In the 1950 s and 1960 s, most shallow lakes in the Netherlands shifted from macrophyte-dominated clear water lakes, towards algae-dominated turbid water lakes. Eutrophication, i.e. increased nutrient loading, is the main cause of the deterioration of the lake ecosystems. Other perturbations, such as the loss of lake-marginal wetlands (nutrient filters, habitat for pike, Esox lucius) and chemical pollution toxic to zooplankton, will have reinforced the effects of nutrient enrichment. The lake restoration strategy has been concentrated on the reduction of the external phosphorus (P) loading. However, so far this approach did not result in the water quality (in terms of transparancy, phytoplankton species, fish stock etc.) desired. A more comprehensive approach to lake ecosystem functioning may provide additional tools for lake restoration. Algal blooms in lakes will develop when the algal production is high and the algal losses are low. Production is controlled by the supply of nutrients and light. Consumption of algae by zooplankton is a major loss process. In this thesis attention is focused on both sides of the algal balance: (1) the control of the external and internal (from the sediments) P loading, and (2) biomanipulation, the manipulation of fish communities aiming at increased consumption of algae. Reduction of the planktivore fish stock may enhance the zooplankton and thus the grazing on algae. Bream (Abramis brama) and roach ( Rutilus rutilus ) are among the major fish species in many turbid Dutch lakes. Large bream feeds on zooplankton, as well as benthic organisms. Reduction of the benthivore fish stock results in reduced sediment resuspension and P release and less disturbance of rooted macrophytes.Development of the lake restoration strategy (chapter 1)The strategy for lake restoration gradually evolved from solely P stripping from sewage, towards a more comprehensive and ecosystem-based approach. In the Netherlands, P removal at sewage treatment plants is common practice and polyphosphates in ...