| In recent years,cyanobacterial bloom caused by lake eutrophication and global climate change,has become a global environmental and ecological issue.The influence of environmental factors on growth and physiological state of Microcystis is an important basis of understanding the formation of cyanobacterial bloom.Although the current methods can be used to quantitatively analyze the growth rate of cyanobacteria,but they can not be used to indicate the growth and physiological state of cyanobacteria.Several studies have shown that environmental factors can significantly affect the composition of pigment and fatty acids in Microcystis.In this thesis,the composition of pigment and fatty acids were be used to imply environmental factors and physiological state of Microcystis.The effects of environmental factors on the basic physiological indictors of Microcystis cells were aslo analyzed.Afterwards,the physiological state of Microcystis in Taihu Lake was analyzed and their limiting factors were also evaluated.The main results of this thesis are as follows:?1?The macromolecular indicator TOC/protein of Microcystis cells increased with the increasing of temperature.TOC/protein was up to 0.94 at the temperature of 32?.Increasing light intensity leads to decrease in RNA/protein.Polysaccharide/protein firstly increased and then decrease along with the increase of nutrient concentration,?2?With the increase of temperature,?-carotene/protein increased from 18 to 32?,zeaxanthin/protein increased from 18 to 25?.When the temperature was 18?,?-carotene/protein abtained a minimum was 0.03×10-2.However,increasing light intensity resulted in an increase in zeaxanthin/protein.Chlorophyll a/protein also increased with increasing nutrient concentration.The maximum value is 1.9×10-2 at the N concentration of 64 mg L-1;?3?The main fatty acids of Microcystis in culture were C16:0?palmitic acid?and?-C18:3?linolenic acid?,which accounted for 50%70%and 14%30%of the total lipid content,respectively.The content of C16:0 firstly decreased and then increased win increasing temperature.Additionally,?-C18:3 content firstly increased and then decreased with the increase of nutrient concentration.?4?From September 2018 to March 2019,the zeaxanthin/protein and chlorophyll a/protein of Microcystis in Lake Taihu increased firstly and then decreased.Its fatty acids were mainly C16:0?palmitic acid?and C18:1?oleic acid?,in which C16:0 decreased firstly and then increased,but C18:1 showed the opposite trend.Our results suggested that zeaxanthin/protein and oleic acid content could be used as the main indicators of temperature limitation of Microcystis in Lake Taihu.Chlorophyll a/protein could be used as an indicator for N-limitation. |
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