Document Type
Thesis
Abstract
Oysters grow by accretion and lay down calcium carbonate shells in chemical equilibrium with the surrounding water. Here | propose a method to source oyster shells in the Chesapeake Bay region, by matching the geochemical signature of major Virginia rivers to the geochemistry of oyster shells. My main tracers were 87Sr /86Sr, Na, Mg, Ca, and Sr, due to their incorporation into oyster shells during the calcification process. Strontium isotopes differ in their sources— with 87Sr having a large source from continental weathering. | hypothesize that higher 87Sr /86Sr will be shown in the rivers that have greater watershed areas containing high potassium-bearing rock, and trace element concentrations should differ among rivers. Shell and water samples were taken from the four main rivers in Virginia that drain into the Chesapeake Bay (James, York, Rappahannock, and Potomac) at the farthest point upstream that oysters grow in abundance. Oysters were cleaned, adductor muscles scars were cut out and ground into powder, then dissolved in 0.5 molar nitric acid. Samples were analyzed for 87Sr /86Sr via TIMS and trace elements (Na, Mg, Ca, Sr) via ion chromatography. Results showed that the isotopic ratio of 87S /86Sr was significantly different between each river. The concentration of Mg in each river revealed to be another reliable factor for determining differentiation between rivers, however; it did not differ significantly among all rivers. It is apparent that water/bedrock interaction plays a role in shell chemistry, however, until better mechanisms are discovered for quantifying sediment and surface lithology, definite correlations between shell chemistry and drainage lithology cannot be confirmed.
Date Awarded
2016
Department
Geology
Recommended Citation
Brown, Kallie, "Does Shell Chemistry Differ Among Oysters from Different Rivers?" (2016). Geology Senior Theses. William & Mary. Paper 353.
https://scholarworks.wm.edu/geologyseniors/353
