerpa in treated areas. Finally, members of the SCCAT team, Bruce Posthumus and Keith Merkel, updated the group on the California eradication. They have successfully reduced the aerial coverage of Caulerpa in the two invaded sites by over 90%. Given this success, eradication in the U.S., unlike Australia and the Mediterranean, looks promising, though it may be several years before this occurs. One of the ongoing challenges for the eradication efforts in California is the lack of sustained funds for eradication and survey efforts as well as the need for a long-term strategy for stopping the algae's possible spread along the California coast.

Several important outcomes resulted from the conference, perhaps the most important of which was the stunning diversity of eradication methods that have been tried in other invasions. The standard method used in the U.S. eradication is to cover a Caulerpa patch with a tarp and pump chlorine under the tarped area. However, Ante Zuljevic, Institute of Oceanography and Fisheries (Croatia) showed that successful local eradication could be attained with suction dredging, particularly in softer sediment habitats. Alan Millar, Royal Botanic Gardens, Sydney (Australia), discussed the Australian invasion and documented how local eradication could be achieved using rock salt in shallow areas on hard substrate where little of the plant is below the substrata. The Europeans also found that using tarps without chlorine is effective in killing Caulerpa. Other methods have also been attempted, including hand harvesting, covering with a sand layer, copper infused cloth, and other techniques. Although the U.S. method has been very effective, it is good news that there are alternatives that could be used in the future if Caulerpa is found in a more ecologically sensitive place, or in a more wave influenced habitat where tarps may not be feasible.

Overall, a number of new areas were revealed that are in need of additional information and should be priority for future discussions. One area that was awash with alternatives included methods and technologies for monitoring existing infestations and detecting new invasions. A number of developing technologies including side-scan sonar, multi-beam sonar, and laser imaging technology show promise for broad-scale surveys. All the participants agreed that many more questions were raised than were answered, but all viewed the conference as successful.

Thursday, January 31, 2002
Holiday Inn Bayside, 4875 North Harbor Drive, San Diego, CA 92106-2394

8:30 am Introduction by Dr. Ted Grosholz, University of California, Davis
Welcome by San Diego Councilmember Scott Peters

9:00 am Dr. Paul Silva, University of California, Berkeley

9:30 am Dr. Alex Meinesz, University of Nice-Sophia Antipolis, France

10:00 am Break

10:30 am Dr. Jeanine Olsen, University of Groningen, The Netherlands

11:00 am Dr. Giulia Ceccerelli, University of Sassari, Italy

11: 30 am Ante Zuljevic, Institute of Oceanography and Fisheries, Croatia

12:00 pm Lunch

1:00 pm Dr. Alan Millar, Royal Botanic Gardens Sydney, Australia

1:30 pm Dr. Ligia Collado-Vides, National University of Mexico

2:00 pm Dr. Valerie Paul, University of Guam Marine Laboratory

2:30 pm Dr. Cynthia Trowbridge, Oregon State University

3:00 pm Break

3:30 pm Dr. Steve Murray and Susan Frisch, California State University, Fullerton

4:00 pm Dr. Susan Williams, Bodega Marine Lab, University of California, Davis

4:30 pm Dr. Lars Anderson, USDA, Exotic and Invasive Weed Research
Summary of U.S. Invasion and Management

4:50 pm Dr. Alex Meinesz, Summary of Mediterranean Invasion and Management

5:05 pm Dr. Alan Millar, Summary of Australian Invasion and Management

5:15 pm Questions and Discussion of Research: All Speakers

6:00 pm Dinner Reception at the Berkeley Ferry Boat

Friday, February 1, 2002
California Room, Holiday Inn Bayside, San Diego

8:00 am Continental Breakfast

8:30 am Introduction by Dr. Ted Grosholz, University of California, Davis
Welcome by San Diego County Supervisor Pam Slater

8:45 am Management Successes and Failures in Mediterranean
Dr. Alex Meinesz and Dr. Thierry Thibaut, University of Nice-Sophia Antipolis, France

9:10 am Management Successes and Failures in Australia
Dr. Alan Millar, Royal Botanic Gardens Sydney, Australia

9:40 am Management Successes and Failures in the U.S.
Bruce Posthumus, San Diego Regional Water Quality Control Board

Keith Merkel, Merkel and Associates

10:00 am Break

10:30 am Discussion and Development of Management Options for Caulerpa Invasions in Southern California

12:00 pm Outreach and Education in the U.S., Europe and Australia
Dr. Ted Grosholz, Dr. Alex Meinesz, and Dr. Alan Millar

12:30 pm Lunch

1:30 pm Prioritizing Management Strategies for Caulerpa Management in U.S.
Facilitator, Leigh Johnson, California Sea Grant Extension Program
1. Prioritize options for eradication/control
2. Prioritize options for monitoring importers and retailers
3. Criteria for transition from eradication to long-term control
4. Future regulatory and political goals

3:00 pm Break

3:20 pm Prioritizing Caulerpa Research Needs in U.S.
Facilitator, Dr. Paul Olin, California Sea Grant Extension Program
1. Criteria and methods for evaluating success of treatment options
2. Methods for discriminating Caulerpa taxa
3. Measuring collateral impacts of eradication
4. Growth rates, mechanism of spread, invasibility in other habitats

4:15 pm Developing a Strategy for Caulerpa Education in the U.S.
Facilitator, Carl Bell, University of California, Cooperative Extension
1. Increase awareness, commitment, leadership in recreational public
2. Educate and involve aquarium industry regarding Caulerpa alternatives
3. Develop new management practices to minimize future introductions
4. Educate agencies, wardens, customs staff about regulations/findings

5:00 pm Conclusions and Wrap-up


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