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Open Access Publications from the University of California

Investigation of the Invasive Kelp, Undaria pinnatifida: Dispersal Mechanisms and Methods for Controlling Zoospores


This study applied laboratory experiments in order to study the ability of the invasive kelp Undaria pinnatifida sporophytes to produce zoospores under the stress of heavy defoliation and light deprivation in order to further understand potential vectors of spread, namely ballast water and detached fragments. The ability of microscopic Undaria pinnatifida zoospores to develop, after being subjected periods of light deprivation, was also investigated to examine the ability of zoospores to spread through ship ballast tanks. Treatments with 0.1% acetic acid in seawater and a mixture of 90% tap water and 10% seawater were analyzed for their efficiency at both preventing zoospore release from sporophylls and inhibiting zoospore development into the gametophyte stage. Results of the experiment indicated that defoliated Undaria pinnatifida sporophytes can continue to produce zoospores after 28 days of light deprivation and zoospores can germinate after being subjected to at least 14 days of light deprivation. Results also demonstrated sporophytes can continue to produce zoospores for at least 56 days after heavy defoliation by removal of lamina and holdfast leaving only the sporophyll. Both acetic acid and tap water treatments proved successful at preventing 100% of observed zoospores from germinating after a week of incubation. Both acetic acid and tap water treatments also significantly reduced the ability of 2 sporophyll tissue to release zoospores after incubation for two hours. Results of this study validate the assertion that Undaria pinnatifida propagules can be transferred through ballast water and demonstrates the ability of sporophyll tissue to survive a trip in ballast water as well. Acetic acid and tap water both demonstrated promising ability to inhibit zoospore germination and could prove to be an inexpensive, low environmental impact means of eradicating microscopic zoospores from marine equipment or habitats

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