The Dynamics of Metals in the American Oyster, Crassostrea virginica. II. Environmental Effects1

The dynamics of Mn, Fe, Zn, Cu and Cd in the shell and soft tissues of the American oyster, Crassostrea virginica, were observed in oysters exposed in situ to a metal-contaiminated environment from September, 1972 until August, 1973. Zn and Cu accumulated in soft tissues of exposed oysters reaching levels of 4100 rg Zn/gm and 450 rg Cu/gm compared to 1700 pg Zn/gm and 60 pg Cu/gm for controls (dry weight basis). The relative enhancement of metals in oyster soft tissues exposed to the contaminated environment over controls reflected the pattern of metal contamination in sediments. Although growth of the oysters, as measured by soft tissue dry weight and shell dimension, was identical, shells of exposed oysters were significantly thinner than controls (16%). Trace metal incorporation into shell was affected with Mn deposition surpressed and Fe, Zn and Cu slightly increased. Uptake of metals by oyster soft tissues was seasonally dependent with rapid uptake occurring in the summer and fall but delayed uptake occurring in the early spring. Introduction interpretation of data. On the other hand The uptake of metals by oyster soft tissues laboratory studies have a tendency to use high when exposed to environmental conditions dose levels which make it hard to extrapolate modified by human activities has been obback to the effects at environmental concenserved in field surveys (Hiltner and Wichtrations, and are aiways piagued by the mann 1919; Chipman et al. 1958; McFarren question as to whether or not the physicalet al, 1961; Pringle et al. 1968; Kopfler and chemical speciation of a dosing metal is Meyer 1969; Huggett et al. 197 1; Windom similar to that encountered by the oyster in and Smith 1972; Kopfler and Mayer 1973) the rea1 wor1d. and studied in the laboratory (Chipman et al. In order to overcome these difficulties 1958; Pringle et al. 1968; Shuster and Pringle several “field experiments” (Seymour 1966; 1969; Preston 1971; Romeril 1971; Kerfoot Preston 1967; Ikuta 1968; Roosenburg 1969; and Jacobs 1973). These studies have proDrobeck and Carpenter 1970; Wolfe 1970; vided a great deal of insight into the problem Kopfler and Mayer 1973) have been carried of metal accumulation, but they also have out to study the uptake or loss of metals mo;nr Av,,.,h,xoLP frnm o th~nvat:r.ol n-;-t nf LUUJ”’ UIU”.“UtiRD II”lll LL CIIti”L~CI~cII y”“‘L “1 under real world conditions. These studies view. Field surveys are useful for identifying combine the laboratory approach with field metal contamination hot spots of pubfic conditions, thus allowing a more realistic health concern, but in general only provide a setting for the experiment with respect to snapshot picture of metal dynamics. Seasonal concentration and physical-chemical speciaeffects have not been taken into consideration tion. The major drawback to this approach is in sampling programs and the sampling of the lack of control over various conditions. natural populations with their high level of However, if experimental stations are carebiological variability causes difficulties in fully chosen so as to match as many environ1 This research was jointly supported by grants from mental factors as possible-salinity, temperathe National Science Foundation-Research Applied to ture, light, food supply (both quantity and National Needs Program (NSF RANN GI-34869), and quality), etc.-these studies complement the the National Institute of Environmental Health Sciunderstanding of metal cycling provided by ences (ES 000454). laboratory experiments.