Didemnum vexillum is a type of sea squirt with the descriptive and rather disgusting moniker of rock vomit. It is an invasive species that spreads voraciously over rocks, sea shells and even ship hulls. Oddly, the recent discovery of the rock vomit in a harbor near Sitka, Alaska, marks the confirmation of its first appearance in that region.
Rock vomit gets its name from the fact that it feeds on the sea water’s tiny plankton and decaying plant material. It can be poisonous to marine life, particularly commercially important species of fish.
In the words of Linda Shaw, a biologist with the National Oceanic and Atmospheric Administration (NOAA):
“It’s a crazy organism that smothers other creatures while producing acidic toxins that in turn prevent anything from growing on it… Rock vomit creates a type of barrier between ground fish and their food and has been causing problems worldwide.”
The Alaskan harbor has been searched several times, but due to the extreme depths of the water, divers could not comb the entire area. Refusing to give up, a remotely-operated submersible from the NOAA was deployed which captured video tape of much of the affected area. Researchers are determined to learn as much as they can about this destructive organism, as its presence costs the Alaskan aquaculture industry at least $500,000 annually.
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