The Site is a shallow freshwater lake formed by geological uplift after deglaciation, which isolated the coastal bay from the sea. The lake is surrounded by freshwater marshes and shrub marsh with vegetation including extensive reedbeds, deciduous woodland and scrub. The Site supports various species of breeding and staging wetland birds and provides shelter for waders and ducks. About 210 bird species have been observed including several nationally red-listed species such as the nationally endangered Eurasian penduline tit Remiz pendulinus and the nationally vulnerable northern pintail Anas acuta, common swift Apus apus and ruff Philomachus pugnax. The wetland plays an important role in water purification and sediment trapping. Some parts of the Site are used for agriculture and grazing, sport fishing, hunting, canoeing, and birdwatching. The main threats to the ecological character of the Site relate to pollution from agricultural effluents, airborne pollutants and high mercury concentrations. The Site is managed by private owners and a conservation plan is being implemented for the part covered by the Natura 2000 designation.