Ian Davidson, from the Smithsonian Environmental Research Center, explains how the canvas enclosure will kill D.vex. The eradication testing is being led by ADF&G biologist Tammy Davis. Tim Sundlov is coordinating the participation of the Bureau of Land Management, which controls the intertidal areas. Other members of the Smithsonian team diving in Sitka are Michelle Marraffini and Greg Ruiz. (KCAW photo/Robert Woolsey)
A multi-agency effort is underway in Sitka to eradicate an invasive sea organism before it can spread to other parts of the Alaskan coast.
A team of scientists from the Smithsonian Institution is testing several methods of killing an invasive sea squirt called D.vex, before launching a full-scale assault later this summer.
Two years ago D.vex was a threat. Now, it’s a target.
Ian Davidson, originally from Ireland, works for the Smithsonian Environmental Research Center. He’s unfolding a heavy canvas dome on the floor of the Sitka Sound Science Center, while about 20 interested Sitkans look on.
It’s about 6 or 7 feet wide, and it will be used to poison, suffocate, or otherwise kill Didemdum vexillum.
I can’t help but think that we’ve seen this idea before.
1980s TV commercial – Black Flag Roach Motel. Roaches check in, but they don’t check out!
Davidson has designed an underwater D.vex motel.
“This enclosure has a vent pipe on the outside. And then we’ve got a heavy chain inside that gets velcroed right here. And we’ve got sandbags around the rim of it as well. So the idea is to create an enclosure, well-sealed, that anything we put in there, the concentration will be retained for four hours.”
And what Davidson and the other members of the Smithsonian team plan to put under the dome are large amounts of salt, lime dust, or chlorine. All three have proven deadly to D.vex in the lab. This is the first field test.
Right now D.vex is confined to a relatively small area in Sitka’s Whiting Harbor, just off the airport runway, where there used to be an oyster farm. The next closest invasion is over one-thousand kilometers away in Canada.
Davidson says this is an opportunity.
“The occurrence in Sitka represents a really big jump in its distribution on the Pacific Coast of North America. It’s what makes it an interesting candidate for assessing feasibility for eradication. It got up here at one point, possibly through aquaculture activity, the most likely scenario, but it’s not known exactly what it was. But it’s not inevitable that it would come back, if we were able to get rid of it.”
D.vex looks like bad carpeting. It’s nickname is “sea vomit.” This image is from Whiting Harbor. (ADF&G photo)
Other than our conspicuous desire to kill it, D.vex has nothing in common with the cockroach. It’s a small tunicate, or sea squirt, that grows in colonies which cover the ocean floor like bad carpet from the 1970s. D.vex is native to Japan, where it’s controlled by biological mechanisms which aren’t fully understood. It started turning up elsewhere around the globe in the 1990s — the Mediterranean and New Zealand — possibly transported in the bilge water of ships.
On the Eastern Seaboard of the United States, D.vex has blanketed many square kilometers of the famous Georges Banks, once a rich area for scallops and other seafood.
The field test in Sitka is being conducted from the Alaska Department of Fish & Game’s research vessel Kestrel. This is the first of four trips planned by the Smithsonian and ADF&G to Whiting Harbor. Davidson says it will take about 3 weeks to see if D.vex dies under each of the three proposed treatments.
Once the team has a so-called “proof of concept,” they’ll attempt a bay-wide eradication.
And then, hopefully, it will It should be goodbye D.vex.
TV commercial – Don’t worry, we’re sending them to a motel. Motel? Right, the Black Flag Roach Motel.
