With the socio-economic development and increased occurrence of extreme climate,many lakes in Yunnan Province have experienced severe threats such as water quality deterioration and degradation of ecological and environmental functioning.To identify the main environmental stressors threatening the subtropical large and shallow lakes,we conducted multi-proxy sediment analyses for Lake Qilu,including the application of physio-chemical(grain size,nutrients) and biological(pigments,diatoms) indicators.Combined with modern meteorological monitoring and lake survey data,we reconstructed a two-century history of hydrodynamic changes,cyanobacteria bloom and lake eutrophication,and identified the driving factors for the succession in diatom community structure.The composition of sediment grain sizes generally remained stable until 1958 with a relatively high content of fine clays before showing frequent fluctuations and a rapid increase of coarse particles after the 1960s.The construction of a catavothre draining project led to a stronger control of water level and hydrological fluctuation in Lake Qilu,resulting in a smaller magnitude of grain size fluctuation and a lower content of sandy components during the period of 1981-2000.More recently,both lake dredging and a continuous decrease of regional precipitation caused strong fluctuations of grain size components and a higher content of sandy sediments.The sediment pigment content,an indicator for lake production,increased slowly since the middle 19th century before showing an accelerating trend after the 1960s.During the period of 2000-2005,the dredging of the shallow lake basin significantly decreased the nutrient release from lake sediments,resulting in an abrupt drop of algal production.The spike of cyanobacterial pigments may suggest the existence of massive cyanobacterial blooming in Lake Qilu around the years of 1998,2008 and 2012-2013.Multivariate analyses further showed that diatom community composition has significantly shifted several times with a sustained decreasing trend in the percentage of benthic diatoms.While nutrient enrichment played a major role in structuring diatom assemblages over time,the anthropogenic regulation of lake hydrology and habitat availability were also found to synergistically affect the community succession of diatoms.Our multi-proxy results revealed that a combination of increased nutrient control,reduced hydrological regulation and enhanced climate mitigation should be applied altogether for sustainable management and ecological restoration of subtropical large lakes in Southwest China.