Ultrastructural changes in Dunaliella minuta following acute and chronic exposure to copper and cadmium.

The ultrastructural changes taking place after short-term acute exposure to copper, cadmium and a combination of the two metals were examined. Additionally, the effects of long-term (8 months) exposure to ambient concentrations of these metals were investigated. Exposure to 0.34 microM cadmium affected the photosynthetic potential of this alga, by reducing the relative volume of the chloroplast by 23.27%. It also led to 74.6% increase in the relative volume of starch granules. Cells challenged with 0.34 microM cadmium and 7.57 microM copper had 33.49% larger volumes than controls, and their relative lipid volumes increased by 170%. In contrast, the relative volume of their pyrenoids decreased by 41.46%. Similar results were obtained after chronic exposure to 4.9 x 10(-4) microM copper with the relative volume of the pyrenoid being 28% smaller than the controls.