The researchers studied the phytoplankton in Hangzhou West Lake for two years and analyzed the effects of eutrophication control measures from 1980 to 2000. They found that despite efforts to control eutrophication, the lake's phytoplankton density increased by 55.4%. However, in one area where control measures were implemented, the water became clearer, algae decreased, and the lake shifted from phytoplankton to macrophyte dominance. This suggests that restoring the ecosystem with macrophytes is an effective way to combat eutrophication in the lake.