Study On The Indication Of Submerged Macrophytes On Ammonia Nitrogen Concentration In Dianchi Lake Basin

Most of lakes in China face the threat of water eutrophication,and the decline and disappearance of submerged macrophytes in eutrophic lakes are common.The increase of pH is an important factor in the intensification of eutrophication,Ammonia nitrogen is the main nitrogen source of eutrophication,which is the direct absorption and utilization of nitrogen in submerged plants.We suspect that submerged plants may be sensitive indexes of ammonia nitrogen concentration change.In this paper,The response models of submerged macrophytes to ammonia nitrogen concentration in water were studied under different pH values.To explore the dominant factors leading to the decline and disappearance of submerged plants and submerged plants were used as indicator organisms for ammonia nitrogen concentration change.Which can further evaluate the eutrophication status of lake water and provide scientific basis for the restoration of submerged macrophytes and water environment management.we investigate the ammonia nitrogen concentration in submerged plant death in different pH environment,mainly through cultivating submerged macrophytes(Hydrilla verticillata,Ceratophyllum demersum and Potamogeton pectinatus)under the condition of indoor,and combining with field investigation data of submerged macrophytes,water quality monitoring data and related mathematical statistics analysis results,To investigate the indication of submerged macrophytes to ammonia nitrogen concentration in water under different pH values.we find the indicator organisms of ammonia nitrogen concentration in the streams flowing into Lake Dianchi(River Chuanfang,River Daqing,River Hai,River Baoxiang).The main research finding are as follows:(1)There are five kinds of submerged macrophytes in the streams flowing into Lake Dianchi,which are Hydrilla verticillata,Ceratophyllum demersum,Potamogeton pectinatus,Potamogeton crispus and Ottelia acuminate.There are significant differences in the species and community characteristics of submerged plants in different rivers.Hai river without any submerged plant growth,Hydrilla verticillata is the dominant species of the lower reaches of the Chuanfang river andthe Daqing river,Ceratophyllum demersum and Potamogeton pectinatus are the dominant species of the Baoxiang river and Ottelia acuminat is only in the Chuanfang river.(2)The results of mathematical statistics show that ammonia nitrogen and pH are the dominant factors of water pollution in the streams of Lake Dianchi basin,Ammonia nitrogen is the most important environmental factor that drives submerged plant distribution characteristics and community structure changes,and the correlation between ammonia nitrogen and submerged macrophytes is the most significant.Ceratophyllum demersum and Potamogeton pectinatus prefer eutrophic and alkaline environments compared with Hydrilla verticillata.(3)Indoor culture found that low concentrations of ammonia nitrogen promote submerged plant growth,but high concentrations of ammonia nitrogen inhibit its growth,Hydrilla verticillata,Ceratophyllum demersum and Potamogeton pectinatus have a certain tolerance to ammonia nitrogen concentration,and the tolerance of Potentilla anserina is the strongest,followed by the tolerance of Ceratophyllum demersum and the tolerance of Hydrilla verticillata is the weakest,but high concentration of ammonia nitrogen inhibits the growth of submerged macrophytes and even leads to its death.The field survey found that the water body has a ammonia nitrogen concentration of below 0.5mg/L in the river reach in which Hydrilla verticillata as dominant species,Ceratophyllum demersum and Potamogeton pectinatus are the occasional species.When the water body has a ammonia nitrogen concentration rise to 0.5~1mg/L in the river reach in which Hydrilla verticillata as dominant species,Ceratophyllum demersum and Potamogeton pectinatus are common associated species.The water body has a ammonia nitrogen concentration of1mg/L~3mg/L in the river reach in which Ceratophyllum demersum and Potamogeton pectinatus as dominant species,Hydrilla verticillata are the occasional species.the river water has a ammonia nitrogen concentration of more than 8 mg/L in the river reach in which Hydrilla verticillata,Ceratophyllum demersum and Potamogeton pectinatus have completely disappeared.The analysis results are consistent with the results of indoor culture,The presence or absence of Hydrilla verticillata,Ceratophyllum demersum and Potamogeton pectinatus and itscommunity structure change are sensitive to the change of ammonia concentration in water.(4)The effect of ammonia nitrogen concentration on the mortality of submerged macrophytes is limited by pH value.When the pH value increases,leading to submerged plant death of ammonia nitrogen concentration threshold decreased.When the pH value increases,the ammonia nitrogen concentration resulting in the deaths of submerged macrophytes is reduced.For example,as the pH rises from 7 to8.5,the lowest ammonia nitrogen concentration resulting in the death of Hydrilla verticillata is reduced from 12mg/L to 2mg/L,the lowest ammonia nitrogen concentration resulting in the deaths of Ceratophyllum demersum is reduced from more than 16mg/L to 3mg/L,and the lowest ammonia nitrogen concentration resulting in the deaths of Potamogeton pectinatus is reduced from more than 16mg/L to 8mg/L.Therefore,submerged plants decline and disappear,is the result of water quality indicators of ammonia nitrogen and pH combined effect.There have a good response to the changes of ammonia nitrogen concentration in the water,and under different pH conditions,there is a large difference in the response pattern.The preliminary results of this study show that the appearance or not of Hydrilla verticillata,Ceratophyllum demersum and Potamogeton pectinatus and the changes of community can be used as a aquatic bioindicators of the pollution of ammonia nitrogen concentration in water environment.Therefore,control of pH and ammonia nitrogen concentration in water ecosystem pollution control of lake ecosystems is a powerful measure to control the decline and disappearance of submerged plants.This is also an important measure to maintain the biodiversity and stability of the lake water ecosystem.