The Dynamics of Metals in the American Oyster, Crassostrea virginica. I. Seasonal Effects

The seasonal dynamics of Mn, Fe, Zn, Cu and Cd were investigated in a genetically similar population of hatchery-reared American oysters, Crassostrea vir,qinica. maintained in plastic trays in the Rhode River, a tributary of the Chesapeake Bay. Samples were collected monthly from September, 1971 through May, 1973. Annual cycles resulting in the turnover of large portions of the body burden were observed for all metals studied. Subtly different patterns of metal dynamics were observed as a result of the reduction in biological variations realized by employing genetically similar oysters. Metals are grouped into two classes according to their dynamics; (1) Mn and Fe concentrations in soft tissues are significantly correlated with shell deposition. A high rate of Mn turnover in soft tissues (approximately 2 times the body burden per day) occurs during the shell growth season. (2) Zn and Cu concentrations are not correlated with shell growth. Zn and Cu body burdens exhibit a gradual increase during the spring and early summer followed by a rapid loss during August-September in which 33% of the Zn and 50% of the Cu is lost in less than 4 weeks. Cd behavior is similar to Zn and Cu with a 50% reduction in body burden during an II week period between July and October. Introduction problems. For this reason, an understanding The ability of the American oyster, Crassof the environmental and biological factors ostrea virginica, to accumulate high concenwhich determine the dynamics of metals in trations of metals in its soft tissues is well the soft tissues of oysters must be developed, documented (Hiltner and Wickman 1919; particularly with respect to the impact of Rodansky 1920; Rose and Rodansky 1920; human activities on the basic processes inSevery 1922; Coulson et al. 1932; Chipman et volved. This paper is the first of a series of al. 1958; McFarren et al. 1961; Galtsoff 1964; Papers directed toward this goat. Here we Brooks and Rumsby 1965; Pringte et al. 1968; consider the baseline seasonal dynamics of Kopfler and Mayer 1969; Shuster and Pringle Mn, Fe, Zn, Cu, and Cd in C. virginica under 1969; Roosenburg 1969; Wolfe 1970a; Hugnatural conditions. gett et al. 1971; and Windom and Smith Seasonal fluctuations in the metal compo1972). From a public health point of view, the sition of oysters have been suggested by accumulation of metals in human food reseveral researchers (Galtsoff 1942, 1964; sources should be considered with some deMcFarren et al. 1961; Pringle et al. 1968; gree of concern because of the implications of Kopfler and Mayer 1969; and Roosenburg certain metals in chronic and acute health 1969). Galtsoff ( 1964) has carried out detailed investigations specifically designed to study ‘This research was jointly supported by grants from this phenomenon. His data clearly show a the National Science Foundation-Research Applied to seasonal pattern for the concentrations of National Needs Program (NSF RANN GI-34869), and Mn, Fe, Cu and Zn in soft tissues: elevated the National Institute of Environmental Health Sciences levels of metals in the summer are followed (ES 000454). by depressed levels in the winter. Our data