Effects of Iron on Growth and Intracellular Chemical Contents of Microcystis aeruginosa

Objective To investigate the effect of iron on the growth. physiology and photosynthesis of cyanobacteria Methods A gradient of iron concentrations was employed to investigate the growth, photo-pigments (chlorophyll A and phycocyanin), and cell chemical contents (C, N, P) of Microcystis aeruginosa in response to different iron additions Results The specific growth rate during the exponential growth phase, as well as the cell chlorophyll A and the phycocyanin content, was limited by iron below 12 3 mu mol Fe L-1 The growth was inhibited when the iron concentration was at 24 6 mu mol Fe L-1 The cell chlorophyll A and the phycocyanin content were saturated when the iron concentration was above 12 3 mu mol Fe L-1 and declined slightly at 24 6 mu mol Fe L-1 At a low iron concentration (about 6 15 mu mol Fe L-1 and less). the cell nitrogen and carbohydrate content were iron limited, and the variation of the cell phosphorus content was similar to that of the nitrogen and carbohydrate, with a transition point of 12 3 mu mol Fe L-1 Conclusion The variation of cynobacteria growth is synchronous with that of the photo-pigments or the cell chemical content, and there exist relationships among photosynthesis, growth and internal chemical content, which could be useful for the growth estimation from the cell characteristics