Environmental Evolution of Chincoteague Lagoon-Marsh System as Inferred from the Sediment Record

The Chincoteague lagoon, located on the Eastern Shores of Maryland and Virginia, is protected along its length by Assateague Island but is exposed through the Ocean City Inlet to the north and the Chincoteague Inlet to the south. The lagoonal system harbors many acres of ecologically important marshlands, providing habitat for diverse species and filtering out run-off associated contaminants, and also protect the mainland from wave and tidal energy caused by storm events. Historically pristine, and still pristine compared to its Del Marva counterparts, Chincoteague Bay is now threatened by recent rapid population growth and consequential modification of its watershed. This study uses Pb-210 and Cs-137 radioisotopes and sediment core trace metal (Al, Fe, Cu, Zn, Pb, Cd, Mn, BA, and As) profiles to evaluate the impact of anthropogenic changes in sediment delivery and the overall environmental evolution of Chincoteague Bay over the past century. 

Our results shows that the eastern side of the lagoon is dominated by sands from Assateague Island via storm overwash and wind transport, whereas the western side of the lagoon receives muddy sediments from the mainland. From the Pb-210 estimates, the lagoon is receiving relatively low average sediment accumulation rates ranging from 0.10 g/cm²/yr on the eastern side to 0.167 g/cm²/yr at the marsh site but these rates have been progressively increasing. Though trace metal values remain low at all locations, most metals exhibit a trend of increasing enrichment with time. With the current expansion in housing developments on the mainland in close proximity to streams draining into the lagoon, if better management practices are not put in place to counter their impacts, both sediment accumulation rates and trace metal concentrations may be significantly higher in Chincoteague Bay in the next few years.