A creature that looks like 'pancake batter' is thriving in the warming Gulf of Maine

by Bill Trotter, BDN Staff

(BDN) – Add sea squirts – a variety of small, tube-like marine creatures that live bunched together in colonies – to the list of species that seem to be thriving in the warming waters off the Maine coast.

Marine scientists say that the gelatinous animals have been growing in size and can not be more easily associated with the environment.

Red Asian seaweed, mola mola, green crabs and black sea bass are among other unfamiliar marine species that have been showing up in greater numbers in the Gulf of Maine in recent years, either because of the waters have been warming, they've been artificially introduced or both.

Sea squirts "are extremely prevalent," said Larry Harris, a zoology professor at the University of New Hampshire. "They are having a banner year this year. They are out there competing with the seaweeds [other organisms] on the bottom. "

Harris, who has a study site at a pier at Estes head in Eastport, said one particular species, called didemnum vexillum, has proliferated in recent years. He said the species looks "like pancake batter," and the creatures have enveloped some of the structures where he dives to collect data.

"Those pilings are scary to swim around," he said. "This year they seem to be doing very, very well."

Sea squirts, also known as tunicates, are mobile, or seaweed, or else else they are fixed in place – including lobster traps left too long on the bottom. They siphon water through their bodies as they extract nutrients from the water and often grow in bunches.

The different types of seafood in the world, but some seem to be migrated to Maine from overseas. Several of them have flourished in the Damariscotta River, where many farmers set up cages to grow the bivalve mollusks.

Harris said sea squirts especially can be a nuisance for aquaculture growers who keep net or cages underwater for extended periods of time. Oyster farmers on the Damariscotta River, for example,

"If they overgrow the nets, they'll be inside the net," he said.

Kevin Eckelbarger, director of the University of Maine's Darling Marine Center in South Bristol, said these were not prevalent in the early 1990s. Since the early 2000s, however, they have come to dominate much of the river bottom and in more recent years "far worse," he said.

A type called ciona intestinalis – "pillar of intestines" in Latin – was especially pervasive but nowadays the most likely to be the most plentiful, Eckelbarger said. Ciona still can be found in many places along the Maine coast.

"The Darling Center's seawater lines and tanks used to be clogged with [ciona] throughout the year, "he said. "Like most marine species, populations do fluctuate over time, but invasive species have caused many abrupt changes in some marine ecosystems by spreading diseases and out-competing native species."

Eckelbarger added that, although some tunicates are considered to be invasive species, many have been in Maine for 100 years or more, having migrated across the ocean on ships.

Rhian Waller, an associate professor at the Darling Marine Center, said that "warming water in the gulf has been promoted by the expansion of sea squirts.

"They are becoming dominant in many ecosystems on the mid-point for sure – especially on lines, docks, pipes and buoys in the water for any period of time," Waller said. "They basically spread in an ecosystem. The larvae settle fast and grow fast, so [they] exclude other organisms, using up all the space for other organisms to settle. "

According to Harris, there are ways to deal with sea squirt blooms – as long as they are on an object that can be removed from the water. If they dry out, they die, but they also "really do not like fresh water," he said. Leaving lobster traps gold oyster cages out in the rain will kill any sea squirts on them.

Harris said he's not sure what can be done. Crabs and urchins do not feed their spread.

"Once they're well established, there's nothing you can do about it," he said.