Erken, Research lake in Stockholm County, Sweden

Erken is a research lake in Stockholm County used for scientific study of freshwater ecosystems. The water body supports ongoing investigations into aquatic life, water quality, and environmental changes affecting northern European lakes.

Uppsala University's limnological laboratory at Erken traces its origin to a donation: in 1928 Carl Malmén gave the university his farm Norr Malma, on the lake's southern shore, as the site for a research station. The station has since carried out long-term environmental monitoring of the lake.

The lake's name is also borne by Erkenlaboratoriet, Uppsala University's limnological station on the southern shore at Norra Malma säteri. The station studies the lake's water chemistry, vegetation and fish community; test fishing has recorded perch, bream, pike, zander and burbot. The water was formerly used as drinking water for Norrtälje kommun.

Access to the site is restricted as it functions as an active research facility rather than a public destination. Visitors interested in the scientific work should contact the university directly to arrange any visits or learn about the research programs.

The research station maintains one of Europe's longest continuous records of water measurements spanning many decades of observation. This exceptional dataset provides insights into how freshwater ecosystems change over extended periods.