Killing Rock Vomit in Whiting Harbor, Alaska: A Thought Experiment

Guest blog post by Monaca Noble, Marine Invasions lab, Smithsonian Environmental Research Center

How do you control an invasive species? This is the question we are asking you to ponder through our thought experiment. For this experiment we have provided information about the invasive tunicate, the impacted area, and the results from a recent research project that tested various control methods and are asking you to use this information to generate ideas for control. Sure, we can come up with ideas on our own, but it is much more fun and interesting to hear what ideas others have. As an incentive, we will be taking the best ideas submitted by December 16th and posting them on our website in January.

In 2010 scientists discovered the invasive tunicate Rock Vomit (Didemnum vexillum) at an old aquaculture farm in Whiting Harbor, Sitka, Alaska. The area was promptly surveyed and the extent of the invasion mapped. The tunicate was found on the farm and a variety of substrates on the seafloor beneath. Rock Vomit is notorious for overgrowing large areas impacting fisheries, shellfish beds, sensitive marine environments and aquaculture equipment.

In an effort to protect and stop the spread of the tunicate in the harbor, the Alaska Department of Fish and Game, Smithsonian Environmental Research Center, U.S. Fish and Wildlife Service, University of Alaska Southeast, National Oceanic and Atmospheric Administration, and San Francisco State University’s Romberg Tiburon Center, began a collaborative effort to stop its spread.

Researchers prepare samples of Rock Vomit for use in immersion experiments that test possible methods of control. Photo by Kimberly Holzer (SERC)
Researchers prepare samples of Rock Vomit for use in immersion experiments that test possible methods of control. Photo by Kimberly Holzer (SERC)

The main role of researchers at the Smithsonian Environmental Research center was to test possible management options to rid the harbor of the tunicate and stop its spread. Experiments were completed using five different immersion treatments, freshwater, high salinity brine, hypoxia, acetic acid, and chlorine bleach to see which, if any, would be effective at killing the Rock Vomit in the harbor. These experiments were completed at the scale of the Ziploc bag and have not been tested at larger scales.

To see the results of these experiments and participate in our thought experiment, visit our website at http://www.serc.si.edu/labs/marine_invasions/feature_story/November_2013.aspx. We would very much like to hear your ideas on how to solve this complicated invasive species problem.

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