Submitted to: Journal of Aquatic Plant Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/24/2005
Publication Date: 1/15/2005
Citation: Anderson, L.W., Tan, W., Woodfield, R., Mooney, R., Merkel, K. 2005. Use of sediment bioassays to verify efficacy of caulerpa taxifolia eradication treatments. Journal of Aquatic Plant Management. 43: 1-9.
Interpretive Summary: The invasive marine plant (alga) called Caulerpa, has spread since 1985 to nearly 30,000 acres in the Mediterranean where it now affects ecosystem in six countries. This species was found near San Diego, CA in 2000, and threatened thousands of miles of US marine tidal ecosystems that are vital to normal food- chain functions, commercial fisheries, and other economic enterprises. In response to this invasion, a rapid response eradication program was begun. To help verify the effectiveness of the eradication methods, bottom samples from the areas where Caulerpa was growing were placed in secure facilities, and under conditions that would permit Caulerpa to grow if eradication treatments failed. The results reported in this paper showed that the practice of covering Caulerpa with tarps and injecting chlorine killed the pest, and that the seeds of a native marine plant, eelgrass, that were present at the time of treatments survived. This information, coupled with underwater (SCUBA-diver) surveillance has provided verification and quality assurance of this $5 million, multiagency program. Successful completion of eradication is projected for 2006.
Technical Abstract: Infestations of the marine alga Caulerpa taxifolia were discovered in Agua Hedionda Lagoon, California in 2000. Rapid response actions included containment under pvc tarps coupled with injection of liquid sodium hypochlorite. To assess the efficacy of these treatments, replicated sediment cores were removed from representative treated sites and transferred to grow-out facilities. Similar cores from un-infested (control) sediments were removed, inoculated with viable explants of C. taxifolia and placed in grow-out facilities. Results from two sampling periods (1 year, 2 years posttreatment) showed that no viable C. taxifolia emerged in cores, and that inoculated 'control' sediments supported normal growth. Eelgrass (Zostera marina L.) seedlings emerged from native seed-banks in 'treated' cores, which also supported growth of some invertebrates (annelid worms and hydroids). This study provided essential verification of C. taxifolia eradication efforts, and demonstrates the feasibility of incorporating quality control/ quality assurance components in rapid response actions. Results of this study also suggest that seeds of eelgrass are viable for at least two years.