Environmental Conditions in the Baltic Sea Region
The Baltic Sea is unique: the largest body of brackish (low-salinity) body of water in the world, it is also distinguished by its division into a series of basins of varying depths, separated by shallow areas or sills. The many rivers flowing into the Sea are the reason for its brackish character. Furthermore, the link with the North Sea is very narrow, the shallowest sill being only 18 m deep. Thus inflows of salt water must be extremely forceful to penetrate and renew the deepest waters of the Baltic Proper.
Nine countries share the Baltic Sea coastline; Sweden and Finland to the north, Russia, Estonia, Latvia and Lithuania to the east, followed by Poland in the south, and Germany and Denmark in the west. About 16 million people live on the coast, and around 80 million in the entire catchment area of the Baltic Sea. The catchment area includes part of Belarus, the Czech Republic, Norway, the Slovak Republic and Ukraine, as some of the rivers find their sources here.
The Baltic Sea is a semi-enclosed sea of about 415 000 km2 (Figure 2- 1). Proceeding from the northern end, it includes the Bothnian Bay and the Bothnian Sea. At the southern end of the Bothnian Sea, the island of Aland divides the Aland Sea from the Archipelago Sea. The Gulf of Finland is the eastern arm of the Baltic Sea. The central portion of the Sea, known as the Baltic Proper, includes the Eastern and Western Gotland Seas. To the east and south are the Gulf of Riga, and the Gulf of Gdansk. Moving to the west are the Bornholm and Arkona basins, followed by the Sound, the Belt Sea and the Kattegat.
In fact, the Baltic Sea has always been characterized by the interaction of fresh and saltwater sources. Geologically a young sea, it has undergone enormous changes since the last ice age. At the end of the Baltic Ice Lake period, about 10 000 years ago, cold saline water intruded into the area, forming the Yoldia Sea, which covered mainly the present Baltic Proper and the Gulf of Finland. At the end of this phase, only limited areas of stagnant ice remained in Sweden, and a progressive upheaval of land cut the oceanic connection to Baltic Sea basin, changing it to a fresh water basin (the Ancylus Lake). Because the continuing uplift was greater in the north, the floor of the lake tilted and a new contact with the ocean was established about 7 500 years ago, resulting in the Baltic Sea as we now know it.
The variable frequency of the saltwater inflows from the North Sea is primarily determined by complex meteorological processes over Northern Europe and the North Sea. Although the shallower water in the Baltic Proper is renewed by a more or less continuous inflow through the Belt Sea and the Sound, the deepest water is renewed only periodically. During this century, major inflows have occurred approximately every 11 years, but have recently been less frequent. The last major inflow of such saline water took place in 1976. The bottom water can remain stagnant for long periods in the main deep basins of the Baltic Sea. Thus there is a distinct layering of the water characterized by surface waters of lower salinity and a warm top layer in summer time, the deep water with higher salinity, and the near-bottom water which is the most saline.
The shallowest sills between the Baltic Sea and the North Sea are located in the Belt Sea, the Sound and west of the Arkona Basin. The sill depth is 18 m in the Belt Sea and 8 m in the Sound. The sills impede the inflow of saltwater, although certain meteorological and hydrographic conditions do occasionally permit highly saline water to pass the sills. If these waters are of greater density than the water which already occupies the deep basins, a replacement will occur.
The ecological importance of this infrequent renewal of the bottom water is related to oxygen consumption. Between inflows, oxygen is continuously consumed in the near-bottom water, principally through oxidation of organic material which sinks down from the upper layers. If the deepest water is not replaced by new inflows, its dissolved oxygen will be entirely consumed, creating anoxic conditions, leading to the formation of hydrogen sulfide, which is toxic to organisms. Thus the serious lack of oxygen in the bottom water is accompanied by a deterioration of the benthic community, followed by a disappearance of all higher forms of life. The size of the bottom areas with reduced conditions for life varies from year to year. The current area of dead bottoms, which are found in the Gulf of Finland, in the Baltic Proper, the Belt Sea and the Kattegat, is 100 000 km2, which is about one third of the entire area of the sea floor. Anoxic conditions in the bottom water also cause sediment-bound phosphorus to be released into the water. The brackish character of the Baltic Sea also plays an important role in its ecology. Water circulation in the Baltic Sea is weak. Surface water movement is most affected by winds, a significant factor in water mixing and distribution of pollutants. In winter, the Baltic Sea is largely ice-covered, which renders it even more vulnerable to the effects of pollution. Finally, many rivers bringing freshwater, especially to the Baltic Sea Proper, also carry with them many polluting substances.
The Baltic Sea is one of the best studied seas of the world, and this has contributed to a greater awareness among the public and politicians about its pollution problems. Today, intensive monitoring is coordinated in all the Baltic Sea countries and a periodic evaluation of the state of the Sea is carried out under the auspices of the Helsinki Commission.
Pollution of the Baltic Sea probably began as early as the Middle Ages, when wastewater from the medieval and post medieval towns of Europe, aggravated by poor hygienic conditions, was discharged into the Baltic Sea. This was later compounded by wastes from small industrial establishments. The first signs of marine pollution arose near the cities lying on the shores of the enclosed parts of the Baltic Sea. In these early times, marine pollution occurred only locally. In the late 19th and early 20th centuries, the marine areas affected by pollution grew in the regions where industrialization developed and use of fertilizers in agriculture intensified.
When recreational use of the sea became more popular, eutrophication and poor hygienic conditions caused unpleasant consequences in the coastal waters and beaches. The other natural resources of the sea were not yet threatened, however.
Since the middle of the present century, the environmental situation has deteriorated rapidly in many parts of the Baltic Sea. The areas affected by pollution have grown, especially along the coasts of the formerly centrally planned economies. The type of pollutants changed considerably, as industrial and agricultural wastes came to contain more toxic substances dangerous to living resources. Many coastal areas are now as seriously affected as some heavily polluted inland waters. The various airborne pollutants that have created background contamination in nearly all the oceans of the world have considerably affected the Baltic Sea region. Together with stagnation of the deeper water, the pollution of the Baltic Sea has now become a threat to its living resources.
Many harmful or toxic and persistent substances not found in the natural environment, such as PCBs, DDT, polychlorinated camphenes, and polychlorinated terphenyls (PCTs), have found their way into the Baltic Sea. Other examples of harmful substances detected in Baltic Sea biota in the 1980s are chlorinated terpenes, halogenated paraffins, polyaromatic hydrocarbons (PAH) and chlorinated pesticides, such as chlordane and dieldrine. These substances are highly toxic and some are also bioaccumulating. The ban on the use of mercury compounds, in particular in the pulp and paper industry, and a drastic reduction of mercury discharges from the chlorine-alkali industry, have resulted in some decrease of mercury concentrations in fish, but many coastal water areas are still seriously contaminated.
Human activity is also responsible for the increase of certain natural substances in the Baltic Sea, such as nutrients (phosphorus and nitrogen compounds), heavy metals and hydrocarbons. There are also other substances, such as artificial radioactive isotopes and by-products from industrial production of chemicals and pharmaceuticals, which are likely to cause harmful effects in the Baltic marine environment. Oil spills are another danger, the effects of which depend on the magnitude and location of the spill and the time of year. Coastal marine life, including birds, is the most sensitive to oil contamination.
Water exchange varies according to area. The water between the Gulf of Bothnia and the Baltic Proper is exchanged mainly through the Aland Sea, deeper and more open than the Archipelago Sea. These inflows are partly composed of low-salinity, low density surface waters of the Baltic Proper, and have small salinity and density variations. In the Gulf of Bothnia, vertical density difference is further reduced and therefore the stratification is considerably weaker than in the Baltic Proper. Water entering the Bothnian Bay comes primarily from the surface layer of the Bothnian Sea. Even strong winds can cause mixing of the layers. Salinity levels measured in the Bothnian Sea and in the Bothnian Bay have generally remained stable, although a slight decrease has been observed in the near-bottom layer during the last 15 years.
In the Central Baltic Proper and the Gulf of Finland, the area with insufficient oxygen conditions for macrofauna (currently about 100 000 km* with less than 2 ml oxygen/l in bottom water) has fluctuated in extension from year to year, but has not increased over the last 25 years. In the deepest areas of the Eastern Gotland Basin, however, the long stagnation period has led to a continuous decrease in oxy,gen, and hydrogen sulphide concentrations are now the highest ever measured. On the other hand, decreasing salinity and a consequent lowering of the halocline, together with increased vertical exchange, has allowed oxygen to penetrate more deeply into the intermediate layers (90-100 m) and improved life conditions at the sea floor in this depth range. In the late summers of the 198Os, eutrophication led to repeated oxygen depletion for the first time in the Kattegat. In the Bothnian Sea, vertical convection is suppressed during the winter, leading to oxygen decrease there, and a clearly negative trend wah observed between 1965 and 1988. In the Bothnian Bay, however, no similar trend has been signalled. The large supply of fresh water to the Bothnian Bay together with weak stratification prevents the basin from stagnating. Oxygen depletion has never been detected in the near bottom water.
Reliable data on trace elements and persistent organic compounds in the open Baltic Sea are limited. It should be noted that waterborne pollutants first enter the Baltic Sea in its coastal zones from local point sources; therefore, concentrations of harmful substances are generally higher in those areas than in the open Baltic Sea.
Trace element concentrations in fish and shellfish have not changed remarkably since the early 1980s. In general, mercury values in biota do not significantly differ from those in the North Sea and the North-East Atlantic. Compared with background levels, elevated mercury concentrations have been found in the Sound and southern Bothnian Sea, although there has been a decrease in the latter in recent years. Both mercury and lead loading are high in the Kattegat and the Sound. Cadmium concentrations have been on the rise in fish from the northern part of the Bothnian Bay. The reason for this is not fully understood, although the inverse relationship between salinity and cadmium uptake in the biota might explain the increase to a certain extent. Zinc and copper have shown similar trends. In the Kattegat and the Belt Sea, lead concentrations in fish and shellfish appear to be decreasing. It is possible that this is already an effect of the increased use of unleaded petrol. Metal loading from anthropogenic sources is lowest in the Bothnian Bay and increases southward to the Baltic Proper, although zinc loading is high in the Bothnian Sea, due to geological conditions. Loads of cadmium, lead and mercury are highest in the Baltic Proper, corresponding to five to seven times the background level.
As a result of the ban on certain harmful substances, some positive changes have been observed. DDT levels in biota have decreased since the 1970s and are currently stable. Following the ban on technical HCH, there is an ongoing decrease of alpha-HCH concentrations. Furthermore, concentrations of PCBs appear to be stabilizing at lower levels, especially in the Baltic Proper, ;1s a result of its declining use since the 1960s. However, concentrations of organochlorine residues in fish from the Baltic Proper are still 3 to 10 times higher than in catches from the Northern Atlantic. Among several new contaminants that have been identified are a considerable number of organic substances potentially harmful to the environment. Toxaphene, lindane (gamma -HCH), dibenzofurans, dibenzodioxins and coplanar PCBs have been detected in the Baltic Sea ecosystems.
Unusually intense algal blooms indicating increasing eutrophication appear to occur more frequently in the Kattegat and the Belt Sea and in the Gulf of Finland. There is evidence that phytoplankton primary production has doubled within the last 25 years in the area from the Kattegat to the Baltic Proper, reaching a high level in the 1980s. Primary production is accompanied by a doubling of the biomass and its subsequent sedimentation. Decomposition of algae decreases the oxygen levels in bottom waters. Consequently, low oxygen concentrations in late summer and autumn were often observed in the 1980s in the southern Kattegat, the Belt Sea, the Sound and the Arkona Basin, resulting in fish mortality and damage to bottom animals.
In a discussion of the state of the coastal waters of the Baltic Sea, two general observations can be made:
In the Gulf of Bothnia, heavy metals (such as arsenic, cadmium, mercury and lead) and persistent organic substances are a threat to the environment. Airborne and waterborne metal emissions can be traced in the sediments and organisms of the Gulf of Bothnia and along both the Swedish and Finnish coasts. Intensive pulp and paper production has affected the biota of many coastal ecosystems in the Baltic Sea. High concentrations of organochlorines are found in the sediments of coastal areas near pulp and paper mills. Nitrogen, especially NO,, has increased since the 1970s. Although the Gulf of Bothnia is one of the few areas not suffering from eutrophication to the point of oxygen depletion, local effects of the land-based pollution load are seen in several coastal areas of both countries surrounding the Gulf.
Estonia, and Latvia in particular, discharge waste waters to the Gulf of Riga. The principal river discharging to this part of the Baltic Sea is the Daugava. However, the pollution problems of this shallow bay area are primarily due to local discharges. During the 1980s freshwater run-off to the Bay was high, contributing to a decrease in salinity. In addition, phosphorus and nitrogen values have increased, oxygen concentrations have clearly decreased, and changes in the biota have been observed. A well-known problem in the Gulf of Riga is contamination o f coastal waters by insufficiently treated sewage water discharges near the large beaches, which have now been closed to swimming and recreation for more than two years.
Vilnius and Kaunas, the largest cities in Lithuania, dispose of their wastewaters through the Nemunas River into the semi-enclosed Kurskiy Bay. Other sources include smaller municipalities, the pulp and paper industry and agriculture. Water quality is so deteriorated that the Bay is eutrophied and fish resources have decreased. To improve the situation, construction of a biological treatment plant has begun in Vilnius. Other pollution discharges to the coastal waters originate from Klaipeda and Palanga, both in Lithuania.
In the Kaliningrad region, discharges originating in the city of Kaliningrad, together with the industrial plants and farms located in the drainage area of the region cause local pollution problems in the coastal waters.
A considerable amount of nutrients and toxic substances are discharged to the Baltic Sea from Poland. The majority of the pollutants is carried by river flows. The largest of the ten rivers flowing to the Baltic are the Vistula (draining the territories of Belarus, Poland, Slovak Republic and Ukraine) and the Oder/Odra (draining the territories of the Czech Republic, Germany and Poland). While increasing eutrophication is a consequence of elevated nutrient inputs, some of the coastal waters are polluted also by toxic substances, such as heavy metals, chlorinated hydrocarbons and oil. The most polluted areas of the Polish coastal waters are the Gulf of Gdansk and the Pomeranian Bay, both of which absorb significant pollution loads through river outflows. Intensive primary production has been observed in these areas. Along the more open Polish coast, the problems are similar to those in the open Baltic Sea. In the late 1980s hydrogen sulphide was detected in the Gulf of Gdansk in high concentrations. The decrease in fish catches along the entire Polish coast during the last decade has been attributed to changes in living conditions for fish, but overexploitation of certain fish stocks may have played an important role in these changes as well.
The coastal waters are characterized by increasing eutrophication. Several areas are seriously deteriorated by a high nutrient input, and recreation has been significantly limited in these areas. Coastal effluents are subject to high organic and nutrient loads.
In Denmark, summer conditions in the coastal waters depend principally on nitrogen input. The coastal waters, especially the closed inlets, can retain and decompose nutrients, usually during the summer, whereas the major part of nitrogen runoff during the winter months reaches the open waters. Increases in winter concentrations of nitrate and phosphate in the waters have been recorded annually during recent decades. Heavy algae production, especially in the spring, is a common phenomenon in Danish open waters, and in many inlets and bays mass occurrence of plankton algae, some of them toxic, has become an annual phenomenon. During the 1980s oxygen depletion in Danish waters was more frequent, longer lasting and stronger than ever before.
Although only part of Germany is located in the catchment area of the Baltic Sea, its coastal waters are also subject to ecological problems, particularly around Mecklenburg-Vorpommem. Thanks to effective measures in the catchment area of Schleswig-Holstein, considerable reduction in discharges of nutrients and other harmful substances has been achieved, especially from urban areas.
In many local areas of Sweden, especially in the archipelagoes, eutrophication is the main problem, particularly in relation to the nitrogen cycle. Together with Denmark, Sweden has contributed to the heavy nutrient loading of the Kattegat and the Sound. The Laholm Bay in particular suffers from eutrophication, which has resulted in fish mortalities and large scale damage to marine life.
In the brackish water of the Baltic Sea, fish are a mixture of marine and freshwater species. Marine species such as herring, sprat and cod dominate in open waters, while both marine and freshwater species inhabit coastal areas. Extreme increases in catches have occurred during the last 50 years, when the annual yield has grown from some 100 000 to 1 000 000 tons. Between 1965 and 1975, there was an apparent increase in the productivity of fish in the Baltic Sea. Herring, sprat and cod represent about 90% of the total catch. Salmon and eel are also economically important. Yearly, somewhat more than 100 000 tons of the Baltic Riigen herring is caught in waters adjacent to the Baltic Sea.
The value of the catches, which amounts today to about 540 million ECU per year, is an indication of the considerable economic importance of these living resources. Another important aspect is the fact that considerable quantities of nitrogen and phosphorus are removed from the Baltic via this activity.
Currently the situation of the pelagic and demersal stocks of the Baltic Sea as a whole varies considerably. While herring and sprat stocks are in good condition and even underexploited, there has been a drastic decline of the two cod stocks (the eastern stock more depleted than the western) mainly because of naturally caused poor recruitment and high fishing pressure during the last decade. The year-classes since 1986 are believed to be among the lowest on record. The International Baltic Sea Fishery Commission was obliged to drastically reduce the Total Allowable Catch (TAC) for the entire Baltic Sea.
Of great importance to the fishery are the coastal areas of the Baltic Sea which serve as spawning, nursery and feeding areas for several species of fish. Data on the state of the coastal waters, mainly with regard to eutrophication and metal contamination, have recently been compiled by HELCOM. The effects of eutrophication are limited to observations on phytobenthos. Two processes in particular have been noted: a change in the species composition and a restriction of the depth range of the vegetation zone. Both processes have had negative impacts on the coastal fish populations. Along many of the coasts around the Baltic Sea there are problem areas regarding eutrophication and/or metals. Fresh water species, which occur mainly in the archipelagos, may be subjected on a local scale to considerably more pollutants than the marine species.
The effects of eutrophication in archipelago areas are well documented outside Helsinki, where herring have disappeared from the most polluted areas. Changes in fresh water species correspond well with changes observed in eutrophied lakes. In the Stockholm archipelago, similar changes have also been noted. In the Polish coastal waters, where oxygen levels have declined drastically due to pollution, this has resulted in considerable decreases in the abundance of cod. In some shallower parts of the Polish coast, there has been a decreasing trend in the appearance of whitefish. Studies of areas close to pulp and paper industries along the Swedish coast of the Gulf of Bothnia. where both nutrients and organic substances are discharged, indicate changes in the fish community similar to those reported from the Helsinki area. In many river systems in the Baltic Sea catchment area salmonid species have disappeared. A common feature in the shifts of the fish communities due to environmental degradation is a decrease in the abundance of the commercially more important fish species.
Oxygen deficiency in the bottom waters during the summer and autumn has had serious effects on the stock of Norway lobsters in the Kattegat and on commercial demersal species in the Belt and Arkona Seas. Oxygen deficits may also be linked to an increased occurrence of certain viral diseases in the dab population in the Kattegat.
It is difficult to distinguish between the effects of pollution, fishing and natural factors on fish stocks in the open Baltic Sea. Fish populations are known to be influenced by changing salinity and by oxygen conditions in the deep waters. This applies particularly to cod. This species, spawning in deep waters in the Bornholm Sea, Gotland Deep and Gdansk Deep has been seriously affected by the decreasing salinity of the Baltic Sea and the low oxygen concentrations of the bottom waters. The pelagic cod eggs require a minimum salinity of eleven permil to float and an oxygen level of at least 3 ml/l to survive. The northern border for reproduction is the Gotland Deep and successful spawning is dependant on an influx of saline water from the North Sea. Successful reproduction of cod in the Baltic Sea has not been observed for the last IO years. At present, the only significant area where salinity levels and oxygen conditions are conducive to cod spawning is the Bornholm Basin.
The low level of development of industries and agriculture in the formerly centrally planned economies, has permitted a comparatively high level of biological diversity to remain in the coastal ecosystems. However, the economic restructuring process now occurring could amplify the threat to the considerable biological diversity of coastal wetlands and their important role as natural filters.
At the turn of the century, the Baltic Sea seal populations comprised several hundred thousand individuals. During recent decades, harbour seal, ringed seal and grey seal populations have declined rapidly. Several reasons, among others, hunting and modem fish gear, have contributed to this almost catastrophic reduction in seal populations. However, from an environmental point of view the most important cause in recent times is considered to be toxic substances. Because the seals are at the top of the food chain, the accumulation of toxic substances has caused reproductive failures. Thanks to measures taken by the Baltic Sea States, a slow recovery of the populations has begun. Baltic grey seals are now estimated to number about 3 000 and ringed seals about 5 500-6 000. The harbour seal is found only in the western Baltic Sea and is represented by only about 200 individuals. Organochlorine levels (DDT, PCBs and HCB) are still very high in the seals (higher than the levels permitted for human consumption of fish).
Other effects of pollution on the living resources concern toxic chemicals and oil spills. The main known effect, discovered in the 197Os, of DDT and also to a certain extent of PCBs in the Baltic Sea, was the decrease in eggshell thickness of birds feeding on fish and mussels. This was particularly true for razorbills, guillemots, black guillemots, and white-tailed eagles. Oil spills and discharges are a danger especially in sheltered coastal waters, where currents and wave action are weak and oil accumulates. Birds are extremely vulnerable, as the oil coats their feathers, and mass mortalities can occur even from relatively small spills.
Aquaculture is the farming of aquatic organisms, including fish, molluscs, crustaceans and aquatic plants. The most important fish farming activity in the Baltic Sea countries is salmon and trout farms located on rivers, lakes and in coastal waters. Fish production in freshwater includes both the cultivation of young fish for transfer to coastal farms, where they are fed intensively to reach a marketing size, and the production of smaller "portion-size" fish for direct marketing. While aquaculture has been seriously affected by pollution of coastal waters, it can itself constitute a source of pollution. Trends towards intensification in some coastal regions have caused ecological impacts such as eutrophication and changes in the coastal ecosystems. The type and scale of any ecological change associated with coastal aquaculture depend on the method of aquaculture, the level of production and the biological, chemical and physical characteristics of the coastal waters.
The significance of fish farming as a nutrient source for the Baltic Sea as a whole is marginal. Total annual production is somewhat less than 50 000 tons. It has been estimated that, in 1989, fish farming accounted for I .5% of total phosphorus and 0.4% of total nitrogen loads to the Baltic Sea and Skagerrak. Although the effect on the Baltic Sea as a whole is minimal, adverse effects have appeared on a local scale. All fish farming results in discharges of pollutants such as organic matter and nutrients to the aquatic environment, but the natural conditions of the recipient waters determine to a great extent the character and extent of the effects. While nutrient enrichment and eutrophication of open coastal waters is unlikely, this can occur in semi-enclosed coastal areas, such as fjords, inlets, lagoons and archipelagos, which have a restricted exchange of water.
It has also been suggested that the release of dissolved organic compounds together with other components of the diet such as vitamins, influence the growth or toxicity of particular species of phytoplankton in the surrounding waters. There is also concern that the use of pharmaceuticals and antibiotics in the fish farms will lead to undesirable effects outside the farm’s boundaries. Net cages in lake and coastal fish farms are often treated with antifouling pesticides, some of which contain organotin compounds that can have harmful effects on the environment.
As late as 1950 the Baltic Sea was still regarded as environmentally "healthy". Large-scale industrialization had not yet made its impact, there were few automobiles, and intensive agriculture and forestry making widespread use of fertilizers and pesticides was only commencing. However, since then the situation has changed dramatically. Pollution now threatens the waters, land and air in the entire catchment area - and ultimately the health and well-being of the 80 million people who live there.
There is a wide diversity of pathways by which pollutants reach the Baltic Sea environment. Coastal outfalls discharge directly to estuaries, bays and sea gulfs. Rivers act as large-scale collectors and carriers of wastewater from diverse sources within their drainage basins and offload them to the Sea. Many contaminants are transported to the sea directly through the atmosphere - about 40% of the total nitrogen input is deposited in this way.
The precise data on polluting aqueous inputs to the Baltic Sea were not available during the preparation of the Joint Comprehensive Programme due to the fact that the pollution load compilation (PLC-2) based on 1990 data followed its initial timetable, which differed from the Task Force schedule. Although pollution load data presented by the countries in the National Plans of 1991 were very useful for preparation of the Programme, their aggregation proved to be more difficult. At present, the Second Pollution Load Compilation (PLC-2) has been completed. Further Pollution Load Compilations shall also serve the Programme in the long run as a follow-up instrument. The structure and the coverage of the Pollution Load Compilations in future would, however, require revisions according to Programme needs.
An important factor contributing to the degradation of the Baltic Sea is the destruction of its wetlands, particularly in the western parts of the catchment area. Mostly during the last century, coastal wetlands were ditched and drained in order to meet the demands of expanding modern, intensive agriculture. Wetlands have also been dredged or filled to make room for urban and industrial developments, including harbours. The consequences were not so visible until anthropogenic pressure on the Baltic Sea intensified. In recent decades, however, the disappearance of wetlands has had deleterious effects on nutrient balances.
A host of political and economic causes also contribute to the environmental change and degradation of the Baltic Sea. These include inadequate economic policies, inefficient economies, legislation without appropriate enforcement mechanisms, weak institutional arrangements and many others. These causes vary for each of the countries of the Baltic Sea catchment area.
In the market economy countries (Denmark, Finland, Norway, Sweden and the old Länder of Germany), municipal and industrial pollution loads have been significantly reduced in the last decades, and new policies are being introduced to better control waterborne and airborne emissions from industrial sources. Product control measures have also been introduced which have reduced the use of hazardous compounds. There is still scope for improved control of some industries, such as pulp and paper plants. The total farming area in these countries is much smaller than in the other Baltic region countries, but because intensive agricultural practices involve high use of chemical fertilizers, better policies are needed to control nutrient releases.
The situation is different in the formerly centrally planned economies (Belarus, the Czech Republic, Estonia, Latvia, Lithuania, Poland, Russia, Slovak Republic, Ukraine and the new Federal Lander of Germany). The overall pollution load from different sources is high. Several concrete programmes are being undertaken to alleviate the situation (some of them with foreign assistance), but the economic situation of these countries seriously constrains the possibilities of a quick recovery.
There are multiple causes of environmental change and degradation of the Baltic Sea, not all of which have been sufficiently documented to date.
The areas of the Baltic Sea receiving excessive amounts of untreated or insufficiently treated municipal wastewater are the Gulf of Finland, the Gulf of Riga and the Eastern Gotland and Bomholm basins. Existing facilities (including sewer systems and treatment plants) are insufficient, overloaded, and poorly maintained and operated. Moreover, large quantities of highly toxic industrial wastewater are discharged to municipal sewage systems. Pre-treatment of industrial wastewater is an absolute necessity for biological treatment processes to operate efficiently. Without pre-treatment, there are also serious problems with sludge disposal.
In other parts of the Baltic, there have been substantidl reductions in the pollution load discharged by municipalities during the last twenty years. The load of organic substances has been reduced from 50 to 95 percent and that of phosphorus from 75 to 90 percent. For example, in Sweden and Finland, the average reduction efficiency for BOD and phosphorus in municipal sewage treatment plants exceeds 90 percent.
In the Baltic Sea region, the pulp and paper industry plays (beside river-borne humus) a significant role in the discharge of oxygen consuming, nutrient-rich and slowly degradable substances to the receiving waters. A distinction must be made between old and new mills. The old sulphite mills are characterized by heavy discharges into water of organic substances or substantial emissions of SO2 or both. Most of the old mills are located in the formerly centrally planned economies (Karelia, St. Petersburg region, Estonia, Latvia, Lithuania and Poland).
Pulp and paper production is concentrated in Sweden and Finland. In the former, the region with the highest concentrations is the catchment of the Bothnian Sea and the Bothnian Bay. The Finnish pulp and paper industry is located in the catchments of both the Gulf of Finland and the Gulf of Bothnia. Over the past five to ten years, discharges of chlorine compounds have been minimized by internal process measures and by improved wastewater treatment (especially activated sludge treatment which also results in less discharges of organic matter and nutrients). Intensive R & D is carried out in order to achieve closed circulation of process water in chemical bleaching and to further substitute chlorine and sulphur containing chemicals. Some mills have already ceased to use chlorine bleaching. chemicals. It is expected that gradually chlorine-free production will dominate.
In the formerly centrally planned countries, the legacy of the past is monumental. Although industrial restructuring is taking place, it will be many years before environmental effects are more visible. As industrial enterprises in those countries become economically more efficient, environmental improvements will to a large degree be side effects of the overall change, provided that the principles of Best Available Technology and Best Environmental Practice are fully recognized and applied.
In the Baltic Sea catchment area, about 400 million tons of solid waste are generated annually. In Denmark, Finland, Sweden and Germany, hazardous wastes are handled separately from both household waste as well as from regular industrial waste and are properly treated. Unfortunately, this is not the case in the remaining countries of the Baltic Sea, where there are thousands of uncontrolled dumpsites which contribute significantly to contamination of local aquifers, rivers, and ultimately the Baltic Sea.
A major problem with dumpsites in Belarus, the Czech Republic, Estonia, Latvia, Lithuania, Poland, Russia, the Slovak Republic and Ukraine is the lack of separation of various kinds of waste. Moreover, very large volumes of solid waste have already been deposited. The St. Petersburg landfills and dumpsites contain about 195 million tons of mineral wastes. In Poland, the accumulated amount of solid wastes is estimated at 1 500 million tons. The destruction of solid waste through uncontrolled incineration, without proper flue gas treatment, often causes pollution over a wide area. In addition to the above mentioned disposal of waste on land, it should be noted that hazardous substances such as oil from sunken ships, poisonous gases, ammunition and industrial waste are known to be present in the Baltic Sea, due to intentional or accidental dumping.
International trading in industrial and hazardous waste has been attempted in the region (export to the formerly centrally planned economies). To date, all the littoral countries of the Baltic Sea region, except for Lithuania, had signed the Base1 Convention. It has also been signed by the CEC. Estonia, Finland, Latvia, Norway and Sweden have ratified this Convention, which came into force on 1 May, 1992.
Radioactive substances are present in the Baltic Sea naturally and as the result of human activities. The main source of artificial radionuclides in the Baltic Sea is fallout (radiocaesium) from the Chernobyl accident. The second most important source is fallout (radiocaesium and radiostrontium) from nuclear weapons tests in the atmosphere. Furthermore, minor amounts of radioactive pollution from European reprocessing plants (Sellafield and La Hague) are found in the Baltic Sea from the inflow of saline North Sea water. Normal authorized discharges from the nuclear power plants in the Baltic Sea area can only be detected locally in very small amounts (Denmark, Estonia, Latvia, Norway, and Poland have no nuclear power plants). Some local soil contamination from uranium ore processing and military uses of radioactive materials does occur.
With regard to nuclear waste disposal, Sweden has one for low and intermediate radioactive waste at Forsmark. The repository is constructed in bedrock at about 60 meters depth under the seabed and is accessible through two tunnels to the shore. There is one such repository in Finland, on land close to the seashore and below the local seabed level. At Sillamae in northeastern Estonia, there is a waste deposit, probably with radioactive waste, close to the Baltic Sea shore; investigation of the character of the waste and the management of the deposit should be carried out to determine the risks and assess the need for possible measures to be undertaken. Latvia has one low-level waste storage located close to the Daugava river. Recently, it has been modernized and should not be a cause of concern. In Lithuania, tritium concentrations in groundwater in the region of the radioactive depository of the Ignalina nuclear power plant are from 1000 to 10 000 times higher than the background values. Russia is also known to have some low level waste storage facilities, but no more information on this subject was available to the Task Force. Safety features of all these installations should be subject to regular inspection and control.
Approximately two-thirds of the total NO2 emissions from mobile sources in the Baltic Sea catchment comes from engines fueled by petrol and one-third from diesel engines. The use of unleaded petrol is still very limited in all the countries located on the southern and eastern shores of the Sea. The contribution of NO2 from mobile sources to total NO2 emissions in the Western and Northern European countries varies from 60 percent in Finland to 76 percent in Norway, while in the Eastern European countries it does not exceed 35 percent, since almost all major point sources of NO2 are coal-burning electric power plants.
In the Nordic countries and Germany, several measures to reduce traffic emissions have recently been taken or will be in the near future. Regulations concerning car and lorry exhaust have been passed, according to which Best Available Technology must be applied. There is a wide use of lead-free petrol, reduction of lead content for other petrols, and of the sulphur content of diesel oil. It is indicative that in Finland, for example, prior to marketing of lead-free petrol and tax reductions for catalytic converters, the share of traffic in lead emissions was over 90 percent. Economic incentives (lower priced lead-free petrol) have been introduced and will be further used to enhance the above measures. Research activities as well as control measures will also be intensified.
Impacts of nitrogen and phosphorus from agriculture on the Baltic Sea contribute significantly to the overall nutrient load. The total contribution from atmospheric deposition and runoff from agriculture is about 400 000 tons/year, which is about 40 percent of the total nitrogen load to the Baltic Sea. Somewhat over 50 percent of this amount (206 000 tons/year) comes from agricultural runoff from the areas bordering the eastern and southeastern Baltic coast (from St. Petersburg region to Schleswig-Holstein region). It is estimated that about 10 percent of the total phosphorus load originates in agriculture.
The nutrient inputs from agriculture include ammonia volatilization, nitrogen leaching (nitrate and organic nitrogen), phosphorus leaching and erosion, and discharge of farm waste such as effluents from animal houses, manure storage, and silage heaps. Ammonia volatilization and nitrate leaching have an almost equal share in the nitrogen load of the Baltic Sea. The source of atmospheric ammonia is almost exclusively animal manure, produced not only in the Baltic Sea catchment area but also, among others, in the North Sea catchment in Germany, the Benelux countries, and France. Nitrate leaching derives in general from the overuse of both commercial and animal fertilizers, but also from the low utilization efficiency of animal manure. The impact of pesticides on the Baltic Sea is not fully studied as yet, but it is a serious problem which deserves special attention in further investigations.
Important agricultural areas are located in Russia, Estonia, Latvia, Lithuania and Poland, with the latter accounting for about 40 percent of arable land in the entire catchment area. Except in Poland, large former state owned farms dominated; their average size was more than 5 000 ha. In Poland, the ownership structure is different; the farms are mostly privately owned with an average size of about 5 ha only. Agricultural productivity can be characterized as medium to low intensive. Although livestock density is low, large animal farms or the so called “bio-industries” are the cause of the most serious and difficult problems in handling animal manure.
Southern Sweden is cultivated intensively. In Finland, the most intensive farming is located in the southwest and also in the catchment area of the Gulf of Bothnia (e.g. Ostrobothnia); however, dairy farming is nowadays most intensively practiced in the east.
Danish agriculture is very intensive in the use of fertilizers. For example, in the Danish part of the Belt Sea catchment (total area of 12 382 km2), input of nitrogen from cultivated areas to the Sea equals some 30 000 tons annually. Just to indicate how much agriculture in the Baltic Sea catchment area may vary, the total annual input of nitrogen from Polish agriculture in the Vistula river basin (166 400 km2) is some 50 000 tons annually.
New agricultural strategies must be developed for the formerly centrally planned economies in the Baltic Sea catchment area. As agriculture intensifies, the overuse of chemical fertilizers and pesticides must be avoided and alternatives developed. Large-scale livestock husbandry should also be abandoned. In Denmark, Sweden, Finland and Germany, there is also a need for further control of nutrient leaching.
Product control measures:
Several measures have been taken in some of the Baltic Sea countries in order to reduce the use of hazardous substances such as pesticides, cadmium and mercury. A serious effort, however, should be made to implement HELCOM recommendations concerning product control.
Source: The Baltic Sea Joint Comprehensive Environmental Action Programme. HELCOM. Helsinki, 1993. (Balt. Sea Environ. Proc. No. 48), pp. 2-1 - 3-20