Balticsea 2020

Living coast: Living coast held information meeting for residents at Björnöfjärden

On 13 March Emil Rydin and Linda Kumblad, the project managers for BalticSea2020´s large-scale project Living coast, held an information meeting for residents in the Björnöfjärden catchment area.

The purpose of the meeting was to provide information about the project, which has been running in the area since 2011, the eutrophication situation at the start of the project, and the action and measures that have been taken since then. Last but not least, Emil and Linda presented the results of the project, i.e. how much each measure has reduced the nutrient load in the bay and how the bay environment has been improved.

At the start of the project Björnöfjärden was one of the most eutrophic bays in the Stockholm archipelago. Today, almost 8 years later, the bay is well on its way to regaining a good environment, or achieving so-called good environmental status, with clear water, abundant flora and fauna, a natural fish community and oxygenated bottoms with benthic animal life. Getting to this point, however, has meant a great deal of hard work for Emil and Linda!

Before the measures were implemented, phosphorus (nutrients) came from the catchment area´s agriculture activities, horse farms, small sewage systems, and Säby Manor Farm, a conference centre in the northern part of            Linda and Emil on stage at the Gustavsberg Theatre on Ingarö. About 90                  Björnöfjärden.
people attended the information meeting. Photo: BalticSea2020. 

Most of the phosphorus entering the bay, however, came from the bay´s bottom. Old phosphorus discharges have been stored in the sediment for decades and then released into the body of water as the bottom waters become anoxic. Consequently, nutrient levels in the body of water increase, which further drives eutrophication.

In order to reduce eutrophication in Björnöfjärden, it was necessary to take action to stop phosphorus leaching from all sources. And the results have been excellent:

Measures involvning local agriculture: by structure liming the soil, establishing phosphorus ponds with lime filter beds and tile draining with lime admixture, it is calculated that phosphorus leaching from fields can be reduced by around 80 % (38 kg/year).

Measures involving local horse farms: daily manure-clearing of pastures, storage of manure on a sealed manure plate, protection zones around ditches, soil stabilisation and drainage of trampled land are calculated to reduce nutrient leaching from the horse farms by around 70 % (17 kg/year).

Measures to improve local sewage systems: a new sewage system at the conference centre and cider press at Säby Manor Farm is calculated to reduce phosphorus discharges to the bay from this source by at least 70 % (45 kg/year). Thanks to increased supervision, sewage system advice and financial support, the amount of phosphorus reaching the bay from small sewage systems has been halved. Compensation has been paid to private property owners who have switched to a sewage solution where toilet waste is collected and transported away from the area. These measures are calculated to reduce phosphorus discharges to the bay from private sewage systems by 50 % (80 kg/year). By equipping the outdoor toilets in Björnö nature reserve with closed tanks, nutrients and infectious agents from toilets are taken care of instead of leaking out to the bay. This measure is calculated to reduce the phosphorus discharge from the outdoor toilets by 3 kg/year.

Measures to reduce phosphorus leaching from the bay´s bottom: using aluminium treatment on deep, anoxic bottoms has halted phosphorus leaching from sediment in the bay. Aluminium binds the phosphorus to the sediment and thus stops the phosphorus leaching back into the water. The measure is calculated to have reduced the phosphorus supply to water by just over 80 % (600 kg/year).

Measures to strengthen pike stocks in the bay: the creation of a pike wetland enables the pike stock to be strengthened, which in turn can counteract the effects of eutrophication. Pike eat small fish so that more of the bay’s zooplankton remains and eats phytoplankton. In this way pike help to reduce phytoplankton blooms (algal blooms). A fishing ban has also been introduced during the spawning season to protect the pike. Last but not least, bladderwrack has been planted in several locations in the bay. Belts of blatterwrack are important for fish fry and small animals that live here, which in turn provide important food for fish and birds.

In order for these excellent results to stand the test of time, it is important that additional phosphorus is not added to Björnöfjärden. Living coast will now continue to carry out sampling and analyse the results in order to further evaluate the effectiveness of the measures in the long term.

We would like to thank all residents in the area who attended the information evening and posed some interesting questions!

Are you interested in more information about Living coast? You can take a look at the project’s website by clicking here. Or why not download the project’s summary?

Emil warns against composting latrine waste in the garden.                         Linda describes the exciting love life of bladderwrack.
Over five weeks latrine waste from one person adds so much                      Photo: BalticSea2020.
nutrient content to the soil that you would need to grow 200 kg
of carrots to use it all! That is why it is better to use a closed
tank for toilet waste before sending it on to a municipal waste-
water treatment plant; otherwise the latrine waste risks contri-
buting to eutrophication of lakes and the sea.
Photo: BalticSea2020.