Study On Adsorptions Of Microcystis Aeruginosa To Some Nutrient Elements

According to the survey of the United Nations Environment Programme (UNEP),30%to40%of the world water body is in a state, of eutrophication. And in these water bodies, blue-green algal blooms, whose dominant species is Microcystis has become a serious environment disaster. However, how did Microcystis become the dominant species in the blooms while studies have found that the water body is also suitable for many other kinds of algae to grow. The detailed mechanism will need to be further gone into. Algae blooms needs adequate nutrition while Microcystis blooms can move vertically and horizontally in natural water body under the effect of wind, water and the pseudo null cell. That often causes a rapid change of nutritional environment. Therefore, the ability to quickly acquire large number of nutrition is particularly critical for Microcystis to become dominate species when they get go the new environment. This paper comparatively studies N-and P-adsorption in different environments of two different forms of Microcystis and strains of Chlorella, and to further explore the Microcystis cell wall polysaccharides in nutrient adsorption process.The results showed that Microcystis achieved large N-and P-adsorption in a short period of time (30min) at different nutrient concentrations, this ability was significantly higher than that of Chlorella. Groups of Microcystis has notable higher capacity on N-and P-adsorption than that of single cell algae, and the adsorption increased remarkably as the nutrient concentration in the environment raised. As the main components of algae call wall, extracellular polysaccharide is higher contained in Microcystis group than other algae and single cell Microcystis, and these extracellular polysaccharide had apparent adsorption ability in some metal ions (such as Ca, K, Mg etc.), inorganic nitrate (NO3-, NH4+) and inorganic phosphate (PO43-). These results suggest that extracellular polysaccharides help Microcystis to adsorb nutrient in the environment.pH and temperature has an effect on N-and P-adsorption of Microcystis to a certain degree, and the effect is more remarkable when the element concentration of N and P is low. High pH inhibit nitrate adsorption, but significantly promote ammonium and phosphate adsorption of Microcystis. This effect consists with the fact that high pH promotes nitrate reductase and inhibits alkaline phosphatase activity. This may be the result of long-term adaptation of pH rising in the environment which was caused by strong photosynthesis. Low temperature is favorable for Microcystis to adsorb nitrate and ammonium salt, is not conducive to the adsorption of phosphate.The above findings show that the ability of contending for nutritional elements in the environment of Microcystis is higher than that of other algae, and it is still higher of Microcystis group than that of single cell Microcystis, this has a positive significance to its rapid growth and the formation of the absolute dominant species.