An invasive species of aquatic plant that has cropped up around the country may have gained a foothold in the Potomac River and Mattawoman Creek since it first appeared there last summer, state and federal scientists said.
The plant, native to South America, is commonly called water lettuce. It can grow to blanket large sections of water, making it impassable by motor boat, preventing submerged grasses from getting sunlight and endangering fish by inhibiting oxygen from entering the water.
Scientists are not sure if the plant survived the winter, so they plan to search for it along the two waterways in early July, said Mark Lewandowski, a biologist with the Maryland Department of Natural Resources.
‘‘If it’s not in many places, that’s probably a good sign,” he said. ‘‘If we find it in as many places as last year, we may have a problem on our hands.”
Lewandowski said he and others from the U.S. Geological Survey and the Interstate Commission on the Potomac River Basin will focus their search along a large stretch of the Potomac south from Washington, D.C., and along the entire Mattawoman, which runs from Brandywine to the Potomac and forms the boundary between Prince George’s and Charles counties.
Nancy Rybicki, a USGS hydrologist, said she first found the plant in the area last year during a survey along a 20-mile segment of the Potomac and up and down the Mattawoman.
‘‘Every cove we went into in Mattawoman Creek, we saw more colonies,” she said.
It is unclear how water lettuce, which is sold at most aquarium supply stores, got into area waterways, Lewandowski said.
‘‘Nothing’s definitive. But more than likely, it’s something from an aquarium owner or pond owner who dumped it,” he said.
Water lettuce, which is a widespread problem in Florida, has been found in isolated spots as far north as Massachusetts and as far west as California, Rybicki said.
‘‘It’s so prolific,” Rybicki said. ‘‘It grows so fast that it could really block the water surface.”
Lewandowski said that even if the water lettuce has spread this year, it can still be eradicated through what would likely be a large-scale, multiyear effort.
The Maryland DNR is urging recreational boaters, fishermen and hikers to keep an eye out for the plant, and if they see it, to scoop it out of the water or report its location, Lewandowski said.
People who want to dispose of water lettuce from an aquarium or garden pond should first dry it in the sun or put it into a trash can, he said.
Kelly Canavan, president of the Accokeek, Mattawoman, Piscataway Creeks Communities Council, said the presence of water lettuce is another sign of the Mattawoman’s declining health.
‘‘It’s surprising, and it’s sort of bizarre, when you look at things that are disappearing and things that are popping up,” said Canavan, of Accokeek. ‘‘It makes you worry about the health of the creek.”
E-mail Andy Zieminski at azieminski@gazette.net.
