Baltic Sea large marine ecosystem

June 2, 2011, 2:14 pm
Source: NOAA
Content Cover Image

Mixed flock of Mute swans and other pelagic birds, southern tip of Oland, Sweden. @ C.Michael Hogan

caption Location of the Baltic Sea Large Marine Ecosystem. (Source: NOAA)

The Baltic Sea Large Marine Ecosystem (LME) is characterized by its temperate climate. It is enriched by a high level of nutrients. It is a semi-enclosed sea, strongly influenced by human-induced eutrophication, river runoff and a lack of rapid exchange with the adjacent ocean. Intensive fishing is the primary force driving the LME, with eutrophication as the secondary driving force. The Global Environment Facility (GEF) is supporting an LME project in the Baltic Sea, to address critical threats to the coastal and marine environment, and to promote ecosystem-based management of coastal and marine resources. Information is available on the GEF-sponsored Baltic Sea LME Project. LME book chapters and articles pertaining to this LME include Kullenberg, 1986, and Jansson, 2003.


caption (Source: NOAA)

The shallow Baltic Sea LME is one of the largest brackish water bodies in the world. It is essentially a fjord that is 1500 kilometres (km) long with an average width of 230 km. The sea is divided into basins and includes the Gulf of Finland and Gulf of Bothnia. Large-scale meteorological conditions determine long-term fluctuations of salinity and temperature in the deep and bottom waters. Large pulses of North Sea water cause deeper areas to flip between oxic and anoxic conditions (Jansson, 2003). For hydrodynamic processes (Jansson, 2003). The Baltic Sea receives freshwater from river runoff, with a maximum in May and a minimum in January or February. For more information on oceanographic characteristics and trends, and for oxygen conditions, (Kullenberg, 1986). The Baltic Sea LME and its catchment area have a range of ecotones and biological diversity. Its brackish waters contain a mixture of marine and freshwater species. The coastal areas serve as spawning, nursery and feeding areas for several species of fish. The Baltic Sea LME is considered a Class I, highly productive (>300 grams of Carbon per square meter per year) ecosystem based on SeaWiFS global primary productivity estimates. There are changes in the productivity of the near coastal and offshore waters from eutrophication. See a summary of "Eutrophication in the Baltic Sea". The traditional monitoring program for plankton used by the countries surrounding the Baltic Sea LME has proven to be unreliable in detecting rapid changes in the ecosystem e.g. toxic phytoplankton blooms and marked regional variations. Despite long-time observations, the dynamics of the system are not understood well enough to explain long-term changes or to make reliable predictions. Dynamic models need to be developed that can be used to investigate the response times of various ecosystem components to marked natural events. An augmentation to the ICES inter-disciplinary monitoring program will be implemented to improve the quality of temporal and spatial coverage of the Baltic Sea LME. Ships of opportunity will assess changes in the plankton communities especially in relation to fish. There will be coordinated ICES surveys in the near shore and open sea.

Fish and Fisheries 

caption LME: Baltic Sea. Source: NOAA

The Baltic Sea LME has both marine fish in high salinity waters and freshwater species that cannot tolerate high salinity and are found near the coast. The Food and Agriculture Organization (FAO) 10-year trend shows an increase in the catch from 650,000 tons in 1990 to 900,000 in 1999 (FAO, 2003), with a peak in 1997. The average level is 800,000 tons. The LME is characterized by predominant catches of small pelagic clupeoids (herrings, sardines and anchovies) that represent almost 80% of the total identified shelf catches. Cods, hakes and haddocks represent the second largest group for Baltic Sea catches of herring, sprat, and cod from 1910 to 1995. (Jansson, 2003) The cod catch increased in the late 1970s, as did the total fish catch. The stocks seemingly benefited from an increased input of nutrients (Otterlind, 1983). Degraded water quality has had an impact on the Baltic Sea LME and its productivity. The Global International Waters Assessment (GIWA) has issued a matrix that ranks LMEs according to the sustainable exploitation of fisheries and the predicted direction of future changes. GIWA characterizes the LME as severely impacted in terms of overfishing, but the impact is decreasing (see the GIWA web site). See the Baltic Sea Fishery Commission Report. The recovery of depleted fishery resources and damaged habitats can be achieved in the coastal areas and in the open sea through cooperative action by the countries bordering the LME. At present, the countries in the Eastern part of the Baltic Sea do not have the same capacity to conduct spatial and temporal fish stock or pollution impact surveys as those in the Western Baltic Sea. The Baltic Sea Regional Program of ICES and HELCOM will be implemented in part to provide financial support to the recipient eastern Baltic bordering nations (Poland, Latvia, Estonia, Lithuania, Russia) in extending the ICES fisheries surveys eastward. Action plans are being developed to determine Total Allowable Catches (TACs) for salmon, cod, sprat and herring. For long-term changes in the Baltic Ecosystem, see Kullenberg, 1986. The University of British Columbia Fisheries Center has detailed fish catch statistics for this LME.

Pollution and Ecosystem Health 

caption Galen R. Frysinger, Source: NOAA

The Baltic Sea has a drainage basin area that is four times larger than the Sea itself. For a detailed map of the Baltic Sea’s drainage basin, see Jansson, 2003. The Baltic Sea’s ecological deterioration has been caused in recent years by an increase of point source industrial and non-point source agricultural pollutants and by the non-sustainable use of living marine resources. The increase in anthropogenic impacts is leading to environmental change and degradation. The need to address the problem of agricultural inputs into the Baltic Sea LME has been highlighted in the Baltic Sea Joint Comprehensive Environmental Action Program (JCP). There is a degradation of coastal water quality from pollution, harmful algal blooms and contaminant loading. It has been subject to outbreaks of fish kills, marine mammal and seabird mortalities and invasive species. The pollution problems are transboundary and difficult to address on an individual country basis. For more information on eutrophication, metals in sediment and fish, PCB and DDT water pollution, see Jansson, 2003. Anoxic conditions are on the rise due to climatic variations (see Pedersen, 1982), and the increase of organic material (see Anon., 1984). Data collection is fragmented, although ICES (the International Council for the Exploration of the Sea) has developed a program for measuring the effects of pollution and natural environmental changes on the productivity of Baltic living marine resources. For an understanding of eutrophication in the Baltic Sea, see this document. See a study of "Present conditions in the Baltic Marine Environment".

Socio-economic Conditions 

caption Baltic Sea Drain Large Marine Ecosystem. (Source: NOAA)

Baltic 21 is an initiative on the part of the Prime Ministers of the Baltic Sea Region to develop an Agenda 21 for the Baltic Sea Region. Baltic 21 statistics indicate that the fishery industry contributes significantly to the regional and local economy. Sustenance fishing is critical to the social and economic welfare of the coastal communities in the eastern Baltic Sea. The countries bordering the Baltic Sea must develop effective strategies for the management of their shared resources and promote sustainable fishery practices. Sustainable management is needed to provide social and economic benefits to farming, coastal and fishing communities, and sectors such as businesses and tourism. Few but large population centers and harbors are found along the eastern and southern borders of the Baltic Sea (see Bruneau, 1980). There are conflicting human uses of the Baltic Sea with waste disposal, sea transportation, fishing, aquaculture, and recreation.


The coastal countries involved in this LME’s governance are Sweden, Finland, Estonia, Latvia, Lithuania, Poland, Russia, Denmark and Germany. However, the Baltic Sea catchment area is vaster and includes non-coastal countries such as Belarus, Ukraine, the Czech Republic and the Slovak Republic (see Kindler and Lintner, 1993, map page 9). The JCP (see above) was prepared under the coordination of the Helsinki Commission (HELCOM). It was adopted as a strategic action program for the region by the Ministers of Environment in 1992, and was updated in 1998. The JCP recognizes the need to use an ecosystem-based management approach that recognizes the freshwater, coastal and marine resources together. The Global Environment Facility (GEF) is supporting an LME project in the Baltic Sea (see above). Agencies collaborating in the GEF project include the Baltic Sea Fisheries Commission and ICES. The project integrates land, coastal and open sea activities and aims to strengthen local and regional capacity. The project brings jointly-planned monitoring and assessment surveys. The JCP considers agricultural inputs as a priority issue. For more information on institutional evolution for meeting sustainable development, see Jansson, 2003. There is a need to develop the technical, scientific, and local capacity of the eastern Baltic countries in order for them to fully participate with western Baltic countries in improving the long-term sustainability and socioeconomic benefits for this LME. Institutional evolution has resulted in the banning of hazardous substances and in programs for decreasing emissions of nutrients and wastes from industries and the transportation sector.


Articles and LME Volumes

  • Baltic 21.
  • FAO, 2003. Trends in oceanic captures and clustering of large marine ecosystems—2 studies based on the FAO capture database. FAO fisheries technical paper 435. 71 pages.
  • Jansson, B.-O., 2003. The Baltic Sea. In: K. Sherman and G. Hempel, Large Marine Ecosystems of the World – Trends in Exploitation, Protection and Research. ISBN: 0444510273.
  • Kullenberg, G. 1983. The Baltic Sea. In Estuaries and Enclosed Seas, Ed. By B.H. Ketchum, vol 26, Ecosystems of the World, Elsevier, Amsterdam, 500 pp.
  • Kullenberg, Gunnar. 1986. "Long-term changes in the Baltic Ecosystem." In Kenneth Sherman and Lewis M. Alexander (eds.), Variability and Management of Large Marine Ecosystems (Boulder: Westview, 1986). AAAS Selected Symposim 99. ISBN: 0813371457.

Other References

  • Anonymous, 1984. Iltsvind of Fisksedod I 1981. Omfang og Arsager. In Danish; Miljostyrelsen, Strandgade 29, 1401 Copenhagen K. 247pp.
  • Bianchi, TS, P. Westman, T. andren, C. Rolff and R. Elmgren, 2000. Cyanobacterial blooms in the Baltic Sea: natural or human induced? Limnol. Oceanogr. 45:716-726.
  • Bonsdorff, E., E. Blomqvist, J. Mattila and A. Norkko, 1997. Coastal eutrophication—causes, consequences and perspectives in the archipelago areas of the Northern Baltic Sea. Estuar. Coastal Shelf Sci. 44:63-72.
  • Brugmann, L. 1981. Heavy metals in the Baltic Sea. In The State of the Baltic, Ed. By G. Kullenberg, Mar. Pollut. Bull. 12 (6):214-218.
  • Bruneau, L. 1980. Pollution from industries in the drainage area of the Baltic. Ambio, Special issue on the Baltic p. 145-152.
  • Dybern, B.I. and Fonselius, S.H. 1981. Pollution. In The Baltic Sea, pp. 351-382. Ed. By A. Voipio. Elsevier Oceanography Series 30, Amsterdam. 418 pp. ISBN: 0444418849.
  • Ehil, U. 1981. Hydrology of the Baltic Sea. In The Baltic Sea, pp. 1230-134. In The Baltic Sea, pp. 123-143. Ed. By A. Voipio. Elsevier Oceanography Series 30, Amsterdam. 418 pp. ISBN: 0444418849.
  • Flinkman, J., Aro, E., Vuorinen, I., and M. Viitasalo, 1998. Changes in northern Baltic zooplankton and herring nutrition from 1980s to 1990s: top-down and bottom-up processes at work. Mar. Ecol. Prog. Ser. 165:127-136.
  • HELCOM, 1996. Third Periodic Assessment of the State of the Marine Environment of the Baltic Sea, 1989-93; Background document. Balt. Sea Environ, Proc. No. 64B. Helsinki Commission - Baltic Marine Environment Protection Commission. 252 p.
  • ICES. 1980. Assessment of the marine environment of the Baltic Sea Cooperative Research Report 63, ICES, Copenhagen, 97 pp.
  • Jansson, B.O. 1978. The Baltic - a systems analysis of a semi-enclosed sea. In Advances in Oceanography, pp 131-184. Ed. By H. Charnock and G. Deacon, Plenum Press, Oxford. ISBN: 0306400197.
  • Jansson, B.O. 1984. The Baltic Sea and the nutrients. In The Baltic Sea - an environment worth protecting. Symposium in Karlskrona, Sweden. June 1984.
  • Kindler, J. and S.F. Lintner, 1993. An Action Plan to clean up the Balitc. Environment, volume 35, number 8, pp. 7-31.
  • Otterlind, G. 1983. Ostersjon och overgodningen. Yrkesfiskaren no. 18-20, in Swedish, Marine Research Laboratory, 45300 Lysekil, Sweden.
  • Pawlak, J. 1980. Land-based inputs of some major pollutants to the Baltic Sea. Ambio Special issue on the Baltic, pp. 163-167.



Disclaimer: This article is contains information that was originally published by the National Oceanic and Atmospheric Administration. Topic editors and authors for the Encyclopedia of Earth have edited its content and added new information. The use of information from the National Oceanic and Atmospheric Administration (NOAA) should not be construed as support for or endorsement by that organization for any new information added by EoE personnel, or for any editing of the original content.




(2011). Baltic Sea large marine ecosystem. Retrieved from


To add a comment, please Log In.