Eutrophication, or the addition of nutrients, causes a huge negative environmental impact in the Baltic Sea. Nutrients from human-caused sources such as agriculture, wastewater and atmoshperic nitrogen pollution from fossil fuel combustion have during the last 200 years turned the Baltic Sea from oligotrophic (low nutrient content) clear water sea into an eutrophic (high nutrient content). The higher nutrient content leads to the increased growth of algae, which in turn disturbs the balance in the ecosystem. The excess of organic matter produced under these conditions depletes the oxygen when it is decomposed, which kills plants and animals living at the lowest levels of the sea. Today huge areas in the Baltic Sea are completely void of life due to lack of oxygen.
Sources and solutions
To tackle this problem, the most important action is to stop nutrients from reaching the sea in the first place. As agriculture runoff is one of the main contributors to eutrophication, using less fertilisers would reduce eutrophication. Taking care of agricultural waste such as manure, for example by producing biogas, would also contribute to a reduction. Another source of anthropogenic nutrients is wastewater from municipal and domestic treatment plants, boats and other sources. Nitrogen in fossil fuels combustion emissions also end up in the sea, and better methods of removing it from the waste gases would also reduce eutrophication.
It is also possible to remove the nutrients that are already in the sea. Although it is difficult to reduce the level to any significant extent, it is possible to mediate the local effects of eutrophication. Examples of ways of reducing the nutrient content are mussel farming and filtering of sea water. The effects of eutrophication and hypoxia can also be reduced by artificially oxygenating the water or the sea bed.
For technologies dealing with these issues, please look in the meny on the left hand side.