Manipulation of whole-lake ecosystems and long-term limnological observations in the Brandenburg-Mecklenburg Lake District, Germany

An accompanying technical use of ecological effects from pelagic food-web interactions (biofiltration) or from sediment (nutrient remobilization) can speed up recovery of lake ecosystems and can make restoration programs more effective after external load reductions. At present the comprehensive use of multiple ecotechnological controls for water quality is limited because our knowledge of the many complex interactions. indirect effects and above all the long-term effects of such operations is insufficient. Beginning in the 1960s we started long-term limnological analyses of the trophic interactions between community structure and the flow of matter under ''manipulated'' conditions in whole-lake experiments at Lake Stechlin (manipulated water circulation and waste heat), Lake Haussee (biomanipulation) and Lake Fuchskuhle (lake-dividing). This paper summarises changes in abiotic and biotic structures and functions of the manipulated lake ecosystems and discusses the possibilities and limitations of ''whole-lake'' experiments.