ACCUMULATION OF SILVER AND LEAD IN ESTUARINE MICROZOOPLANKTON

Accumulation of Pb and Ag by the estuarine ciliate Fabrea salina was m easured using the gamma-emitting radioisotopes Pb-210 and Ag-110m. Vol ume/volume concentration factors for Ag-110m in the ciliate ranged fro m 7 to 40 x 10(3); concentration factors of Ag-110m in F. salina from the dissolved phase and from radiolabeled algal food were comparable. The concentration factor of Pb-210 Obtained from the dissolved phase w as 2 x 10(2); there was no detectable assimilation of Pb-210 from alga l food. Because estuarine microzooplankton can concentrate some partic le-reactive trace metals out of ambient water, they can serve as a sou rce of these metals for animals which consume them. For comparison, up take of these radioisotopes from the water by Various size fractions o f natural particles in Hudson River (New York, USA) water was determin ed. Half of the added Ag-110m and <36 % of the added Pb-210 remained i n the dissolved (i.e. <50 kDa) phase, with the remainder partitioned a mong different fractions of the suspended particulate matter, includin g the fraction containing the microzooplankton. Naturally occurring Ag and Pb concentrations in Hudson River suspended particulate matter sh owed a fractionation pattern similar to that of the radioisotopes. Com parison of Ag/Al and Pb/Al ratios in particles from the lower Hudson i ndicated an enrichment factor of 1 to 2 orders of magnitude for these metals over particles from other estuaries.