Date Awarded


Document Type


Degree Name

Doctor of Philosophy (Ph.D.)


Virginia Institute of Marine Science


Bruce J. Neilson


A model of zinc accumulation by the American oyster, Crassostrea virginica, is developed by relating in-situ zinc body burden to time-integration of uptake. Short-term uptake rates are estimated in laboratory by introducing &\sp{lcub}65{rcub}&Zn to oysters of various weights in aquaria with salinities of 18&\perthous& and 12&\perthous&. Uptake of &\sp{lcub}65{rcub}&Zn by an oyster: (1) varies as a power function of the body weight (soft tissue dry weight) of the oyster (&dy\over{lcub}dt{rcub}& = kW&\sp{lcub}\beta{rcub}&), (2) is inversely related to the salinity of ambient water, and (3) increases linearly with ambient concentration. Zinc body burdens of oysters of various weights from oyster beds with different salinity regimes of the James River and of the Rappahannock River are measured. When the zinc body burden of oysters is fitted to a power function of body weight (y = aW&\sp{lcub}\rm b{rcub}&), the values of power, b, are 1.33, 1.30, and 1.06 for salinities of 13, 15, and 20&\perthous&, respectively, in the James River and 1.16 for a nominal salinity of 18&\perthous& in the Rappahannock River. The values of b agree with the values of &\beta& derived from the &\sp{lcub}65{rcub}&Zn uptake experiments; b = &\beta& + 1. The model is calibrated using data for Horsehead Shoals and Nansemond Ridge, two sites in the James River having average salinities roughly the same as those used in &\sp{lcub}65{rcub}&Zn laboratory studies. The model is verified by the use of data for Wreck Shoal, a mid-salinity sampling site of the James River, and the pooled data for the Rappahannock River sampling sites. The weight-specific zinc concentration of an oyster increases continuously, but rate of the increase is reduced as the oyster grows larger. Both uptake parameters, k and &\beta& vary with salinity. It is suggested that the body weight effects, and their variation with salinity, should be incorporated in the design of monitoring programs for trace metals as well as in experimental studies.



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