Patterns and trajectories of macrophyte change in East China’s shallow lakes over the past one century

Macrophytes play important roles in maintaining ecosystem health and stability of shallow lakes. Better understanding of their long-term dynamics has important theoretical and practical significance for both lake ecosystem restoration and eutrophication control. However, the knowledge about the historical status and changing patterns of macrophytes in China’s shallow lakes is still controversial and lacks systematic research. Here, we reviewed and synthesized the published records of submerged macrophytes from 14 typical shallow lakes in the eastern plain covering the past 100 years. The results suggest that submerged macrophytes have experienced three clear stages of change: rare period (the 1900s-the 1950s), growth period (the 1950s-the 1980s), and recession period (the 1980s-now). This finding is different from the traditional understanding that submerged macrophytes were abundant in the early 20th century and have been degrading since then. On this basis, we proposed the possible evolution pattern (less-more-less) of submerged macrophytes in the eastern plain lake region over the past 100 years, which provides new perspectives about the long-term evolution process of macrophytes in shallow lakes. Furthermore, we found that the decline of submerged macrophytes during the regime shift shows a gradual process at the interdecadal scale; this finding contradicts the classical regime shift theory that macrophytes decline sharply during the critical transition. This study has important theoretical value for the restoration of the eastern plain lakes in China from “turbid lake” to “clear lake”, especially for establishing the historical reference condition and restoration path of macrophytes.