Markermeer is a large shallow reservoir (average depth 4m, 700 km2) in the Netherlands resulting from the damming of a large saltwater inlet (1932). It is a Ramsar site and historically provided home to a diverse community of bird and fish species. Over the past decades, Markermeer has undergone numerous restoration and biodiversity conservation measures to counteract the observed decline in Ramsar target species, such as the common tern, and crested ducks. Measures ranged from nutrient abatement programs and most recently, the creation of the Markenwadden wetlands to trap sediment and establish nursing grounds for bird species. Feeding the ecosystem model Ecopath with long-term monitoring data we investigated the mechanisms behind the decline in target species, as well as simulated the effect of potential restoration measures on foodweb functioning.
Results/Conclusions
Our approach showed that - in contrast to the prevailing opinion by water managers- productivity of Markermeer has not reduced over the past decades, but rather a pelagic-to benthic shunt has taken place. Similar pelagic-to benthic shunts have been observed recently in some of the Great Lakes as well. In my talk, apart from showing the wax and wane of ecological quality of Markermeer, I will guide the audience through the quirks and perks of European nature management legislation, and will give examples on the engineering approach the Dutch have towards lake management.