Every year millions of people visit Southeast Alaska by cruise ship, but in recent years a surprising hitchhiker has been sailing through the frigid waters, not in a stateroom, but stuck to the bottoms of the massive ships, hiding from plain sight.
According to a collaborative team of researchers and citizen scientists based in the small coastal town of Ketchikan, invertebrate filter feeders known as bryozoans, or “moss animals”, have been turning up in Alaskan waters in recent years, which normally wouldn’t be much of a shock.
What’s different now is that these coral-like organisms are sticking around because the temperature is becoming just right for them. They glue themselves to hard surfaces in colonies to form large masses as they filter food from the water. They are typically found in warmer seas around the world. Researchers say Alaska’s warmer waters are now allowing them to stick around, making the remote ocean their home.
Left: A crab in Ketchikan covered in the invasive tunicate Botrylloides violaceus. Right: A fouling panel used to monitor for invasive species. Linda McCann/SERC
Smithsonian scientists teamed up with researchers from Temple University and the University of Alaska Fairbanks to hang hard plastic squares from local docks in order to track the tiny creatures. For several years, citizen scientists checked on the squares to identify and log what sort of species were growing on them.
“It’s a really obvious bryozoan species,” said lead author Laura Jurgens in a statement. “It’s the only purple thing in a forest of brown. So when you see it, you kind of gasp.”
Along with the branching bryozoan Bugula neritina, the team also recorded evidence of "leathery" invertebrates known as tunicates making their way northward – both organisms appear to be spreading throughout the region in greater numbers every year.
“It’s really important to know when new non-native species show up. They may be tiny invertebrates, but they can create big problems,” explained Jurgens, whose work was published in BioInvasions Records. “Early detection means you have a better chance of controlling them before the populations get established. In other places, like California, Oregon, and Washington, these organisms have displaced local marine animals or had economic impacts by fouling boats, fishing or aquaculture gear.”
Located just 185 kilometers (115 miles) north of British Columbia, Ketchikan is one of Alaska’s southernmost port cities and is a gateway to the state’s more remote waters as ships head north. Tracking invasive species here is a challenge, but could serve as an effective way to detect hitchhikers before they become a bigger issue.
