Aquatic Sciences Meeting, Albuquerque 2001

PC03 Undergraduate Education

Date: Tuesday, February 13, 2001

Location: Southwest Hall

Chang, B, , University of Virginia, Charlottesville, VA 22903 & University of Delaware, Lewes, DE 19958, , USA, bc8z@virginia.edu

CHARACTERIZATION OF THE SUBTERRANEAN MIXING ZONE BETWEEN GROUND AND ESTUARINE WATERS AT CAPE HENLOPEN, DELAWARE.

Five chemically distinct ground and surface water masses (A - E) were observed in an 80-meter cross-section across the beachface at a groundwater seepage site at Cape Henlopen, Delaware. This site was initially identified by thermal infrared imagery and the anomalous distribution of a brackish-water polychaete, Marenzellaria viridis. A is the surface estuarine water with high salinity and low DIN and DIP. B, found below the dune line, is fresh and characteristic of local surface groundwater with high nitrate. The composition of C, below the beachface at the high-tide level, reflects the mixing between A and B by the tide and swash. D is found 2 m below the beachface, is fresh, has negligible DIN and intermediate DIP and reflects discharge from an upgradient pond. E is found in sediments at the base of the beachface, has intermediate salinity, and high ammonium and DIP. This composition reflects a mixing between A and D with the diagenetic addition of DIP and ammonium. These results indicate that the beachface is a reactive mixing zone with local ecological significance.

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Aquatic Sciences Meeting, Albuquerque 2001

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