To address the threats of global warming and human activities to freshwater shallow lake ecosystems, it is imperative to comprehend the long-term evolutionary history of lake ecosystems under external forces. However, short-term records are insufficient to distinguish the effects of climate change and human activities. This study applied n-alkanes in a sediment core retrieved from Lake Nvshan in the Huai River basin in eastern China to investigate ecological changes over the past 1800 years. Carbon isotope compositions of long-chain (C2731n-alkanes revealed that they were mainly derived from floating and submerged plants, which enabled us to monitor the evolution of aquatic macrophytes in lake sediments. Prior to the Little Ice Age, the growth of floating and submerged plants in Lake Nvshan declined steadily, but underwent a significant expansion afterwards. Before ∼1400 CE, the development of aquatic macrophytes was controlled by the hydrological condition, which regulated nutrient supply from the watershed. After 1700 CE, however, anthropogenic activities became the dominant factor influencing the evolution of lake macrophytes, leading to an increase in erosion and nutrient input, potentially resulting in a shift from submerged plants to a system dominated by floating plants and algae. This research emphasizes the effect of various stressors on the long-term development of lake macrophytes, and provides insight into how freshwater shallow lakes can be safeguarded in the face of global changes.

Fluctuations of aquatic macrophytes in a shallow lake in eastern China over the last 1800 years: Evidence from n-alkanes