Spatial-temporal Distribution And Sources Of Organic Matter In Caohai Lake,Guizhou Province

Lakes are important aquatic ecosystems,and there is a strong material energy exchange with terrestrial ecosystems.The lake carbon and nitrogen cycles have an important impact on the biogenic element cycle and lake ecosystems.Organic carbon and nitrogen are important components of lake carbon.Among them,the sources of organic carbon are complex,there are many influencing factors,there are internal and external sources.Further understanding of organic carbon can provide important scientific data for the sources of lake water pollution and the mechanism of carbon and nitrogen migration and transformation.There are few studies on the carbon cycle of plateau grass type shallow lakes in China.Therefore,a deep understanding of the process of lake carbon cycle can provide a basis for formulating reasonable eutrophication control strategies.This study selects the Caohai Nature Reserve in Weining County,Guizhou Province as the research object.Measuring the concentrations of Particulate Organic Carbon(POC),Particulate Organic Nitrogen(PON),Dissolved Inorganic Carbon(DIC),Dissolved Organic Carbon(DOC)and their stable isotopes in the water body during the wet season,normal season and dry season.Revealing the spatial and temporal distribution of different forms of carbon in grassland and seawater Controlling factor.Finally,by determining the potential end-member values of the particulate matter,the SIAR isotope model is used to quantitatively trace the source of the water particulate organic matter.The main conclusions were as follows:(1)The water chemistry index of Caohai Lake has obvious seasonal changes,which is mainly controlled by the photosynthesis of aquatic plants in the lake.(2)The POC contents of Caohai has obvious seasonal difference,which is expressed in wet season>normal season>dry season,showing a trend of gradually decreasing POC contents from east to west.The distribution of POC contents is mainly controlled by algal biomass,and foreign sources and sediment resuspension are also important sources.The seasonal difference of the ?13CPOC values of the Caohai is obvious,and the ?13CPOC values of wet season is about 2.2‰ more positive to the dry season.The POC of grassland seawater mainly comes from submerged plants and is controlled by photosynthesis.The spatial distribution of ?13CPOC is also affected by algae distribution and external input.(3)The seasonal difference of PON contents in Caohai is not significant,and its content change is mainly affected by human input,animal excretion and plant decomposition.There is no obvious seasonal change in the ?15N value of Caohai,and the distribution characteristics of the three periods are almost the same.Its spatial distribution is mainly affected by the pollution of different lakes and the distribution characteristics of aquatic plants and algae.(4)The DIC contents of Caohai seawater has obvious seasonal changes,which is expressed in wet season<normal season<dry season.The seasonal difference of DIC content is mainly controlled by the photosynthesis of aquatic plants,and the spatial variation is controlled by the distribution of aquatic plants.The ?13C value of DIC in Caohai Sea has obvious seasonal difference.The dry season is more positive to the normal season,and the normal season is more positive to the wet season.The ?13CDIC of the water body in the dry season is mainly controlled by the isotopic fractionation caused by the CO2 exchange at the water-gas interface;The ?13CDIC of the water body in the wet season and normal season is mainly controlled by the terrestrial input.(5)The seasonal change of DOC content in Caohai water body is significant,which is expressed in wet season>normal season>dry season.Its contents is affected by aquatic plant activity and foreign input.The ?13CDOC values of Caohai in the three periods are not much different,indicating that the sources of DOC in Caohai are close at different periods;?13CDOC is mainly controlled by photosynthesis of submerged plants in the space.(6)The particulate matter of the water body of Lake Caohai is mainly controlled by the resuspension of sediments and submerged plants during the wet season;the particulate matter of the water body in the normal season is mainly controlled by the resuspension of sediments and emergent plants;The water particles in the dry season are mainly controlled by sediment resuspension.The source of particulate organic matter in the eastern lake area of Caohai is mainly controlled by fecal sewage and submerged plants;the source of particulate organic matter in the central lake area is mainly controlled by sediments and submerged plants;the source distribution of particulate matter in the western lake area is relatively even.