Prediction Of Water Temperature Change In Qinghai Lake And Its Effect On Gymnocypris Przewalskii Under Climate Change

Qinghai Lake is an important water body t hat maintains the ecological security of the Qinghai-Tibet Plateau,and climate change has increasingly affected the lake environment and aquatic ecosystem on the Qinghai-Tibet Plateau.As the thermal conditions change of Qinghai Lake change,the resources of the only aquatic economic fish in the lake,Gymnocypris przewalskii,are threatened to a certain extent,it is important to clarify the characteristics of future lake temperature changes in Qinghai Lake to maintain local ecological security.However,there is a lack of research on the survival temperature indicators of Gymnocypris przewalskii,the thermal conditions of Qinghai Lake,the evolution of lake temperature under climate change,and the suitability of living temperature of Qinghai Lake naked carp.Based on this,this paper selected Qinghai Lake as the research area,combined with literature research,to sort out and determine the suitable temperature range for the survival of Gymnocypris przewalskii,using one-dimensional Freshwater Lake Model（FLake）as the research tool,we used the lake temperature observation data of Qinghai Lake,MODIS surface temperature data,reanalysis data and the conventional meteorological data of three global climate models in the Sixth International Coupled Model Comparison Profram（CMIP6）to access the ability of the global climate models to simulate historical climate change in Qinghai Lake was evaluated.We assessed the ability of the GCMs to simulate the historical climate change of Qinghai Lake using conventional meteorological data from three GCMs of the 6th International Coupled Model Interaction Program（CMIP6）,predicted th e evolution of Qinghai Lake temperature under four different emission scenarios,and elucidated the driving mechanism of lake temperature change and its possible influence on the future growth temperature of Qinghai Lake nudibranchs.Meanwhile,after modif ying the FLake model parameters,we simulated and evaluated the water temperature changes at the inlet of Qinghai Lake and the suitability of Gymnocypris przewalskii breeding,and explored the future river water temperature trends and possible impacts on Gymnocypris przewalskii breeding activities.（1）The upper limit of suitable temperature for the growth of Qinghai Lake naked carp is 20℃,the temperature above 25℃is not suitable for growth.The optimal spawning temperature is 6～17.5℃,no breeding activity above 17.5℃;the suitable hatching water temperature is 16～19℃,above 21℃is not suitable for the hatching of Qinghai Lake naked carp.（2）Reanalysis data and historical meteorological data from the CMIP6 multi-model ensemble are better than indivi dual models.2015～2100,the annual mean lake surface temperature of Qinghai Lake continues to increase under all four scenarios,and due to differences in the Shared Socioeconomic Pathway（SSP）and radiative forcing,the warming rates of lake surface temperature in low emis sion scenario（SSP126）,medium emission scenario（SSP245）,medium to high emission scenario（SSP370）and high emission scenario（SSP585）were 0.17℃·（10a）^-1,0.31℃·（10a）^-1,0.51℃·（10a）^-1and 0.69℃·（10a）^-1,respectively.In the SSP126 scenario,the warming rate of lake surface temperature after 2050 is lower than that in the historical period,while in the SSP245,SSP370 and SSP585 scenarios,the warming rate around 2050 is higher than that in the historical period,in which air temperature is the main dri ving factor for the increase of lake surface temperature.In the future,the monthly and daily maximum lake surface temperature in different stages will appear in August,and in the near future（2020～2040）,the difference between different scenarios is sm all,and the daily average lake surface temperature is basically below 20℃,which will not affect the Gymnocypris przewalskii.In the middle period（2041～2070）,the differences between the scenarios gradually increased,and the Gymnocypris przewalskii would be threatened to some extent.In the long term（2071～2100）,the daily average lake surface temperature in August will basically exceed 20℃,and the daily maximum temperature will even reach 23.21℃,which will cause a serious threat to the growth of Gymnocypris przewalskii.（3）FLake model can well simulate the changes of river water temperature.2015～2100,the warming rates of water temperature at the inlet of Qinghai Lake under four different discharge scenarios of SSP126,SSP245,SSP370 and SSP585 are0.14℃·（10a）^-1,0.30℃·（10a）^-1,0.52℃·（10a）^-1and 0.67℃·（10a）^-1,respectively.It is slightly lower than the change rate of the lake surface temperature,very close to the change rate of the lake surface temperature.In the 21st century,when the rate of SSP126 scenario increases,the water temperature at the entrance of Qinghai Lake will have little effect on the reproduction of Gymnocypris przewalskii.In the middle period,SSP245 and SSP370 scenarios had little infl uence.In the long term,the suitable spawning and hatching time of SSP245 and SSP370 scenarios was advanced and significantly shortened,which affected the breeding activities of Gymnocypris przewalskii to a certain extent.In the high emission scenario SSP5585,the long-term harm degree of SSP245 and SSP370 was reached in the middle term.In the long-term SSP585 scenario,the breeding activities of Gymnocypris przewalskii would be at a high risk.