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Research Technical Report

Growth rates and disturbance response of the invasive kelp, Undaria pinnatifida in Monterey Harbor, CA

Rodriguez, G. (April 2008)

A Capstone Project at California State University, Monterey Bay


Biological invasions are attributed to about half of all endangered species declines worldwide. Undaria pinnatifida is an annual brown subtidal alga (Phaeophyceae, Laminariales) native to Japan, China, and Korea, where it is cultivated and sold as wakame. Undaria is the only invasive kelp in the world, and it was introduced to Monterey Harbor in 2001. The purpose of this study is to better understand the growth patterns of this invasive alga, Undaria pinnatifida, in the newly invaded range of the Monterey Bay, California. We characterized in situ sporophyte growth of Undaria in Monterey Harbor and tested how simulated grazing damage and incomplete removals (~80-90% of blade removed) affected sporophyte reproductive capacity (maximum sporophyll size). In Monterey Harbor, both average sporophyte growth rates and average maximum total lengths were greater than previously published data from Santa Barbara Harbor in southern California. When damaged, sporophytes grew slower, proportional to smaller plants and maximum sporophyll size (reproductive capacity) was also reduced. Further study is needed to determine the level of disturbance that is likely to result in reproductive failure.