Still-Water Dwellers

One in a series of periodic stories related to the Delaware River Watershed Initiative, a project funded by the William Penn Foundation to protect and restore the basin’s water quality and overall ecological health.


By Alissa Falcone

The old proverb says that “still waters run deep,” but Academy scientist Meghan O’Donnell is going one step further and asking “run deep with what?”

To find answers, she’s looking at the parts of the Schuylkill and Brandywine-Christina watersheds in the Delaware River Basin that are lentic, or slow-moving and without any current. There, she’ll search for macroinvertebrates (think: insects, small crustaceans, crayfish and mollusks) that can act as bioindicators to reflect the environmental conditions of the area. Typically, samples are taken from lotic, or areas where the current is strong in the center of the water column, because that’s where the area is teeming with diversity.

O'Donnell holds a salamander at her research site.
Academy scientist Meghan O’Donnell holds a salamander fresh from the stream.

“There aren’t metrics for indicators of biological integrity for lentic areas,” she says. “In lentic areas, there is lower dissolved oxygen and increased sedimentation; you will find different kinds of macroinvertebrates that tend to have a high population of predators and air breathers.”

Since the organisms she’s looking at are as slow-moving as their watery habitat, O’Donnell says that the tolerance level of the macroinvertebrates sampled tells a lot about the long-term conditions of the aquatic environment. The various bioindicators give insight into the water conditions, but that’s not enough for O’Donnell.

She’s still taking water samples and measuring pH, water temperature, conductivity, stream depth and width, and soil and vegetation cover at the sample sites to learn even more about the macroinveterbrates’ habitat and impact from land use.

In the future, O’Donnell hopes to compare her specimens’ tolerance level to pollutants to those sampled in the lotic areas, and potentially establish a lentic Index of Biotic Integrity, or IBI, to gauge the health based on what families of organisms are found.


To read some other stories in this series,visit Sediment and Small HabitatsInvasion of Knotweed, Index for the Delaware, Funds for the Delaware,Tales of a Watershed Scientist, and Fish Ecology in Pictures.

This article first appeared in EXEL, Drexel University’s research magazine.


Photos by: ANS

Leave a Reply

Your email address will not be published. Required fields are marked *