Can Turbidity-Tolerant Submerged Macrophytes Improve Water Quality in Subtropical Lakes?

摘要

The existence of alternative stable states and hysteresis underpinned by positive feedback mechanisms explains why it is often difficult to restore submerged macrophytes in shallow lakes. It is especially difficult to restore water quality of turbid tropical lakes. It has been speculated that transplanting macrophytes tolerant of high turbidity may help the system escape from the turbid state, but systematic assessments are so far largely lacking. Here we conducted a mesocosm transplanting experiment in a shallow lake of subtropical China to mimic macrophyte restoration. We transplanted three common native turbidity-tolerant submerged macrophyte species in shallow-water mesocosms and monitored water quality within one growing season. Our experiment demonstrated that following artificial recolonization, the submerged macrophytes could indeed persist in turbid shallow water. However, the persistence of submerged macrophytes cannot significantly improve water quality, and cannot reverse the ecosystem state of tropical shallow lakes within one growing season. Our results thus provide useful implications to the current lake restoration practices. In real-world situations, it may not be realistic to anticipate rapid restoration through macrophyte transplantation only. Monitoring the long-term effects of macrophyte transplantation is imperative for lake restoration. Our work highlights the need to harness the nuanced hidden complexity for tropical lake restoration and calls for attention to alternative stable states among practitioners of lake management.