Macrophyte refuges, prey behavior, and trophic interactions: Consequences for lake water clarity

Background/Question/Methods Macrophytes may enhance grazing on phytoplankton by providing a refuge for zooplankton against fish predation. Loss of macrophytes can trigger sudden degradation of water clarity (regime shift) in lakes. However, the presence of piscivores may drive planktivorous fish to the littoral refuge with macrophytes. To address the possibility of regime shifts, I here constructed an empirically-based model that combined population dynamics of organisms with game theory for optimal habitat selection, taking into consideration the trophic structure, lake size, and eutrophication.

Results/Conclusions The model showed that macrophytes generally acted as a refuge for zooplankton, rather than for fish. The model predicted that regime shifts were more likely in small, shallow lakes, and that the presence of macrophytes raised the possibility of regime shifts. The present study demonstrated that the fast dynamics of animal behavior could lead to regime shifts, in connection with slower variables such as nutrient loading.