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The Living Coast project has contributed towards a healthier Björnö Bay

One of the Foundation's largest demonstration projects "Living Coast" has been published in the highly rated scientific journal Environmental Science & Technology

During the summers of 2012 and 2013, the BalticSea2020 Foundation carried out an aluminium treatment project on the anoxic bottoms of Björnö Bay. The purpose was to help the bay’s sediment regain the ability to bind phosphorus. After the treatment, the Björnö Bay has achieved the same water quality it had in the 1950s. 

The BalticSea2020 Foundation has been working on the project ”Living Coast” in Björnöfjärden in Stockholm’s Archipelago since 2010. We want the project to show that a healthy environment can be regained in eutrophic bays. A good environment, or a good ecological status, is characterised by clear water, a rich plant and animal life, a natural supply of fish, and oxygen rich seafloors with bottomdwelling creatures. According to the EU Water Framework Directive, all water must reach good status by 2021, or at the absolute latest by 2027.

A miniature Baltic Sea
The Björnö Bay resembles a ”miniature Baltic Sea”. The bay is heavily eutrophic, with little water exchange and extensive sea floors deprived of oxygen. Nutrients (phosphorus and nitrogen) that reach the Björnö Bay and contribute to eutrophication (overfertilization) come primarily from human activities occurring in the area around the bay. However, the largest supply of nutrients to the water comes from the sediment in the bays. Here, huge amounts of nutrients have been stored for many decades, and the natural ability to bind phosphorus has been weakened as the bay has been increasingly overfertilized resulting in increased expansion of anoxic bottoms. To take measures against ”the sins of old”, the anoxic bottoms were treated with aluminium during 2012 and 2013. The aluminium treatment has resulted in a renewed ability to bind phosphorus and a reduction by half of the phosphorus content in the bay’s water.

- This means the treatment works well, i.e. that the sediment can once again bind phosphorus. In just three years, the bay has gone from being heavily eutrophic to having clearer water of good quality. We also see that animals and plants are beginning to recuperate, even if this takes time and requires more work until we reach our goals, says Emil Rydin, Project Manager for BalticSea2020.

”We are committed to ensuring a healthier Björnöfjärd”
The use of environmental engineering such as aluminium treatment is disputed. The method has been considered impractical due to the large treatment area and to unknown effects on the environment. Another concern is that these methods may reduce the commitment to measures on land.

- On the contrary, with our project at the Björnö Bay, we see an increased awareness on the part of the property owners around the bay and the municipality of Värmdö. They are improving the handling of sewage and taking measures at horse farms to reduce the risk of nutrient leaching. We are committed to ensuring a healthier Björnö Bay, says Linda Kumblad, Project Manager for BalticSea2020.

To preserve the good water quality of the bay, it is imperative that the flow of nutrients from land is reduced. To achieve this, the project has carried out various agricultural initiatives, measures related to horse farms, and improvements in the management of sewage. Predatory fish and remediation of seafloor vegetation have similarly been the subject of recent initiatives.

The overall goal is to produce a white paper to describe the project’s findings and conclusions regarding the restoration of eutrophic archipelago areas and the associated costs. The white paper will be presented later this year.

The article "Remediation of a Eutrophic Bay in the Baltic Sea" by Emil Rydin, Linda Kumblad, Fredrik Wulff, and Per Larsson has been published in Environmental Science & Technology and is freely accessible here.

What is aluminium treatment?
The aluminium solution used at Björnöfjärd is the same substance that is used for drinking water purification in our larger municipal water systems. The method is effective, and the treatment has been used to restore lakes for more than 40 years in Sweden, USA, and Europe. No negative side effects have been seen to date so long as the water is not excessively acidic. The Baltic Sea is no different from lakes, but in addition the Baltic Sea has the capacity to buffer the water andprevent it from becoming acidic.

About BalticSea2020
BalticSea2020 was founded by Mr Björn Carlson through a donation of 500 million SEK. The assets shall finance projects that are action-oriented, innovative and contributes to a healthier Baltic Sea. The foundation also works to spread knowledge and information about the Baltic Sea to decision makers, authorities, schools and individuals.

For more information, please contact:

Doc. Linda Kumblad, Project Manager BalticSea2020
Tel: +46 (0)8 673 97 63, +46 (0)733 79 98 16

Doc. Emil Rydin, Project Manager BalticSea2020
Tel: +46 (0)8 673 97 66, +46 (0)707 15 91 84

Ida Mårtensson, Communications and Events BalticSea2020
Tel: +46 (0)8 673 97 64, +46 (0)707 50 23 36