Eutrophication is one of the main threats to the biodiversity of the Baltic Sea and is caused by excessive inputs of nutrients to the marine environment.

​Eutrophication is driven by a surplus of the nutrients nitrogen and phosphorus in the sea. Nutrient over-enrichment causes elevated levels of algal and plant growth, increased turbidity, oxygen depletion, changes in species composition and nuisance blooms of algae.

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Photo: Samuli Korpinen 

According to the latest HELCOM assessment on eutrophication, in 2007-2011 almost the entire open Baltic Sea was assessed as being eutrophied and only the open Bothnian Bay was assessed as being unaffected by eutrophication.

HELCOM strives to achieve the Baltic Sea Action Plan goal of: A Baltic Sea unaffected by eutrophication.