Cadmium and manganese flux in eelgrass Zostera marina I. Modelling dynamics of metal release from labelled tissues

Release of cadmium and manganese radionuclides from eelgrass leaves and root-rhizomes into seawater and seawater plus 1×10^-4 disodium ethylenediaminetetraacetate (EDTA) was monitored over periods of 6 h following incubations of 1 to 98 h. Flux of both isotopes from tissues is initially rapid and enhanced by the addition of EDTA. The initial release rate is independent of incubation time, indicating desorption of metals from exterior tissue surfaces. High initial release rates become rapidly attenuated. Fitting a power curve to the data proved valuable in inferring uptake capacity of tissues from observed metal release characteristics. In addition to desorption, and diffusion from intercellular spaces, diffusion from cells and biologically controlled release could be described with the aid of curve fits. Manganese apparently is released more slowly during later phases of release than is cadmium, pointing to greater biological accumulation potential.This research was supported by grants to B. H. Brinkhuis from the New York Sea Grand Institute and the Nassau-Suffolk Regional Planning Board, and by a Jessie Smith-Noyes Fellowship and Sigma Xi grant to W. F. PenelloMarine Sciences Research Center Contribution No. 247