We investigated historical changes in temperature and phytoplankton in Fuxian Lake (FX) and Dianchi Lake(DC), two plateau lakes in Southwest China. We detected sterols and alkyl diols as algal biomarkers (dinoflagellates, diatoms, eustigmatophytes, cyanobacteria, and chlorophyta) in the sediment cores by using GC-MS. We characterized sedimentary organic matter (SOM) via Rock-Eval analysis to obtain TOC, S2, the hydrogen index (HI), and refractory carbon (RC), and measured nutrients such as total phosphorus (TP) and total nitrogen (TN) in the sediment cores. The results showed that the sedimentation rates measured by 210Pb dating ranged from 0.02 to 0.30 g cm-2 yr-1 and 0.07 g cm-2 yr-1 in FX and DC, respectively. In the past 100 years, total phytoplankton biomarker concentrations ranged from 2.25 µg g-1 to 59.1 µg g-1 and from 2.20 µg g-1 to 76.4 µg g-1 in FX and DC respectively. Primary productivity derived from the S2 and HI parameters showed an increasing trend in FX, while it showed a trend of first increasing and then decreasing in DC. Cyanobacteria and chlorophyta were the two dominant phylum in the two lakes. Algal growth was controlled primarily by temperature and nutrient availability. Principal component analysis (PCA) and multiple linear regression analysis showed that the major factors controlling the historical change in phytoplankton growth were TN and temperature in FX and DC.

Multiple organic proxies and lipid biomarkers in the sediment core samples collected from Luoma Lake and Hongze Lake in Jiangsu are used to expound the relationships of global warming with lacustrine productivity and depostion of polycyclic aromatic hydrocarbons. Total organic carbon, S2, and hydrogen index in sedimentary organic matter were obtained with the Rock-Eval analysis. Nutrient status such as total phosphorus and total nitrogen was measured in the sediment cores. The source apportionment modeling and statistical analyses demonstrated that algal organic matter and bacteria organic matter showed an increasing trend and an obvious enrichment effect on PAHs, which was also related to the increasing temperature and algal productivity in the lakes. Global warming enhanced the lacustrine productivity and the accumulation of polycyclic aromatic hydrocarbons. The rapidly increasing ecological risks of PAHs in LM and HZ indicated the impact of global warming and human activities in the last 60 years. Therefore, the internal cycling and the input of contaminants and nutrients in the lakes should be controlled to reduce the algal growth in LM and HZ.