Maximum lake surface water temperatures changing characteristics under climate change

Lake surface water temperature (LSWT) plays an important role in the metabolism of aquatic organisms, and is also an important indicator in lake ecosystems which affects the ecology and biogeochemical processes of lakes. The current research mainly focuses on the long-term trends of LSWT and the impact of climate warming on LSWT. Researchers have not paid enough attention to the study of extreme changes in trend of LSWT. An ice-free lake in China called Dianchi Lake was selected as our research area. We carried out a quantitative analysis of and provided a discussion on the changes in the maximum lake surface water temperature (MLSWT) from 2001 to 2018 at two timescales (month and year) based on MODIS 11A2 composite product data and water temperature environment of cyanobacteria outbreaks. The results showed that the MLSWT of Dianchi Lake increased between 2001 and 2018 and continued to exceed the temperature threshold (17.6°C) for cyanobacterial outbreaks during some timeframes and that the duration of high temperatures also increased. This phenomenon will extend the suitable growth period of cyanobacteria and will have a complex and long-term impact on water quality, the lake ecological environment, and the growth of aquatic organisms.