Characteristics of Basic Physicochemical Characteristics of Microcystis Colony Formation in the Critical Causes of Algal Blooms
Eutrophic water often experience algal blooms,with Microcystis being the dominant species that triggers algal blooms.It usually exists in the form of colonies,and the formation of Microcystis colonies is the critical causes in the important stages leading to algal blooms.This purpose is to reveal the mechanism of blooms through the morphological characteristics of Microcystis colony formation and the physicochemical properties of extracellular polymeric substances(EPS).The results showed that Ca2+effectively induces the formation of Microcystis colonies,which consisted of three stages:cell aggregation,colony amplification,and colony maintenance.The stages of cell aggregation and colony amplification were dominated by the cell adhe-sion mechanism.Individual cells rapidly aggregated to form loose Microcystis colonies within 1 day of the ex-periment starting.The experimental groups with Ca2+mass concentrations of 100 mg/L,500 mg/L,and 1 000 mg/L achieved the maximum median diameter of 28.12 μm,29.40 μm,and 33.26 μm at 5 d,3 d and 3 d,respectively.During the colony maintenance stage,large colonies broke up into smaller ones,but the algal cells preserve the colony shape by cell division mechanism,and the median diameter was stable at 18.19 μm to 20.39 μm by day 9.Extracellular polymeric substance of different components played unique function in the three stages of Microcystis colony formation.Soluble extracellular polymeric substance plays a key role in the cell aggregation stage,whereas bound extracellular polymeric substance contributes significantly to ampli-fication and maintenance of Microcystis colony.This proposes a method for evaluating Microcystis colony morphological characteristics while also analyzing secretion patterns and physicochemical properties of extra-cellular polymeric substance.It emphasizes the role of soluble extracellular polymeric substance in the colony aggregation,providing a theoretical foundation for understanding the mechanism and action of Microcystis colony formation in the early stages of algal blooms.
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