Estuaries, which can be considered as the most resource rich, biodiverse, and increasingly densely populated areas in the world, have often been dammed and are partly or fully reconstructed. Many of these artificially compartmentalized and constructed areas suffer from reduced natural dynamics and anthropogenic induced stressors. Whereas damming for safety and water security were the main focus in the first half of the 20th century, ecology, biodiversity and natural values have recently become increasingly important. An example of such a novel ecosystem created by damming a previous estuary with a history of changing focus on its ecosystem services, is lake Markermeer in the Netherlands. This resulted in many studies commissioned by governmental organizations on the ecology of lake Markermeer over the last decades. Since only a minor part of these studies have been published in peer reviewed journals, valuable abiotic and biotic data on lake Markermeer is scattered. In this report, we first aim to combine the knowledge from all these studies on lake Markermeer and the larger IJsselmeer area with monitoring data to provide a historical overview of the ecological developments of lake Markermeer during its forty years of existence and derive the main hypotheses and suppositions on the causes of its ecological deterioration. Secondly, we elaborate on their likelihood of impeding the ecology of lake Markermeer based on retrieved data support, perform a multivariate analysis and provide a synthesis on the ecological functioning and future of the lake.