On the trail of invasive species
By Peter J. Hanlon
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Deep-sea biologists have multi-million dollar submersible vehicles. Physical oceanographers rely on networks of satellites and buoys. And marine invasive species experts use spatulas and nets. Clearly the latter are not the gear-heads of the marine research world.

Despite the lack of high-tech equipment, the search for non-native species has an international appeal. Organisms from literally any point on the globe can be transported to the Gulf of Maine through the ballast of cargo ships, the baitfish industry, the release of aquarium pets into the wild and fouling on the bottom of recreational boats.

It’s a big step for a handful of hitchhiking organisms on a cargo ship to transition from pioneers to reproducing population, but unfortunately the Gulf of Maine is full of examples of species that have made the leap. Introduced species such as the European green crab and Asian shore crab prey on commercially valuable shellfish throughout the Gulf. The green algae Codium fragile (also known as “dead man’s fingers”) has been known to replace entire kelp and eelgrass beds within New England and Atlantic Canada. A fast-growing tunicate (Didemnum sp.) was found in 2003 to be smothering a large area of the continental shelf like a mat on the productive scallop fishing beds of Georges Bank.

Making an ID
Researchers are aware of the many ways that non-native species can find their way into Gulf of Maine waters, but the question of which invasive species exist within the Gulf is difficult to answer. Since 2000, a team of scientists from throughout the United States, Canada, the Netherlands, Brazil, Wales, Italy and South Africa have participated in three “rapid assessment surveys” of marine invasive species in the northeastern United States coordinated by the Massachusetts Bays Program and MIT Sea Grant.

The weeklong surveys are invaluable opportunities for taxonomic experts to quickly and accurately identify marine species and determine whether they may be newly introduced organisms that threaten the Gulf of Maine’s ecosystems, and if they are introduced, where they are from and how they got here. Since the scientists monitor the abundance of both native and non-native species, they are also able to examine how the presence of introduced species is affecting the native ecosystem.

The third and most recent rapid assessment survey was conducted in July 2007. A team of 20 scientists spent eight days visiting 17 sites stretching from Woods Hole, Massachusetts to Rockland, Maine. The team visited permanently floating docks and piers at each site, ensuring that they examined a structurally similar habitat type at each location likely to have a variety of marine organisms and several years of growth underneath. The docks and piers selected were also located in areas likely to have numerous pathways for non-native species to be transported, such as active shipping ports.

On the road
With such a large crew and demanding schedule, the days were planned down to the minute. Each day started out with an early wake-up at the scientists’ hotel. After a quick breakfast, the crew loaded into two vans and headed to the day’s first site. As one might expect of vans full of taxonomists, conversations steered towards, well, taxonomy, with the occasional friendly scientific jousting.

Once at the site, the scientists poured out of the vans, found a spot on the docks and, for the next hour, lay down at the edge of the dock and scraped as many organisms (both native and non-native) from the sides as they could find. The equipment used was simple — spatulas to scrape the organisms off and a net to catch them.

Sometimes the organisms were attached to ropes and buoys — or in one case a long stretch of plastic sheeting — that were dragged onto the dock for examination. One scientist brought his wet suit and snorkeling gear to collect and photograph species that prefer the relative darkness under the docks.

Many of the common organisms could be identified right away and were put back in the water. A team member recorded the identified species. A representative sample of all the organisms found at each site was collected in a plastic bag and taken back to the lab that evening for identification.

It was common to see researchers huddling together over a stretch of rope that had just been hauled up, blanketed with brightly-colored organisms, and discussing the identity of the attached species. Most of the scientists had distinct areas of expertise and brought jars to collect specific organisms of interest. So when, say, a club tunicate was found, a research assistant would grab a sample and bring it to the ascidian (sea squirt) expert.

After an hour or so, the researchers began to organize their findings and headed back to the vans to gulp down some cold drinks — no small detail during a late July heat wave — and hit the road to inspect another site, sometimes a few hours’ drive away. By late afternoon, the group had visited three sites.

Once back from the field, the day was far from over. The scientists headed off to the lab where they remained for up to six hours on some nights with only short breaks for pizza or Chinese or whatever quick dinner awaited them. The researchers took shifts identifying the species under a stereo microscope, which allows viewing in three dimensions. The generalists wrote down the species that they knew and passed on any questionable finds to the specialists. Once all of the species were identified, a sample of the organisms found at each individual site was placed in a jar as a permanent record to be kept in a museum.

Many of the non-native species documented during the 2007 survey had been observed in the previous two surveys (see sidebar), but this year did reveal an alarming discovery: the northward expansion of Grateloupia, a non-native red seaweed, into Cape Cod Bay and at a survey site in Boston. The significance of this new species isn’t yet understood, but it may impact other native seaweeds.

Next steps
While the survey was successful, it is just one of the steps in the fight to control the spread of marine invasive species. The goal of those involved is to continue their research by repeating the process every several years to keep pace with potential future invaders and their impact on native species. To fill the gap between surveys, several citizen volunteer monitoring programs have been established recently within the Gulf of Maine, and survey organizers continue to hold workshops for coastal scientists, managers, government agency personnel and graduate students to give them the skills necessary to identify non-native species.

Equally important is the effort to develop management plans and rapid response protocols to address any new non-native species in the Gulf, a task headed by organizations such as the Northeast Aquatic Nuisance Species Panel, Massachusetts Aquatic Invasive Species Working Group and Maine Marine Invasive Species Working Group. Prevention is the focus of the plans, but should a new harmful species be introduced, a rapid response protocol is needed to let federal, state and local officials know what technologies they have available to prevent an emergency.

Scientists monitoring non-native species in the Gulf of Maine may not have the elaborate high-tech equipment required by other marine researchers. Instead, regional and international cooperation among coastal scientists and managers — armed with a few spatulas — is the best way to effectively prevent and control future invasions in our borderless marine ecosystems.

Peter Hanlon is outreach and policy coordinator for the Massachusetts Bays Program in Boston, Massachusetts.

Examples of invasive species found on the most recent census

European Green Crab (Carcinus maenas)
Where is it? Established from Delaware to Nova Scotia, it is the most common crab species in many locations throughout this range.

Why is it a problem? One of the Gulf of Maine’s dominant benthic predators, it feeds on clams, oysters, crabs and mollusks and often is blamed for the collapse of Maine’s soft shell clam industry.

Colonial Tunicate (Didemnum sp.)
Where is it? Spreading in the Gulf of Maine, it was first observed in Maine and Woods Hole, Massachusetts, in 1988, and since has been reported from Maine to Connecticut.

Why is it a problem? It grows over a variety of surfaces, altering marine habitats and threatening to interfere with fishing and aquaculture. It grows aggressively over bivalves and may smother them or interfere with their growth, and has no known predators.

Sheath Tunicate (Botrylloides violaceus)
Where is it? Its range stretches from the Gulf of Maine to Florida.

Why is it a problem? It can grow over other organisms such as shellfish, competing for food and resources and possibly leading to the other organisms’ death.

Green Fleece Algae (Codium fragile)
Where is it? It covers a region from the Gulf of St. Lawrence to North Carolina.

Why is it a problem? When this species becomes established in shellfish beds, wave energy can lift the algae. As the algae floats away, it carries its host shellfish away from its normal habitat, resulting in another common name for this species, “oyster thief.”

© 2007 The Gulf of Maine Times