Research Technical Report

An Integrated Response to a New Coastal Invasion: Monitoring and Managing Undaria pinnatifida in Monterey Bay

Lonhart, S. (March 2003)

Oral Presentation at the International Conference on Marine Bioinvasions, San Diego, CA

ABSTRACT

The Asian kelp Undaria pinnatifida, recognized as a marine threat because of its record of rapid spread and high abundance in invaded regions elsewhere, was first reported in 2001 from a site in the Monterey Bay region, California. Already widespread in other parts of the world, Undaria has recently appeared in various southern California harbors from Los Angeles to Santa Barbara. Because of its rapid population growth, high density, canopy-forming growth form and potential availability as a source of food and habitat for invertebrates, Undaria could have profound influences on the structure and function of our highly productive and speciesrich coastal reef ecosystems. The population reported from Monterey Harbor is the northern-most known occurrence of the alga along coastal California. Regional agencies and researchers are collaborating to study: 1) the spatial extent of the invasion, 2) habitat associations, 3) seasonal dynamics of growth and reproduction, and 4) the costs/benefits of different potential eradication methods. This effort is also being used to create a regional management structure and decision-making process for rapid response to future coastal invasions.

Because the distribution of Undaria in central California is unknown, we are surveying in situ the four harbors in the Monterey Bay region and various adjacent natural sites along the open coast. To determine the phenology of the alga in its new environment (which can vary regionally), we use stratified random sampling to encompass all habitat types within each study site and across all seasons. Although eradication efforts rarely succeed, we will experimentally evaluate different methods of removal within the harbor. Concurrent with measuring the response of Undaria to eradication efforts, we will monitor community composition in each of the treatments, employing multivariate analysis to assess community-wide impacts of the eradication methods and the presence/absence of Undaria in experimental plots.