GROWTH HISTORY AND CLIMATE SEASONALITY OF THE EASTERN OYSTER COLLECTED FROM COLONIAL SHELL MIDDENS, WESTMORELAND VIRGINIA

The Chesapeake Bay has seen a significant loss of oyster reef habitat since the Industrial Revolution. The demise of the fishery is largely thought to reflect anthropogenic changes in sedimentation and nutrient loading in the region. Stratford Hall Plantation in Westmoreland County, Virginia has been the focus of years of archaeological investigation such that the middens of the plantation have yielded several dozen specimens of the Eastern oyster, Crassostrea virginica. Artifact-dated archaeological deposits from the colonial plantation in the Northern Neck region of Virginia, therefore, have the potential to provide a Colonial seasonal climate record for the Chesapeake Bay region.

New sclerochronologic techniques using the variable pressure Scanning Electron Microscope allow for an unprecedented seasonal and weekly growth record. Twenty-seven oysters excavated at the Stratford Hall site, were carefully selected on the basis of pristine preservation to include 100% shell completeness and minor evidence for physical and chemical abrasion. By observing the internal umbo of the larger valve, we’ve determined that the average age of the samples is approximately six years. In general, most oysters demonstrate a reduced growth rate with increasing age. The highest rates of growth correspond to the intervals April to September which suggest highly productive spring through summer conditions on the oyster reefs in the Colonial Potomac Estuary.