AVAILABILITY OF COPPER FROM PHYTOPLANKTON AND WATER FOR THE BIVALVE MACOMA-BALTHICA .2. UPTAKE AND ELIMINATION FROM CU-64 LABELED DIATOMS AND WATER

The amount of copper taken up via algae and water by Macoma balthica from the Oosterschelde sea arm, S.W Netherlands, was established using the radioisotope Cu-64. As far as we know, this isotope has never been used before in marine food chain studies. As a model food source the marine diatom Phaeodactylum tricornutum was allowed to accumulate Cu-64 for 1 d. These labelled algae were fed to the clams in the presence of the complexing agent EDTA (0.27 mM). EDTA was added to prevent uptake of dissolved Cu-64 that could be leaking from the labelled diatoms. In control experiments, unlabelled diatoms were fed to M. balthica in the presence of dissolved Cu-64 (with and without EDTA) in order to assure a similar filtration activity. In repeated experiments with varying particulate/dissolved copper ratios, uptake through food always turned out to be at least as efficient as uptake from the water. It was concluded that Cu, associated with food, is well available for uptake by M. balthica.