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The influence of two metals, copper and cadmium, was studied on the growth and ultrastructures of cyanobacteriumAnabaenaflos-aquaegrown at three different temperatures: 10°C, 20°C, and 30°C. The highest concentration of chlorophyllawas observed at 20°C and the lowest at 10°C. Both toxic metal ions, Cu2+ and Cd2+, inhibited growth of the tested cyanobacterium. Chlorophyllaconcentration decreased with the increase of metal concentration. A 50% decrease in the growth ofA. flos-aquaepopulation, compared with the control, was reached at 0.61 mg l-1 cadmium and at 0.35 mg l-1 copper (at 20°C). Copper at all temperatures tested was proven to be more toxic than cadmium. At 3 mg l-1, the lysis and distortion of cells was observed; however, after incubation at 9 mg l-1 cadmium, most of the cells were still intact, and only intrathylakoidal spaces started to appear. Copper caused considerably greater changes in the protein system ofA. flos-aquaethan did cadmium; in this case, not only phycobilins but also total proteins were destructed. The aim of this study was also to identify the place of metal accumulation and sorption in the tested cyanobacterium. Analysis of the energy-dispersion spectra of the characteristic x-ray radiation of trichomes and their sheaths showed that cadmium was completely accumulated in cells but was not found in the sheath. Spectrum of the isolated sheath after treatment with copper exhibited only traces of the metal, but isolated cells without a sheath showed a high peak of copper. [ABSTRACT FROM AUTHOR]