The Baltic Sea is the biggest brackish water body worldwide – having a mixture of salt water and fresh water. Its unique biodiversity is, however, threatened by a phenomenon called eutrophication. Eutrophication is essentially due to an overabundance of the nutrients nitrogen and phosphorous in the water. The sources are manifold – they can come from the atmosphere, runoff waters from agricultural fields as well as wastewater, just to name a few. The Baltic Marine Environment Protection Commission – Helsinki Commission, known as HELCOM, has created a website that gives detailed information on the causes and effects of eutrophication. The HELCOM report “State of the Baltic Sea” (English) gives a good overview. Other helpful resources can also be found in our link collection for “Further Information Online”

One of the effects of eutrophication is an excessive growth of plants, such as phytoplankton, which in turn causes other ecosystem changes. The accelerated growth of algae and other water plants yields problematic ecological consequences. When the algae decompose they consume corresponding amounts of oxygen, which creates dead zones at the bottom of the Baltic Sea.

An increase of dead zones at the sea bottom makes animal life there impossible. Thus, biodiversity decreases and the situation worsens. Furthermore, foam formation occurs and the degradation of washed up algae on the beaches causes unpleasant odours. This creates problems for the environment and communities along the coast – including the livelihoods associated with tourism.

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