Uptake of Cadmium by Marine Bacteria and Transfer to a Deposit Feeding Clam

摘要

The heavy metals that are of most interest in contemporary pollution studies are largely partitioned into or in solid phases in the marine environment, and the bottom sediments constitute the major reservoir. This laboratory study looks at part of one potential pathway whereby sediment-derived cadmium-a toxic element of no known biological utility-may be taken up by the secondary benthos, and then transferred directly to man. Two concentration of inorganic cadmium spiked with 109Cd tracer, were added to mono-specific marine bacteria cultures during the log growth phase. Uptake of the cadmium by or onto the bacteria cells was in the 87 to approximately 100%. These bacteria were subsequently presented as the sole additional food source to batches of deposit-feeding clams (Macoma balthica) maintained in 11C aquaria for periods ranging from 14-54 days. In order to lengthen the contact times, the substrates were renewed periodically to introduce additional supplies of the cadmium-labelled bacteria. The experimental design required that the clams ingest the bacteria as their sole or major food source.