Two invasive species take root in Farm Pond in Oak Bluffs

Gonionemus vertens, also known as “the clinger," is growing in numbers and in geographic range. –Annette Govindarajan/Woods Hole Oceanographic Institution

Farm Pond in Oak Bluffs, home to Vanessa the sea serpent and her golden egg, is also home to two species of invasive fauna that appear to be flourishing — Gonionemus vertens, a diminutive jellyfish with a knee-buckling sting, and Halichondria panicea, a sponge that can do heavy damage to the already struggling eelgrass beds.

Gonionemus is also known as “the clinger,” because it spends its life clinging to eelgrass. It caught the public eye last summer after a “swarm” stung a 17-year-old girl in Waquoit Bay, Falmouth, sending her to the emergency room with respiratory failure and partial paralysis.

Oak Bluffs shellfish constable David Grunden said he first discovered a small number of clingers in Farm Pond and Sengekontacket Pond in 2007, but their numbers weren’t significant until last year, when they showed up in numbers in Farm Pond, connected by a culvert to Nantucket Sound.

Last week, sitting on the shores of Farm Pond aside a bucket full of clingers and mustard-colored sponges packed in Tupperware, Mr. Grunden, Mary Carman, research specialist at the Woods Hole Oceanographic Institution (WHOI), and shellfish department intern Kallen Sullivan, spoke to The Times about the rapid growth of Gonionemus and Halichondria panicea in the 33-acre pond.

Clingers on the march

Ms. Carman said that in the past year, Gonionemus has significantly increased in numbers and in geographic range.

“The population has gone up considerably,” she said. “They are spreading, there’s no doubt about that. We also found them in Sengekontacket this summer. We didn’t see them there last year.”

The stinging clinger also appears to be spreading its reach on Cape Cod. A July 29 report in the Mashpee Enterprise stated that Gonionemus has been showing up this summer in unprecedented numbers, and in new locations.

“We have never seen this many Gonionemus before,” Richard H. York Jr., acting director to the Mashpee Department of Natural Resources said. Mr. York said that several people had been stung, including a town employee who was reaching into the water from a dock. “Mr. York reported the assistant was fine after they applied a paste of Adolph’s meat tenderizer immediately after the sting, which contains papaya extract, and gave her Benadryl,” the article reported.

In the past year, Gonionemus has entered new territory north of the Cape, and as far south as the New Jersey shore, where its arrival has led to the postponements and cancellations of a number of water-based events.

“A man in New Jersey was stung and ended up in the hospital for two days on morphine,” Ms. Carman said. “I was told he punched holes in the wall in the ER because of the pain. It is curious we have the stinging form here and now it’s showing up in New Jersey. They might have spread from here to New Jersey from recreational boats skipping down the coast, or it might be a separate invasion. We don’t know.”

Packs a wallop

There are two forms of Gonionemus, one is toxic, the other is not.

“The non-toxic clingers were first documented in Eel Pond in Woods Hole in 1894,” Mr. Grunden said.

“They were also discovered in Connecticut and Muskeget Island, off of Nantucket in the late 1800s, and there were no reports of anyone being stung,” Ms. Carman said.

Gonionemus seemingly disappeared during an eelgrass blight in the 1930s. The first reported sting from a toxic clinger was on Cape Cod in 1990.

In the Pacific Ocean, the toxic clinger is found in waters around Japan and Russia. The non-toxic form is found in the waters of Washington, Oregon, and California.

“We think there was a separate invasion of the toxic form, which may have been transported in a ship’s ballast,” Ms. Carman said. “You could infer that the introduction of the stinging form was on the Cape, but you don’t want to point fingers. They can attach to oysters when they’re in the polyp stage, so it’s possible aquaculture is helping to spread them, but we don’t know that for sure either.”

Part of what makes the presence of clingers so vexing is that they are so small, between the size of a dime and a quarter, and they’re extremely well camouflaged, almost completely translucent except for a thin brown, orange, or purple border and two thin lines that cross in the center.

That also makes researching Gonionemus risky business.

Ms. Carman was stung on the lip while snorkeling in search of the diminutive jellyfish in Farm Pond. “It felt like five hypodermic needles being jammed into me at once,” she said.

Mr. Grunden reported the first evidence of toxic Gonionemus on the Vineyard when he was stung in Farm Pond and Sengekontacket Pond in 2007. “It packs a wallop,” he said.

In July 2010, Tay Evans from the Department of Fish and Game, and Holly Bayley, from the National Park Service, were stung in Sage Lot Pond, in Mashpee. What started as an eelgrass survey ended up in the Falmouth Hospital emergency room.

“We were snorkeling and a bunch of them got flushed into my wetsuit,” Ms. Evans told The Times. “At first it felt like a bunch of bee stings but it was the second phase that was so different. There was abdominal pain, really bad pain in my back, and I started having difficulty breathing.”

Ms. Evans said a colleague drove her and Ms. Bayley to the hospital, but became so concerned that he stopped at the Mashpee fire station so she and Ms. Bayley could be taken by ambulance.

“The doctors didn’t know what they were seeing, but a colleague of mine kept one of the jellyfish and identified it,” Ms. Evans said. “For several days after, I was feeling these strange, intense pains, like neurons firing throughout my body. I ended up having a fever as well. The doctors gave me Benadryl and painkillers and I just slept for a couple of days.”

As a species, jellyfish are a canary in a coal mine — their numbers can increase as water quality decreases. “Loss of biodiversity may be aiding them,” Ms. Carman said. “Jellyfish can handle poor water conditions, like the increased acidity and warming temperatures that come with climate change. The past few years there have been jellyfish blooms all over the world, not just here.”

“Lower oxygen levels push predators out,” Mr. Grunden said. “That can lead to the jellyfish becoming the apex predator, so the species that typically feed on jellyfish aren’t around.”

At this point, it’s not clear why such a small animal, that feeds on plankton, has such a powerful sting. It’s also not clear what predators, if any, can keep the toxic Gonionemus in check.

Ms. Carman and WHOI biologist Annette Frese Govindarajan wrote a paper on the “Possible Cryptic Invasion” of the toxic Gonionemus, that was published in the scientific journal “Biological Invasions” in December, 2015. The paper underscored the need to unlock some of these mysteries about Gonionemus, stating: “These new observations are cause for public health concern, particularly as warmer temperatures associated with climate change may promote G. vertens blooms and thus the likelihood of dangerous human-jellyfish interactions in a populated, tourism-dependent region.”

Unwelcome sponge

Halichondria Panicea can’t put a person in the hospital, but it has the potential to do much greater damage to Farm Pond than Gonionemus.

“This is the first year we’ve studied the sponge and its impact on eelgrass, and we’re very concerned about it,” Mr. Grunden said.

Mr. Grunden said he first noticed the sponge in 2011, but like Gonionemus, it’s had a recent growth spurt. “It’s been a minor player but it’s definitely growing. It really popped this summer,” he said. “The eelgrass is already stressed because of the high nitrogen levels in the pond. Plants need light for photosynthesis and [Halichondria] Panicea can block out sunlight. That’s a big reason we’re studying it.”

Ms. Carman said there are other concerns as well — the sponge grows where algae, a nutrient for snail grazers, would otherwise grow; and it can impede eelgrass reproduction by blocking the release of its seed.

This summer, Ms. Carman and Ms. Sullivan began the only known study that’s investigating interactions between spider crabs and Halichondria.

So far, it has yielded some good news. It appears spider crabs, already abundant in Vineyard waters, find the sponge very tasty and may help keep the sponge in check. Ms. Sullivan, who departed the Island last week to study marine biology at St. Andrews University in Scotland, put the two together in a controlled environment and filmed a spider crab quickly devouring the sponge off of blades of eelgrass.

Asset to town

Ms. Carman said that over her four years of research on Farm Pond, she’s developed an affinity for the place that Vanessa the Serpent calls home. “I very much appreciate the Oak Bluffs Community Preservation Committee (CPC) for the funding support they have provided to me to monitor this pond,” she said. “There’s been some very exciting discoveries that have come out of this work. Farm Pond is very special. It’s an asset to the town and to the Island, and I don’t think people pay much attention to it.”

Ms. Carman is in the fourth year of the five-year CPC grant. She was originally funded so she could study Farm Pond before and after the long awaited second culvert is opened.

“We better get an extension on that grant,” Mr. Grunden said shaking his head. Mr. Grunden began working on the culvert over a decade ago. Numerous studies have been done, significant grants have been won, and a mountain of red tape has been scaled. But, according to Mr. Grunden, the plan for the new culvert is now stalled at the Department of Transportation.

Correction – a previous version of this article had a reference to Ms. Sullivan as Ms. Cullen.