Estuary beachfaces topic of Aug. 18 lecture

William Ullman, professor of oceanography

4:24 p.m., Aug. 10, 2005--The most common source of fresh water to the ocean is from rivers and streams. However, in coastal plain areas, such as southern Delaware, a significant amount of freshwater enters through the estuarine beachface, or below the high-tide line. These freshwater seepage zones result from the direct discharge of groundwater to the beachface and may play a significant role in the intertidal ecology of the coastal zone.

At 7 p.m., Thursday, Aug. 18, at UD’s College of Marine Studies campus in Lewes, William Ullman, director of the oceanography program and professor of oceanography, will give a presentation titled "Down Below the High-Tide Line: The Hydrology, Hydrochemistry and Ecology of Estuarine Beachfaces." Ullman's lecture is part of the Ocean Currents Lecture Series, held the third Thursday of each month, from April through September, on the Lewes campus.

Estuaries are unique ecosystems where fresh water from rivers and streams mixes with salt water from the ocean. This is most obviously seen when seawater comes rushing in at high tide to submerge and flood the land with salt water. However, the mixing of fresh and salt water also takes place below the ground surface in what is now being called the "subterranean" estuary.

"Mixing of fresh and saline water occurs in these estuarine beachfaces, and so they have been characterized as subterranean estuaries," Ullman said. "During this mixing process, there are interesting physical, chemical and biological processes taking place that affect the ecological health of estuaries such as the Delaware Bay and Delaware's Inland Bays."

According to Ullman, the water that enters the estuary through groundwater pathways is typically loaded with nutrients such as nitrogen and phosphorus. These nutrients can contribute to plant growth in the estuary, particularly in the intertidal zone where significant freshwater seeps occur.

"These freshwater seepage zones support a distinctive, diverse and productive intertidal community of organisms that is not found elsewhere," Ullman said.

A member of UD's faculty since 1986, Ullman conducts research on projects involving the chemistry of surface waters. In addition, he uses airborne thermal-infrared imagery to identify regions where groundwater discharges directly into coastal areas of Delaware.

A native of Ann Arbor, Mich., Ullman earned a doctorate in geophysical sciences from the University of Chicago, a master's degree in atmospheric and oceanic sciences from the University of Michigan and a bachelor's degree in geology from Yale University.

The lecture will held in Room 104, Cannon Laboratory, at the Hugh R. Sharp Campus, 700 Pilottown Road, Lewes. The hour-long talk will be followed by light refreshments.

While the lecture is free and open to the public, seating is limited and reservations are required. To reserve your seat, call (302) 645-4279.

Photo by Kathy F. Atkinson

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