Balticsea 2020

Living coast

BalticSea2020 started the project Living coast in 2011. It is a large-scale demonstration project carried out in a bay in Stockholm’s archipelago where different measures are tested and evaluated in order for the eutrophic bay to recover. The project is led by associate professors Linda Kumblad and Emil Rydin.

Background and Objectives
Living coast is carried out in Björnö- fjärden in the municipality of Värmdö, an archipelago bay that has many similar- ities with Baltic Sea, and can be seen as a "Baltic Sea in miniature". The bay has limited water exchange and, at the beginning of the project it was heavily eutrophicated with a high prevalence of anoxic bottoms. Nutrients (nitrogen and phosphorus) that enters the bay from the catchment area derrived partly from natural sources such as the forest, but when the project started most nutrient load was due to human activities, such as agricultural activities, run-off from poor sewage treatment solutions, horse management and leaching from the "sins of the past". The sins of the past refer to phosphorus discharges from previous years, stored in the sediments and leaching back into the water when the bottoms becomes anoxic. Read more about eutrophication here.

Purpose and goal
The goal of the project is to show that it is possible to recover close to natural conditions in a eutrophic bay. A good environment, or a “good ecological status”, is characterised by clear water, abundant flora and fauna, a natural fish community and oxygenated bottoms with benthic animal life.

Measures to improve water quality
Both in Björnöfjärden and the area around the bay, the project has implemented measures to reduce nutrients entering the water to counter-act the effects of eutrophication.

To stop the benthic phosphorus release from the sins of the past, the anoxic bottoms in the bay were aluminium-treated during the summers of 2012 and 2013. Aluminium binds phosphorus and prevents it from leaching back into the water again. After the aluminium treatment, the bay regained the same water quality as it had in the 1950s. Read more about aluminum-treatment here.

Photo: Joakim Odelberg.

In order to retain the water quality in the bay several measures were undertaken:

Nutrient losses from agricultural activities was, for instance, minimized by structural liming of the soil. Another measure made was constructing sedimentation ponds with lime filters. Read more about structure liming and sedimentation ponds with lime-scale filters here.

To obtain good drainage, and thereby further minimize the leaching of nutrients from the farmland, so called tile drainage were established. The tile drain leads away excess water from the field in buried pipes entering the main ditch. Lime was mixed into the soil surrounding the drainage pipes, which effectively binds the phosphorus dissolved in the water. The measure can be effective up to about 30 years.

Poor sewage treatment solutions in the area have been improved by installing “sluten tank”. In addition, a so-called latrine station has been built for property owners who want to retain their dry toilet, but needs a disposal site other than their own garden. Read more about measures for sewage treatment solutions here.

Nutrient leaching from the area´s horse farms has been reduced with several measures. The most important was to collect the manure, also in pastures, and store it so it will not leak to the surroundings.

To strengthen the pike stock in Björnöfjärden, and in the archipelago beyond, the project has constructed a pike wetland adjacent to the bay. In addition, a pike fishing ban has been introduced by the Swedish Agency for Marine and Water Management in the bay in spring, to avoid disturbance of the spawn.

The project has also implanted bladderwrack to regain the natural vegetation in Björnöfjärden. Read more about the restoration of vegetation clad bottoms here.

Spread knowledge
The experience has been summarized in a book that describes how eutrophied archipelago areas can be restored and what it costs. The book disseminates the project results and the lessons learnt from it to countries around the Baltic Sea.
Please find the Living Coast’s White Paper here. Pages: 64.
If you want to learn more, see the complete White Paper on our website (in Swedish) here. Pages: 124
For a six pages summary of the project, please click here.

From 2019 the project Living Coast (II) is led by the Stockholm University Baltic Sea Centre, under the leadarship by Linda Kumblad and Emil Rydin. The work is carried out in close collaboration with BalticSea2020 - initiator and the main financier.