The 64 cm sediment diatoms, representing a timescale from 1938 to 2020 A.D., were analyzed to reconstruct the evolutionary history of Yilong Lake in Yunnan Province, China. Some main diatoms with important environmental indicating significance were selected through Principal Component Analysis (PCA). In addition, their ecological affinities indicated that the PCA sample scores 1 and 2, which were the main factors affecting the environmental change of Yilong Lake, corresponded to pH value and eutrophication, respectively. According to the pH value and the eutrophication data obtained from the PCA, the lake had successively gone through six major stages. Though high pH value and eutrophication had been the main characteristics for a long time, the quality of Yilong Lake was gradually improved through planned treatment in the last decades. The drying up of the lake under natural conditions resulted in an increase in pH values and high eutrophication. Meanwhile, the impact of human activities played a more important role in lake evolution: unreasonable human development in lake basins led to abnormal changes in pH values and eutrophication, and planned and targeted treatment could restore the natural state of the lake.

To investigate the influence of land use landscape patterns on lake water quality in the basin, the land use and water quality data of the Yilong Lake Basin from 1993 to 2023 were analyzed with a geographic information system, remote sensing, and landscape ecology methods in this research. The results show that (1) the land use landscape pattern and water quality of the Yilong Lake Basin had significant changes: the lake surface area, farmland, and shrubland declined, with grassland showing the sharpest decrease and serving as the main source of conversion to other land types, while forest land expanded and built-up land increased by five times. The landscape pattern analysis showed that the aggregation degree of the core habitat in the basin increased and the landscape had decreased patch density and increased heterogeneity. Regarding water quality, the concentrations of total nitrogen (TN), total phosphorus (TP), and ammonium nitrogen (NH₄⁺-N); permanganate index (I_Mn); and biochemical oxygen demand over 5 days (BOD₅) decreased. Furthermore, the concentration of dissolved oxygen (DO) increased and the concentration of chlorophyll-a (Chl-a) fluctuated for a long time but did not decrease dramatically at the end of the period compared with the beginning. In general, the eutrophication degree of Yilong Lake slightly decreased. (2) The landscape configuration strongly shaped the water quality: the redundancy analysis (RDA) revealed that the edge density (ED), landscape shape index (LSI), largest patch index (LPI), and patch density (PD) were negatively associated with the eutrophication of Yilong Lake (TN, TP, NH₄⁺-N, Chl-a), whereas the contagion index (CONTAG) was positively associated; the Shannon’s diversity index (SHDI) was closely linked with TN and I_Mn but negatively with DO; and the patch cohesion index (COHESION) had a low interpretation power for water quality changes. In particular, larger and more cohesive ecological patches supported a higher DO, while an increased patch density was linked to an elevated I_Mn and reduced DO. These results indicate that the restoration of key ecological patches and enhanced landscape cohesion helped to improve the water quality, whereas increased patch density and landscape heterogeneity negatively affected it. (3) In the past 30 years, the ecological management and protection work on Yilong Lake, such as returning farmland to forests and lakes, wetland restoration, and sewage pipe network construction, achieved remarkable results that were reflected in the change in the relationship between land use landscape pattern and water quality in the basin. However, human activities still affected the dynamic evolution of water quality: the expansion of built-up land increased the patch density, the reduction in shrubland and grassland weakened natural filtration, and the rapid urbanization process introduced more pollution sources. Although the increase in forest land helped to improve the water quality, the effect was not fully developed. These findings provide a scientific basis for the management and ecological restoration of plateau lakes. Strengthening land use planning, controlling urban expansion, and maintaining ecological patches are essential for sustaining water quality and promoting the coordinated development of the ecology and economy in the Yilong Lake Basin.

Macrophytes play a crucial role in maintaining the health of lake ecosystems. A thorough understanding of their long-term evolutionary processes and patterns is of great theoretical and practical significance for ecosystem restoration and mitigation of lake eutrophication. The succession process and driving factors of macrophytes in the Lake Erhai aquatic ecosystem were systematically analyzed using the investigation of macrophytes, literature research, and classification. A survey conducted in July 2022 showed that the macrophyte community in Lake Erhai is seriously degraded, with species numbers notably lower than historical levels from a decade ago (2011). The distribution area declined by over 70% compared to its peak in the 1980s. Over the past 60 years, the macrophyte community of Lake Erhai has undergone successive processes, including expansion, peak, decline, and stabilization. The dominant populations gradually transitioned from being indicative of clean water to pollution-tolerant species. The driving factors of the macrophytes succession of Lake Erhai were the development of cascade hydropower projects on the Xi’er River and the increased outflow capacity of Lake Erhai; these have resulted in substantial fluctuations in water levels, the eutrophication of the lake, pollutant discharge exceeding Lake Erhai’s environmental capacity, and substantial climate change in the Lake Erhai basin. Our research provides important theoretical references for ecological restoration and management of early eutrophic lakes in China.

Identification and analysis was conducted on the diatoms from the 19 cm sediment of the P6-10 core, drilled from China’s 29th Antarctic Expedition, to attempt to semi-quantitatively reconstruct the annual sea surface temperature (SST) of Prydz Bay from 1893 to 2013. There were 30 species within the 12 genera of diatoms found, and the main contributors were Fragilariopsis curta, F. cylindrus, F. sublinearis, F. ritscheri, and Thalassiosira antarctica. They were divided into three categories based on their ecological affinity. The percentages of four specific species, i.e., F. curta, F. cylindrus, F. ritscheri, and F. separanda, which might be low SST indicators, were added together to represent the SST of Prydz Bay. With the help of cluster analysis, diatom assemblages were divided into diatom zones. Therefore, SST changes were divided into five stages by both the percentage of those four diatom species and the diatom zones: the high-temperature stage from 1893 to 1903, the cooling stage from 1903 to 1936, the stable and warm stage from 1936 to 1983, the low-temperature stage from 1983 to 1996, and the temperature rising stage from 1996 to 2013. On the multidecadal scale, SST change was affected by adjustments to solar radiation. On the contrary, the ENSO events mainly affected SST on the interannual scale. In addition, regarding the unique geographical environment (such as regional atmospheric circulation and a wind field) in Prydz Bay, volcanic eruptions and the like also played important roles in some exceptional periods.