Competitive Effects of Calcium and Magnesium Ions on the Photochemical Transformation and Associated Cellular Uptake of Iron by the Freshwater Cyanobacterial Phytoplankton Microcystis aeruginosa

• DOI: 10.1021/acs.est.5b01583
• Publication Date: 2015-07-01T15:03:27Z
• Authors: Manabu Fujii; Anna C. Y. Yeung; T. David Waite
• Keywords: Ethylenediaminetetraacetic acid; Microcystis aeruginosa

Photochemical reduction of iron and uptake by Microcystis were investigated in a freshwater medium (pH 8) containing range calcium (Ca) magnesium (Mg) ion concentrations (0.002–20 mM). In the chelator ethylenediaminetetraacetic acid (EDTA), 50-fold increases net photochemical formation rates unchelated ferrous (Fe(II)′) observed as concentration or metal (Me) was increased to exceed EDTA. Kinetic modeling transformation processes indicated that facilitated Fe(II)′ is attributed Me-promoted photoreductive dissociation ferric iron-EDTA complex. Suwanee River fulvic acid, contrast, competitive effect Me on appears be negligible due weak binding affinities Me. The cellular rate EDTA-buffered system ∼3-fold excess condition where observed, whereas presence resulted decrease (by up 5-fold). likely caused transporters other entities involved intracellular transport. findings this study indicate significant Ca Mg natural waters Microcystis, with magnitude depending strongly ligand type.