Historically, international environmental agreements on shared transboundary waters have dealt with exploitation of natural resources like oil, minerals, forests, fisheries, shipping and trade. Presently the focus is on environmental issues relevant to conservation, restoration, protection, sustainability over-fishing, pollution, invasive species and climate change. Global assessment indicates a lack of international agreements between multiple users. A brief review of major conventions and agreements is offered with emphasis on the Great Lakes Water Quality Agreement on the North American Great Lakes and the European Water Framework Directive, since they appear to be ecologically sound and predominantly ecosystem-based. This article exemplifies the history behind these agreements with examples of environmental threats and consequences (eutrophication, pollution, invasive species and loss of biodiversity). It is concluded that such ecosystem-based agreements are essential for all large aquatic ecosystems shared by multiple users or countries for holistic and integrated management of aquatic resources.

Introduction

Waterbodies form natural physical barriers and therefore often delineate geopolitical boundaries, which implies that nations share watersheds (also called catchment areas, catchment basins, drainage areas, river basins, water basins or waterbodies). International transboundary waters range in size from oceans to rivers, including lakes, wetlands, aquifers and groundwater.

Protecting shared waters requires a commitment to cooperation and collaboration between nations linked by water. Differences in political regimes, administrative systems, legal and jurisdictional frameworks can all hinder the achievement of good quality management of internationally shared waters (Norman and Bakker, 2013). Management of transboundary waters requires biospheric, global, regional and local, as well as waterbody specific, international environmental agreements (IEAs) agreements (Vallentyne, 1993). Many existing IEAs deal with marine waters, and the focus has traditionally been on the ownership of natural and geological resources like fisheries, minerals and oil. More recent agreements, like those listed in Table 1, are directed towards environmental management and pollution prevention.

IEAs are meant to evolve over time and are subject to periodic review, revision and/or replacement. The main objective of the 1972 London Convention was to prevent dumping of refuse at sea, creating hazards to human health and marine life. Drafted in 1972, it entered into force in 1975 when 15 nations had it ratified. As of 2013, there were 84 Contracting Parties to the Convention. The London Convention was upgraded and will eventually be replaced by the London Protocol of 1996, extending protection to the sea and seabed from ‘all sources’ of pollution including operational vessel discharges (IMO, 2012). The other international water agreements listed in Table 1 have similar histories of development and structure with a call, a draft and subsequent ratification by nations and further modification as scientific knowledge and governmental policies evolve.

Agreements on freshwater have been directed towards water extraction for drinking water and agriculture (irrigation), hydroelectric power, wetlands, flood control, navigation, fishing and economic development. Altogether 400 international treaties have been signed from 1820 to 2007 (Oregon State University transboundary waters database). Among these 38 are between Canada and United States including the Great Lakes Water Quality Agreement, and 3 are between Sweden and Norway.

An examination of agreements affecting the North American Great Lakes (Lakes Ontario, Erie, Huron, Michigan and Superior) and Lake Vänern in Sweden exemplifies differences in approaches taken by Canada and United States on the Great Lakes – St. Lawrence River basin and by Sweden (and Norway) for Lake Vänern as influenced by the European Community (European Commission, 2000). This article is based on a presentation at the International Symposium on State of Lake Vänern Ecosystem (SOLVE) in Vänersborg, Sweden, June, 2012. It deals with agreements relating to freshwater lakes in Europe and North America from an ecological and “ecosystem approach” perspective. Other relevant papers dealing with Lake Vänern such as historical development of the lake (Drotz et al., 2014) and progress in the implementation of the European Water Framework Directive (WFD) (Phillips, 2014) are also included. The article focuses on the background development of the current lake management systems in the Great Lakes and Lake Vänern and how their history has influenced the successful management of these large lakes. An attempt is made to highlight similarities in problems, and differences in approaches for their management.

Historical background of Great Lakes and Lake Vänern agreements

Negotiation over the control of the North American Great Lakes started with the peace treaty between the United States and Great Britain that ended the American Revolution in 1783 (Linton and Hall, 2013). That treaty drew a border through the middle of the Great Lakes that was challenged during the war of 1812 with both sides negotiating for the exclusion of the other from the Great Lakes. In the end the border dividing the lakes remained in place (Linton and Hall, 2013). By 1909, the Boundary Waters Treaty (BWT) was signed allowing use of boundary waters of the United States and Canada in ways that would not interfere with usage by the other country. The major issues at that time were apportionment of hydropower and a growing concern over public health due to typhoid and cholera (Read, 1998–1999). The International Joint Commission (IJC) was established as part of the BWT to mediate disputes over boundary waters. The IJC consists of 6 commissioners who have sworn to undertake their duties faithfully and impartially to seek consensus solutions in the joint interest of both the countries (Norman et al., 2013).

Although there has been an increase in local scale organization of environmental management of the North American Great Lakes since the 1990s (Norman and Bakker, 2013) the large size of these lakes, (>300 km long) and the large number of stakeholders using them complicates any local agreement and has kept the organizational scale of environmental management national. The IJC also keeps activities focused at the bi-national level.

As in the Great Lakes, initial treaties concerning Lake Vänern dealt with border placement during the dissolution of the Swedish-Norwegian union in 1905 (Oregon State University transboundary waters database). Lake Vänern was ceded completely to Sweden with a portion of the watershed belonging to Norway. Until Sweden joined the European Union in 1995 and the subsequent creation of the European Water Framework Directive in 2000, management of Lake Vänern has been the sole responsibility of the Swedish government.

Eutrophication and phosphorus abatement

Through the twentieth century human stress on shared waters increased. Pollution, water extraction and overexploitation of fisheries were widespread. As the degradation of the environment became readily apparent, political will to stop degradation lead to the formation of new national and international agreements to reduce pollution.

In the 1960s and early 1970s widespread algal blooms in the lower North American Great Lakes such as Lakes Erie and Ontario (Vollenweider et al., 1974) and eutrophication of embayments and the near shore areas of Lake Vänern (Welch and Lindell, 1978) had raised concerns with the public. In Sweden in the 1960s, organic loading from pulp and paper industries reached a peak and urban sewage treatment was also an isssue (Wilander and Persson, 2001). A Swedish Environmental Protection Agency was initiated in 1967 and laws that sought to reduce discharges into all waters were enacted in 1969 (Lönnroth, 2010). In the United States and Canada in 1972 a bi-national Great Lakes Water Quality Agreement (GLWQA, 2012) set basin wide water quality objectives and standards for municipal and industrial pollution control. In 1972 the GLWQA was focused on phosphorus and bacterial reduction.

A major contribution behind the GLWQA was the convincing evidence presented by Vollenweider et al. (1974) that eutrophication was explained in a majority of lakes, including the North American Great Lakes and large lakes in Sweden, by phosphorus loading (Figure 1). The wide applicability and acceptance of Vollenweider’s empirical relationships resulted in regulations on sewage treatment and reduction of polyphosphates in detergents in the Great Lakes region (Vallentyne and Johnson, 1970; Schindler, 2006). Targets for total phosphorus (TP) in the Great Lakes were established and the results of phosphorus reductions are apparent in all lakes, especially Lake Ontario (Figure 2). In Sweden phosphorus management focused on sewage treatment works and phosphorus precipitation (Willén, 2001; Wilander and Persson, 2001) and the clean-up of large industrial polluters. Organic loading by pulp and paper industries on Lake Vänern was reduced by 80% due to the closure of several unprofitable factories and increased efficiency in the remaining ones as well as improved water treatment processes in industry (Willén, 2001). These management actions resulted in a reduction in total phosphorus in Lake Vänern (Wilander and Persson, 2001).

Models reveal general relationships, but when data on chlorophyll and TP from thousands of European lakes were evaluated it was found that for any particular chlorophyll concentration there was a 100 μg l−1 variation in TP (Phillips et al., 2008). In Lake Vänern from 1979 to 1999 significant reductions in total P were seen, but there was no concomitant reduction in chlorophyll a (Vänerns vattenvardsforbund, 2011). In more recent years (1992–2011) increasing trends in both chlorophyll and major phytoplankton groups have been seen in both L. Vänern and several other Swedish lakes, in spite of decreasing trends in TP (Weyhenmeyer and Broberg, 2014). This pattern of reduced phosphorus coinciding with an initial decline in chlorophyll a that did not continue despite continuing reductions in phosphorus is also seen in a Lake Ontario embayment, the Bay of Quinte (Leisti et al., 2012). Thus, the Vollenweider model explained the general pattern, but for some ecosystems there may be some unknown specific factors and complex biological and environmental relationships to consider when defining the ecosystem’s health. Factors affecting ecosystem health can be found anywhere in the watershed or even further afield (e.g. acid rain). The only way to analyse and elucidate these relationships is through integrated scientific monitoring and research on causal relationships.

Towards the ecosystem approach

In time, research approaches changed from individual projects to multi-disciplinary, multi-trophic projects which required collaboration from various experts, often between agencies. This is the birth of the ecosystem approach.

Multiple stresses and interactions affecting ecosystems ensure that it is challenging to prove causal relationships. Testing requires multidisciplinary teams collecting and analysing complex data sets. This is particularly important for large lakes. Generally large lakes are more difficult to manage than smaller lakes because of many known and unknown factors. Research on large lakes requires special considerations for reasons described below:

  • A scientifically sound sampling program must evaluate a great number of sampling stations

  • Large size means slow response to environmental impacts. This also implies that response to environmental management is slower than for smaller lakes.

  • Large lakes may have higher species diversity than smaller lakes with more complex foodwebs. This implies that a stress on one part of the can affect the entire foodweb, and therefore species other than those affected directly. A variety foodweb of experts may be needed to fully evaluate the foodweb.

  • Large lakes are often regulated for ship traffic and hydroelectricity. These manipulations may affect immigration of invasive species, the impacts of which are difficult to predict and control.

  • Regulations for hydroelectricity will not only affect fish migration but also river gravel size (spawning substrate), shore erosion and vegetation, which will also affect spawning of many fish species.

  • Since large lakes (or their watersheds) are generally shared by more than one nation, they require international cooperation both for scientific monitoring and research (with standard methods) to understand the whole ecosystem. Cooperation is also necessary for environmental management and regulatory action for maintaining ecosystem function.

  • A large lake and its watershed may be regulated by laws at the international, national, provincial and municipal level. Representatives need to be empowered to make decisions and have the capacity to carry out assigned initiatives. Local actors are more susceptible to political pressure especially where there is no overarching provincial or national standard to be met. Jurisdictional fragmentation leads to confusion as to who is to play what role and to what degree of responsibility (Norman and Bakker, 2013). Effective coordination and cooperation between these governments is necessary if the system is to achieve good health status.

In the 1980s the ecosystem approach gained momentum almost simultaneously in North America and Sweden’s management strategy with a focus on smaller scale sources of pollution and the effects of non-industrial activities like agriculture, forestry and transport on the environment (Vallentyne and Beeton, 1988; Lönnroth, 2010). A new Swedish Ministry of the Environment was created in 1987 and local authorities had a strengthened role in relation to environmental protection and biodiversity (Lönnroth, 2010). Sweden joined the European Union (EU) in 1995 and in 2000 the EU Water Framework Directive was initiated which called for the prevention and reduction of pollution, promotion of sustainable water usage, environmental protection, improvement of aquatic ecosystems and mitigation of the effects of floods and droughts on a watershed basis for all watersheds in the EU (EU, 2000). The European Water Framework Directive organized the management of water into local river basins charged with creating a river basin management plan, which includes monitoring of ecological quality, hydromorphology, nutrients (N and P) and a set of priority pollutants for each river basin. This monitoring results in site-specific classifications of all waterbodies (lakes, rivers, groundwater reservoirs) across the EU. This classification (on a 5-grade scale) is intended to identify waterbodies which do not reach “good ecological quality.” This watershed approach once again linked Norway and Sweden in the management of the Klaralven basin of which Lake Vänern is a part.

The ecosystem concept was launched in North American Great Lakes management as early as the 1970s when it emerged as a viable and holistic approach for the new management of the Great Lakes (Lee et al., 1982). Consequently the GLWQA underwent revisions in 1978 when the ecosystem approach to management was adopted by the governments of Canada and the United States (Caldwell, 1988) integrating social, economic, and environmental interests (Great Lakes Research Advisory Board, 1978; Christie et al., 1986; Regier, 1992; Munawar, 1992). Further revision in 1987 expanded GLWQA focus towards the restoration of Beneficial Use Impairments (BUIs) in ‘Areas of Concern’ (AOCs), through the development of local level Remedial Action Plans (RAPs) (Hartig and Vallentyne, 1989; Vallentyne and Munawar, 1993). It implicated land-use based non-point sources of pollution. This changed the scale of management to a local level in the AOCs and eventually led to the 2012 revision of the GLWQA that included species and habitats and not only pollutants in the agreement. The AOC management practices in the Great Lakes are similar to the smaller scale River Basin Approach adopted by the WFD. A watershed approach shifted focus from a one-topic agency creating laws to enforce their mandate (e.g. eutrophication or toxic pollutants) to a collaborative and integrated approach requiring years of negotiations with multiple agencies at all levels of government, non-governmental agencies and the public to come up with an optimal plan for the watershed (Sabatier, 2005).

Conclusions

A comparison of these two ecosystem-based Agreements; Great Lakes Water Quality Agreement and European Water Framework Directive, indicates both similarities and differences of approaches (Table 2), but the environmental threats and problems are the same. The GLWQA has undergone long term development, progressing from phosphorus abatement to adoption of ecosystem approach and restoration/remediation plans. The recently signed 2012 agreement deals with 10 annexes and more importantly emphasizes science as the foundation of the Agreement. In addition to nutrients and AOCs it includes important parameters like invasive species, discharges from the vessels and climate change. The Water Framework Directive is relatively young and currently going through a developmental phase. It has a promising list of 11 annexes. It adopts a different strategy of directly addressing all waters in Europe by river basin and to manage surface and ground waters through river basin plans. Within these plans main pollutants and environmental quality standards, which include ecological assessments, are addressed (Table 2). The implementation of these extensive annexes in Canada, the United States and Europe is a demanding task requiring considerable cooperation between stakeholders, researchers, managers, governments and politicians.

An ecosystem approach to aquatic science and large lake management may create more research questions than solutions. Although we will always strive to improve our scientific understanding of the environment we must encourage local knowledge to manage shared waters. As scientific understanding changes, management plans must also change. Science-policy feedback is necessary to keep management on course. Often management is directed through sustainability principles and must negotiate competing social, economic, political and community interests. The international ecosystem-based agreements are necessary to reach the target of ecosystem-based management of these precious bodies of water.

Finally, the dissemination of the concepts of ecosystem approach and health to water managers at a global level is the responsibility of the scientific community. Needless to say, the establishment of international agreements, such as the GLWQA and the WFD, are necessary for the conservation of all ecosystems shared by multiple user states. The exchange of information on the ecological status of various aquatic ecosystems is essential and interactions between Great lakes researchers are vital. Co-operative research projects, international standardization of techniques and conferences like SOLVE and the Aquatic Ecosystem Health and Management Society’s Great Lakes of the World (GLOW) conferences play a very important role in bringing aquatic experts together. Advancing communication technology has revolutionized our ability to reach colleagues across the world quickly. It is hoped that the GLWQA and the WFD will serve as ideal examples for other large ecosystems where multiple users should adopt a “borderless” approach for the protection of aquatic ecosystem health in a holistic and integrated fashion.

Acknowledgements

We are grateful to the Organizing Committee of the SOLVE symposium (Sweden) for giving us the opportunity to present this article to promote the ecosystem-based management of large ecosystems. Thanks to Alice Dove of Environment Canada for providing the up-to-date diagram of the phosphorus concentration in the Great Lakes. The assistance of Heather Niblock is greatly appreciated for patiently editing several versions of this manuscript. Thanks are also due to Iftekhar Fatima Munawar, Mark Fitzpatrick and Jennifer Lorimer who assisted in the development of the presentation in Sweden and the preparation of this manuscript for publication.

The text of this article is only available as a PDF.

References

Black Sea Commission
,
2014
. http://www.blacksea-commission.org/_convention.asp
(Accessed March 2014)
Caldwell, L.K.,
1988
.
Implementing an ecological system approach to basin-wide management
. In: L. K. Caldwell (ed.),
Perspectives on Ecosystem Management for the Great Lakes: a Reader
. pp.
1
29
.
State Univ. New York Press
,
Albany
.
Convention on Biological Diversity
,
1993
. http://www.cbd.int/convention/
(Accessed March 2014)
.
Drotz, M. , Wängberg, S.-Å. , Jakobsson, E. , Gustavsson, E. , Göran Nilsson, L.,
2014
.
Lake Vänern: A historical outline
.
Aquat. Ecosyst. Health Mgmt.
17
(
4
),
323
330
.
European Commission
,
2000
.
The EU Water Framework Directive
. http://ec.europa.eu/environment/water/water-framework/index_en.html
(accessed Dec 2013)
Christie, W.J. , Becker, M. , Cowden, J.W. , Vallentyne, J.R.,
1986
.
Managing the Great Lakes as a home
.
J. Great Lakes Res.
12
,
2
17
.
Great Lakes Research Advisory Board
,
1978
.
The Ecosystem Approach: Scope and Implications of an Ecosystem Approach to Transboundary Problems in the Great Lakes Basin
.
Great Lakes Regional Office, International Joint Commission, 100 Ouellette Avenue, Windsor, Ontario, Canada
.
Great Lakes Water Quality Agreement (GLWQA)
,
2012
. https://www.ec.gc.ca/grandslacs-greatlakes/default.asp?lang=En&n=45B79BF9-1
(accessed March 2013)
Hartig, J.H. , Vallentyne, J.R.,
1989
.
Use of an Ecosystem Approach to Restore Degraded Areas of the Great Lakes
.
Ambio
18
(
8
),
423
428
Hollis, D.,
2013
.
United Nations Convention on Law of the Sea (UNCLOS), 1982
.
Retrieved from
http://www.eoearth.org/view/article/156775
Interim Secretariat for the management of Lake Tanganyika
,
2003
.
The convention on the sustainable management of Lake Tanganyika
. http://www.ltbp.org/FTP/LAKECONV.PDF
International Maritime Organization
,
2002
.
MARPOL 73/78 Consolidated Edition, 2002 Articles, Protocols, Annexes
,
Unified Interpretations of the International Convention for the Prevention of Pollution from Ships, 1973, as modified by the Protocol of 1978 relating thereto
,
London
.
International Maritime Organization
,
2012
.
Information leaflet no 49E The London convention and protocol: Their role and contribution to protection of the marine environment
.
Accessed Dec 2013 at
http://www.imo.org/OurWork/Environment/LCLP/Documents/2012%20LCLP%20leaflet%20Web.pdf
Karydis, M. , Kitsiou, D.,
2012
.
Eutrophication and environmental policy in the Mediterranean Sea: a review in
Environmental Monitoring and Assessment
184
(
8
),
4931
4984
.
Lee, B.J. , Regier, H.A. , Rapport, D.J.,
1982
.
Ten ecosystem approaches to the planning and management of the Great Lakes
.
Journal of Great Lakes Research
,
8
(
3
),
505
519
.
Leisti, K.E. , Doka, S.E. , Minns, C.K.,
2012
.
Submerged aquatic vegetation in the Bay of Quinte: Response to decreased phosphorous loading and Zebra Mussel invasion
.
Aquat. Ecosyst. Health Mgmt.
15
(
4
),
442
452
.
Linton, J. , Hall, N.,
2013
.
The Great Lakes. A Model of Transboundary Cooperation
. In: E. Norman , A. Cohen and K. Bakker (Eds.),
Water Without Borders? Canada, the United States, and Shared Waters
, pp.
221
243
,
University of Toronto
.
Lönnroth, M.,
2010
.
The Organisation of Environmental Policy in Sweden: A Historical Perspective
.
Swedish Environmental Protection Agency Report 6404
.
Munawar, M.,
1992
.
Aquatic ecosystem health and management: an integrated and multidisciplinary approach
.
J. Aquat. Ecosyst. Health
1
(
1
):
xiii-xvi
.
Norman, E. , Bakker, K.,
2013
.
Rise of the Local? Delegation and Devolution in Transboundary Water Governance
. In: E. Norman , A. Cohen and K. Bakker (Eds.),
Water Without Borders? Canada, the United States, and Shared Waters
, pp
47
69
,
University of Toronto Press, Toronto
.
Norman, E , Cohen, A. , Bakker, K.,
2013
.
Introduction
. In: E. Norman , A. Cohen and K. Bakker (Eds.),
Water Without Borders? Canada, the United States, and Shared Waters
, pp.
3
23
,
University of Toronto Press, Toronto
.
Oregon State University
.
Transboundary Freshwater Dispute Database, Department of Geosciences
:
<
http://www.transboundarywaters.orst.edu
> (Accessed Dec 13, 2013)
Phillips, G.,
2014
.
Progress towards the implementation of the European Water Framework Directive (2000–2012)
.
Aquat. Ecosyst. Health Mgmt.
17
(
4
),
424
436
.
Phillips, G. , Pietiläinen, O.P. , Carvalho, L. , Solimini, A. , Lyche Solheim, A. , Cardoso, A.C.,
2008
.
Chlorophyll-nutrient relationships of different lake types using a large European dataset
.
Aq. Ecol.
42
(
2
),
213
226
.
Ports and Maritime Organization
,
2014
. http://maritimesafety.pmo.ir/en/marineenvironmentprotection/regionaltreaties/kuwaitconvention
(Accessed March 2014)
.
Ramsar Convention on Wetlands
,
2014
. http://www.ramsar.org/cda/en/ramsar-home/main/ramsar/1_4000_0__
(accessed March 2014)
.
Read, J.,
1998-1999
. ‘
A sort of destiny’: The Multi-Jurisdictional Response to Sewage Pollution in the Great Lakes, 1900-1930. Scientia Canadensis: Canadian Journal of the History of Science, Technology and Medicine Volume 22 - Volume 23, 1998-1999
, p.
103
129
.
Regier, H.A.,
1992
.
Ecosystem integrity in the Great Lakes Basin: an historical sketch of ideas and actions
.
J. Aquat. Ecosyst. Health
1
(
1
),
25
37
.
Sabatier, P.,
2005
.
Swimming Upstream: Collaborative Approaches to Watershed Management
.
MIT Press
,
Cambridge, MA
.
Schindler, D.W.,
2006
.
Recent advances in the understanding and management of eutrophication
.
Limnol. Oceanogr.
51
(
1, part 2
),
2006
,
356
363
.
Thomas, S.,
2011
.
The Water Framework Directive: to succeed or not to succeed?
In: Waterworld (accessed Dec 10 2013
http://www.waterworld.com/articles/wwi/print/volume-26/issue-5/regulars/legal-perspective/the-water-framework-directive-to-succeed-or-not-to-succeed.html
)
.
UNECE (United Nations Economic Commission for Europe)
,
2014
. http://www.unece.org/env/water/text/text.html
Accessed March 2014
UNEP (United Nations Environmental Program)
,
2014a
.
Regional Seas East Africa
http://www.unep.org/regionalseas/programmes/unpro/easternafrica/
Accessed March 2014
.
UNEP (United Nations Environmental Program)
,
2014b
.
Regional Seas Red Sea and Gulf of Aden
http://www.unep.ch/regionalseas/main/persga/redconv.html
Accessed March 2014
Vallentyne, J.R.,
1993
.
Biospheric foundations of the ecosystem approach to environmental management
.
Journal of Aquatic Ecosystem Health
.
2
(
1
),
9
13
.
Vallentyne, J.R. , Beeton, A.M.,
1988
.
The ‘Ecosystem’ Approach to Managing Human Uses and Abuses of Natural Resources in the Great Lakes Basin Environmental Conservation, Vol. 15, (1)
,
58
62
.
Vallentyne, J.R. , Johnson, W.E.,
1970
.
A visual demonstration of the Beneficial Effects of Sewage Treatment for Phosphate Removal on Particulate Matter Production in Waters of Lakes Erie and Ontario
.
J. Fisheries Res. Board of Canada
27
(
8
),
1493
1496
.
Vallentyne, J.R. , Munawar, M.,
1993
.
From aquatic science to ecosystem health: a philosophical perspective
.
Journal of Aquatic Ecosystem Health
2
(
2
),
231
235
.
Vänerns vattenvårdsförbund
,
2011
.
Vänern – Årsskrift 2011. (Vanem-Annual report 2011.) Rapport nr 66
.
Available as a pdf file at
www.vanern.se
(in Swedish)
.
Vollenweider, R.A. , Munawar, M. , Stadelmann, P.,
1974
.
A comparative review of phytoplankton and primary production in the Laurentian Great Lakes
.
J. Fish. Res. Board Can.
31
,
739
762
.
Welch, E. , Lindell, T.,
1978
.
Phosphorus Loading and Response in Lake Vänern Nearshore Areas
.
Environmental Science and Technology
12
(
3
),
321
327
.
Weyhenmeyer, G.A. , Broberg, N.,
2014
.
Increasing algal biomass in Lake Vänern despite decreasing phosphorus concentrations: A lake-specific phenomenon?
Aquat. Ecosyst. Health Mgmt.
17
(
4
),
341
348
.
Wilander, A. , Persson, G.,
2001
.
Recovery from eutrophication: Experiences of reduced input to the four largest lakes of Sweden
.
Ambio
30
,
475
485
.
Willén, E.,
2001
.
Four Decades of Research on the Swedish Large Lakes Mälaren, Hjälmaren, Vättern and Vänern: The Significance of Monitoring and Remedial Measures for a Sustainable Society
.
Ambio
30
(
8
),
458
466
.