Two Oregon Coast Aquarium divers returned to the Triangle, the appropriately named area of protected ocean waters between converging jetty lines at the mouth of the Umpqua River. We know the invasive marine invertebrate Didemnum vexillum to have been established since at least February, and we came in part to do a trial of one possible eradication method.
View the Triangle - 7.24.2010 in a larger map
Most eradication methods attempt to smother D. vex, depriving it of oxygen, often adding acetic acid (think vinegar) or sodium hypochlorite (bleach), toxic to the tunicate and hastening the process. If a substance with enough grip to encapsulate the colonies underwater could be developed, it may work to control younger colonies on substrate too irregular to wrap with plastic.
Dr. Gordon Anderson has worked on a possible solution to a different problem - a gel to prevent fatal box jelly stings to swimmers in Australian waters. The emulsion of vinegar, cellulosic material, and petroleum jelly seemed to have potential in our situation. Unfortunately this attempt failed on several scores. This particular gel did not adhere well to our target underwater. More seriously, the colonies have spread out and become more lobate, even growing out onto the blades of kelp. Summer has brought masses of filamentous algae to the subtidal rocks, making an effective seal around the tunicates seem improbable.
Those with a pharmacology or chemistry background can surely see other approaches to creating a compound with the requisite qualities, and the Oregon Department of Fish and Wildlife would value your contribution. Applied in a timely manner, it might well control an infestation.
The divers also made an initial deployment of temperature data loggers at depth. While colonies potentially reproduce all year assexually via fragmentation, the colonies develop sexual organs in response to rising temperatures and brood their larvae internally. Once they begin releasing larvae, they may continue to do so well into the season of cooler water temperatures. The data loggers will serve to track the conditions within the Triangle to identify the prime period of reproduction.
John Estabrook and Lorne Curran dove this day, and Dylan Curran provided boat support. Thanks to Larry Davisson for use of his kayak.