TEMPORAL AND SPATIAL VARIATIONS OF HEAVY METAL CONCENTRATIONS IN DEVELOPED AND UNDEVELOPED MARSHES ON SKIDAWAY ISLAND, GEORGIA

As part of an NSF-funded Research Experience for Undergraduates (ACRES), a 3-year study on the temporal and spatial variation of heavy metals in back barrier marshes began in summer 2002. Marshes and estuarine systems are a breeding ground for many economically important marine organisms, so an understanding of how metals migrate and/or are sequestered in estuarine sediments will further our ability to preserve these fragile environments. The trace elements investigated were Cr, Co, Ni, Co, Cu, Zn, Ba, and Pb. It was anticipated that these trace element concentrations would vary both spatially and temporally.

Four 50 cm long push cores were recovered summer 2002 from high and low marsh areas in moderately developed and undeveloped estuarine margins on Skidaway Island, Georgia. Cores were sub-sectioned every two centimeters. Samples were processed according to D. H. Loring and T. T. Rantala (1992), and a Finnegan Element II ICP-MS was used for the geo-chemical determinations. Lead concentrations in both low marsh cores increase from bottom to top by approximately 200%, while both high marsh cores exhibited an approximately 300% increase in lead concentrations. Concentrations of copper displayed a similar trend. Both low marsh cores showed a concentration increase of approximately 150% while the high marsh Cu concentration increase was approximately 700-1000%.

An interesting pattern was observed in the cores A spike of heavy metal concentrations (~ 30% increase in all concentrations) occurred at 16cm depth in the low marsh core from the undeveloped area. The high marsh core from the developed area exhibited a similar spike in metal concentrations at approximately 30cm of core depth. Radioisotope data would indicate that these anomalies are the result of human-induced mixing or bioturbation of the area.