Seasonality Determinations from Archaeological Oyster Shells: An Experimental Evaluation of Incremental Shell Growth

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Waselkov With National Science Foundation support Dr. Waselkov and his colleagues will study the growth patterns in Eastern oysters (Crassostrea virginica) to determine the relationship between growth and seasonal changes in water temperature. The goal of the work is to determine whether analysis of oyster shells will permit determination of the season when the oyster was collected. Preliminary evidence indicates that such an approach is possible in temperate waters where significant seasonal variation in temperature occurs. It is less clear whether the same pattern holds in warmer areas such as the Gulf of Mexico. The investigators will examine oyster growth from two locations, Alabama and Maryland, with several methods. Oysters will be marked and grown under known conditions for two years before being harvested. Temperature will be electronically logged. Both wild and hatched spawned oysters (of known) age and will be stained with tetracycline in a sequence that will allow spatio- temporal identification of growth patterns throughout the annual cycle. Analytic methods will include traditional optical micrometry, digital image analysis with time series analysis and use of a scanning proton microprobe. The successful development of this technique will have important archaeological implications. Oysters formed a major dietary item in many areas of prehistoric North America and are widely found in archaeological sites where they are well preserved. Scientists wish to understand how prehistoric peoples with simple technologies subsisted in a wide range of environments and made use of available natural resources. To do this, they attempt to determine the seasons and length of time individual sites were occupied. This can be extremely difficult to do and the proposed oyster shell study will, hopefully, provide a technique to accomplish this.