Scientist warns that increased shipping could turn Casco Bay into ‘bioinvasion hotspot’

A Maine scientist is raising the alarm that Casco Bay could become a “bioinvasion hotspot” after finding three new invasive species in three years.

Thomas Trott, a marine ecologist who lives in Biddeford, in a recent study tied their arrival to an increase in international shipping. And while the three species in question don’t spell ecological disaster, Trott believes they’re a harbinger of damage that could befall the bay if more ships come to Portland and there aren’t better safeguards in place.

One of the so-called “invaders,” called the ribbed bryozoan, forms button-sized colonies on blades of eelgrass. Another, S. prolifica, encrusts mussel shells and barnacles. The third is a type of beach flea.

Trott, who teaches at Suffolk University, traced all three back to the North Sea, between Great Britain and the rest of Europe (where the organisms, originally from Japan, are also invasive). He looked at international shipping routes and found that the Icelandic shipping company Eimskip, which visits Portland once per week, has ports in the North Sea. The ribbed bryozoan has also been spotted in Nova Scotia, in the Gulf of St. Lawrence, Newfoundland, Norway, Sweden and the U.K., all locations where Eimskip has ports.

“This spike (in invasive species) matched a rise in commercial shipping from the Northeast Atlantic to Portland, Maine, suggesting this seaport is shifting towards becoming a bioinvasion hotspot,” Trott wrote in a paper published this summer in the Journal of the Marine Biological Association of the United Kingdom.

‘ECOLOGICAL ROULETTE’

Of the three, the ribbed bryozoan that colonizes on eelgrass blades is the only one that could pose a threat. The discovery in Casco Bay is so new that it’s not yet clear what the long-term impacts could be, but Trott isn’t optimistic.

Eelgrass is a critical part of the marine ecosystem – it provides habitat and food for species all along the food chain, including juvenile lobsters. Its underwater meadows help keep the bay healthy by absorbing nutrients, stabilizing the ocean floor and reducing erosion. The plant is also valued for capturing carbon, which is important for slowing global warming.

“When those plants get covered by organisms, it reduces the ability of the plant to photosynthesize, and so it produces less sugar as a result of that,” he said. “For anything that’s feeding on eelgrass … it won’t have the same value as something that isn’t covered with stuff growing on it.”

Casco Bay’s eelgrass meadows are already vulnerable. The impact of warming waters, algae blooms and invasive green crabs cleaved their numbers by more than 50% between 2018 and 2022.

Trott wasn’t aware of ways the other two species could cause harm. In other areas where they’ve lived for a longer time, like the North Sea, there haven’t been any noticeable changes. But in his paper, Trott warned against dismissing the organisms.

“Indifference risks playing ecological roulette in a time of unprecedented unpredictability,” he wrote. “The detection of three invasives in the course of three years in Casco Bay, each of them new to the Northwest Atlantic, gives a strong signal of more introductions to come.”

Trott emphasized that the introduction of the three species is a result of increased traffic on the ocean, rather than a changing climate. However, climate change can still have untold impacts on the invasive species.

Just look at green crabs, which Jeremy Miller, a researcher at the Wells National Estuarine Research Reserve, said are the invasive species poster child. Green crabs were brought over as stowaways on ships over 100 years ago, but they’ve only started to wreak havoc in the last 15 or so years, decimating the state’s softshell clam fishery.

“Those really cold, hard winters that we used to get in the Gulf of Maine would freeze the marshes through and kill off 70-80% of these invasive species,” Miller said. “(But) now their numbers are through the roof because the Gulf of Maine isn’t as cold as it used to be.”

It’s hard to know how an invasive species will react in a new environment, and it’s even harder to predict when that environment is also changing.

“It’s just a matter of time until one of the species is another green crab or another something that’s just going to hammer one of our keystone species like lobster,” Miller said.

MORE SHIPPING, MORE STOWAWAYS

Shipping is responsible for 60% to 90% of marine “bio-invasions,” or introductions of invasive species.

In some cases, the organisms are transported through ballast water, which is water a ship takes on to stabilize at sea, then discharges closer to its destination to take on cargo. In others, they cling to the hull of the ship and accumulate in a process known as biofouling.

Federal laws and an international agreement have been passed to regulate ballast water, but biofouling remains largely unaddressed. There are new technologies being used to curb the buildup of these creatures on boats and some countries like Australia and New Zealand have stringent regulations, but they’ve not been universally adopted.

Researchers at McGill University in Montreal estimate that the growing international shipping network could yield a three- to 20-fold increase in global marine invasion risk by 2050. The 2019 study suggests that maritime trade will outweigh climate change as a driver of invasion.

Gylfi Sigfússon, president and CEO of Eimskip USA, said in an email that all of the company’s ships that call on Portland are equipped with ballast water treatment systems that clean the water to meet strict international standards to minimize the risk. He did not answer questions about biofouling or whether it’s something the company has considered.

The new research comes amid rapid growth for the city’s International Marine Terminal and Eimskip. Last year was record-breaking for the terminal, with roughly 44,000 20-foot-equivalent shipping containers crossing the dock.

Over the last decade, Eimskip has worked to grow trade by steadily increasing the number and size of vessels that operate on its Transatlantic Green Line Service.

Officials said last year marked a return to normal, following rapid growth from a pandemic-driven shipping boom. This year has so far been less auspicious, with a 23% year-to-date decline, according to data from the Maine Port Authority. Eimskip attributed the decrease to industry-wide challenges.

Chelsea Pettengill, the port authority’s interim executive director, acknowledged the decline but said she expects that the opening of a new, massive cold-storage facility early next year will be a boon for the region.

Eimskip’s transatlantic route has been good for Maine in many ways – it’s helped the state avoid problems like shipping delays and major supply chain disruptions that have plagued areas with larger ports, for instance.

And transporting goods around the world on boats is still more environmentally friendly than other options, like planes that emit over 55 times more carbon dioxide per ton of cargo every kilometer they travel, according to the Climate Action Accelerator.

Trott’s not suggesting Maine needs to cut back on shipping. There’s a delicate balance between the benefit of revenue generated from shipping against the potential revenue loss from bringing something bad to the port.

“But it’s still a chance, (while) the income from shipping is not a chance,” he said. “It’s actually happening.”

‘THE WRITING ON THE WALL’

Miller, at the Wells Reserve, leads the Marine Invader Monitoring and Information Collaborative in Maine. Also called MIMIC, the collaborative is a network of trained volunteers, scientists, and state and federal workers who monitor marine invasive species along the Gulf of Maine. Volunteers monitor sites in Rhode Island, Massachusetts, New Hampshire and Maine. The Wells Reserve, which is partly funded by the National Oceanic and Atmospheric Association, coordinates Maine’s MIMIC activities.

Miller has been monitoring invasive species in Casco Bay for 15 years and has had a front-row seat as the number and range of invasive species has increased.

On an early October afternoon, the last of MIMIC’s monthly checks of the year, Miller lay on his stomach, his head dangling over the side of a floating dock in South Portland. He reached into the water and plucked out a club tunicate, a small, bulbous organism also known as a “sea squirt” for the jet of water it shoots out when squeezed.

Tunicates are the most commonly observed invasive species in Casco Bay, he said, pointing to another variety on top of the sea squirt called colonial tunicates – “an invasive covered with an invasive.”

Colonial tunicates are fouling organisms, so they grow on whatever they can. They’re prolific, smothering and outcompeting native species. And they’re hard to get rid of. When chopped up, say by a pressure washer, each piece can form a new colony.

Miller hauled a plastic cage off the side of the dock, covered in all manner of vegetation and organisms including tunicates and Japanese skeleton shrimp. The cage was equipped with small plates of different materials to test what surfaces the organisms like best. He estimated the cage weighed about 45 pounds – 43 of which were invasive species.

“The amount of biomass that they’re putting onto things is pretty extreme,” he said.

When he started in 2008, a cage like that would have very little on it by October. But the warming waters made the problem “explode” and now it’s not uncommon to find species as late as December.

“Ten years ago, people really weren’t that interested in that kind of stuff, but as scientists, we saw the writing on the wall,” Miller said.

As the problem has intensified, with invasive species now creating economic challenges for aquaculture operations and wild fisheries, people have started to pay more attention.

“This is becoming a huge problem in Maine because this has started to hit people’s back pockets,” Miller said. “People don’t start caring until we start talking about lobster or aquaculture, people’s money, (but) there is very much an intrinsic value … because we want to understand how our natural communities are changing.”

‘WE NEED MORE CANARIES’ 

Trott and Miller bemoaned the lack of state and regional funding for invasive species management.

The MIMIC program gets some funding from the Casco Bay Estuary Partnership, a federally funded agency that helps to fund research in and around the bay. The director has been giving the Wells Reserve $5,000 each year for MIMIC, which has allowed Miller to expand the monitoring program up the coast.

But beyond that, much of the research funding is scraped together through grants or is self-funded.

The Maine Department of Inland Fisheries and Wildlife has a comparatively robust invasive and non-native species monitoring program for inland bodies of water. The Maine Department of Environmental Protection and the Department of Agriculture, Conservation and Forestry monitor for terrestrial and aquatic plant species.

The Department of Marine Resources does not have a person dedicated to monitoring or controlling invasive species in the ocean. The department instead monitors invasives by participating in and conducting an urchin dive survey, the Maine/New Hampshire Trawl Survey and the scallop survey, according to a spokesperson.

Dakota Stankowski, aquatic invasive species coordinator for IFW, focuses her efforts on education, stressing the importance of the “clean, drain, dry” protocol for boaters when taking their vessels out of the water and before putting them back in. Like in the ocean, boating is one of the major vectors for invasive aquatic organisms in the state’s inland bodies of water.

Zebra mussels, for example, are microscopic in their larval stage, so even a small puddle left in a boat could be enough to bring a few to a new lake or river. Once a species is in the water, it is significantly harder – sometimes impossible – to remove.

But the in ocean, container ships like Eimskip’s stay in the water, so something like “clean, drain, dry” doesn’t apply, Stankowski said.

Meanwhile, Trott noted, that Canada has extensive tracking and ocean monitoring programs with departments and funding dedicated to the issue. Canada still has work to do to improve regulations, but the difference, he said, is like night and day. “I’ve never been able to wrap my head around it,” Trott said.

The MIMIC survey and the Rapid Assessment Survey – another invasive species monitoring program by the Massachusetts Office of Coastal Zone Management – have helped identify numerous new species in the Gulf of Maine over the years.

However, the MIMIC survey does not have the resources to do a benthic (samples taken from the ocean bottom) or e-DNA survey that would more effectively detect the animals. Miller said the crew monitors for 16 species of invasives but that there are easily another 20-plus that are present, but too hard to find or identify. A 2008 report identified 33 invasive species in Casco Bay, but Miller estimated there are likely now more than 40.

“When we start looking closely, we seem to find new invaders almost annually,” he said.

Trott stressed the importance of early detection in controlling the spread of invasive species and said if people see something unusual, they should report it or do their research, rather than just assuming someone else has already seen it.

People often think of invasive species as the canary in the coal mine, he said, but that’s not the case. “The canary in the coal mine is saying ‘Hey, there’s some poisonous gas in here,’ so when these (invasive species) show up, it’s the person that discovers them that is actually the canary,” he said. “We need more canaries.”

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