Tyresö-Flaten is a lake

Lake

A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

 in Tyresö Municipality

Tyresö Municipality

Tyresö Municipality is a municipality in Stockholm County in east central Sweden on the coast of the Baltic Sea. Its seat is located in Bollmora.Most of Tyresö Municipality lies within the Stockholm urban area.-History:...

, just south of Stockholm

Stockholm

Stockholm is the capital and the largest city of Sweden and constitutes the most populated urban area in Scandinavia. Stockholm is the most populous city in Sweden, with a population of 851,155 in the municipality , 1.37 million in the urban area , and around 2.1 million in the metropolitan area...

, Sweden

Sweden

Sweden , officially the Kingdom of Sweden , is a Nordic country on the Scandinavian Peninsula in Northern Europe. Sweden borders with Norway and Finland and is connected to Denmark by a bridge-tunnel across the Öresund....

.

The lake forms part of the Tyresån Lake System

Tyresån Lake System

Tyresån Lake System is a number of lakes in Sweden with a common basin of 251.5 km2....

 and as such is considered important for recreational activities such as angling and bathing. Common fish species include Perch

European perch

The European perch, Perca fluviatilis, is a predatory species of perch found in Europe and Asia. In some areas it is known as the redfin perch or English perch, and it is often known simply as perch. The species is a popular quarry for anglers and has been widely introduced beyond its native area,...

, Zander

Zander

Zander is a species of fish. The scientific name is Sander lucioperca , and it is closely allied to perch. Zander are often called pike-perch as they resemble the pike with their elongated body and head, and the perch with their spiny dorsal fin. Zander are not, as is commonly believed, a pike and...

 Pike

Northern Pike

The northern pike , is a species of carnivorous fish of the genus Esox...

, Lake trout

Trout

Trout is the name for a number of species of freshwater and saltwater fish belonging to the Salmoninae subfamily of the family Salmonidae. Salmon belong to the same family as trout. Most salmon species spend almost all their lives in salt water...

, Carp Bream

Carp bream

The common bream, freshwater bream, bream, bronze bream or carp bream, Abramis brama, is a European species of freshwater fish in the family Cyprinidae....

, and Roach

Rutilus

Rutilus is a genus of fishes in the family Cyprinidae, commonly called roaches. Locally, the name "roach" without any further qualifiers is also used for particular species, particularly the Common Roach Rutilus (Latin for "shining, red, golden, auburn") is a genus of fishes in the family...

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Environmental impact

When water stagnate in late summer hydrogen sulfide

Hydrogen sulfide

Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...

and oxygen shortage occurs in lake sediments. However, level of bacteria are low and the lake is considered safe for bathing. No contaminations except nutritive salt have been reported.