Rock vomit: An invasive, ugly sea squirt threatens U.S. waters

Credit: NOAA

It's a creature that gives “gross morphology” a new meaning, in that it resemble beef gravy mixed with chaw spit. It bears both male and female sex organs and will excrete acid on anything that tries to touch it. It goes by the charming name of “rock vomit,” and it's threatening to choke U.S. waters with its noxious brown ooze.

Chances are that kids who signed up for oceanography degrees never imagined they'd be poking instruments into what looks like the contents of a baby's diaper. But rock vomit is currently at the center of a study in Alaska, where it was found in the waters last June. Scientists from NOAA’s Auke Bay Laboratories are using a remotely operated submarine to hunt down the sea puke to understand how large of a stranglehold it's gotten on the local ecosystem.

Rock vomit, or Didemnum vexillum, is actually a species of sea squirt – small, potato-shaped invertebrates that cling tenaciously to hard surfaces like docks, ship hulls, other marine creatures and (obviously) rocks. It's an invasive species most likely hailing from Japan that now can be found worldwide, from New Zealand to northern Europe to New England.

Want a closer look at the vomit? Fine, here:

The problem with rock vomit is that it spreads so quickly that it can overrun the marine environment, suffocating bivalves and putting a disgusting barrier of goo between fish and their sea-floor prey. It has few if any natural predators (understandable) and prevents other organisms from growing on it with acidic toxins.

In Alaska, scientists are worried that the vomit will harm commercial fish and aquatic-plant colonies, a $500,000-a-year industry. The good news is that the crew from NOAA hasn't uncovered evidence of a wide infestation, although they're still prowling the waters with their submarine. Once the study is complete, they plan to work with AmeriCorps to devise strategies to control or eradicate this fouling organism.

The sooner the better – just looking at it makes me want to vomit.