Lake Kolon is a fen and marshy area in a former river branch, which is characteristic of the Danube floodplain. The complex of habitats includes a large reed bed, wet meadows, fen woods, pastures, hay meadows and sand dunes. The Lake itself was once affected by drainage and is now nearly completely overgrown by vegetation. Only small parts, where peat was extracted and artificial open water surfaces were created, have remained open. It hosts a regionally large population of a vulnerable indigenous fish species, the European mudminnow (Umbra krameri), and is an important wintering and breeding ground for large numbers of herons and waterfowl such as the ferruginous duck (Aythya nyroca) and moustached warbler (Acrocephalus melanopogon). The Site plays an important role in groundwater recharge and discharge and in local climate modification. Human activities include reed harvesting, mowing, forestry and agriculture. Potential threats to the Site’s ecological character include water regulation, extensive agricultural pollution, falling groundwater levels, increasing exotic species and eutrophication.