The Effects of Iron on Growth and Physiology of the Cyanobacterium <i>Microcystis aeruginosa</i>

To determine the effects of iron on the growth of the cyanobacterium Microcystis aeruginosa, a series of growth and iron uptake experiments were conducted. Studies included the effects of iron and organic iron-binding chelators on batch cultures of known bacteria and on the natural community of Lake Erie, where blooms of M. aeruginosa have been documented since 1995. Results of growth rate studies under iron limitation suggest that M. aeruginosa uses an active, high-affinity transport system to acquire iron after a lag time at initial limitation. Further studies indicate that cells continue to take up nutrients and possibly metals, while their growth rate is slowed prior to activation of the high-affinity transport system. Studies to observe iron effects on the natural community of Lake Erie demonstrate that 60% of the iron uptake occurs in the picoplankton (0.2 - 2 μm size fraction) and that DFB is effective at sequestering iron in natural communities.