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Michelle Slater sends fruits and veggies adrift in the Saco River as part of invasive plant species study

Newly sent-off produce floats in the Saco River as part of Slater's drifter study

, Maine — If residents along the Saco River start to notice fruits and vegetables floating in the current, there is no need for alarm.  No produce trucks have flipped over into the water.  No one’s garden is being carried out to sea.  Rather, the bobbing oranges, lemons and summer squash are part of a scientific “drifter study” conducted by Michelle Slater, a University of New England graduate student in the Department of Marine Sciences.

Slater, who is being advised by Pamela Morgan, Ph.D., associate professor and chair of the Department of Environmental Studies, received a Maine Wetland Research Stipend grant from the Maine Association of Wetland Scientists (MAWS) to study the ways in which water current patterns in the Saco may affect the propagation of a troublesome form of the plant species, Phragmites australis, commonly referred to as “P. australis” or simply “Phragmites,” a tall grass that can grow up to fifteen feet in height, which has begun to invade southern Maine.

There are native forms of the species that are not problem-causing.  However, the invasive form, first introduced from Europe in the late 1700s to early 1800s in ballast material from ships, is considered a nuisance by many, as it alters natural marsh systems.

While seed dispersal is the most common method of P. australis propagation, another way in which the plant reproduces is through floating pieces of rhizomes, an underground network of stems, which help to anchor the plant in the ground.  According to Slater, rhizomes are sometimes dug up through human disturbances as well as by natural processes.  The uprooted rhizomes travel on the current, settle in new places, and begin to colonize under the right conditions.

Slater’s goal is to mimic the floating rhizomes with oranges, lemons, and summer squash in order to track the paths that the currents take them.  This will help identify how the plant may be spreading, what conditions are favorable and unfavorable to its colonization, and which areas might be at risk for future colonization.  Ultimately, Slater hopes that the research will yield answers to the question of how to curb future spreading of the plant, as the effects on a marsh system with uncontrolled Phragmites can be devastating.

Slater explained: “The invasive form of Phragmites is of special concern because it is extremely robust and out-competes other marsh plants.  Therefore, it can completely transform a marsh system.  This reality is distressing because it is believed that humans may play a role in the spread of P. australis through various activities including construction on or near marshes. Since the introduction of the invasive form to the United States, extinction of other lineages has occurred due to its aggressive nature.”

The choice of produce to use in the study was not random.  Lemons, oranges, and summer squash, all biodegradable, of course, were selected because not all Phragmites rhizomes are of a uniform shape and, therefore, all do not float in the same way.  Not only are lemons, oranges, and summer squash buoyant and brightly colored, which will aid in spotting them in their new locations, but the variety of shapes that they come in proved in preliminary testing to cause the produce to travel through water in a variety of ways that roughly mimic the trajectories of P. australis rhizomes.

Produce send-offs will occur at various times throughout the summer at locations where some of the large P. australis patches currently exist in the Saco River (near the dam near the Saco sewage treatment plant, in the middle of the estuary, and at the river mouth).  Multiple send-offs are needed in order to discern how different tidal cycles and river flows affect the produce’s movement.

A small group of undergraduate students in the Department of Environmental Studies who are serving as lab members will go on excursions to search for the released produce in order to identify settlement locations.  Slater is hoping that homeowners along the shores of the Saco River will participate in this study, too, by being on the lookout for fruit and vegetables that wash up on shore.  Each piece of produce will be coded with its own number.  Anyone who finds a washed up fruit or vegetable should go to the study’s website to enter its code.  Names of those entering codes will be later placed in a drawing for a prize.

For more information or to find out when the next produce send-off is scheduled, access the facebook page link on the study's website.

(News release posted June 20, 2013)