The Effect Of The Extract Of Carex Cinerea On The Growth And Competition Of Microcystis And Scenedesmus In The Beach Of Poyang Lake

With the development of social economy and the increase of human activities,more and more lakes are overloaded with pollution,water quality is deteriorated and eutrophication is becoming more and more serious,which leads to a large number of phytoplankton blooms.How to effectively prevent and control the algae blooms is an urgent problem to be solved.At present,some achievements have been made in the field of Allelopathy and algal inhibition of aquatic plants at home and abroad,mainly focusing on the influence of a certain aquatic plant on the growth of a single algae.However,there is often a resource competition relationship between algae and algae in the eutrophic water body,which has an important impact on the growth of algae and the formation of water bloom.Therefore,the research on the influence of aquatic plants on the growth and competition of algae It is of practical significance to prevent and control the outbreak of water bloom.Poyang Lake is the largest fresh water lake in China.In recent years,the water quality shows a downward trend,and the Dominant Algae in the lake have been succeeding and increasing gradually.However,lichen ash is one of the dominant plants in the beach of Poyang Lake,with strong growth capacity.In this paper,two kinds of algae,Microcystis aeruginosa and Scenedesmus obliquus,which are common in Poyang Lake,were selected to study the effect of the concentration of the extract of Carex cinerea in eutrophic water on the growth of two kinds of algae under different culture modes(single culture and mixed culture),and the competition relationship between the two kinds of algae and the effect of the extract of Carex cinerea on the growth of two kinds of algae with the change of nitrogen and phosphorus nutrient levels Based on the competitive effects of the two algae,the competitive advantages of Microcystis aeruginosa and Scenedesmus obliquus in the common growth process were discussed.The results are as follows:(1)The results showed that the concentration of allelochemicals and the way of algae culture had significant effect on the growth of Microcystis aeruginosa and Scenedesmus obliquus,and the higher the concentration of the extract,the lower the growth ability of the algae In addition,the extracts of 6.0g/l,12.0g/l and 24.0g/l significantly increased the density of the algae in the mixed culture,which indicated that the above extracts had better application prospects in the treatment of cyanobacteria bloom.(2)Different levels of nitrogen and phosphorus have different effects on competition between Microcystis aeruginosa and Scenedesmus obliquus.Under the medium nutrition level,the existence of Microcystis aeruginosa and Scenedesmus obliquus can stimulate each other's growth,but under the eutrophication level,the mutual inhibition of the two algae is not obvious,while under the super eutrophication level,the competition and inhibition between Microcystis aeruginosa and Scenedesmus obliquus are stronger,and the inhibition ability of Microcystis aeruginosa is stronger.The results showed that Microcystis was easy to become dominant species in the water with medium and low nitrogen and phosphorus concentration,and Scenedesmus was easy to become dominant species in the water with high nitrogen and phosphorus concentration.(3)There were significant differences in the competition between Microcystis aeruginosa and Scenedesmus obliquus under different nutrient levels.In the extracts of 6.0g/l,12.0g/l and 24.0g/l,the presence of Microcystis promoted the growth of Scenedesmus(?<?),and the Scenedesmus occupied the competitive advantage;in the super eutrophic level,the presence of Microcystis inhibited the growth of Scenedesmus(?>?),and the Microcystis occupied the competitive advantage;in the extracts of 48.0g/l and 72.0g/l,the Microcystis and Scenedesmus occupied the competitive advantage Algae from the level of mutual promotion changes to the level of eutrophication,the level of competition and inhibition.Microcystis and Scenedesmus are not easy to grow in the high concentration of nitrogen and phosphorus nutrition and the extract of Carex cinerea.(4)The content of MDA in the cells of Microcystis aeruginosa and Scenedesmus obliquus has a positive correlation with the density of algae.The higher the concentration of the extract,the lower the density of algae.With the increase of the concentration of the extract,the content of MDA in the cells of Microcystis aeruginosa and Scenedesmus obliquus accumulates,which leads to the destruction of cell membrane structure,indicating that the allelochemicals are cells The main cause of death.