title: Electrolyte Cations Binding with Extracellular Polymeric Substances Enhanced Microcystis Aggregation: Implication for Microcystis Bloom Formation in Eutrophic Freshwater Lakes.
abstract: The hydrodynamic and structural properties of Microcystis extracellular polymeric substances (EPS) in electrolytes with different valences and ionic strengths were investigated via using dynamic light scattering, the fluorescence excitation emission matrix coupled with parallel factor (EEM-PARAFAC) analysis, two-dimensional correlation spectroscopy (2D-COS), and cryogenic transmission electron microscopy (Cryo-TEM). The hydrodynamic diameters of EPS colloids exhibited no variation for monovalent NaCl but a substantial increase for divalent CaCl2 and MgCl2. However, the negative electrophoretic mobilities for all complexes indicated that charge neutralization would not be the main mechanism for EPS aggregation. Application of EEM-PARAFAC and 2D-Fourier transform infrared (FTIR)-COS revealed obvious electrolyte binding potential with both fluorescent phenolic and aromatic compounds and nonfluorescent polysaccharides. The complexation model showed that divalent Ca(2+) and Mg(2+) exhibited a strong binding capability with phenolic -OH, aromatic C═C, and polysaccharide C-O groups, while the monovalent electrolyte exhibited negligible association with these groups. Such a strong complexation can bridge each individual biomolecule together to form EPS aggregates and Microcystis colonies, as supported by in situ Cryo-TEM and light microscope observation, respectively. Given the increased concentration in natural ecosystems, electrolyte cations, especially divalent cations, would play increased roles in Microcystis bloom formation and thus should be considered.
authors: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences , 73 East Beijing Road, Nanjing 210008, China.|Key Laboratory of Integrated Regulation and Resource Development of Shallow Lakes, Ministry of Education, College of Environment, Hohai University , Nanjing 210098, China.
authors: Huacheng
authors: H
authors: Xu
authors: College of Materials Science and Engineering, Nanjing Forestry University , Nanjing 210037, China.
authors: Hua
authors: H
authors: Lv
authors: College of Materials Science and Engineering, Nanjing Forestry University , Nanjing 210037, China.
authors: Xin
authors: X
authors: Liu
authors: Key Laboratory of Integrated Regulation and Resource Development of Shallow Lakes, Ministry of Education, College of Environment, Hohai University , Nanjing 210098, China.
authors: Peifang
authors: P
authors: Wang
authors: State Key Laboratory of Lake Science and Environment, Nanjing Institute of Geography and Limnology, Chinese Academy of Sciences , 73 East Beijing Road, Nanjing 210008, China.
authors: Helong
authors: H
authors: Jiang
mesh_terms: D002412:Cations; D004573:Electrolytes / Q000378:metabolism; D060106:Lakes; D046931:Microcystis / Q000378:metabolism*; D011108:Polymers / Q000737:chemistry
chemical_list: D002412:Cations; D004573:Electrolytes; D011108:Polymers