The impact of iron and chelators on Lake Kinneret phytoplankton

The response of natural phytoplankton populations from LakeKinneret to the addition of iron (Fe) and chelator (EDTA) wastested by following growth patterns and determining the algalcomposition initially and at the end of the experiments; algalgrowth rates and yield were measured by in vivo chlorophyllfluorescence. Although the pattern of growth response varied,usually some stimulation of phytoplankton growth rate and yieldwas observed with chelator and/or Fe addition in comparisonto unsupplemented samples. However, the major impact of Fe andEDTA on the phytoplankton appeared to be expressed as changesin the algal population composition. There were clear taxonomicdifferences in the response to Fe addition, which in nearlyall experiments stimulated outgrowth of Bacillanophyta and Chlorophyta,compared with the effect of EDTA alone or with Fe which enhancedthe development of Cyanophyta, in addition to Bacillariophyta.The availability of Fe and/or chelators therefore appears tobe important in determining the composition of the phytoplanktonpopulations in Lake Kinneret and presumably in other aquaticenvironments.