Effective measures against eutrophication

Living Coast ProjectEffectivemeasures againsteutrophication– a story about regaininggood ecological status in coastal areasLinda Kumblad & Emil rydinEffEctivE mEasurEs against Eutrophication • 1Seven years ago, Björnöfjärden in Värmdö Municipality wasone of the most eutrophic bays in the Stockholm archipelago.Oxygen-free “dead zones” were widespread and nutrients wereleaking from a number of different sources.After the implementation of remediation measures, Björnöfjär-den is now a healthy bay with clear water and rich plant andanimal life and is on the way to having a natural fish communityand oxygenated bottom waters with bottom dwelling animals.This is the Living Coast’s White Paper that describes theproject’s implementation, results, costs, conclusions and re-commendations. If you want to learn more, see the completeWhite Paper on our website (in Swedish).www.balticsea2020.org.© published bv Balticsea2020, June 2018Authors: Linda Kumblad and Emil rydinGraphic design and original: maria Lewander/grön idé aBIllustrations: Anna-Lena Lindqvist/Lindqvist Grafik&InfoDesign ABPhotos: Living coast project, unless otherwise stated.2 • EffEctivE mEasurEs against EutrophicationClean water in Björnöfjärden againDuring 2011, the BalticSea2020 Foundation initiated the Living Coast project. The objec-tive was to show that it is possible to restore a eutrophic bay and to find out what it costs andwhat other lessons can be learned from such a project. The project has been permeated by ascientific approach and has had the goal to summarise and communicate results, approachesand experiences.The project was conducted in Björnöfjärden, a bay that can be described as a “miniatureBaltic Sea” because of extensive eutrophication, limited water exchange and large areas ofanoxic (oxygen depleted) bottom waters. Within the project we implemented measures thatreduce the supply of the nutrients nitrogen and phosphorus from land and bottom sedimentsto the water, thereby regaining good water quality and an improved environment. The pro-ject mainly focused on phosphorus as more measures have been developed to reduce thephosphorus supply. In addition, it is often phosphorus that regulates eutrophication in BalticSea archipelagos.On the basis of the results in Björnöfjärden, we aimed higher and calculated what emissionreduction the measures could contribute if they were fully implemented, such as along thewhole of the Swedish Baltic Sea coast.The objective of the project was achieved. This publication is the Living Coast’s WhitePaper (1.0) which describes preparatory studies, implementation, actions, results, costs andconclusions.We hope that our work inspires and motivates to more remediation work and that this textcontributes to knowledge and experience on how the work can be done. The Water Fram-ework Directive applies to the Baltic Sea coastal waters and the Living Coast project hopes tostrengthen the water management efforts with the knowledge and experience gained duringthe work of restoring Björnöfjärden. On our website, www.balticsea2020.org, you can findmore information about the Living Coast project, the complete white paper, the project’s sci-entific publications and other documentation./Linda Kumblad and Emil Rydin, BalticSea2020EffEctivE mEasurEs against Eutrophication • 3dvS/dATSeLOhnILAM:OTOhPContentsEutrophication a major challenge for the Baltic Sea...5Living Coast – a full-scale remediation project...9preparation, evaluation and action...13Measures to reduce nutrient losses from agriculture...17Horse keeping also contributes to eutrophication...23Toilet waste must be removed from the coast...27Excess phosphorus is bound in the sediment...31Measures to strengthen predatory fish stocks...37Potential actions and effects...41Björnöfjärden has regained good water quality...47Living Coast from a Baltic Sea perspective...53conclusions & recommendations...58References...604 • EffEctivE mEasurEs against Eutrophicationeutrophication– a major challengefor the Baltic SeaIn the Baltic Sea, eutrophication is a widespread problem that degradeswater quality, affects plant and animal life and causes oxygen deficiencyin the bottom waters and sediments, both in the offshore areas and inthe coastal zone. The effects of eutrophication occur when there is anexcess of nutrients in the water. Some algae then grow unrestrained atthe expense of others, leading to consequential effects throughout theecosystem. Eutrophication also has a negative impact on recreation andtourism.EffEctivE mEasurEs against Eutrophication • 5édInörg/nOSTgneBreP:OTOhPThe Vicious circlePhytoplankton and other algae rely on nutrients such as nitrogen and phosphorus. When thealgae die, they sink to the bottom where they are decomposed by bacteria and bottom fauna.During decomposition, oxygen is consumed in the bottom water and the nutrients are relea-sed again. If there is plenty of oxygen in the bottom water, phosphorus can bind to the iron inthe sediment, but if the oxygen runs out, the iron loses its phosphorus-binding ability. Thenthe phosphorus leaks back into the water and becomes available for phytoplankton and otheralgae. More algae growth, in turn, contributes to even more organic material to be brokendown, and even more anoxic bottoms; a ”vicious circle” arises.Where do the nutrients come from?About one third of the nitrogen and one tenth of the phosphorus that reaches the Baltic Sea isnaturally supplied by rivers and streams1. The remainder is a result of human activities in thecatchment area, such as discharge from sewage with poor treatment, wastewater treatmentplants and industrial operations, agriculture and forestry, and reaches the Baltic Sea mainlyvia rivers (Figure 1). Nutrients from the catchment area mainly come from the areas wherea lot of people live and where there is most farmland. However, the release of phosphorusfrom the sediment (the internal load) is the predominant source of phosphorus to the BalticSea waters.The nutrient supply from the Baltic Sea catchment area to the sea has decreased over thepast thirty years, and is down to roughly the same levels as in the mid-20th century4 (Figure2). The eutrophication status throughout the Baltic Sea has gone from ”bad” (red) at thebeginning of the 1980s to ”unsatisfactory” (orange) or ”moderate” (yellow)5 (Figure 3). TheNutrients that reach the Balticreason that eutrophication persists and the recovery takes a long time is the large amount of Sea mainly enter via riversnutrients that already are present the sea, where they are turned over year after year4, and that bring nutrients from, forexample, wastewater treatmentthe Baltic Sea’s limited water exchange that means that nutrients that end up in the sea, stayplants, industrial operations,for a long time. forestry and agriculture.6 • EffEctivE mEasurEs against EutrophicationkCOTSreTTuhS/MLOhnAfeTS:OTOhPSources of nutrients in the Baltic SeaPhosphorus (%/year) Nitrogen (%/year)Forests 19%Agriculture 6%Forests 1%Small sewage Small s ewagesystems 6% systems 8%Internal load Agriculture 53%80% Wastewatertreatmentplants 6% Wastewatertreatme ntOther 1% plants 10%Other 10%FigurE 1. Source distribution of phosphorus and nitrogen to Baltic Sea waters. The size of the external nutrientload to the whole Baltic Sea (31 thousand tonnes of phosphorus/year and 826 thousand tonnes of nitrogen/year) isfrom Helcom’s PLC-6 (2018)2 and the source distribution of the external nutrient load from Arheimer, et al. (2012)1.The internal phosphorus load is estimated by Savchuk (2018)3 to 100–150 thousand tonnes of phosphorus/year.The internal nitrogen turnover in the Baltic Sea is complex and is not in the diagram of nitrogen sources.The load from the catchment area Eutrophication status in the Baltic Sea10 Ecological statusNitrogen HighGoodModerate5 UnsatisfactoryBad0Phosphorus60402001850 1900 1950 2000 1920 1940 1960 1980 2000FigurE 2. The load of nitrogen and phosphorus in the FigurE 3. The aim of the Baltic Sea Action Plan is for the BalticBaltic Sea from the catchment area increased significantly Sea to be unaffected by eutrophication. However, it takes timefrom the 1950 to 1980, and then decreased as a result of to achieve positive results and it was only in recent years thatmeasures. Figure data from Gustafsson (2012)4. the ecological status has improved. The figure is from Andersenet al. (2015)5 and the line represents a five-year average.EffEctivE mEasurEs against Eutrophication • 7)raey/sennot000,001(negortiN)raey/sennot000,1(surohpsohPBALTiC SEA CONVENTiON AND BALTiC SEA ACTiON PLANThe Baltic Sea Convention (Helcom) was established in 1974 to protect and im-prove the Baltic Sea environment. Helcom decided on an action plan, the BalticSea Action Plan (BSAP), where the necessary measures were identified to restorethe Baltic Sea to good ecological status by 2021. In order to reduce eutrophication,Helcom has estimated how much nitrogen and phosphorus emissions from eachcountry in the Baltic Sea catchment area will need to be reduced annually. Accor-ding to the latest agreement from 2013, Sweden needs to reduce its emissions byalmost 10,000 tonnes of nitrogen and just over 500 tonnes of phosphorus per year.In Sweden, water authorities drew up 2015 ambitious action programmes for theEU Water Framework Directive, which would also meet the Swedish BSAP quota,but after a government decision in 20166 , the action programmes were stronglywatered down. Although much has been done since 2013 and water quality is betterin many places, much remediation work remains to be done, both for Sweden andother countries around the Baltic Sea.The BSAP does not take into account the nutrients that have already reached thesea from land, the so-called internal nutrient load. The commitments in the BSAPare not legally binding, which can be a contributing factor to the slow pace of theremediation work.Eu WATEr FrAMEWOrk DirECTiVE– an incentive for the Living Coast projectUnder the EU Water Framework Directive (WFD), all surface waters must achievegood ecological status by 2027. An important component in order to do this is to re-duce eutrophication. In the work on the WFD, environmental quality standards andaction programmes are decided every six years. The first management cycle endedin 2009, the following 2015 and the next 2021. A work cycle begins with the map-ping of the environmental status and assessment of the water status and impact.Based on this, action programmes, management plans and environmental qualitystandards are set. The action programmes are binding for authorities and munici-palities, but not for individual users or landowners.The water management work in Sweden is divided into five different water districtsand is led by the water authorities in the respective districts under guidance fromthe Swedish Agency for Marine and Water Management (SWAM) and the GeologicalSurvey of Sweden (SGU).The Water Framework Directive applies to the Baltic Sea coastal waters and theLiving Coast project hopes to contribute knowledge and experience gained duringthe work of restoring Björnöfjärden to the water management efforts.8 • EffEctivE mEasurEs against EutrophicationLiving Coast– a full-scaleremediation projectSeven years ago, Björnöfjärden at Ingarö in Värmdö Municipalitywas one of the most eutrophic bays in the Stockholm archipelago.Oxygen-free “dead zones” were widespread and nutrients wereleaking from a number of different sources. Now Björnöfjärdenis healthy and has clear water, with a rich plant and animal life.The bay is also on the way to having a natural fish communityand oxygenated bottoms with bottom-dwelling animals.EffEctivE mEasurEs against Eutrophication • 9Successful results after action against eutrophicationThe project’s systematic remediation efforts have reduced the supply of phosphorus toBjörnöfjärden’s waters by around 70 per cent. Eutrophication was caused by nutrients leach-ing from poor sewage systems, agricultural activities, horse keeping and from earlier dischar-ges stored in the sediment of the bay. This phosphorus is released when the sediment becomesoxygen-free. Björnöfjärden’s environment also improved due the fact that the water exchangewith the nutrient-rich bay outside is limited. If the water exchange were greater, the waterquality in the bay outside would control the water quality that can be achieved in Björnö-fjärden.Where do the nutrients come from?In the area around Björnöfjärden, there are almost 1,000 homes, a farm, some horse farmsand a conference centre with a cider press, brewery and distillery operations.The nutrients (phosphorus and nitrogen) that reach the bay from the catchment area comepartly naturally from forests and open land, but mainly from human activities in the formof leakage from agriculture and horse keeping, as well as emissions from homes with poortreatment of toilet waste (Figure 4). The nutrient supply was reduced by various measuresdescribed on pages 17–40. Y Nutrients from the catch-ment area reach BjörnöfjärdenBefore the project started, the largest phosphorus source to the bay’s waters was frommainly via ditches. The supplythe phosphorus emissions of earlier years stored in Björnöfjärden’s bottom sediment (Figure varies widely over the year.4). The accumulated phosphorus leaked back to the water to a much larger extent when the Most will come during thespring when the snowmeltsediment became anoxic. This is because iron, which usually binds phosphorus in sediment,brings nitrogen and phosphorusloses its ability to bind phosphorus in anoxic conditions. with it in both dissolved formThe natural annual phosphorus load was estimated at 58 kg phosphorus, assuming relati- and bound invely low losses from forests (1075 hectares, 0.04 kg phosphorus/hectare, 43 kg phosphorus/year) and open land/pasture (243 hectares, 0.06 kg phosphorus/hectare, 15 kg phosphorus/year).Phosphorus supply to BjörnöfjärdenBefore action: approx. 840 kg/year After action: approx. 240 kg/yearFigur 4. These figures showFor est and open land 7% Forest and open land 24%where the phosphorus thatreached Björnöfjärden’s waterAgriculture 5%Agriculture 7% came from at the start of theHorse keeping 2% project 2011 and when themeasures implemented haveSmall Internal Horse keeping 4% reached full effect (% per yearsewage load 42% from the respective nutrientsystems 10% Small sewage source).systems 17%Säby manor farm 6%Säby manor farm 5%Internal load 71%10 • EffEctivE mEasurEs against EutrophicationBjörNöFjärDENBjörnöfjärden’s surface area is 1.5km2 and the catchment area (the landarea that supplies the bay with waterfrom, for example, precipitation) is 15km2. The maximum depth of the bayis 25 metres. At a depth of about sixmetres, there is a strong stratification,amoxtayhsgeserenms-.ofUrc elneind(eeh,ribgthheteliwgthe heteenr dmt )wofocorliwnmaeot,e sitrti osfSäbyvikenthe year, and the area of the anoxic a limited waterexchange withbottom area corresponds to about Nämdöfjärdenoutside.half the bay’s area. The bay’s water isbrackish, with a salinity that variesbpNnaeeätrrmrwmodewiöellfnsej hä.aTrapdhlpleeornwowoxasi umt ttersaaritidete,exl acyinhs4 da. t0nhtgrhaoeenudwagvh5ite.ha5r a geBjörnöfjärden Nämdöfjärdenwater exchange period is about threem timon et fh os r. lT oh ci asli ascatil oo nn gtoe pn ro ou vg idheh ao l mdi en ag-InfjäT ro dr ep ne-surable local effect.The corresponding nitrogen contribution was 1,560 kg of nitrogen/year (forests: 1,074 kgnitrogen/year, open land/pasture: 486 kg nitrogen/year)7. In the calculations, it is assumedthat the land in the catchment area without modern human influence would consist of wood-land and extensive pasture and would have no point sources.The human phosphorus load (180 kg/year) consists mainly of sewage emissions and agri-cultural leakage. There are just over 850 residential buildings without municipal sewage con-nections, located both on moraine and on clay soil7. About 200 properties had illegal or de-fective sewage solutions at the start of the project9. Originally, development consisted mainlyof summer cottages with small plots, but recently, more and more properties have been usedfor accommodation year-round10.Source distribution of nutrients from Björnöfjärden’s catchment areaPhosphorus (kg/year) Nitrogen (kg/year)FigurE 5. Before action Other sewage systems,was taken, approximately262 kg (8%)240 kg of phosphorus andover 3,000 kg of nitrogen peryear were estimated to haveOther sewagereached Björnöfjärden from Forest andsystems,the catchment area. Based open land,45 kg (19%)on the average nutrient loss 58 kg (24%)per unit area and land type,Forest andand average nutrient emis- Small sewagesions from different types systems, open land,of small sewage systems. Small sewage Arable land and 1,079 kg (32%) 1,560 kg (47%)Figures from Erlandsson etsystems, horse keepingal. (2013) 7.83 kg (34%) 55 kg (23%)Natural Arable landimpact (24%) and horse keeping,439 kg (13%) Anthropogenic NaturalAnthropogenic impact (53%) impact (47%)impact (76%)EffEctivE mEasurEs against Eutrophication • 11Intensive agriculture of approximately 45 hectares of the catchment area and about thirtyhorses kept in the area also contribute to Björnöfjärden’s eutrophication.In addition to this is the nutrient load from Säby conference facility and Smakriket Säby withits cider press, brewery and distillery operations in the north of the bay. A few years intothe project, when more information from the area became available, it was found that thesewage systems of Säby conference and Smakriket Säby worked significantly worse than firstestimated10, which means that the annual load to the catchment area was about 20 per centhigher than first estimated.The load estimates are based on the source distribution analysis of eight different sourcesaggregated into the four largest: forests, arable land, open land (incl. pasture and gardens)and small sewage systems (incl. community facilities) (Figure 5).Internal load dominantAlthough nutrient leaching from Björnöfjärden’s catchment area is significant, the lar-gest phosphorus supply to the water came from the bay’s sediment (Figure 4), which alsoapplies to nitrogen11. This is because the load to the bay exceeded the sediment’s ability tostore phosphorus for many decades. Phosphorus released when, for example, algae is brokendown, leaks back to the water instead of being bound in the sediment. The situation is exa-cerbated by the sediments having been anoxic for decades, which reduces the phosphorus-binding ability. The phosphorus inclined to leak, which is estimated to be unreleased to thewater over time, consists in Björnöfjärden’s sediments of organically bound phosphorus andamounts to 1.5 g phosphorus/m2 (12).Anoxic areas spread in the 20th centurySediment cores examined to reconstruct the oxygen situation in the bay indicate that atBjörnöfjärden’s deepest point (25 m), oxygen deficiency has occurred for at least 200 years13.However, the large increase in the spread of anoxic bottom waters occurred during the 20thcentury, especially in the 1960s to 1970s (Figure 6). It was during this time that the nutrientload from the bay’s catchment area by all indications accelerated, in pace with the expansionof summer accommodations around the bay. During that period, the nutrient levels were alsovery high in the entire Stockholm archipelago as a result of poor wastewater treatment14.Strong algal blooms in the archipelago were common, unlike today when the algae bloomsoften originate in the offshore areas, where the phosphorus that drives the blooms mainlyis released from the deep bottoms of the offshore areas. Imports of algal blooms from Näm-döfjärden may have been a source of nutrients for Björnöfjärden, along with increased nu-trient loads from the catchment area. The strait between Björnöfjärden and Nämdöfjärdenwas dredged in 1968, which probably increased the influx of heavier and saltier bottomwaters. If the dredging led to a less frequent exchange of bottom water since then, meaningthat the exchange of oxygenated bottom water decreased, it may also have contributed to thegreater expansion of anoxic bottom areas15.Anoxic bottom areas in Björnöfjärden 1920–2015100FigurE 6. The percentage ofbottom areas deeper than80 8 metres in Björnöfjärdenthat has been anoxic atleast during the summer in60 the past.402001925 1935 1945 1955 1965 1975 1985 1995 2005 201512 • EffEctivE mEasurEs against Eutrophication)sertem8>(%saeramottobcixonaegatnecrePPreparation,evaluationand actionBefore the remediation work started, the bay and the catchment areawere examined for a year in order to obtain a clear picture of thebaseline and thereby measure the effects of remediation. At the sametime, a nearby bay, Fjällsviksviken, with similar eutrophication pro-blems was examined but no action was taken. The use of a “compa-rison bay” made it possible to distinguish the effects of remediationfrom the results of variations in weather between different years. Toreduce nutrient supply to the bay, remediation measures were imple-mented in the area around the bay and in the water. These measuresled to a significant improvement in the environment in Björnöfjärden.EffEctivE mEasurEs against Eutrophication • 13regOLOkeneTTAvSegIrevS:OTOhPMonitoring of Björnöfjärden and FjällsviksvikenA sampling programme in which water chemistry, plankton and sedimentation traps werestudied on a continuous basis16 is supplemented once a year with studies of, for example,extension of anoxic bottoms17, fish stocks18.19, benthic fauna20 and underwater vegetation21, 22,23. In addition, the water level is continuously measured in the bays16, as well as the waterexchange between Björnöfjärden and Nämdöfjärden outside. The sampling started in 2011and is scheduled to last until 2022.Water chemistry and plankton are measured between 15 and 20 times a year, both inBjörnöfjärden’s and Fjällsviksviken’s various sub-basins and also just outside the respectivebays. In order to detect the concentration differences between surface water in different partsof the bay at the time for sampling, a so-called volume-weighted and depth-integrated samp-ling procedure is used. Several surface water samples from the different parts of the bay aremixed together into a sample that is analysed and represents the entire surface water abovethe thermocline for the respective basin24. In addition, at the deepest point in each sub-basin,three water samples are taken at specific depths, evenly distributed between the thermoclineand the bottom, for the measurement of nutrients and hydrogen sulphide. At the deepestpoint of the bays, temperature, salinity and oxygen are measured at one-metre intervals fromsurface to bottom. Sedimentation of nutrients and materials in the bays is also measured insedimentation traps placed above and below the thermocline.The fish communities of the bays are monitored using multi-mesh gillnets18, trap netsand juvenile fish sampling using small underwater detonations19. The density and speciescomposition of the benthic fauna are examined20 and the composition and depth spread ofthe vegetation belt are inventoried in annual diving investigations21,22,23. Concentrations ofaluminium in bladderwrack, benthic fauna and perch are also measured annually to see if thealuminium treatment of the bottoms to stop the bay’s internal load contributed to increasedlevels in plants and animals25.Both Björnöfjärden and Fjällviksviken are also included in the Svealand Coastal WaterManagement Association (SKVVF) surveys, in which a large number of stations are studied,which form the basis for the status classification of Svealand’s coastal waters according to thewater management assessment program.Björnöfjärden’s contributing water courses Y Water quality in Björnöfjär-den (above) and in the catch-In order to identify nutrient sources and appropriate measures in the catchment area and to ment area (below) is examinedmore than 15 times a year inevaluate the effects of action, water samples are also taken in all major waterways26. In someorder to be able to monitor howwaterways, samples are taken only in the outlet, in others samples are taken at several points the environment changes asto be able to distinguish the effects from different sub-areas or activities (Figure 7). New a result of reduced nutrientsupply due to remediationsampling points were added when new sources were discovered or when measures were im-measures.plemented. Sampling is usually done once a month, but more often during high water flowsduring spring and autumn. In order to calculate the transport of nutrients from different sub-catchment areas, water flow calculations from SMHI are used. This type of study is the basisfor assessing the nutrient contributions of different sources and the effects of remediationmeasures. It often needs to run for several years as differences in precipitation between yearsaffect when the nutrient transport takes place.FigurE 7. The Björnöfjärdencatchment area (thicker red line)has been divided into ten smallersub-catchment areas (dashedred lines). The levels of nitrogenand phosphorus in the contribu-Säbyviken tayi erneagrsw(tsua adt me ier pdwliaanyrgosuponofditnh2te s0s mteimaa rrekesea dasa limited water in red).exchange withNämdöfjärdenoutside.Björnöfjärden NämdöfjärdenInfjäT ro dr ep ne-14 • EffEctivE mEasurEs against EutrophicationMLOhredeSkIrderf:OTOhPY The ecosystem is studied Measures to reduce eutrophicationeach year in both Björnöfjär-den and in the comparison bay In order to reduce the nutrient supply to the water and to counteract the effects of eutrophica-Fjällsviksviken. To be able totion, a number of measures were implemented, both in the Björnöfjärden catchment area andidentify changes, it is importantto both be able to compare with in the bay itself (Figure 8, page 16). The total supply of phosphorus from the various sources,what it looked like before the external and internal, ranges from approximately 3 kg to 600 kg per year. All measures aremeasures started and whatimportant, but the greatest effect on the total phosphorus reduction was from the aluminiumchanges occur naturally, forexample due to variations in treatment of sediment, followed by improved private sewage systems.temperature and precipitation. The next page summarises the measures implemented in and around Björnöfjärden. Moreinformation on the prerequisites and implementation of the respective measures can be foundon pages 17–40.All measures are importantImmediately after the aluminium treatment, phosphorus levels in the bay’s water decreasedrEAD MOrE ABOuT... and after just a few months the levels were cut in half. It has positively affected the underwa-the project’s investigations ter environment in many ways, as described on pages 47–52.and analyses in the Living Land measures are estimated to cut in half the nutrient transport from land to the bay incoast projects completethe long run. It will take a few years before the measures have been fully effective, because aWhite Paper.large amount of nutrients are stored in the soil and ditches for a long time.Although the aluminium treatment binds the most phosphorus and provides a rapid effect,it is very important to also minimise the nutrient supply from land; otherwise new nutrientstores are built up in the sediment that begins to leak to the water again.EffEctivE mEasurEs against Eutrophication • 15regOLOkeneTTAvSegIrevS:OTOhPLarger sewage systems, 45 kg/ Pike wetland Small sewage systems, 80 kg/yearyear through a new sewage through a new sewage through increased supervision, sewage systemsystem at the conference system at the conference counselling and financial support, thecentre and cider press at Säby centre and cider press at phosphorus reaching the bay frommanor farm, these phospho- Säby Manor Farm, these small sewage systems has beenrus emissions to the bay are phosphorus emissions to cut in half. Compensation hasestimated to decrease by at the bay are estimated to been paid to private propertyleast 70%. decrease by at least 70%. owners who have switchedto a sewage solution wheretoilet waste is collected andtransported away from thearea.Agriculture, 38 kg/yearBy liming the fields to improve soil structure,installing phosphorus ponds with lime filterbeds and trench draining with lime in-mixture, the phosphorus leakagefrom the fields is estimated tohave decreased by just over 80%.implantation of bladderwrackBladderwrack has been plantedin several locations in the bay.seaweed belts are importantfor fish fry and small animalsthat live here, which in turnprovide important food for fishand birds.Horse keeping, 17 kg/yearthrough the daily manure-clearingof pastures, storage of manure on awatertight manure plate, protec-tion zones around ditches, soil sta-bilisation and drainage of trampledland, nutrient leaching from thehorse farms has been reduced byaround 70%.Fishing ban internal load, 600 kg/year Outdoor toilets in the nature reserve,To regain a strong pike With aluminium treatment 3 kg/year By equipping the outdoorpopulation, fishing bans of deep and anoxic bottoms, toilets in Björnö nature reserve withwere introduced during phosphorus leakage from closed tanks, nutrients and infectiousthe spawning season. the bay’s sediment has been agents from toilets are taken care ofstopped. Aluminium binds the instead of leaking out to the bay.phosphorus to the sedimentand thus stops the phospho-rus leakage to the water. Themeasure has reduced thephosphorus supply to water by after actionjust over 80%.yet to be addressedcannot be correctedFigurE 8. in order to reduce the nutrient supply to the water and tocombat the effects of eutrophication, a series of measures were imple-mented, both in the Björnöfjärden catchment area, and in the bay itself.The total supply of phosphorus from the various sources ranges from 3to 600 kg per year. All measures are important, but the greatest effecton the overall phosphorus reduction was from aluminium-treatment ofsediment, followed by improved private sewage systems. These diagramsshow the effectiveness of the measures to reduce the phosphorussupply from the various sources. The size illustrates relative differencesin annual supply from the sources.16 • EffEctivE mEasurEs against EutrophicationMeasures toreduce nutrientlosses fromagricultureAgriculture is today the single largest source of nutrients from land to the BalticSea and accounts for about half of the total nutrient supply2. Since the 1950s, theagriculture in Sweden has undergone rapid development to intensify the produc-tion on ever larger farms, which are often specialised in plant or animal produc-tion27, 28. This development, combined with extensive trenching, has contributed tonutrient losses from operations that reach the Baltic Sea to varying degrees, wheresensitive environments become eutrophic and are damaged28.EffEctivE mEasurEs against Eutrophication • 17Measures have reduced the supply – but more needs to be doneMeasures in areas such as wastewater treatment, industry, forestry and agriculture have redu-ced the nutrient supply to the Baltic Sea, which today is judged to have returned to the levelsof the 1960s (for phosphorus)4. In agriculture, the measures have, for example, resulted inimproved manure handling, fertilisation restrictions and counselling to farmers, as well asopportunities for financial support for certain environmental protection measures. Neverthe-less, more efforts are needed, at the same time that a resource-efficient food production ismaintained.Today, large quantities of nutrients are imported into the Baltic region in the form ofcommercial fertilisers for plant production and feed for livestock30. The manure produced inthe region is poorly used; only half of the nutrients in the manure is converted to harvestedcrops31. The rest remains in the ground or is lost to air or water, and contributes to eutrophi-cation. The nutrient flow is largely one-way. For efficient nutrient utilisation without nutrientleaching to the environment, the cycle of nutrients needs to be closed. It is also important totake good care of the fields through careful crop selection, cultivation techniques, working ofthe soil and manure yields, as well as to ensure that the soil has a good structure and gooddrainage conditions so that crops can use the nutrients in the soil effectively.Choice of measuresIn order to increase nutrient utilisation and minimise the impact of agriculture on the BalticSea, both short- and long-term measures are needed, both at the farm level and at the BalticSea catchment level.• Examples of large-scale/structural measures are to introduce economic incentives to re-duce imports of commercial fertiliser and animal feed and thereby stimulate increasedrecycling of livestock manure to plant production in order to close the nutrient cycle to agreater extent.• Examples of measures at the farm level are having safe manure handling, avoiding over-dosing with fertilizer, using stored phosphorus in the soil, keeping the soil overgrownduring the autumn, liming the fields to improve soil structure, installing lime filter ditches,protection zones along waterways, phosphorus ponds and lime filter beds.It is crucial for a high action effect that the right measures are implemented in the rightorder, at the right place and at the right time32. Often 90 per cent of the nutrient losses in acatchment area are from 10 per cent of the area, during 1 per cent of the time. Consequently,site-specific knowledge is important.There are a number of different measures that can be implemented to minimise nutrientleaching from agricultural activities. Within the Living Coast project, several different agricul-tural measures were implemented: structure liming, phosphorus ponds with lime filter beds,two-step ditches and lime-filter ditches, see pages 20 – 22.rEAD MOrE ABOuT...how to reduce nutrient load in the Baltic sea in the complete Living coast White paper and inreports from SLU33,34 and the Swedish Board of Agriculture32. An action catalogue is availa-ble in the water authorities’ Water Information System of Sweden (www.viss.lansstyrelsen.se). The Goodla project has gathered readily accessible knowledge about environmentalmeasures in agriculture on film. The project is run by SLU and LRF and is financed by Formas(https://www.slu.se/institutioner/mark-miljo/samverkan/goodla/).Y For farm-level actions to besuccessful, local involvementand good knowledge of the siteare required. The agriculturalmeasures at Björnöfjärdenwere implemented in coopera-tion with the farmer of SäbyFarm.18 • EffEctivE mEasurEs against EutrophicationPrerequisites for agricultural measuresResponsibilityIt is the farmers’ responsibility to ensure that the necessary environmental measures are im-plemented. The county administrative board has responsibility for the activities for which apermit is required, but the supervision is often delegated to the municipalities. The require-ment for agricultural companies to reduce nutrient leaching to bodies of water that do notachieve good ecological status is possible regardless of whether environmental aid from, forexample, the Rural Development Programme is obtained or not. However, such call for actionhave not yet been made in Sweden.For agricultural companies with activities subject to permits (with animal husbandry),environmental improvement measures in accordance with the Environmental Code can bebinding for individual farmers. The instruments available for this are supervision and self-inspection. For other agricultural companies (and horse keeping), the action potential is incooperation, consultations, recommendations, agreements and compensation, where opp-ortunities for environmental aid and compensation in the rural development programme orother funding have a crucial role in actions taking place.FinancingSupport for the financing of agricultural and horse keeping activities is mainly carried outthrough the Rural Development Programme (administered by the Swedish Board of Agri-culture) and LOVA grants (local water manangement projects administered by the countyadministrative board). Both require co-financing.Y To obtain high efficiencyof actions, t is crucial that the Counsellingright measures are implemen-Counselling plays a key role in the remediation work in agriculture. The counselling projectted in the right order, at theright place and at the right time. Greppa Näringen [Getting hold of nutrients], which is a collaboration between the Board ofAgriculture, the Federation of Swedish Farmers (LRF) and the county administrative boards(2001-2020), has led to an annual reduction in nutrient leaching by 790 tonnes of nitrogenand 15-30 tonnes phosphorus, while at the same time helping to make every single farm moreresource-efficient, according to the project itself.LiViNg COAST on measures in the agricultural landscapeThe pace of action in agriculture is too low to achieve the objectives of, for ex-ample, the Water Framework Directive, Sweden’s national environmental targetsor the Baltic Sea action Plan (BSAP).The municipal supervision of agricultural activity is inadequate. The fact that ac-tion is not being required to a greater extent may be due to there not being enoughoverview and knowledge to identify the main nutrients sources.The individual farmer, with unique knowledge of his or her land, can often by smallmeans reduce nutrient losses to waterways. Clear incentives are needed thatreward farmers who minimise the nutrient loss from their activities.Agricultural measures (and other measures) need to be carried out on the basis ofa catchment area perspective. the county administrative boards have an im-portant role as initiators, coordinators, catalysts and driving forces, and the workshould be coordinated by a catchment officer or action coordinator.The costs for a necessary pace of action need to be identified and distributedbetween agricultural companies and the public sector, and a long-term plan forinvestment needs to be developed. Short-term, unpredictable investments are atrisk of being ineffective, which is why better evaluation of action effects is neces-sary.There is room to reduce the impact of agriculture on the Baltic Sea without theneed to reduce production. Structure liming can even increase crop yield.EffEctivE mEasurEs against Eutrophication • 193Agricultural measures 2within Living Coast 4 21Before1STruCTurE LiMiNgAfterClayish soil is often compact (left).in structure liming, burned lime orquenched lime is mixed into the soil. Itmakes the soil more porous (right), so thatthe crop’s roots more easily access waterWater and nutrients. The crops grow better andphosphorus leaching can be reduced by upnutrientsto 50 per cent.2P HOSPHOruS PONDc WiTH LiME FiLTEr BEDb A phosphorus pond with lime filter bedscan reduce nutrient transport by up to 60 per 3L iME FiLTEr DiTCHcent for phosphorus and 25 per cent for nitro- in trench draining, excess water is di-a gen. Water from the fields’ drainage system verted from the field into buried pipes.is collected in the deep part of the pond (a) When the pipes are dug down, lime is mixedwhere large phosphorus-rich particles sink into the soil. The lime is active for about 30to the bottom. Smaller particles are trapped years and binds the phosphorus that is dis-among aquatic plants in the shallow part (b). solved in the water into the soil around thePhosphorus in dissolved form is trapped in pipes. Trench draining is necessary for thethe lime filter beds (c). Phosphorus that is crop to grow well. If it grows poorly, nutrientstrapped in the pond can be dug up and re- leach out of the field instead of being takenused on the field. up in the crops.1. STruCTurE LiMiNg FigurE 9. If the proper agri-cultural methods are used,Structure liming is a well-known agricultural measure that makes the soil structure of clay the harvest will be good, whilesoil more fine-grained and porous, so that water and nutrients are kept in the soil and the leaching of nutrients and organicmaterial is minimised. In coope-roots can grow deeper. The measure contributes both to a reduction in nutrient transport andration with Säby Farm, located atto a better growth of the crop, and does not require specific maintenance. Björnö fjärden, four agriculturalStructure liming is suitable in well-drained fields in the southern and central part of Swe- mea sures were implemented toreduce the impact of the farm:den where soils with a high clay content are common35.structure liming, phosphorusponds with lime filter beds, limeStructure liming in figuresfilter ditches and two-stageditches.• Structure liming can cut in half phosphorus losses from arable land that has a clay contentover 20 to 30 per cent36,37.• In Sweden, the action potential is the largest in Östergötland, Uppsala, Västmanland andSödermanland counties. So far, only just over 4 per cent of the country’s suitable arableland has been structure limed38.• Today, there is uncertainty about the long-term effect of structure liming. The duration af-fects the treatment cost which varies between SEK 900 and 2,700 per kilogram of phospho-rus, depending on whether the effect lasts for 30 or 10 years, respectively. It is uncertainwhy the effect of the structure liming of some clay soils appears to fade within a decade,as seen in the structure liming at Bornsjön.20 • EffEctivE mEasurEs against Eutrophication4T WO-STAgE DiTCHES Y At Säby Farm at Björnöfjärden, structure liming and phosphorus ponds with lime-filter beds, amongtwo-stage ditches can other measures, have reduced the nutrient load from agriculture to the bay by just over 80 per cent. inreduce nutrienttransport the middle of the picture, the narrow phosphorus pond is visible with the lime filter bed on the right. Toand promote biodiversity. the left of the pond is a pile of structure lime to be incorporated into the clay field.at high water levels, waterspreads out on grass plateauswhere nutrients are absorbedConditions for structure limingand particles are trapped. Therisk for erosion decreases andThere are recommendations from, among others, the Board of Agriculture and the Greppaaquatic animals thrive in themiddle trench. Näringen project on where and how to implement the structure liming. But it is up to theindividual farmer to take the initiative and implement the measure. Funding support can besought primarily from the county administrative boards’ LOVA grants, but also from the Boardof Agriculture’s Rural Development Programme.rEAD MOrE The structure liming in Sweden has mainly been carried out in the scope of major remedia-ABOuT... tion projects. In order to increase the pace of action and to improve the structure liming ofindividual farmers, the following are needed:structure liming in “soil-• More targeted financing support for structure liming. The measure is often too expensivestructure improvementmeasures – structure without support financing.liming of clay soil” (SLU), • Driving forces that coordinate and administer the measure for larger areas, as farmers findat Goodla (SLU/LRF) it difficult and financing support is sometimes uncertain.and the websites of the• A quicker response to decisions on financing support so that the applicant can have timeGreppa Näringen projectfor the structure liming during the short period of the year in which circumstances areand Project Born.suitable.There is also more infor-mation in the full Livingcoast White paper and2. PHOSPHOruS POND WiTH LiME FiLTEr BEDthe report ”Structureliming on a large scaleNutrient transports from arable land and land around livestock farms may be reduced if run-– what is required andoff water is led through a phosphorus pond with lime filter beds. The installations should bewhat does it cost” 38.located close to the source of the pollutant, preferably high up in the catchment area nextto agricultural land with high phosphorus losses. For the phosphorus pond to be effective,it must be large enough to even out the flow so that most of the water flow is led throughthe lime filter. At optimal placement, the installations are cost-effective measures, but theyrequire relatively extensive supervision and maintenance to maintain good functioning.EffEctivE mEasurEs against Eutrophication • 21Phosphorus ponds with lime filter beds in figuresrEAD MOrE• For the most arable land inclined to leaching in the Baltic Sea coastal areas, phosphorusABOuT...ponds with lime filter beds are estimated to be a suitable measure for about 15 per cent ofphosphorus ponds withthe area, and lime filter beds alone are suitable for another 55 per cent39.lime filter beds in the• The average treatment effectiveness seen over 20 years for the installations is up to 60 per complete Living coastcent for phosphorus and 25 per cent for nitrogen39. White paper and the report“action potential in agri-• Optimally placed installations can be cost effective, SEK 500-1,300/kg phosphorus assu-culture and the possibilityming a life span of 20 years39. of reduction with lime filterbeds and phosphorusConditions for phosphorus ponds and lime filter beds ponds”39.It is up to individual farmers to establish phosphorus ponds and lime filter beds. Financingsupport can be applied for from the Rural Development Programme through the SwedishBoard of Agriculture. To increase the rate of action so that more phosphorus ponds with limefilter beds are built, environmental aid compensation needs to be increased by around 20 percent. This is to cover the loss of income for arable land that is decommissioned and the cost ofestablishment which is often higher than what the level of aid is calculated for. The paymentprocedures for environmental aid also need to be streamlined and simplified39.It is difficult to get an installation with optimal function, in part because the function isaffected by many factors:• Water flow: Nutrient retention is only effective at low water flow rates.• Size: The larger the pond, the lower the water flow and the greater capture of nutrients.• Age: when vegetation in the shallow part of the pond is established, the purification ef-ficiency increases.• Extreme events: Downpours, pond embankment collapses, faeces from flocks of birds andY A phosphorus pond will notmore, can significantly impair the pond’s function.be effective at purifying the• Establishment/adjustment: during excavation, surfaces are exposed to erosion, which for water until after a few yearsa period increases turbidity and export of nutrients to waterways. when vegetation that preventserosion from the pond itself hasestablished.3. LiME FiLTEr DiTCHESGood drainage of fields is necessary both for the crop to grow well, and for minimising fertili-zer leaching from the field. If the crop grows badly, nutrients leach out of the field instead ofbeing taken up by the crop. In trench draining, excess water is diverted from the field into bu-ried pipes that flow into ditches surrounding the fields. With lime filter ditching, lime is mixedinto the soil that surrounds the trench drainage pipes. The lime effectively binds phosphorusthat is dissolved in the water, and the measure is assumed to work for about 30 years. Withinthe Living Coast project, lime filter ditches were built, but are not yet evaluated, as there isnot yet enough data.4. TWO-STAgE DiTCHESFields are dependent on ditches for good drainage, but ditches speed up the transport of nu-trients from the fields to the sea. Two-stage ditches can be built to reduce nutrient transportwhile increasing the biodiversity of the agricultural landscape. The two-stage ditches have amiddle trench, which is surrounded by higher, plant-covered terraces. In normal flows, the Y When a lime filter ditch iswater goes into the middle trench and at higher flows, the water rises onto the terrace where installed, the lime is mixed intothe backfilled soil. The limenutrients are absorbed, nitrogen escapes to the air and nutrient-rich soil particles are trap-binds phosphorus that is dis-ped among the vegetation. The risk of erosion from the edges of the ditch is small. Both the solved in the water.middle trench and the terrace are good environments for plants and hiding places and fee-ding areas for animals. Within the Living Coast project, two-stage ditches were built, but willnot be evaluated. This is because the two-stage ditch was built relatively late in the projectand it takes a few years before the ditch acquires the intended function.22 • EffEctivE mEasurEs against Eutrophicationhorse keepingalso contributesto eutrophicationIn Sweden, horse keeping is an extensivesmall-scale business often conducted byprivate individuals as a leisure pastime40.It is common for horse manure to behandled carelessly and that pasturesare used so intensively that thevegetation cover is worn down,which leads to nutrient leaching andeutrophication.EffEctivE mEasurEs against Eutrophication • 23Living Coast’s1measures at2horse farms347 cm Paddex10 cm soil/sand100% 20 cm macadamsoil weaveDräneringsrörapprox.50% approx. 35% approx.15%Nutrient loss 1D AiLy MANurE CLEAriNg 2P rOTECTiNg THE SOiL 3P rOTECTiON zONESfrom a horse farm The phosphorus loss from avoid having more than two horses About half of thecan be reduced a horse farm can be cut in per hectare of pasture in order not remaining phospho-by about 90 per half if the pastures are cleared to wear down the vegetation cover. With rus can be bound by plantscent through four from manure daily, the ma- fewer horses in the pasture, stabili- in protection zones alongmeasures: nure is stored on a watertight sation and good drainage where the ditches and waterways.manure plate and returned ground is easily trampled, for example The horses should be keptto arable land where the nu- at gates and feeding locations, nutrient away from ditches with thetrients are recirculated. losses are further reduced. help of fencing.Daily manure clearing and avoiding a bare soil-surface FigurE 10. There are manymost important measures that can be done onhorse farms to reduce nutrientAn adult horse excretes as much nutrients as it receives through its feed41. The phosphorus losses. Horse breeders can doseveral themselves throughleaves the horse mainly via its faeces, if it is not over-fed, then some also ends up in the uri-changed routines and smallne42. This often leads to high nutrient levels in soil where horses are kept 43, 44, 45,46. Some of the efforts on the farm, whilemanure that is not removed from pastures is tied up in the soil, but the soil’s vegetation cover other measures require work bycontractors for various types ofneeds to be complete in order to hold the nutrients from the horses. If the soil is saturatedinstallation work and construc-with nutrients or the vegetation cover is worn down, the risk is very high for nutrient losses to tion.waterways, lakes and the Baltic Sea. Measures are therefore most important where many hor-ses are kept on a small area, especially if the horses are kept close to ditches and waterways.Horse keeping in figures• In Sweden, there are just over 100,000 properties where horses are kept47, most of which(75 per cent) only have one to five horses48. About 75 per cent of the horses are in or nearlarger towns49.• The most horses are in Skåne, Västra Götaland and Stockholm counties47.• At more than 2-3 horses per hectare, the soil is worn down and leaks nutrients50.• Nutrient loss would decrease 20-30 per cent if the compound feed was excludedfor recreational horses51.24 • EffEctivE mEasurEs against EutrophicationThe four measuresreduce nutrient leachingby about 90%.ground levelvegetation layersand+lime productgeotextileLime bedd+macadamDrain pipeapprox.10%4L iME FiLTErDitch water down-stream of a horsefarm can be furtherpurified if the water is ledthrough a lime filter bedin s ditch where dissolvedphosphorus is bound.Y if more than two to three horses are kept per hectare of pasture, the soil is at risk of being worn sohard that the vegetation cover breaks down and the soil’s ability to bind nutrients deteriorates signifi-cantly.Conditions for measures on horse farmsResponsibilityHorse keepers are are responsible for ensuring their activities do not damage the environ-ment or interfere with the surroundings. Small-scale horse activities are not covered by theBoard of Agriculture’s rules on animal husbandry in agriculture, but are by general rules ofconsideration in the Swedish Environmental Code52. In addition, there are regulations andgeneral guidelines issued by the Swedish Board of Agriculture and the Swedish Environmen-tal Protection Agency to be followed. The municipality may also decide on local regulationsfor manure handling53. In practice, the regulation of the small-scale horse farm is unspecificand the supervision of the horse farms is sparse or non-existent. This contributes to that thepace of action is low.FinancingSo far, there has been no special support financing earmarked for measures that reduce nu-trient losses from horse keeping. Within the new LOVA ordinance (Swedish Ordinance on lo-cal water management projects)54, the possibility of support financing for measures on horsefarms should be considered.Supervision & CounsellingIt is the municipalities that are responsible for supervising to ensure that horse keeping iscarried out in accordance with the Environmental Code, regulations and general guidelines.There is no advisory programme like ”Greppa Näringen” aimed at horse breeders. It would bedesirable to have an initiative from equestrian organisations.EffEctivE mEasurEs against Eutrophication • 25Horses in summer grazingcontribute very little, if at all,to the nutrient load on the sur-rounding waters. They also helpkeep the landscape open. If thehorses also are fed concentra-tes, however, it entails a netsupply of nutrients that riskcontributing to eutrophication,especially if the horses are keptclose together and the ground isworn too hard.LiViNg COAST on measures at horse farmsThe environmental impact of horse keeping is underestimated, the municipalsupervision is deficient and the rate of action is too low. The number of horsesin sweden is growing and it has become obvious that horse activities contributeto eutrophication. The problem is extensive, and what is crucial to the environ-mental impact of horse keeping is the number of horses in relation to the areathey are kept on. Most important is to collect and manage manure right and toensure that the ground is not worn too hard. Nutrient losses from horse keep-ing can be fixed relatively easily, but small-scale horse farms fall between thecracks, both in terms of regulation and supervision, which is why the pace ofaction is behind. In addition, horses are often kept by private individuals or as-sociations with limited finances and environmental knowledge. They often leasestables, which further complicates the implementation of measures.To REDUCE THE ENvIRoNMENTAL IMPACT oF HoRSE kEEPING, THE FoLLoWING IS NEEDED:• Information to horse owners: Horse breeders often do not know that horsescontribute to eutrophication. Horse owners are a large and diverse target group,which can be difficult to reach. Readily available information and concreteadvice on measures are needed, preferably within the framework of an advisoryprogramme.• Adapting legislation to small-scale horse keeping: Existing regulations are notadapted to the prevailing reality, where many operators have a few horses, oftenon a small area. In the Environmental Code, there is support for requiring action,but this rarely happens. New regulations are needed, which clarifies that:1) It is important to collect and manage manure in a safe way2) The environment is damaged when many horses are kept on a small area3) Horses should not be kept next to ditches and waterways.• Supervision of horse farms: municipalities need to exercise supervision in areaswith horse farms to ensure that the environment is not harmed, and to informabout measures required to reduce the impact. rEAD MOrE ABOuT...measures at horse farms in• Increased support financing: It can be costly for an individual horse owner withthe complete Living coasta few horses to implement measures. In order to quickly improve the situation, White paper and in theit may be cost-effective to investigate opportunities for grants for demolition report “nutrient leachingfrom horse keeping in Swe-and remediation of old manure storage areas and construction of new watertightden – national overviewmanure slabs. These are the most expensive, but at the same time the most and proposed measures”51.important measures.26 • EffEctivE mEasurEs against EutrophicationdvS/dATSeLOhnILAM:OTOhPToilet waste mustbe removed fromthe coastIn Sweden, more than one million people live in proper-ties that are not connected to a municipal wastewatertreatment plant55, and many summer cottages add tothis. Instead of municipal sewage treatment, they havesmall private sewage systems or dry toilets. The smallsewage systems are estimated to account for roughlythe same amount of emissions to lakes and the sea asthe municipal wastewater treatment plants55,56.EffEctivE mEasurEs against Eutrophication • 27kCOTSrETTuHS/APALiSNrOkDiAg:OTOHPLand-based treatment is not enough on the coastCommon technical solutions for the treatment of toilet waste in small sewage systems are sep-tic tanks and infiltration bed, phosphorus trap with an infiltration bed, mini-treatment plantsor closed tanks. Dry toilets with private handling of toilet waste on the plot is also common,but are rarely included in compilations57. A report from 2017 shows that more than 80 percent of Sweden’s small sewage systems have septic tanks, infiltration plants or filtration beds,or unknown technical solutions55. In other words, most have a treatment technology thatrelies on soil purification.What technical solution a sewage system has and how the sewage is managed affectsemissions58. In coastal and archipelago areas, where the layers of soil are thin, the possibilityof soils to bind phosphorus is limited. It is uncertain how well the binding works over time,and several studies indicate that the binding is less than previously assumed59,60,61. With thesetechnical treatment solutions the nutrients accumulate locally, with a high risk of nutrient los-ses to the Baltic Sea, sooner or later (Figure 11). Therefore, in order to protect coastal watersand groundwater in areas where the ability of the soil to bind phosphorus (soil retention)is limited or unknown, sewage solutions where the toilet waste is collected and transportedaway for treatment in wastewater treatment plants are needed. Alternatively, sewage couldbe recycled in for example a hygienification plant (Figure 11).Bathing, dishwashing and laundry water (grey water) no longer contributes to the eu-trophication problems. Nowadays, phosphorus is forbidden in dishwashing and laundry de-tergents, so a very small percentage of the nutrients from a property are found in the greywater. Around 90 per cent of all nutrients leaving a household are in the household’s toiletwaste62.Small sewage systems in figures• More than 35 per cent of Sweden’s small sewage systems have inadequate treatment, andabout half of these are illegal63.• Small sewage systems make up 10 per cent of all domestic sewage systems, but are es-timated to account for as much phosphorus emissions as the 90 per cent connected tomunicipal wastewater treatment plants64.• On average, only about 1-2 per cent of all small sewage systems are improved annually63.• About 80 per cent of the properties around Björnöfjärden that had poor treatment of theirsewage and had inspections and demands set by the municipality implemented measu-res within one year9. Only 40 per cent, voluntarily implemented measures after informa-tion campaigns, sewage system counselling, administrative help and subsidies. The rate of”other” voluntary resolution in the municipality is 3-4 per cent per year.Conditions for fixing defective small sewage systemsIn accordance with the Swedish Environmental Code, small sewage systems are classified asan environmentally hazardous activity that is subject to permit or registration53. Toilet wastehandled in a WC becomes ”water based” and is classified according to sewage legislation,while toilet waste collected in a dry toilet is classified as household waste. Although the originis the same, it falls under different regulations, and is handled differently in supervision andpermit assessments.ResponsibilityIt is the property owner’s responsibility to ensure that the sewage system meets the require-ments of the Environmental Code. The property owner needs to know the system’s capacity,technology and function, as well as the environment’s conditions for receiving and purifyingemissions. This is difficult and requires specialist knowledge. The responsibility of municipali-ties is to examine and grant permits, supervise and monitor and ensure that all small sewagesystems have the necessary permits, and that the sewage systems work as they should65. Mu-nicipalities often provide property owners with an exemption for private treatment of toiletwaste from dry toilets on their own property (plot). The owner is responsible for ensuringthat latrine composting is done correctly66.28 • EffEctivE mEasurEs against EutrophicationLiving Coasts measures for small sewage systemsmany houses with Wc have aninfiltration or filtration bed toMany summer cottages have a dry toilet.purify the toilet waste.Urine and excrement are often compostedand used as fertiliser for plantings on the plot.In areas with thin layers of soil, soil can be Urine and excrement contain a lot of nutrients.saturated with nutrients. The nutrients then To bind nutrients from a person who is a holidaymove on to the groundwater and to ditches, resident about 5 weeks per year, one must cul-which eventually flow into the bay. tivate and harvest 200 kg carrots, for example.Urine and excrement from dry toilets should be emptied ina good sewage solution is to lead toilet waste to a the area’s latrine station, which has a closed tank. The tankclosed tank, and transport the waste to a munici- is regularly emptied by värmdö Municipality. An alternativepal wastewater treatment plant. solution to a dry toilet is to install an incinerating toilet andempty the ash in the garbage.FigurE 11. The top figure illustrates sewage solutions that rely on soil purifying wastewater from nutrients, bacteria and viruses. These typesof purification techniques are not suitable in areas with thin soil layers near lakes and seas. Examples of unsuitable solutions are infiltrationplants, filtration beds, mini-treatment plants (require a lot of supervision and care) and handling one’s own human toilet waste on the plot.The best sewage solutions for properties in areas close to lakes and seas are those where the toilet waste is sorted out and transported awayfrom the area, as the lower figure illustrates. Examples of good solutions are closed tanks, incineration toilets and human waste retrieval oremptying of urine and excrement at a central collection station.EffEctivE mEasurEs against Eutrophication • 29FinancingThere is no support financing that property owners who want to fix their sewage systems canapply for. However, the cost is not always the deciding factor. Few of the property ownerswho did not fix their sewage system within the Living Coast project said that higher subsidiesthan the 10-20 per cent of the total cost they were offered, would have motivated them toimplement measures67.Supervision & CounsellingMunicipalities must conduct supervision to ensure that all small sewage systems have permitsand that they work as they should65. Some municipalities offer sewage system counselling totheir municipality residents, which is very good as this counselling seems to be a factor thatencourages action. Almost all property owners who received visits with counselling and sup-port with permit applications within the Living Coast project, fixed their sewage systems. Thecounselling also contributed to quicker processing and seems to have reduced the number ofappeals.LiViNg COAST on fixing small sewage systemsrEAD MOrE ABOuT...• The municipal supervision is in many places inadequate, and the willingness of fixing small sewage systemsin the complete Living coastthe property owners to voluntarily improve their sewage system to reduce theirWhite paper and in theenvironmental impact is weak. The rate of inspections needs to be increased, report ”Fixing small sewageespecially in the north and south Baltic sea water districts where the largest systems. Experience from theproject ”Help your bay – Im-emissions occur. The coastal zone and areas near lakes and waterways needprove your sewage system”9,to be prioritised, and the focus should be on toilet waste (grey water contains or on the websites of vA-almost no nutrients at all). guiden (the sewage systemguide) and the Swedish• There are major regional differences in property density, soil retention and Agency for Marine and WaterManagement.proximity to eutrophication-sensitive bodies of water, which play a major rolein the impact of small sewage systems on the environment. if there is uncerta-inty about the risk of emissions, the precautionary principle should be applied,and efforts implemented that seek to ensure that toilet waste is collected andtransported away from the area.• Stronger incentives are needed to get a good sewage treatment. today muni-cipalities need to be able to point to emissions from small sewage systems inorder to be able to require measures. This can be done with measurements orcalculations if input data is available, but is difficult in practice.- In practice, it leads to high levels of demands for new small sewage systemswhile older systems are often allowed to continue to emit poorly treated was-tewater into the environment. This is both unfair and bad for the environment.- It needs to be easier to reassess old permits.• The own disposal of toilet waste on the property (the plot) is a forgotten healthrisk and can be a source of eutrophication. it is not a local recycling solution, asis considered by many municipalities. These nutrient sources are rarely includedin load calculations, which means that the environmental impact of sewage/toi-let waste is underestimated.• Few property owners voluntarily choose a recycling sewage solution, amongother things because they are more expensive. In addition, many municipalitieslack the infrastructure and systems needed for handling for recycling, althoughthe recycling of nutrients should be pursued65,68.• Access to sewage system counselling is a factor that increases action. However,despite free sewage system counselling, help with the permit application, anda financial subsidy, there were still many property owners who did not fix theirsewage system within the Living Coast project.30 • EffEctivE mEasurEs against Eutrophicationexcess phosphorusis bound inthe sedimentEven if all nutrient emissions from the Baltic Sea catch-ment area are stopped immediately, it would probably stilltake many decades before the eutrophication ceases, andthe same applies to many coastal areas. This is because thephosphorus emissions of earlier years, which have beenstored in bottom sediments for a long time, leak back intothe water and contribute to eutrophication.EffEctivE mEasurEs against Eutrophication • 31regOLOkeneTTAvSegIrevS:OTOhPW Due to lack of oxygen in thewater, white veils of sulphurbacteria were formed at a depthof about 6 metres. Björnöfjärden2011.What is internal load?During eutrophication, more phosphorus has been transported to a bay, than the bottom sedi-ments can permanently bind (Figure 12). The phosphorus originates from various sources onland and is tied up in organic material, especially plankton, in the water column. Phosphorusis released again when the organic material is mineralized instead of being retained by, for ex-ample, iron, aluminium or calcium. The binding to the different substances varies in strengthand some phosphorus leaks back into the water. This leakage is usually called internal load.Before 1940 2000 After 2015al-treatment2012–2013anoxic watersedimentPhosphorus ≈ Binder phosphorus > Binder Phosphorus ≈ BinderFigurE 12. At the beginning of the 20th centurey, there was a balance between the supply of phosphorusand phosphorus-binding substances to Björnöfjärden. This meant that the internal load was very small.In the second half of the 20th century, more phosphorus was introduced than phosphorus-binding sub-stances, for example due to emissions from agriculture or properties with poor treatment of their sewage.It led to strong internal load and that Björnöfjärden became eutrophic. During the summers of 2012 and2013, aluminium treatment was implemented in the bay where aluminium was added to the sedimentthat could bind the abundance of phosphorus. Measures to reduce the supply of nutrients from landagain led to a balance between the supply of phosphorus and phosphorus-binding substances again,whereby eutrophication slowed down.32 • EffEctivE mEasurEs against EutrophicationregOLOkeneTTAvSegIrevS:OTOhPIf the sediment becomes anoxic, iron loses its phosphorus-binding capacity and the inter-nal load is amplified. Internal load is often a predominant source of eutrophication. Morephosphorus in the water contributes to increased eutrophication and more organic materialto be broken down, more oxygen is consumed, an even greater lack of oxygen and an evengreater internal load. This is usually called the vicious circle (see fact box below).Internal load of phosphorus can be stopped with aluminium treatment. This adds alu-minium that binds the dissolved phosphorus in the sediment. Often the same precipitatingchemical is also used in both drinking water purification as well as wastewater treatmentplants (polyaluminium chloride). The phosphorus bound to the added aluminium can beconsidered permanently bound in the sediment and could in principle be dredged up andreused in the future.HOW ALuMiNiuM TrEATMENT WOrkSBEFOrE TrEATMENT: ”THE ViCiOuS CyCLE”1. Nutrients cause algal blooms. When there is a lot of nutrients in the water, thegrowth of phytoplankton and filamentous algae increases greatly, and there willbe algal blooms.2. Decomposition of algae causes oxygen deficiency. When the algae die, they sinkdown to the bottom where they are decomposed by bacteria and small animals.oxygen is used in the water during the decomposition. If the oxygen runs out,hydrogen sulphide is produced, which is toxic.3. Oxygen deficiency releases phosphorus (P). in a healthy sediment, phosphorusbinds to iron, aluminium or calcium. In anoxic bottoms, iron loses its phospho-rus-binding ability and a large part of the phosphorus is released to the waterand contributes to eutrophication, which in turn leads to even more algal bloomsand even more anoxic bottoms. A vicious circle develops.POST-TrEATMENT: ”HEALTHy ECOSySTEM”4. Phosphorus leakage (P) stops when an aluminium solution (AL) is gently mixeddown into the surface of the sediment. Aluminium permanently binds dissol-ved phosphorus in the sediment and is dosed according to a calculation of theamount of phosphorus likely to leach contained in the sediment.5. Eutrophication ceases. When the phosphorus leaching from the sediment isstopped, the growth of algae, and thus the amount of organic material thatreaches the bottoms, decreases. It leads to less nutrients being released andless oxygen being used.6. The vicious circle is broken. aluminium treatment has bound phosphorus per-manently in the sediment and the phosphorus levels in the bottom water havedecreased by more than 95 per cent. The effect will remain as long as the supplyof new phosphorus from land is limited.EffEctivE mEasurEs against Eutrophication • 33Internal load and aluminium treatment in figures• In Björnöfjärden, the internal load was just over 70 per cent of all phosphorus supplies tothe water. This is similar to the ratio in the Baltic proper, where the external phosphorussupply is estimated to be between 15,000 and 20,000 tonnes annually, while the internalload is estimated at about 100,000 tonnes per year2.• To bind 1 kg of phosphorus in the sediment, 10 kg of aluminium is required. The cost ofbinding one kilogram of phosphorus varies between SEK 400-2,000/kg. The lower costapplies to larger bays.• Aluminium treatment inactivated phosphorus in Björnöfjärden with an average of 1.3 mgphosphorus per square metre and day. After 3.5 years, this corresponds to about 1.5 gphosphorus per square metre and 1.3 tonnes total in Björnöfjärden12.• Aluminium treatment in Björnöfjärden has cut in half the phosphorus level in the water asa whole and reduced the phosphorus level in the bottom water by more than 80 per cent11.Aluminium treatment in BjörnöfjärdenThe predominant source of phosphorus to Björnöfjärdens water was the internal phosphorusload from bay’s anoxic sediments that are deeper than six metres, about 50 per cent of thebottom area (0.7 km2). The internal load was stopped with an aluminium treatment of sedi-ments during the summers 2012 and 2013. This method is a well-known lake remediationmeasure which was used for the first time in a marine environment in Björnöfjärden.The aluminium treatment provided a rapid and clear reduction of available phosphorusin the water11 (Figure 13). The proportion of aluminium-bound phosphorus in the sediment,which can no longer be released to the water, increased significantly11 (Figure 14). This inturn has led to a halving of the phosphorus levels in the water compared with before the alu-minium treatment and compared to the comparison bay.risks of aluminium treatment Björnöfjärden’s bottoms thatare deeper than 6 metres wereAluminium can be harmful to aquatic organisms if it occurs in a dissolved form at high con- aluminium treated in the sum-centrations. The solubility of aluminium is controlled by the pH value of the water. At the mers of 2012 and 2013 with thepH level generally prevailing in the Baltic Sea bottom sediment (around pH 7), the solubility help of a special craft. Xis very low, which means that the risk of precipitation changing to dissolution is very small.From a rig mounted in theThe treatment method used in Björnöfjärden is well proven in lakes69 where it has provi- boat’s fore ran hoses that wereded both reduced phosphorus in the water and more favourable habitats for plant and animal gently pushed down into thesediment surface. Phosphoruslife, without apparent negative side effects.leaching is stopped by addingDuring and immediately after the aluminium treatment in Björnöfjärden, the aluminium the aluminium solution to thecontent increased in the water and in plants and animals. One year later, the levels in the sediment via the hoses. Xwater were equal to, or lower than before treatment, and after another year the levels hadjust a few days after thealso gone down in plants and animals. Traces of the treatment could accordingly be seen in aluminium treatment, thethe form of elevated aluminium levels in the ecosystem, but the increase was not lasting. water of Björnöfjärden becameclearer. XXMETHODS OF STOPPiNg iNTErNAL LOADrEAD MOrE ABOuT...aluminium treatment andThere are three fundamentally different methods to reduce leaching of dissolvedinternal load in the completephosphorus from deeper bottom areas in lakes and coastal areas with poor oxygen Living coast White paperconditions: and in the article ”Re-med-iation of a Eutrophic Bay in• oxygenation that increases the natural phosphate-binding in the surface sedi-the Baltic Sea” 11.ment by dissolved iron oxidising and being able to bind phosphorus.• The addition of phosphorus-binding substances to increase phosphorus bindingunder anoxic conditions.• Dredging to remove sediment layers containing phosphorus likely to leach out.34 • EffEctivE mEasurEs against EutrophicationAluminum bound phosphorusin sediment Phosphorus content in Björnöfjärden and a comparison bay0 100aluminum2 90 treatment4 806 70 Fjällsviksviken8 6010 5012 4014 3016 2012 20201418 2016 10 Björnöfjärden20 0A0l uminumbo3 u0 n0dphosphoru6 s0 (0μ g/g drywei9 g0 h0t)Sep-1 J1 an-1 A2 pr-1 J2 ul-1 O2 ct-12Feb-1 M3 ay-1 A3 ug-1 D3 ec-13Mar-1 J4 un-1 S4 ep-1 J4 an-1 A5 pr-1 J5 ul-1 N5 ov-1 F5 eb-1 M6 ay-1 A6 ug-1 D6 ec-16Mar-1 J7 un-1 O7 ct-17FigurE 13. Aluminium-bound phosphorus FigurE 14. The average concentration of phosphorus in Björnöfjärden is about halfin the top 2 dm of the sediment. Before the compared with Fjällsviksviken (comparison bay) and compared with the period before thealuminium treatment (2012), the concentration aluminium treatment.was about the same size at all depths. Two andfour years after treatment, a lot of phosphorusis bound to aluminium in sediment at approx-imately 2-4 cm deep (2014) and 4-6 cm deep(2016). New sediment that reaches the surfaceeach year contributes to the concentrationpeak being moved downwards.EffEctivE mEasurEs against Eutrophication • 35)mc(htpedtnemideS)l/PTg(surohpsohplatoTgreBLedOMIkAOJ:OTOhPLiViNg COAST on resolving the internal load of phosphorus• Aluminium treatment of deep, anoxic archipelago bottoms is an effective wayto reduce the internal phosphorus load to the water. The cost of phosphorus-binding is lower than for many measures on land.• There is currently no indication that aluminium treatment would be dangerousto organisms in marine bays. For safety reasons, the effects of the Björnöfjärdentreatment will be followed up until 2022 to verify that no unexpected side-effects occur.• An increased phosphorus binding in a restored bay’s bottoms is also importantfrom a larger perspective by reducing phosphorus exports to the outlying archi-pelago.• Future remediation work should include measures both against the externaland internal nutrient load. The percentage of external and internal phospho-rus sources to the water should be reflected in the action conditions. If so, thephosphorus supply that is taking place today will be reduced proportionally toearlier phosphorus supply, which would have a positive effect on the eutrophica-tion situation.• Aluminium treatment of bottom sediments is a means of reinforcing thephosphorus-binding capacity of the sediment in the anoxic bottoms, thusdeactivating and compensating for the pulse of eutrophic phosphorus thatpreviously deficient treatment contributed to. The reduced production of oxygen-consuming materials (especially phytoplankton) resulting from aluminiumtreatment should lead to bottoms that were oxygenated until the middle of the20th century to regain an oxygenated surface sediment and a naturally higherphosphorus-binding ability12.• Today it is unclear whose responsibility it is to identify and correct internalphosphorus load. Perhaps the estimation of a previous load on a body of watermay be the basis for whose responsibility it is to implement and finance themeasure? Perhaps it can be regarded as a “retroactive” purification of untreatedwastewater?• Today, knowledge of how and where phosphorus likely to leach out is accumula-ted is small. With more knowledge of how the phosphorus likely to leach out isdistributed over coastal and seabeds, the method’s possibilities on a larger scalecan be evaluated. Given that the bottoms most likely to leach out are placed sothat aluminium treatment is possible, it would cost about SEk 13 billion to fix 10per cent of the Baltic Sea’s anoxic bottom area (7,000 km2)70 .36 • EffEctivE mEasurEs against EutrophicationMeasuresto strengthenpredatoryfish stocksPredatory fish such as perch and pike are important inthe fight against eutrophication. They are at the top of thefood web and can affect the structure of the rest of the eco-system, but since the middle of the 1990s, predatory fishhave declined along the Baltic Sea coast. The Living Coastproject has implemented several measures to strengthenthe stock of predatory fish in Björnöfjärden.EffEctivE mEasurEs against Eutrophication • 37Predatory fish important to the whole ecosystemPredatory fish have a very important function in the sea, both on the coast and further outto sea. They are at the top of the food web and may affect the structure of the rest of theecosystem (Figure 15). On the coast, pike is the most important predatory fish. Pike eat smal-ler fish, such as roach. If there are plenty of pike in a bay, it reduces the number of roach.Roach in turn eat zooplankton, and if there are few roach, there is a lot of zooplankton left.Zooplankton eats phytoplankton and when there is a lot of zooplankton, they graze a largeportion of the water’s phytoplankton. In this way, pike helps to reduce phytoplankton blooms(algal blooms) that quickly grow when the water is eutrophic and there is a lot of nutrientsin the water. Further out to sea, cod is the most important predatory fish. In the same way asthe pike, cod controls the growth of phytoplankton in the offshore areas.Since the middle of the 1990s, pike and perch have declined along the Baltic Sea coast.This is probably due to a combination of large-scale changes in the Baltic Sea ecosystem asa result of, for example, overfishing and exploitation of nursery habitats, as well as diking offreshwater environments that are important spawning grounds.Wetland to strengthen pike stocksTo strengthen the pike stock in the archipelago, pike wetlands can be created (Figure 16).Near the sea, an embankment is built that catches rain and melt water from the catchmentarea. Pike migrate up into the wetland via a fish migration path where there is enough waterin the spring to allow an adult fish to swim up and spawn and then down to the sea againwhen the spawning is over. In early summer, the water flow decreases so that fish can no long-FigurE 15. Predatory fisher reach the wetland. The pike fry are then protected against predatory fish for a few months. are important to the wholeAt midsummer, the pike fry are ready to swim out into the bay. Then the water in the wetland ecosystem. They are at the topof the food web and may affectis released through a regulating ring. The regulating ring is closed during the autumn for rainthe structure of the rest of theand melt water to again be collected in the wetland for the next spring’s pike spawning. food web.FigurE 16. Pike is a species that like to find wetlands to spawn. To strengthen the pike stock, pike wetlands can be made where thepike can spawn and the pike fry can grow up in a protected environment.38 • EffEctivE mEasurEs against EutrophicationPikE SPAWNiNg iN FrESH WATEr1 2 3 4Spawning in 100,000s of roe Fry grow bigger Moving out tofre s h wat e r the bayEarly in the spring, The pike spawning The pike fry grow Pike fry continue theirpike seek out the areas lasts for a few days. quickly in the wetland life in the bay. The frywhere waterways flow in that time, 100,000s where there is plenty that have grown upout and flood grass of roe are laid and of food and protection. in wetlands are oftenmeadows. Here, the fertilised by the males’ The fry eat zooplank- larger than those in thewater become warm milk. The roe stick to ton, bottom-dwelling sea, and therefore copefaster than in the sea. the blades of grass animals and small fish. better. When the pikePike can migrate up and hatch after a few at midsummer, they become sexually ma-between rocks against weeks. are ready to swim out ture, they often returnthe current. to the sea. to spawn where theyhatched.Fishing banAnother way to protect and strengthen the predatory fish stock in coastal areas is to restrict orprohibit fishing, which has been shown to have a positive effect on, for example, pike74. Theintroduction of new fishing regulations is easier when stakeholders are informed and agree thata fishing ban is needed. The motives must be scientifically based and long-term managementmust be taken into account. It is the Swedish Agency for Marine and Water Management thatmakes a decision on the matter.remediation of vegetated bottomsOn shallow bottoms, bottom-living vascular plants and algae create an important habitatfor animal life in and by the sea. Fish seek out these environments in search of food, to findsuitable spawning and nursery grounds, and to seek refuge. Both plant- and fish-eating birdsare also drawn here. The bottom vegetation also takes up nutrients from land runoff andstabilises the sediments, contributing to clearer water.Y Pike fry that grew up in a Y Areas with bladderwrack are important spawning and nursery environments for fish, among otherpike wetland are often larger things. in Björnöfjärden, attempts were made to replant bladderwrack. The seaweed survives, but itthan those that grew up in the has difficulties to reproduce.bay outside.EffEctivE mEasurEs against Eutrophication • 39regOLOkeneTTAvSegIrevS:OTOhPShallow habitats are, however, sensitive and easily affected by exploitation and eutrophi-cation. Where possible, building docks, dredging, anchoring and intensive boat traffic should rEAD MOrE ABOuT...be avoided, as it has been shown to adversely affect vegetation that is important to fish measures to strengthenpredatory fish stocks in therecruitment72. To speed up the recovery of vegetation in shallow environments, remediationcomplete Living coast Whiteattempts have been made with bladderwrack and pondweeds. The methods tested may have paper and on predatorypotential, but need to be developed further to be reliable more widely. fish on the website of theswedish anglers associa-Shore meadow remediation tion: (www.sportfiskarna.se/rovfisk).Shore meadows are an important biotope that has become unusual since grazing by cattlehas largely ceased in such areas. Reduced grazing pressure means that competitive vegeta-tion, such as reed, often out competes other vegetation. This leads to overgrowth and lossof important functions, such as spawning grounds for coastal pike, and breeding and restingareas for birds.To recreate wet meadows, the reeds need to be sharply cut back and transported awayfrom the area. Areas with thick reeds may need to be cut for another one or two years. In or-der to maintain the wet meadow, grazing, preferably with cattle, may need to be established.Recreating environments often difficult and expensiveIn addition to its important role and function in the ecosystem, predatory fish are of great va-lue for both sports and commercial fishing. Reduced predatory fish stocks along the Baltic Seacoast have led to various measures to strengthen predatory fish recruitment in different partsof the country, for example new spawning and nursery areas have been brought into use andmigration barriers to natural spawning grounds have been removed. These measures havebeen successful in many cases. However, it often takes time (many years) and patience for arecreated/landscaped environment to have the desired function. It can also be very expensiveif you are unlucky in the establishment, or if it involves large areas.Y To try to recreatea wet meadow nextto Björnöfjärden, thereeds were cut downby an amphibious reedcutter.Since reed areas areimportant areas forbirds, cutting thereeds during thenesting season shouldbe avoided. it can also Y in the strait to Björnöfjärden,be good to save some the project investigated howreeds to benefit the much spawning fish migratesbird life. into the bay during the spring.40 • EffEctivE mEasurEs against EutrophicationPotential actionsand effectsBefore actions were taken, the average annualtotal nutrient supply to Björnöfjärden fromthe entire catchment area was estimated tobe about 240 kg of phosphorus and just over3000 kg of nitrogen7,8. About 70 per cent of thephosphorus and 45 per cent of the nitrogenwere due to anthropogenic impact such as agri-culture, horse keeping and sewage. The rema-inder is the background load from the forestand open land.Project Manager Emil rydin next to a pile of lime material for a lime bed.EffEctivE mEasurEs against Eutrophication • 41Potential actions and effectsThis section presents the action potential and the action effect of the respective sources andmeasures. The results are compiled in Table 1 on page 45. The calculations are based mainlyon standard values because there are not yet sufficient time series from the project’s ownThe impact of agriculture on measurements in the catchment area to calculate the action effects; mainly due to inter-yearBjörnöfjärden is estimated tovariations in precipitation.decrease by around 85 per centas a result of the steps taken inAgriculturethe Living Coast project.The total annual nutrient loss from arable land in the area (50 hectares) was estimated tobe 38 kg of phosphorus and 252 kg of nitrogen, assuming the annual area specific loss perhectare before measures was 0.75 kg phosphorus and 5 kg nitrogen7.The action potential, without reducing production, was estimated to be 25 kg of phospho-rus per year if the measures had been fully implemented in the area, which, however, was notsuitable or economically feasible. To reduce the nutrient supply as much as possible:• Most (42 hectares) of the arable area was structure limed, which improves the retention ofphosphorus in the soil and reduces the load by 8-14 kg of phosphorus per year.• Phosphorus ponds and lime filter beds that catch water from 70 per cent of the arable areawere built. The installations trap about 8 kg of phosphorus per year, which leaves thefield in spite of structure liming. Some nitrogen is also trapped.The cost of structure liming, including land mapping, was SEK 5,000 per hectare. It is expen-sive to establish a phosphorus pond with lime filter beds, especially if the establishment doesnot become optimal. The cost of the Living Coast’s phosphorus ponds with lime filter bedswas SEK 360,000 (0.29 hectares) and SEK 725,000 (0.25 hectares). It can be much more costeffective with large installations and better conditions39.Horse keepingThe phosphorus losses from horse keeping in the area (25 horses divided into three stables)were estimated to be about 17 kg of phosphorus per year (1.5 kg phosphorus/hectare andyear; 11 hectares)7. That corresponds to one third of the horses expected turnover in total.The action potential is difficult to assess, but estimated to be about 11 kg of phosphorusper year, which means that the average area-specific loss after measures should not exceedaverage leaching from arable land (0.5 kg phosphorus/hectare year). If the number of horsesper unit area is kept so low that the pastures are not trampled, ditches are protected and themanure clearing of pastures is stored on a watertight manure slab and recycled, most of itshould be able to be rectified. On the other hand, a large amount of nutrients have alreadybeen stored in the soil around the stables and will leak for a long time to come.The action effect is also difficult to assess. Assuming that the measures implemented havethe estimated effect, the nutrient loss should be reduced to about 8 kg of phosphorus per year.However, previous years’ accumulated soil nutrients will continue to contribute to elevatedlevels in ditch water leaving the area, which means that it will take time for the measures tohave full effect. To date, the action effect is estimated to be half of the impact that is expectedto be achieved with the actions taken by the project; meaning about 4 kg of phosphorus peryear.The cost of all measures on the horse farms around the bay was about SEK 1,250,000, andis expected to reduce the phosphorus supply to Björnöfjärden by about 8 kg annually oncethe measures have had full effect.Y Horse farms’ contribution to Small sewage systemsnutrient loss is best minimisedby manure clearing of pastures At the start of the project, the total annual nutrient losses from small sewage systems was esti-and taking care of manure in mated to be about 80 kg of phosphorus and 1000 kg of nitrogen7. The emissions were mainlya good way and making surecaused by the 200 properties (of just over 850) that had illegal or poor sewage solutions.that the horses are not kept sodense to avoid that the vegeta- The action potential to install a closed tank on properties with soil-based purification oftion cover is worn down in the toilet waste is estimated to be 100 per cent.pasture.42 • EffEctivE mEasurEs against EutrophicationHowever, it takes a long time for the measures to have full effect, as there is a lot of nutrientsalready stored in the soil near sewage systems with poor purification.During the project, half of the 200 properties either switched to a closed tank, or theyempty their toilet waste from their dry toilet at the latrine station that the project built. Byextension, this will reduce the load to the bay by about 40 kg of phosphorus and 500 kg ofnitrogen per year. A few years after implementation, the effect is assumed to be on averagehalf of the fixed gross supply to the soil, i.e. about 20 kg of phosphorus per year. Over time,the stored phosphorus remains in the ground, which has not been permanently bound, is as-sumed to have leached out and the effect is then 40 kg of phosphorus per year.The average cost of installing a closed tank was SEK 75,000 per property. The cost of the100 properties that switched from soil-based purification to the closed tank (or equivalent)thus becomes SEK 7,500,000. Since the measure is estimated to reduce the supply to the bayby about 40 kg of phosphorus per year when it has full impact, the purification cost will be Y Sewage solutions relying onthe soil to purify wastewaternearly SEK 10,000 per kilogram of phosphorus seen over 20 years (excluding sludge removalfrom nutrients are not suitablecosts). in areas with thin soils nearlakes, streams and seas.The Nature reserve’s outdoor toiletsTwo dry toilets at the Björnö Nature Reserve supplied Björnöfjärden with about 3 kg ofphosphorus and 15 kg nitrogen per year9. Since both action potential and action effectare estimated to be 100 per cent, the inflow is estimated to have decreased by about 3 kg ofphosphorus and 15 kg of nitrogen per year as a result of the outdoor toilet being equippedwith a closed tank. Unlike fixed small sewage systems, the effect of the installation of thetank is not delayed, since the waste before measure was composted right next to the shoresof the bay.The cost of installing the closed tank on two dry toilets was about SEK 100,000. Over 20years, the purification cost will be around approximately SEK 1,600 per kg of phosphorus, atthe degree of utilisation that prevails today.Säby Manor FarmY Composting urine andThe conference facility at Säby Manor Farm is estimated to produce about 40 kg of phospho-excrement in composting bins isrus and 250 kg of nitrogen per year. A 15-year old infiltration facility with limited purification a common solution for outdoorfunction was disconnected in 2015 and replaced by a system with phosphorus precipitation, toilets in nature reserves. Whendone near the water, it is verya septic tank and a dense filtration bed.likely that nutrients will leachThe action potential is estimated to be 95 per cent (38 kg) for phosphorus and 50 per cent out and contribute to eutrophi-(125 kg) for nitrogen for the new plant71. The action effect is assumed to be the same as the cation.action potential when full effect is reached. Since the installation of the new system, therehas been a lot of fine-tuning problems, which is why the action effect so far is only estimatedat half the action potential, i.e. 19 kg of phosphorus per year.W Säby Manor Farm is locatedright by Björnöfjärden. in orderto minimise the impact of ope-rations, a new sewage systemwas installed.EffEctivE mEasurEs against Eutrophication • 43W Process water from theoperations at Smakriket Säbycontains a large amount oforganic materials and varieswidely in volume over the year.This makes it difficult to use astandard solution for treatingthe water.Smakriket SäbySmakriket Säby with cider press, brewery and distillery operations is estimated to annuallyproduce a total of 5 kg phosphorus and 12 kg nitrogen7.The action potential is difficult to assess. With closed systems, 100 per cent of the nutrientscan be removed, but in practice it is difficult to achieve such a system because large volumesof water must be treated. Different solutions to take care of, and preferably reuse, wasteproducts from the cider press and brewing operations have been tested, but no long-termsustainable solution has yet been set. At present, the action effect is assumed to be half of theemissions, i.e. 2.5 kg of phosphorus per year.SedimentBjörnöfjärdens deep bottoms (> 6 metres) are anoxic sediment accumulation areas and oc-cupy 0.73 km2 (about 50 per cent of the bottom area). Material and new sediment layers areformed on accumulation bottoms. When the organic material is broken down, nutrients aremobilized and stored in the sediment for a shorter or longer period or are released directlyto the water. The storage of phosphorus likely to leach out in Björnöfjärden’s accumulationbottoms is 2.2 tonnes (approx. 3 g phosphorus/m2)12. Overall, the average leaching rate fromthe accumulation bottoms is estimated to be approximately 500 kg of phosphorus per year;an estimate based on the amount of phosphorus bound to aluminium as a result of aluminiumtreatment12. Bottom areas at between four and six metres depth are estimated, on average, tocontribute about 100 kg of phosphorus per year to the water, because the material is also pe-riodically deposited on these bottoms. The total action potential of Björnöfjärden’s sedimentsis thus estimated to be about 600 kg of phosphorus per year.44 • EffEctivE mEasurEs against EutrophicationImmediately after the aluminium treatment, phosphorus losses essentially ceased fromthe deeper bottoms. After 3.5 years, 1,300 kg of phosphorus had been bound to added alu-minium12. An additional 300 kg of phosphorus is assumed to be bound in 2018 and 2019.Then most of the estimated pool of sediment phosphorus likely to leach out (2.2 tonnes) isassumed to be bound to aluminium. The shallower bottom areas (4-6 metres) could alsohave been aluminium treated, but unlike the anoxic deep bottoms, the shallower bottomsare oxygenated and inhabited by plants and animals. For reasons of precaution, the projectrefrained from treating these bottoms; the treatment of the anoxic accumulation bottoms wasestimated to provide sufficient efficacy.The cost of stopping the internal load in Björnöfjärden with aluminium treatment was ap-proximately SEK 9 million, including development costs. The added aluminium (50 g Al/m2)is estimated to be able to bind upwards of 4 tonnes of mobile phosphorus in the sediment,which gives a cost of SEK 2,250 per kg of inactivated phosphorus. The measure broke an an-nual internal load of 0.5 tonnes of phosphorus.Total remediation potential and action effectThe overall effect of all the measures to date in the catchment area is estimated to be a re-duced phosphorus load of approximately 70 kilograms of phosphorus per year (44 per cent),and will increase to 114 kg per year (70 per cent) when each measure reaches full effect(Table 1). The phosphorus supply to Björnöfjärden from the catchment area will thus be cutin half, from about 241 to 114 kg of phosphorus per year.There is still a further approximately 50 kg of phosphorus per year to be reduced beforethe entire action potential is reached, which essentially involves fixing the remaining 100small sewage systems which account for about 40 kg of phosphorus. The remaining actionpotential is judged to be very costly to reach, or involve the cessation of activities (horsekeeping, agriculture, conference activities).TABLE 1. Action potential and action effect for phosphorus supply (kg P/year) from the catchment area (mainly based on standard calcula-tions) and from sediment (mainly based on project measurements) to Björnöfjärden’s water. Numbers in parentheses indicate the action effectwhen the measures have been fully effective.ACTiON POTENTiAL AND ACTiON EFFECT FOr PHOSPHOruS SuPPLyArea Load Action potential remaining Action potential Action potential(kg P/year) (kg P/year) (kg P/year) (kg P/year) (%)Phosphorus from the catchment areaBackground (forest, open land) 58 - 58 - -arable land 38 25 13 22 88Horse keeping 17 11 6 4 (8) 38 (72)small sewage systems* 80 80 0 20 (40) 25 (50)Dry toilets in the nature reserve 3 3 0 3 100Säby Manor Farm 40 38 2 19 (38) 50 (95)Smakriket Säby 5 5 0 2.5 50Total 241 162 79 71 (114) 44 (70)Phosphorus supply from sedimentSediment (4-6m) 100 100 0 0 0Sediment (>6m) 500 500 0 500 100Total 600 600 0 500 83Total phosphorus supply to the waterTotal 841 762 78 571 (614) 75 (80)* Refers to properties with soil-based treatment of toilet waste, including own disposal, excluding grey water.EffEctivE mEasurEs against Eutrophication • 45Decrease in net export of phosphorus from BjörnöfjärdenThere is a continuous water exchange between Björnöfjärden and Nämdöfjärden outside. InNämdöfjärden, as well as in the entire Baltic proper, the nutrient levels are elevated. Thus, thewater exchange will not only mean that nutrients will be exported from Björnöfjärden, butNämdöfjärden’s water is also a source of nutrients for Björnöfjärden. Nutrient bound in, forexample, plankton and particles in Nämdöfjärden’s water can sink out from the water to thesediment when it reaches Björnöfjärden and thus bring nutrients to Björnöfjärden.Before the measures were implemented in and around Björnöfjärden, the annual phospho-rus exports were estimated at about 800 kg from Björnöfjärden to Nämdöfjärden, while im-ports were about 200 kg. Net exports of phosphorus out of Björnöfjärden at the start of theproject were about 600 kg per year.After the measures, phosphorus levels in Björnöfjärden’s water have decreased and areusually lower than in Nämdöfjärden. Total annual exports have been cut in half and are nowaveraging 400 kg of phosphorus, while imports remain the same. Net exports of phosphorusout of Björnöfjärden, after the measures, are thus 200 kg of phosphorus per year, whichmeans a load reduction of about 400 kg of phosphorus per year on the archipelago outside.Since phosphorus levels in Björnöfjärden have fallen to levels corresponding to those inNämdöfjärden, the limit on the water quality that can be achieved in Björnöfjärden has beenachieved. The big challenge now is to further reduce the supply from the Björnöfjärdenscatchment area. Unless it succeeds, the phosphorus levels in the water will slowly increaseagain and new supplies of sediment phosphorus likely to leach out in are built up the bay’ssediments again.W Björnöfjärden waspreviously a phosphoroussource for the archipelagobeyond, but now serves as afilter for nutrients that comefrom the area around thebay. Thanks to the measures,less phosphorus ends up inthe water and what does islargely bound in sediment.46 • EffEctivE mEasurEs against EutrophicationBjörnöfjärdenhas regained goodwater qualityThe reduced nutrient supply to Björnöfjärdenhas led to the bay regaining good water qua-lity in just a few years, and the bay’s plant andanimal life are recovering11.EffEctivE mEasurEs against Eutrophication • 47greBLedOMIkAOJ:OTOhPimproved water quality after measuresPhosphorus levels in Björnöfjärden’s water has been cut in half from about 40 to 20 μg ofphosphorus per litre due to the aluminium treatment in summer 2012 and 201311 (Figu-re 17). This reduction means that the bay has gone from poor to good status in terms ofphosphorus, while concentrations in the comparison bay remain high11.Figure 18 shows the difference in the mean concentration of phosphorus and chlorophyll,and Secchi depth between Björnöfjärden and the project’s comparison bay before, during andafter the aluminium treatment. Before the project started, the concentrations of phosphorusand chlorophyll were higher in Björnöfjärden than in the comparison bay, while the Secchidepth was roughly the same. Chlorophyll is a measure of the amount of phytoplankton in thewater and is controlled among other things by access to nutrients (nitrogen and phosphorus).In turn, the amount of phytoplankton affects the Secchi depth. When there is a lot of phy-toplankton (chlorophyll) in the water, the Secchi depth and thus the light emitted into thewater degrade. Immediately after the aluminium treatment, both phosphorus and chlorophylllevels in Björnöfjärden’s water decreased, and were lower than in the comparison bay. At thesame time, the Secchi depth improved.Aluminium treatment stopped the internal load of phosphorus from Björnöfjärden’s dee-per bottoms. Nitrogen (ammonium), on the other hand, continued to be released, but theconcentration began to fade after a few years (Figure 19), possibly as an effect of reduceddeposition of phytoplankton11. The declining phosphorus supply resulted in reduced algalblooms and increased Secchi depth. In the comparison bay, no clear reduction of nutrients inthe bottom water was measured during the same period (Figure 20).Phosphorus content in Björnöfjärden and a comparison bay100aluminum90 treatment FigurE 17. the average concentra-80 tion of phosphorus in Björnöfjär-Fjällsviksviken den is about half compared with70Fjällsviksviken (comparison bay) and60 compared with the period before the50 aluminium treatment.40302010 Björnöfjärden0Sep-1 J1 an-1 A2 pr-1 J2 ul-1 O2 ct-12Feb-1 M3 ay-1 A3 ug-1 D3 ec-13Mar-1 J4 un-1 S4 ep-1 J4 an-1 A5 pr-1 J5 ul-1 N5 ov-1 F5 eb-1 M6 ay-1 A6 ug-1 D6 ec-16Mar-1 J7 un-1 O7 ct-17Phosphorus, chlorophyll a and Secchi depthin Björnöfjärden and comparison bay FigurE 18. The water quality of the5 Björnöfjärden has been improved dueto the aluminium treatment carriedout during the summers of 2012 and02013. The concentration of phospho-rus and chlorophyll has decreased-5 and the secchi depth has increased inBjörnöfjärden compared to Fjällsviks--10 viken (comparison bay). The figureshows average annual values of thedifference between the concentration-15 of phosphorus (μg tP/l), chlorophyll a(μg /l) and Secchi depth (dm) in Björ-Total phosphorus (μg/l) Secchi depth * 10 (m) Chlorophyll a (μg/l)-20 nöfjärden compared to Fjällsviksvikenat each sampling: before, during andBefore During After aluminum treatmentafter the aluminium treatment.Aug11-Jul12 Aug12-Jul13 Aug13-Jul14 Aug14-Jul15 Aug15-Jul16 Aug16-Jul1748 • EffEctivE mEasurEs against Eutrophicationnahtesrowecnereferecnerefernahtretteb)l/PTg(surohpsohplatoTThe Secchi depth inBjörnöfjärden hasincreased by about onemetre as a result ofthe halved phosphorusconcentration in thewater. XPlant and animal life recoversThe improved water quality has had significant effects on the environment in the bay. Thegreater Secchi depth has resulted in that the bottom vegetation now can spread out and livejust over a metre deeper (Figure 21, page 50). Reduced quantities of phytoplankton that fallto the bottom and decompose have improved the oxygen situation in the bottom water. Thishas allowed fish and bottom-dwelling animals to recolonise median depths. On the really deepbottoms, the situation is still strained with low, or very low oxygen levels, but the levels of hy-drogen sulphide have decreased (Figure 22, page 50). It is a clear sign that there is less organicmaterial that sinks down and decomposes on the deep bottoms.Phosphorus and nitrogen content in the bottom water400 3200FigurE 19. the con- aluminum Björnöfjärdentreatmentcentration of dissolvedphosphorus (phosphate) 300 phosphate 2400in Björnöfjärden’s bot- ammoniumtom water decreasedsharply due to aluminium200 1600treatment in the summersof 2012 and 2013. Thecorresponding reduction100 800did not occur for dissolvednitrogen (ammonium).0 0Sep-11 Jan-12 Jun-12 Oct-12 Mar-13 Aug-13 Dec-13 May-14 Sep-14 Feb-15 Jul-15 Nov-15 Apr-16 Aug-16 Jan-17 Jun-17 Oct-17FigurE 20. In Fjällsviks-viken (comparison bay), 1000 8000no clear reduction in the Fjällsviksvikenconcentration of dissolved 800 (comparison bay)phosphorus (phosphate) or 6000nitrogen (ammonium) was phosphaterecorded during the same 600 ammoniumperiod. Note that the sca- 4000les differ from Figure 19. 40020002000 0Sep-11 Jan-12 Jun-12 Oct-12 Mar-13 Aug-13 Dec-13 May-14 Sep-14 Feb-15 Jul-15 Nov-15 Apr-16 Aug-16 Jan-17 Jun-17 Oct-17EffEctivE mEasurEs against Eutrophication • 49Phosphorus, chlorophyll a and Secchi depth in Björnöfjärden and comparison bay)l/gμ(etahpsohp)l/gμ(etahpsohpgreBLedOMIkAOJ:OTOhP)l/gμ(muinomma)l/gμ(muinommaMaximum depth of attached algae 2012–20177.07.5Fjällsviksviken8.08.59.0Björnöfjärden9.510.02012 2013 2014 2015 2016 2017Lake ball (Aegagropila linnaei)FigurE 21. The maximum depth of lake ball (Aegagropila linnaei) has increased in Björnö-fjärden as water quality has improved. This change is not nearly as clear in the Fjällsviks-viken (comparison bay).FigurE 22. Due to the improved water quality in Björnöfjärden, the environment has recovered in several ways. These changes are not seenin the Fjällsviksviken (comparison bay). The number of fish species living at a depth of 8-10 metres has increased (upper left), the bottomdwellers that have free swimming larval stages have returned to the bottoms of 5-10 metres depths (upper right), the propagation of sulphurbacteria (Beggiatoa sp.) has decreased (lower left) and hydrogen sulphide content at deeper bottoms has decreased (lower right, negativeoxygen values represent hydrogen sulphide content; white indicates that oxygen is missing with hydrogen sulphide not analysed).Improvements in Björnöfjärden compared to the comparison bay805 Number of fish species Bottom-dwelling animals Limecola balthica70 Marenzelleria neglectaPotamopyrgus antipodarum4 60 Pygospio elegans503402 30201100 02012 2013 2014 2015 2016 2017 2012 2013 2014 2015 2016 2017 2012 2013 2014 2015 2016 2017 2012 2013 2014 2015 2016 2017Björnöfjärden Fjällsviksviken Björnöfjärden Fjällsviksviken90 0 20Sulphur bacteria before Oxygen and hydrogen sulphide content80during70 5 10after6050 10 04030 15 -102010 20 -2006-7 m 7-8 m 8-9 m 6-7 m 7-8 m 8-9 m 2012 2013 2014 2015 2016 2017 2018Björnöfjärden Fjällsviksviken50 • EffEctivE mEasurEs against Eutrophication)%(egarevocegarevA)seicepsfo.on(trofferephctaC)m(eaglafohtpedmumuixaM)2m/.dni(ytisneDgood ecological status in BjörnöfjärdenEcological statushigh During 2013 – 2017 (after the aluminium treatment), Björnöfjärden’s water quality has mostgoodmoderate often had ”good ecological status” according to the Svealands Coastal Water Management As-Unsatisfactory sociation investigation programme75. Twice a summer, samples are taken at 175 places loca-Badted along the entire Svealand’s coast and range from the inner to the outer archipelago. Whencomparing water quality in recent years, it is clear that there are few areas that have as goodwater quality as Björnöfjärden (Table 2). For example, only two additional sampling sites (outof a total of 175) achieve good status for total phosphorus. On a couple of occasions duringthe period 2012 – 2017, according to the Svealand Coastal Water Management Association’sclassification, it looks as if the conditions in Björnöfjärden have deteriorated. These occasionsare due to periods of inflow of nutrient rich water from the outlying bays16.TABLE 2. Summary of the Svealand Water Management Association status classification of water qualityat 175 sampling points (of which Björnöfjärden is one) 2011-201775.STATuS CLASSiFiCATiON WATEr quALiTyY Björnöfjärden (encirc- Variable Status of Björnöfjärden Status of Björnöfjärden Number of 175 sites withled) is one of only three bays 2012 (average 2012-2017) good status (averagethat achieve good status for 2012-2017)total phosphorous of the 175 total nitrogen moderate moderate 9locations that are investigatedyearly along the coastline of total phosphorus moderate good 3*Svealand. chlorophyll a good/ moderate good 14*secchi depth moderate good 5** Björnöfjärden is one of these.Y Water in Björnöfjärden. The photographs were taken before and after the aluminium treatment, at roughly the same depth (2-3 meters)but at different times of the year. The picture on the left is from April 2012 and the right from August 2013.EffEctivE mEasurEs against Eutrophication • 51TneMegAnAMreTAWLATSAOCdnALAevS:PAMgreBLedOMIkAOJ:OTOhPMOrE LiFE iN BjörNöFjärDENBEFOrE....Nutrients make the bay eutrophic A lot of roach Nutrients are exportedA lot of nutrients from land reach The most common fish is roach. There is a net export of nutrients fromthe bay via ditches and waterways. There are only fish down to six me- Björnöfjärden to the archipelago outside.The nutrients come, for example, ters deep, where the water is oxic. The nutrients come both from land and fromfrom poor sewage systems, arable the sediment.land and horse farms.Secchi disc measuringtransparency Phosphorus from the sedimentmakes the bay eutrophicTurbid water anoxic sediment binds phospho-A lot of nutrients in the water rus poorly. The phosphoruscontributes to a lot of phyto- is released to the water andplankton that make the water contributes to eutrophication.turbid. Poor light conditions it leads to even stronger growthprevent vegetation from living on of algae that need to be brokendeeper bottoms. down, and thus greater spread ofanoxic bottoms. A vicious circledevelops.Filamentous algae dominateIn the eutrophic bay, filamen-tous algae thrive covering The bottom is deadrocks and outcompeting other from six metres deep, it isbottom vegetation. completely oxygen-free. Here,Bladderwrack and vascular neither fish nor small animalsplants are scarce. can survive. only microorga-nisms can live here.AFTEr....Water is clearhalved phosphorus content in the water givesVegetation spreadsa halved amount of phytoplankton and thusclearer water means that the bottom vegetation can liveclearer water. The sunlight reaches furtherdeeper. Bladderwrack and vascular plants have becomedown and contributes to an increased spreadmore common. In these environments, small animals andof bottom vegetation.fish fry thrive.reduced nutrient transportreduced nutrient supplythe measures have reduced themeasures on land havesupply of nutrients from landreduced the nutrient supply.and sediment. The export ofIn order for the improvedphosphorus from Björnöfjärdenenvironment to persist, theto the archipelago outside hasnutrient supply must notbeen halved.increase again.Bottoms are recolonisedBetter oxygen conditions at theMore pikeintermediate-depth bottomsThere are more fish in the bay.allow fish and bottom-dwellingThe pike wetland helps toanimals to live here again.strengthen the bay’s pike stock.internal load stoppedAfter the aluminium treatment, the phosphorus stays in the sedi-ment and the growth of algae has decreased. When a small amountof organic material needs to be decomposed, there is more oxygenleft in the bottom water. However, in the deepest areas there is stilloxygen deficiency. It will take many years before it gets better here.52 • EffEctivE mEasurEs against EutrophicationLiving Coastfrom a Baltic SeaperspectiveIf all the measures of the Living Coast were doneon a much larger scale, they would together cor-respond to more than the whole of Sweden’s com-mitment to the Baltic Sea Action Plan (BSAP), i.e.the joint action plan for the Baltic environmentagreed by the countries of Helcom.EffEctivE mEasurEs against Eutrophication • 53greBLedOMIkAOJ:OTOhPW To ensure that the Baltic Seawill continue to be a healthysea we can all use, action onland and in water is required, aswell as cooperation across allborders and patience.750 tonnes less phosphorus per year to Baltic Sea waterThe primary objective of the Living Coast project was to show that good ecological status canbe recovered in an enclosed bay. Another goal was to calculate potential, effects and costs onthe basis of Living Coast’s results if the measures around Björnöfjärden were to be applied ona large scale. In addition to results from Björnöfjärden, calculations are based on analyses andinvestigations. They are described briefly on pages 56–57, and in more detail in the completeLiving Coast White Paper.Measures on landIf the land-based measures carried out around Björnöfjärden were to be implemented on alarge scale, for example in the North and South Baltic Sea water districts or along the coast ofthe Baltic proper, phosphorus leakage to the Baltic Sea would decrease by around 200 tonnesof phosphorus per year. The total cost of land measures is estimated at over SEK 30 billion,where measures on horse farms account for more than half.Even if the land measures were to be implemented to this extent, they would still only re-present around 1 per cent of the total phosphorus load from the catchment area to the BalticSea, which amounts to about 32,000 tonnes of phosphorus per year, of which about half is tothe Baltic proper. Furthermore, the phosphorus load from the catchment area consists partlyof hard-bound phosphorus, which probably contributes to a relatively small extent to eu-trophication. In the choice of measures, therefore, measures to reduce dissolved phosphorus(phosphate) should be prioritised, as they provide a greater effect.Sea-based measuresIf anoxic accumulation bottoms in the Swedish coastal zone of the Baltic proper, which areassumed to release phosphorus, would be addressed with aluminium treatment in the sameway as in Björnöfjärden, an annual phosphorus turnover of about 550 tonnes is estimated tobe stopped. The cost of the measure is estimated to be around SEK 3 billion.Despite the fact that the treatment cost of resolving the internal load is much lower thanthe cost of land measures, it is not enough to fix the phosphorus that leaches from the bot-toms. Nutrient supply from land must also decrease, otherwise new nutrients will soon ac-cumulate in the sediment again, which again begins to leach out and regulate eutrophication.How much action is required?An important question is how much phosphorus reduction, both from land and sediment,that is needed in order to stop the spread of anoxic bottom areas and start reducing so thatsediments can begin to store phosphorus bound to iron again.54 • EffEctivE mEasurEs against EutrophicationIt is a complex issue that cannot be answered here, but the possible reduction in loadin different areas and activities can also be made against, for example, Sweden’s reductionquota in BSAP. In such a perspective, the coastal zone is a filter for, among other things, nu-trients and organic matter between land and sea.Choice of action methodWhen selecting the method of action, the cost of treatment often plays a significant role,but an important experience after implementing measures on a broad scale within the Li-ving Coast is that there are many more factors that determine whether or not a measure isultimately effective. It is not possible to strictly rank which action is better than another. Ineach action situation, a catchment area perspective is needed to get an overview of both theload situation and the action potential. Based on this, action plans need to be adapted tothe specific location and in the choice that measures factors such as feasibility, the need forrEAD MOrE ABOuT... supervision and maintenance, the operating costs, the treatment effect in relation to actionexperiences and reflections potential, proportion of eutrophication-driving phosphorus that the measure reduces, etc.from the work on measures need to be taken into account.to combat eutrophication inThe table below summarises what Living Coast’s measures could mean for the Baltic pro-the complete Living coastWhite Paper. per if they were implemented on a large scale and what it would cost. The table also compa-res the measures with regard to different aspects/experiences for each measure.TABLE 3. Summary of the action potential, action effect and cost of action for various sources of phosphorus and measures carried out withinthe Living Coast if measures were to be implemented on a large scale. The table also compares the actions based on other aspects. Whencomparing, a three-degree colour scale (green, yellow, red) is used to try to summarise how well an action is from different aspects.Source: Clay soils Horse keeping Small sewage systems internal load (sediment)Where: N. and S. Baltic N. and S. Baltic Sea Water Coastal areas of S. and Baltic proper coastal zonesea Water Districts N. Baltic Sea WaterDistricts DistrictsWhat: structure liming Daily manure clearing in change to sewage Aluminium treatment of accu-of all arable land pastures and safe manure systems where toilet mulation bottoms.with clay content disposal. waste is collected andover 20 %. transported away.Action potential (ton P/year) 351 83 23 549Action effect (ton P/year) 105 75 21 54930 % 90 % 90 % 100 %Action cost (SEk m) ≈ 4200 ≈ 23 300 ≈ 4700 ≈ 3100Treatment cost at the coast ≈ 2000 ≈15 500 ≈ 100 000 ≈ 800(SEk/kg P)Acceptance of actionknowledge gaps 10-30 years? red?implementation*Care and operation never daily once in a while neverEutrophication-driving 40-80 % 100 % 100 % 100 %phosphorus**response time for action inwater/recipientSummary positive aspects Effective and well- Easy way to make the most Effective and establis- the only established internalknown action. Can of nutrients and avoid hed measure. Also has load measure. Well known forincrease the yield. nutrient losses. a positive effect on freshwater and promising fordrinking water. coastal areas.Summary of negative only works on Labour intensive. Little Little measurement data First effort in brackish water.aspects soils with high measurement data and and lack of consen- important to evaluate the long-clay content. Un- lack of consensus on sus on eutrophication term effect in Björnöfjärden.clear how long the eutrophication effect. effects. Expensive for aluminium is energy-intensiveeffect lasts (10-30 Expensive to install a new private persons. to produce.years). manure slab.* The possibility of bringing the measure into being (need for permits, the importance of finding suitable contractor, requirements on specialistknowledge, etc.)** The bioavailability of the phosphorus that each action reduces, i.e., percentage of dissolved phosphorus (phosphorus of total phosphorus).EffEctivE mEasurEs against Eutrophication • 55How we calculated nutrient losses and action potentialClay fieldsStructural liming of fields in the North and South Baltic Sea water districts can reducephosphorus load on the Baltic Sea by 105 tonnes of phosphorus per year (30 per cent, seeSTRUCTURE LIMINGFigure 22). The cost is estimated to be just over SEK 4 billion (SEK 5900/hectare) and from a Reduction: 105 tonnes P/yearcoastal zone perspective, the treatment cost is about SEK 2,000/kg of phosphorus. Cost: approx. 4 billion SEK-30%Structure liming can reducephosphorus load from clay fieldsto surrounding ditches by about30%, from 500 to 350 tonnes/year.Structure liming can reduce clayfields’ phosphorus load on the BalticSea from 350 to 245 tonnes/year.MEASURES HORSE KEEPINGReduction: 75 tonnes P/year717,000 ha of clay fields in the Cost: approx. 23 billion SEKnorthern and southern Baltic sea 30% retention assumed in lakes and streams between the sourcewater districts. and the coast (decreases from about 150 to 105 tonnes P/year). Baltic properFigurE 22. Field area with a higher clay content than 20 per cent has been estimated from SGU’s arable -80%land map (DSMS) and Statistics Sweden’s statistical data on fields’ utilisation38. Assuming an averageSTRUCTURE LIMINGleakage of 0.7 kg phosphorus per hectare and year39, the phosphorus loss is about 500 tonnes per year.Reduction: 105 tonnes P/yearAt an average retention rate of 30 per cent from the field to the sea, about 350 tonnes of phosphorus perCost: approx. 4 billion SEKyear reaches the Baltic Sea proper’s coastal zone. If clay fields are structure limed, phosphorus lossesare expected to decrease on average by 30 per cent, and the effect remains for 20 years, reducing exportsto the coast by about 105 tonnes of phosphorus per year.-30%SWITCHING TO A CLOSED TANKHorse keepingReduction: 21 tonnes P/yearIf all pastures in the North and South Baltic Sea water districts were cleared of manure daily Cost: approx. 5 billion SEKand the manure is taken care of, so that the nutrients in the manure does not reach the sur-rounding ditches, the phosphorus load can decrease by around 75 tonnes per year (Figure23). The total cost is estimated at about SEK 23 billion, assuming that it costs approximately -90%SEK 2,000 per kilogram of phosphorus that is taken care of on the horse farm, and that theMEASURES HORSE KEEPINGmeasures are effective during a 20 year period. From a coastal zone perspective, the cost isReduction: 75 tonnes P/yearapproximately SEK 15,000 per kilogram of phosphorus. The proportion of phosphorus in the Cost: approx. 23 billion SEKmanure that is presumed to be permanently bound in the soil in the pasture will have a majorimpact on how much horse keeping contributes to the eutrophication of the Baltic Sea. Thesize of the costs will depend on the need to set up new manure slabs, which is costly. -80%ALUMINIUM TREATMENTManure clearing in pastures and safe handling The measures are estimated to reduce Reduction: 550 tonnes P/yearof manure is estimated to reduce the phospho- the phosphorus load on ditches fromrus load from pastures by about 80%, from about 120 to 12 tonnes/year. Cost: approx. 3 billion SEKabout 660 to 70 tonnes/year.The measures are esti-m1ate0d 0to%reduce the phosphorus load fromSWITCHING TO A CLOSED TANKabout 80 to 8 tonnes/year.Reduction: 21 tonnes P/yearCost: approx. 5 billion SEK16,300 horsesin the northern and southern 30% retention assumed in lakes and streams between the sourceBaltic Sea water districts. and the coast (decreases from about 35 to 4 tonnes P/year). Baltic proper -90%FigurE 23. As an average horse produce approximately eight kilograms of phosphorus per year47,52, horsesin the north and south Baltic sea water districts47 produce more than 1,320 tonnes of phosphorus peryear in the form of manure. If horses are in pastures for half of the day76, half of the nutrients are produ-ced outdoors, and about 660 tonnes of phosphorus per year are added to the soil if the pastures are notcleared from manure. of the phosphorus that is added to the soil, 80-90 per cent is assumed to be boundpermanently in the soil; a larger share of pastures in rural areas where the density of horses is assumedto be lower and the ground cover is assumed to hold better and leak less. The rest, about 120 tons ofphosphorus per year, is assumed to reach ditches. At an average retention of 30 per cent from pastures toALUMINIUM TREATMENTthe shore, about 83 tons of phosphorus per year reaches the coast. If 90 per cent of the phosphorus thatReduction: 550 tonnes P/yearloads the pastures (660 tonnes/year) is taken care of, about 67 tonnes/year remain, of which about 12Cost: approx. 3 billion SEKtonnes are assumed to reach ditches, and 8 tonnes finally reach the coast.56 • EffEctivE mEasurEs against Eutrophication -100%STRUCTURE LIMINGReduction: 105 tonnes P/yearCost: approx. 4 billion SEK-30%MEASURES HORSE KEEPINGReduction: 75 tonnes P/yearCost: approx. 23 billion SEKSTRUCT-U8RE0 L%IMINGReduction: 105 tonnes P/yearCost: approx. 4 billion SEKSmall sewage systems-30% If nutrients from properties with individual sewage solutions in the coastal zone are collectedin a closed tank and treated in a safe way, the emissions to the Baltic Sea can be reduced bySWITCHING TO A CLOSED TANKReduction: 21 tonnes P/year just over 20 tonnes of phosphorus per year (Figure 24). Assuming a cost of SEK 75,000 perCost: approx. 5 billion SEK property for the installation of a closed tank or equivalent technical solution where the toiletwaste can be separated and removed, the cost is SEK 4.7 billion. Assuming a lifespan of 20years, the treatment cost from a coastal zone perspective is approximately SEK 100,000 per-90%kilogram of phosphorus.MEASURES HORSE KEEPINGReduction: 75 tonnes P/yearimport of phosphorus is mainly in the form of food, PhosphorusCost: approx. 23 billion SEK and is about 60 tonnes/year. retained inremoval of phosphorus as a result of sludge removal the soil aboutis about 18 tonnes/year. 18 tonnes/ if closed tanks are installed in all theseyear. properties, the phosphorus load on theBaltic sea is estimated to decrease by-80% about 90% from 23 to 2 tonnes/year.ALUMINIUM TREATMENTReduction: 550 tonnes P/yearCost: approx. 3 billion SEK86 000 small sewers without or with poor purificationin the coastal zone of the Baltic proper. Baltic properSWITCHI-N1G0 TO0 A% CLOSED TANKReduction: 21 tonnes P/yearFigurE 24. There are almost 86,000 properties with small sewage solutions along the coast of the NorthCost: approx. 5 billion SEKand South Baltic Water Districts’ coastal zone58. Based on data on the number of homes per property,distribution between year-round housing and holiday housing, time at home, average treatment for diffe-rent types of technical solutions and sewage fractions that are removed via sludge and latrine emptying,these properties annually import 60 tonnes of phosphorus in the form of food, of which 18 tonnes are-90%exported from the coastal zone mainly through desludging 58. An additional 18 tonnes of phosphorus isestimated to be permanently bound in the soil and the remaining 23 tonnes of phosphorus per year areestimated to load coastal waters. If the nutrients from these properties instead are removed from thecoastal zone to 90 per cent, for example through the installation of closed tanks, the leakage is reducedfrom 21 tonnes of phosphorus per year to 2 tonnes of phosphorus per year.Internal load in the coastal zoneALUMINIUM TREATMENTReduction: 550 tonnes P/year If the entire surface that is assumed to release phosphorus in the North and South Baltic SeaCost: approx. 3 billion SEK water districts’ archipelagos were to be treated with aluminium like Björnöfjärden, an inter-nal load in the area at about 550 tonnes of phosphorus per year can be stopped (Figure 25).The cost of binding the mobile phosphorus pool permanently is estimated to be about SEK 3-100%billion, which corresponds to a treatment cost of about SEK 800 per kilogram of phosphorus.Aluminium treatment of accumulationbottoms in the coastal zone is estimated tostop the internal phosphorus load in thesebottoms, from about 550 to 0 tonnes/year.Baltic properFigurE 25. The area of the bottom areas to release phosphorus in the North and South Baltic Sea waterdistricts’ archipelagos was assumed to be the area where fine-particle nutrient-rich material accumula-tes (accumulation bottoms), which was estimated to be about 1,540 km2 77. Assuming that these bottomscontain on average 2.5 tonnes of mobile phosphorus per km2, the sediment in these bottoms is calcula-ted to contain about 3,840 tonnes of phosphorus likely to leach out, which on average is turned overevery seven years78. It provides a leakage of dissolved phosphorus of 550 tonnes of phosphorus per year.If this entire area were to be treated with an aluminium dose equivalent to that of Björnöfjärden(50 tonnes Al/km2), the phosphorus turnover would cease completely.EffEctivE mEasurEs against Eutrophication • 57Conclusions andrecommendationsAfter seven years of work with eutrophication measures, measurements andevaluation, the Living coast project can conclude that:iT iS POSSiBLE TO rEgAiN gOOD ECOLOgiCAL STATuS iN ENCLOSED BAyS!• The internal phosphorus supply from the sediment must be addressed in order toget a quick improvement, while the nutrient supply from the catchment area mustbe minimised in order for the effect to persist.• However, in order to have a clear local effect of actions taken, the water exchangemust be limited, otherwise the effect diminishes quickly when the water is mixedwith nutrient-rich water from surrounding bays.• Eutrophication is driven by dissolved phosphorus and nitrogen that is added tothe water, regardless of where the nutrients come from. Most phosphorous formsin soil and sediment are stable and contribute to a small extent to eutrophication.Measures to minimise the supply of dissolved phosphorus and nitrogen should beprioritised.58 • EffEctivE mEasurEs against Eutrophication/rednAWeLAIrAM:OTOhPédInörgrEMEDiATiON WOrk iS DiFFiCuLT• For effective remediation work, clear goals, adequate competence, financing andpatience are needed.• To appoint a ”catchment officer” to be assigned decision-making mandates andfinancial resources provides strength in the implementation of actions.• The catchment area’s perspective is important, but site-specific knowledge is alsoneeded to identify the major nutrient sources and cost-effective measures.• Strive for work based on smaller catchment areas instead of by county or munici-pality. Gather land users, landowners, municipalities, ditch companies, watercouncils and action coordinators to get a common overview, for example to walkalong watercourses in the catchment. Continuous sampling and evaluation is alsoneeded to make the work effective.TO iNCrEASE THE PACE OF ACTiON, THE FOLLOWiNg iS NEEDED:• Clear incentives to reduce nutrient losses• Increased inspection rate and the opportunity to receive counselling• Possibility to receive support financing for initial investments• Clear goals and positive examplesEffEctivE mEasurEs against Eutrophication • 59references1. Arheimer B., Dahné J., Donnelly C. (2012). Climate change impact on riverine nutrient load andland-based remedial measures of the Baltic Sea Action Plan, AMBIO 41:600–612.2. Helcom (2018). Sources and pathways of nutrients to the Baltic Sea. Baltic Sea Environment Pro-ceedings No. 153.3. Savshuk O.P. (2018). Large-scale nutrient dynamics in the Baltic Sea, 1970–2016. Frontiers in Ma-rine Science 5:95.4. Gustafsson B.G., Schenk F., Blenckner T., Eilola K., Meier H.E.M., Muller-Karulis B., Neumann T.,Ruoho-Airola T., Savchuk O.P., Zorita E. (2012). 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Res. 2012, 17,425-436.62 • EffEctivE mEasurEs against EutrophicationWE WOuLD LikE TO THANk ALL THOSE WHO HAVEBEEN iNVOLVED iN THE LiViNg COAST PrOPjECT iNVAriOuS WAyS!Involved in sampling, analysis, investigations or similar: naturvatten i rosla-gen AB, Sveriges vattenekologer AB, erken Laboratory at uppsala university,ecoloop AB, ekoloagen Miljöjuridik AB, IvL Swedish environmental researchInstitute, TBh consulting hB, Loude consulting OY, JP Sedimentkonsult hB,enveco Miljöekonomi AB, Svensk ekologikonsult AB, Pecab, Sam ekstrandat Werec, Anders Alm at WWf, Lars fladvad at värmdö Municipality, Ingemarrenberg at umeå university, Ann-kristin eriksson-Wiklund, Jakob Walve, ellenSchagerström, Lena kautsky, Sven Blomqvist, Joakim hansen and others atStockholm university, Jonas nilsson and Per larsson at Linnaeus university,Ingrid Wessman, gunnar Torstensson, Pia geranmayeh, Brian huser at SLu,gunno renman at kTh, karin Johannesson at Linköping university, and others.Involved in identifying, proposing and implementing the measures: SäbyManor farm, Smakriket Säby, Säby farm, evlinge farm and all propertyowners in Björnöfjärden’s catchment area, värmdö Municipality, ramböll AB,ecoloop AB, WrS AB, Ingarö Mark och väg AB, WereC, nordkalk, Swedish Ang-lers Association, the County Administrative Board of Stockholm, and others.Important ”sounding boards” and advisors: in particular Björn Carlson, ConradStralka, fredrik Wulff, Per Larsson and ragnar eakins and the rest of theBalticSeaS2020’s Board, and others.Contributed comments on the white paper: The board of BalticSea2020 es-pecially ragnar elmgren and Björn Carlson, Åsa gunnarsson, Margreta ungerand robert Almqvist, Mats Wallin, Mikael gyllström and Jan Pettersson at theSwAM, kerstin rosén nilsson, helena Aronsson, Barbro ulén and Pia geran-mayeh at SLu, Sam ekstrand of Werec, nadja Andreewitch at vallentuna Muni-cipality, Mats Johansson and Anna norström at ecoloop AB, Markus Larssonand ulrika Brenner at Stockholm university, and others.EffEctivE mEasurEs against Eutrophication • 63This book presents the results of the Living Coast project in Björnöfjärden,Stockholm archipelago. The bay that can be described as a “miniature BalticSea” because of extensive eutrophication, limited water exchange and largeareas of anoxic (oxygen depleted) bottom waters. After seven years of work andremediation actions, the bay’s water quality has become much better and plantand wildlife are recovering. The project was initiated by BalticSea2020.The BalticSea2020 Foundation was founded in 2005 and finances projectsthat are action-oriented, innovative and contribute to a healthier Baltic Sea. Thefoundation also works to disseminate knowledge and information about theBaltic Sea to decision-makers, authorities, schools and individuals.The aim is to improve the environment in the Baltic Sea by the year 2020, therebyimproving the quality of life for the approximately 90 million people living aroundthe Baltic Sea.P.O. Box 50005, Lilla Frescativägen 4B, 104 05 Stockholm, Sweden • tel: +46-8-673 97 64 • info@balticsea2020.org • BalticSea202064 • EffEctivE mEasurEs against Eutrophication WWW.BALTiCSEA2020.Org