Is Genetic Diversity Key for Restoring Underwater Grasses?

Carpeting a patch of the Potomac River, this natural bed of wild
celery may help researchers understand how genetics affects
the success of underwater grass restoration.
Photo by Michael Lloyd

The Chesapeake Bay’s underwater grasses and the stock market have at least one thing in common. Investors will tell you that the key to success in the stock market lies in a diversified portfolio. Diversity increases the chance that at least one stock will go up in value, even if the others tank.

Nature works in much the same way. Genetic diversity allows a population of plants or animals to hedge its bets. When faced with an environmental stressor such as a sudden change in temperature or a powerful storm, genetic diversity increases the chance that at least some individuals will be able to survive — perhaps even thrive.

Scientists at two University System of Maryland laboratories recently began to explore the connection between genetic diversity and restoring submerged aquatic vegetation (SAV) in the Chesapeake Bay.

Since their widespread decline in the 1960s and 1970s, efforts to restore the Bay’s grasses over the last several decades have brought mixed results — the grasses have made a comeback in some areas, but in many places they have completely disappeared.

Could a lack of genetic diversity be to blame? Could carefully considering genetic diversity enhance efforts to bring back Bay grasses?

Ecologist Katia Engelhardt of the University of Maryland Center for Environmental Science (UMCES) and geneticist Maile Neel of the University of Maryland College Park want to find out. With funding from Maryland Sea Grant, Engelhardt and Neel have begun to explore the role of genetic diversity in SAV restoration success, specifically that of wild celery, Vallisneria americana, a species of underwater grass that grows in areas with little or no salinity.

Although a favorite food of waterfowl and historically abundant in the Bay, little is known about wild celery’s genetic diversity, explains Engelhardt. “We need to understand how many individuals that differ in genetic make-up are out there,” she says.

By comparing natural populations of wild celery to restored and cultured populations, Engelhardt and Neel hope to identify patterns of diversity. Using samples from various locations including the Susquehanna, Potomac, and James Rivers, they will measure genetic diversity within and among populations of wild celery. Their work is the first-ever experiment to analyze simultaneously the role of three different aspects of genetic diversity in freshwater SAV restoration.

But information on genetics doesn’t automatically give insight into restoration. To study how levels of genetic diversity translate into restoration success, Neel and Engelhardt will conduct a restoration experiment at the UMCES Appalachian Laboratory’s greenhouse. They will plant wild celery colonies ranging from low to high genetic diversity and monitor survival and growth rate as indicators of restoration success.

If high genetic diversity does prove key to successful wild celery restoration, this research could change the way managers approach future restoration projects. “They may have to take into account where their source material comes from and include some genetic diversity in the mix,” Engelhardt says.

At present, large-scale planting and seeding efforts required to meet SAV restoration goals often use only a few mass-produced clones from one site. You can see where this lack of genetic diversity may be a problem down the road, says Bob Murphy, a scientist and director of Ecosystem Solutions in Edgewater, Maryland, a group that conducts applied research on restoration ecology.

This research will have a lot of utility for those on the frontlines of restoration, says Murphy. “This is extremely valuable,” he says. “I’m surprised it’s taken this long for someone to do it.”

-- Jessica Smits