The map shows the mean annual concentration of total phosphorus (TP), expressed as milligrams of TP per litre of water, observed in lakes and reservoirs monitoring stations and reported by EEA member countries via WISE. For most countries the mean annual value is based on observations over the whole year, whereas some countries only collect samples during the growing season (due to ice cover in winter). Total phosphorus includes all phosphorus components in water: phosphate, dissolved organic phosphorus and particulate phosphorus in algal and bacterial cells, as well as in mineral particles (e.g. clay).
High or increased (compared to reference condition) concentration of total phosphorus represents a risk to normal functioning of lake ecosystems, causing eutrophication with potentially harmful or toxic algal blooms in the surface waters, reduced biodiversity, and oxygen deficiency in the bottom waters.
The purpose of the map is to provide an overview of the mean annual value of total phosphorus in lakes and reservoirs across Europe and to enable the user to compare values per country, River Basin District (RBD) or individual monitoring station, depending on the scale of visualisation. Historical data since 1993 can be displayed using the time slider.