Lyme — Preliminary research by interns with Connecticut Audubon over the last two summers shows a pattern might be emerging in a few coves along the southern banks of the Connecticut River: less water celery and more waterweed.

The makeup of the vegetation in the inlets of the Connecticut River is an important factor in the survival of various bird species that stay there during the winter and while they're migrating, said Jim Arrigoni, a Connecticut Audubon conservation biologist who supervised the research.

This summer's interns, Mount Holyoke students Eva Schneiderman and Halee Mahone, found that, based on a survey of about a third of Lord's Cove in Old Lyme, species of Elodea, an aquatic plant also known as waterweed and often used in freshwater aquariums, was more abundant than Vallisneria americana, or water celery. Both plants are native to the region.

They spent the summer using a handheld GPS device and a rake to collect vegetation in one-meter-square plots to determine how much of each kind of vegetation covered the bottom of the cove.

Their results are not complete but reflect the same thing that interns last summer found when they did similar research in Whalebone and Selden Coves, farther north along the Connecticut River in Lyme: that waterweed had replaced water celery as the dominant species of underwater plants.

Several species of ducks seek safe cover there and eat the underwater grasses. Waterweed is less nutritious, so proliferation in the coves at the expense of other plants could be bad news for the habitat and the birds that eat there.

"(Waterweed is) kind of ranked as low to slightly valuable," Arrigoni said, while, as a food source, "water celery is considered to be excellent."

Arrigoni said the research is preliminary, and it is too early to determine what might be causing the shift.

As a researcher with The Nature Conservancy, Juliana Barrett, now a University of Connecticut ecologist, studied the underwater vegetation in the Connecticut River estuaries for a 1997 Department of Environmental Protection study.

Barrett said Wednesday that while it's too early to draw conclusions about the cause or effects of any change in the vegetation there, establishing a baseline will be useful for scientists studying the effects of sea-level rise and as parts of the river get more salty farther north.

"It's fascinating, I think, to just start to look at how vegetation in the cove had changed," she said. "As they build this data (it will) become a very useful baseline from the mid-90s ... to what they're seeing now. And then as sea-level rise really accelerates, what are the implications on submerged aquatic vegetation."

Connecticut Audubon plans to bring more interns in subsequent summers to its Roger Tory Peterson Estuary Center in Old Lyme to continue the research, Arrigoni said.

m.shanahan@theday.com