Cadmium and Zinc Toxicity and Synergism to Floating Aquatic Plants

Abstract Floating aquatic plants have been used in a study of the uptake, toxicity and synergism of cadmium and zinc. Both of the species used were found to accumulate the metals, from even very low levels in solution. Cadmium at 0.01 p.p.m. had an inhibitory effect on growth; and 0.1 p.p.m. was enough to cause death. A concentration factor of up to 9500 times occurred; with clear implications of potential food chain effects. Interspecific competition was found to be a further factor influencing metal toxicity. In natural ‘field’ situations, biological competition is the norm. Cadmium and zinc acted synergistically together. Zinc markedly increased the inhibitory effect of cadmium, even though it was itself stimulatory. The presence of one metal also increased the uptake of the other The ecological implications are discussed.