Effects of Fe~(3+) on growth and photosynthesis of microcystis aeruginosa

The effects of Fe~(3+) concentrations changed between 0～30?000?nmol/L on the growth,biochemical composition and the photosynthesis of microcystis aeruginosa were studied.Ambient levels of physical factors in natural blooms and in BG11 media were used in batch cultures.The results showed that the growth and the biochemical composition(chlorophyll a and protein contents) were limited when Fe~(3+) was below 10?nmol/L.When the concentration of Fe~(3+) reached to 30?000?nmol/L,the growth of this alga was still restained.The chlorophyll aspecific light-saturated photosynthetic rate(P_m),dark respiration rate(R_d) and the apparent photosynthetic efficiency(α) under Fe-replete conditions were significantly higher than those under Fe-limited conditions,whereas the light saturated point(I_k) and the light compensatory point(I_c) showed the contrary.It is evident that the Fe~(3+) deficiency imposed a restriction on the growth and division of microcystis aeruginosa cells.