Still-Water Dwellers - Exel: Drexel University's Research Magazine
 
 

_FEATURE A WATERSHED MOMENT

_Still-Water Dwellers

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?”

_Meghan O’Donnell

O’Donnell is a staff scientist at the Academy of Natural Sciences of Drexel University.

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?”

Lazy_Currents

Macroinvertebrates
are key bioindicators used to assess stream health. To get a full picture, scientists are sampling the critters in often-overlooked slow-moving currents.

To find answers, she’s looking at the parts of the Schuylkill and Brandywine-Christina watersheds 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.

“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.