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BalticSea2020 takes first steps in the Living Coast project to reduce the effects of eutrophication in Björnöfjärden

The BalticSea2020 Living Coast project aims to demonstrate that exposed bay systems can be restored to improve water quality, reduce growth of filamentous algae and regain anoxic bottoms and a natural fish community in a coastal area that is limited but representative of the Baltic Sea. In the Björnöfjärden bay system on the island of Ingarö (Värmdö municipality), the project will put in place various measures to solve problems caused by eutrophication. The project has now begun the first action in the bay: aluminium treatment to bind phosphorus in the bottom sediments.

BalticSea2020 launched the Living Coast project in 2011 to counter eutrophication and its effects in the coastal bays of the Baltic Sea. Achieving the vision of a good ecological status is a challenge. Both the present-day load and the historical burden of nutrients are enormous. To succeed, practical and powerful measures are needed, both on shore and in the water.

After careful studies it has been found that Björnöfjärden and Säbyviken on the island of Ingarö in the municipality of Värmdö are in need of restoration.

- The bay system can be regarded as a ‘Baltic Sea in miniature’: there are high levels of nutrients and extensive anoxic bottoms, which are clear symptoms of eutrophication. With this project, we aim to show that it is possible to improve the ecological status of coastal bays, and reduce eutrophication, says Linda Kumblad, Living Coast project leader at BalticSea2020.

To reduce eutrophication, in addition to reducing discharges into the bay, surplus phosphorus must be bound in the bottoms. In August the aluminium treatment of the bottom of the bay started, an action in which aluminium solution is mixed into the bottom sediments to reinforce their natural binding of phosphorus, thus enabling the bottom to bind more phosphorus. The aluminium solution is the same substance as used in drinking water treatment in our larger water treatment works. The method is effective, and the treatment has been used to fix phosphorus in lakes for more than 40 years in Sweden, as well as in the United States and other parts of Europe. The work is being carried out by Vattenresurs AB.

- Binding phosphorus in the bottom sediments is the first action to be taken in the project, but measures need to be taken both on shore and in the water to succeed in improving the ecological status of the bay. Other planned steps include contributing to reducing inputs of nutrients from private sewerage systems and ditches and restoring a natural fish community, says Emil Rydin, Living Coast project leader at BalticSea2020.

Eutrophication is caused by discharges of nutrients (phosphorus and nitrogen) that contribute to algal blooms, which in turn contribute to dead bottoms when they break down. The reduced stocks of predator fish reinforce these effects. A decrease in phosphorus in the bottom water reduces the growth of algae, which gradually contributes to better anoxic levels of the bottom water, enabling bottom fauna and fish to thrive once again in the bay.

- We anticipate that the first effects of the steps being taken will be visible in the bay in a year’s time. The bay will then gradually improve. We estimate that the bay will return to a good ecological status in four to five years, says Kumblad.

The Living Coast project in the Swedish Television regional news
Watch the news feature on ABC-nyheterna (Swedish Television) on the Living Coast project and our work at Björnöfjärden on Ingarö. The news feature is due to be broadcast on 30 August 2012 on the channel SVT1, but is also available on the SVT website. Click here.

For more information about aluminium treatment, visit the Vattenresurs AB website – www.vattenresurs.se. You will also find more information on our website – click here.