Europe is surrounded by nine sea basins
Source: Stock Imagery
INTRODUCTION |
Europe's seas, as part of the world's oceans, play a key role in maintaining the natural balance of the Earth's biosphere. Covering over two thirds of the Earth's surface, the oceans contain about 97 per cent of the world's water. Interaction between the atmosphere and the oceans and seas has a large influence on climate and weather patterns. Furthermore, plant life in the oceans is an important part of the 'lungs' of the planet, and photosynthesis in the seas and oceans is responsible for the removal of a large amount of carbon dioxide from the atmosphere.
The sea regions covered in this report are: the Mediterranean Sea, Black Sea and Sea of Azov, Caspian Sea, White Sea, Barents Sea, Norwegian Sea, Baltic Sea, North Sea and North Atlantic Ocean. Map 6.1 shows Europe's seas with the main subsidiary seas and bays, and their respective catchment and drainage areas.
Of the countries included in this report all except Austria, Belarus, the Czech Republic, Hungary, Luxembourg, Moldova, the Slovak Republic and Switzerland share coastlines of at least one of these European sea regions. Countries such as Germany, France, the UK, Denmark and Norway have coastlines with at least two major seas while the Russian Federation shares the shores of five European seas.
How human activities affect a given sea area depends very much on the sea's ability to dilute, disperse and assimilate pollutants or other influences. The characteristics which determine this include the circulation of the water, the strength and movement of the currents, the 'flushing' or retention time of waterbodies and the geological diversity of the sea floor. A comparison of some of these characteristics and physical features is shown in Figures 6.1a to 6.1e.
The open oceans, such as the North Atlantic Ocean, due to their vast areas, great depth and efficient water circulation, are still relatively unaffected by human activities compared with coastal areas and enclosed or semi-enclosed seas. The smaller, shallower seas can be classified into those which are nearly completely enclosed by landmasses and those which have a large water exchange with the oceans. The state of the seas which have only limited exchange of water with adjacent oceans is strongly influenced by their water circulation, which reflects the local dominant wind patterns (eg, the Black Sea).
The general nature of the enclosed and semi-enclosed seas is essentially dependent on whether or not the freshwater lost through evaporation is more or less than the amount of freshwater input from precipitation and direct runoff from land. In the case where evaporation is higher than the freshwater input, the surface waters become denser and sink, resulting in considerable vertical mixing of the waters. The oxygen acquired from the atmosphere thus becomes available in deeper waters to foster life. An example of this type of sea is the Mediterranean. In the reverse situation where the freshwater inflow exceeds evaporation the lighter freshwater remains on the surface. When such a sea is also isolated from the ocean, for example by a sill, oxygen becomes depleted and even absent in the deeper water. Often oxygen cannot be replenished and the variety of life-forms becomes much reduced. This is the case for the Black Sea and to some extent the Caspian Sea and the Baltic Sea.
In all seas, estuaries exist where freshwater runoff and sea water mix. They are smaller and shallower than seas, and are more influenced by the neighbouring landmass. Areas of exceptionally rich biological production, they are especially sensitive to the activities of local human populations such as excavation, construction and the discharge of domestic, industrial and agricultural pollutants.
Another important physical feature is the retention or turnover time within the seas. This is more relevant to the enclosed and semi-enclosed seas (eg, the Mediterranean and the Baltic), rather than the more open 'oceanic' seas, for example, the Barents and Norwegian seas and the North Atlantic Ocean. Retention time has a direct influence on how contaminants are retained or accumulated in the marine ecosystem. Values range from 0.1 to 3.9 years in the North Sea to 140 years in the Black Sea (Figure 6.1c). The Caspian Sea is completely land-locked and would largely retain non-degradable contaminants.
The environmental quality and status of a sea is also influenced by the amount or load of contaminants entering the sea and their degradability, persistence and toxicity to aquatic organisms. Total loads entering a sea are not only a function of the population size and industrialisation within its catchment but also on the level of treatment or control, of contaminants in discharges. The type of human activity for example, agricultural or industrial within the catchment is also important in determining the type as well as the quantity of load. The Black Sea and the Sea of Azov have not only the largest catchment of Europe's seas but also the largest population within the catchment (Figures 6.1d and 6.1e): contaminant loads would therefore be potentially higher than in other seas. Europe's northern seas, the White, Barents and Norwegian seas, have by far the smallest populations living in their catchments, relatively small catchment areas, and, in the case of the latter two, relatively large surface areas: these features contribute to the relatively uncontaminated nature of these seas.
An attempt to compare loads of contaminants entering each sea has been made in this report: this should be considered as only approximate as there are likely to be variations in data collection methodology, and for some seas data were not available for all of the different sources or do not exist at all. It should also be noted that the data do not necessarily relate to the same year for all seas; in all cases the most recent available data were used. Figure 6.2 compares the riverine loads of selected contaminants into Europe's seas this source has the most complete dataset. Where riverine data were not available, land-based (riverine and direct discharges) load data have been used. It should also be noted that for some seas, and for the various contaminants, riverine and land-based sources may not necessarily be the most important. For most seas, it has not been possible to differentiate between the contaminant load associated with particulate material and that in the dissolved phase, or to take account of non-conservative estuarine processes that may add to or decrease loads entering the sea. Total gross loads have therefore generally been used. An example of how allowance for contaminant form and estuarine processes may affect total or gross loads entering seas is given for the Mediterranean in terms of mercury, lead and zinc (Figures 6.2b, 6.2d and 6.2e, respectively).
Within Europe there are examples of regional conventions which deal with pollution at a regional or individual sea basis. These will be treated in the sections on individual seas. In addition, there are two global conventions that address marine pollution (Nauke and Holland, 1992). The two conventions are the London Dumping Convention (now the London Convention) and the MARPOL Convention: the former deals with direct disposal of waste into the sea and the latter with ship-borne operations. Both are administered by the International Maritime Organisation. Compared with the other sources of pollution (such as land-based and the atmosphere) these two are generally relatively small. The London Dumping Convention came into force in 1975; enforcement is undertaken through national legislation by the contracting parties. Sixty-seven countries have signed and ratified the convention. MARPOL is now known as the International Convention for the Prevention of Pollution from Ships 1973, as modified by the protocol of 1978 (MARPOL 73/78). The regulations contained in Annexes I (oil) and II (bulk liquid chemicals) are mandatory and must be applied by all parties, while those contained in Annexes III (packaged goods), IV (sewage) and V (garbage) are optional. By June 1992, 72 states, representing 90 per cent of total ship tonnage, had accepted Annexes I and II of the Convention.
COMMON PROBLEMS |
When reading the text on the individual seas it will become apparent that there are problems which are recurrent or common to many of the seas in Europe. These problems, briefly outlined here, not only arise from the direct or indirect consequence of human activities but may also be compounded by the natural variability and changes within the marine environment itself. Most of the problems are associated with, or manifest themselves more noticeably within, the coastal zone of each sea (which is closest to humankind's direct influence). The degradation of the coastal zone has, therefore, been identified as a prominent environmental problem of concern to Europe to be treated in more detail in Chapter 35.
Lack of effective catchment management, control and regulation |
Many of Europe's seas have large multinational catchments which may include states with no seaboard. Contaminants within the seas may originate hundreds or even thousands of kilometres away from the sea. Hence, effective catchment management and pollution control measures require concerted international efforts and cooperation. Not only water quality, but also manipulation of river flows can affect the receiving seas. There is also exchange of water, and hence contaminants, between many of the seas. Contaminants can also be transported by air and in some seas atmospheric deposition can be very significant in relation to total contaminant loads (for example, inorganic nitrogen and some heavy metals, such as cadmium, in the Mediterranean and the North Sea).
As already described in the introduction to this chapter, there are regional conventions covering a number of Europe's seas. Acceptance of these conventions often requires a periodic assessment of loads of contaminants entering the relevant areas from different sources, for example, direct, riverine and atmospheric inputs. These data give not only a quantitative indication of the magnitude of the problem and where control and improvement measures should be targeted, but also of how loads change with time as controls and catchment management are introduced. Standard methodology for the collection of both load and quality data is defined so that results should be directly comparable. For example, sample locations, analytical methods and limits of detection for contaminants are all stipulated. Where standard methodology is not applied, large differences in the estimates of loads and quality measurements may occur.
Coastal zone pollution |
The effect of any contaminant on marine water quality (and hence on sediment and biological quality) depends on its concentration, physico-chemical form (eg, dissolved or associated with particulate material), fate, behaviour, persistence and toxicity in the environment. Chemical contaminants are often placed on lists for priority control and reduction (with the exception of nutrients) on the basis of their persistence, toxicity and bioaccumulation. Nutrients are selected because of concerns over eutrophication. The most important contaminants in the coastal zone are synthetic organic compounds (eg, PCBs, and pesticides such as DDT), microbial organisms, oil, nutrients, litter, and, generally to a lesser extent, heavy metals (eg, cadmium, mercury and lead) and radionuclides.
Eutrophication |
The enrichment of natural waters by nutrients (eutrophication), primarily nitrogen in marine waters but also phosphorus in low salinity waters, has been associated with increased primary productivity and nuisance algal growth in the coastal zones and semi-enclosed and enclosed areas of seas. Increased loads of nutrients to coastal waters of a number of Europe's seas have caused increasing eutrophication (Chapter 35). The consequences of eutrophication can be an increased frequency of algal blooms (sometimes toxic), increased water turbidity, slime production, oxygen depletion in deep waters and mass fish and benthic fauna kills. The major sources of nutrients to coastal waters are from sewage disposal, runoff from agricultural land and atmospheric deposition.
In freshwaters, phosphorus is considered to be limiting to algal growth; in marine waters this role is more likely to be played by nitrogen. Algal production in transitional waters between fresh and fully saline waters (eg, in relatively enclosed coastal waters) would be limited by either nitrogen or phosphorus depending upon whether the transitional area receives important freshwater supplies (eg, the Emilia-Romagna area of the northwest Adriatic Sea (Vollenweider et al, 1992)). In estuaries, factors such as water turbidity, light availability and retention time would be at least of equal importance as nutrient concentrations and availability.
Conflict of uses in the coastal zone |
In many European seas the coastal zone is an important area for human habitation, industry and recreation (see Chapter 35). This inevitably leads to a conflict of use, not only of water (eg, for bathing, surfing, scuba diving and shell fisheries) but also of landuse (eg, harbours and marinas), which can have important secondary effects on the quality of marine environment. The lack of effective coastal zone management can lead to the loss of important components of the ecosystem and habitats, for example dunes and wetlands. Changes such as the construction of ports and tourist facilities result in the loss of habitats. The damming of rivers, resulting in a reduction of freshwater flow, alters the hydrological regime and can have serious consequences. This reduction in freshwater flow generally means a reduced sediment load which may induce coastal erosion.
Offshore activities |
Offshore activities such as oil and gas exploration and exploitation, disposal of waste (sewage sludge, dredged spoil and radioactive waste) and shipping are responsible for the further release of contaminants, especially oil, into Europe's seas. Offshore oil and gas activities give rise to oil pollution of the seabed in the vicinity of the rig when drilling with oil-based muds, and of the water column due to the discharge of oil-contaminated water used in the production process. Oil-contaminated cuttings also cause smothering of biota. In addition, oil contamination may be related to tainting of fish. Solid radioactive waste has been disposed of offshore in a number of seas, though it has been estimated that the risk from contamination from past dumping is very small. Control of these activities requires both international agreements (eg, MARPOL and the London Dumping Convention) and national control measures.
Introduction of non-indigenous species |
There are examples of the introduction of non-indigenous species of flora and fauna, usually accidentally (for example by shipping or by escapes from aquaculture and aquaria), to Europe's seas. In some cases the introduced species have been able to out-compete indigenous species and, if there are no predators or control, may dominate an ecological niche and in extreme cases change the structure, function and balance of the ecosystem (see Chapter 9). Examples of this in the marine environment are the introduction of the tropical alga Caulerpa taxifolia in the Mediterranean, and the predatory comb jelly Mnemiopsis leidyi (a ctenophore) in the Black Sea and Sea of Azov.
Overexploitation of resources |
Europe's seas are important as a source of food (fisheries, shellfisheries and various algae) and also for other resources such as oil, gas, sand and gravel. Overfishing of commercial fish stocks causes changes in the dynamic balance between species. New technologies such as purse seining has added further pressure by increasing catches as well as killing non-target species (see Chapter 24). Shellfisheries may also detrimentally affect the marine environment. Dredging activities disrupt the sea floor habitats, and waste associated with aquaculture farms can cause local deoxygenation and eutrophication problems. Oil and gas exploration and extraction may not only introduce pollutants but may also cause physical disturbance, for example from seismic testing, which might have some detrimental impact.
Sea-level rises and climate changes |
Climatic change and potential global warming are discussed in Chapter 27. One of the predicted consequences of global warming is an increase in global mean sea level. Eustatic (real) changes in the ocean level are affected by many factors, including differences in atmospheric pressure, winds, ocean currents and density of sea water; all cause spatial and temporal variations in sea level in relation to land. Over the last 100 years global mean sea level has been rising, the estimated increase ranging from 0.5 mm per year to 3 mm per year, with most estimates lying in the range 1 to 2 mm per year. This historical rise has been due to the thermal expansion of the oceans, and increased melting of glaciers and the margins of the Greenland ice sheet.
The Intergovernmental Panel on Climate Change (IPCC) has tested a number of climate scenarios, including the worst-case 'business-as-usual emissions' scenario (IPCC, 1990). This scenario predicted that the average global mean sea-level rise from 1990 to 2100 would be about 6 cm per decade (with an uncertainty range of 3 to 10 cm per decade). The predicted rise is about 18 cm by 2030, and 44 cm by 2070. Although over the next 100 years the effect of the Antarctic and Greenland ice sheets is expected to be small, they make a major contribution to the uncertainty in predictions. Any rise in sea level is not expected to be uniform over the globe. Thermal expansion, changes in ocean circulation and surface air pressure will vary from region to region as the world warms, but in an as yet unknown way (IPCC, 1990).
The potential effects of sea-level rise include: permanent inundation of low-lying land; increased frequency of temporary flooding from high tides or storm surges; changes in rates of beach, dune or cliff erosion; and salinisation of groundwater and surface water supplies, wetland ecosystems or agricultural soils. The financial consequences of sea-level rise are potentially great. For example, it has been estimated that the cost to adapt sea defences against high water and to adapt water management systems over the next century to account for a 1 m sea-level rise along the coast of The Netherlands would be about $10 billion (de Ronde, 1993).
Climate change will also potentially affect ocean circulation and mixing patterns, which could have secondary effects on nutrient availability and phytoplankton productivity. At high latitudes warming would result in diminished temporal and spatial extent of sea ice, indeed some models predict an ice-free Arctic. A significant reduction in the extent and persistence of sea-ice would have profound consequences for marine ecosystems, notably of the Nordic seas (IPCC, 1990). A temperature rise or fall of only one degree can have a significant impact on fish migration and reproduction patterns. It is thought that natural changes of these kinds have affected the success of fishing in the Nordic seas, particularly for herring, since the Middle Ages (Bernes, 1993).
Relative importance of common problems |
An indication of the occurrence and relative importance of the common problems within the individual seas (not between seas) is given in Figure 6.5. For example, eutrophication is seen to be the, or a, major concern in the Baltic, Black and North seas, and a smaller relative or more localised problem in the Mediterranean and Caspian seas. In the more open seas, such as the Norwegian Sea and the North Atlantic Ocean with low relative nutrient inputs, eutrophication is not a problem. Coastal zone pollution is seen to be a problem in all of Europe's seas (although very localised in the Norwegian Sea, which has a sparsely populated coastline and a relatively small catchment population). This is discussed in further detail in Chapter 35 concerning coastal zones. Sea-level changes (as a result of climate change) would potentially affect all of Europe's seas.
THE EUROPEAN SEAS: OVERVIEW |
In the rest of this chapter each individual sea is described under the following broad headings:
THE MEDITERRANEAN SEA |
General situation |
The Mediterranean Sea is the largest of the semi-enclosed European seas (see Map 6.1). It is surrounded by 18 countries and has shores on three continents (Europe, Africa and Asia) with a combined population of 129 million people in the catchment draining into sea, and sharing a coastline of 46 000 km. It is one of the leading tourist areas in the world, hosting 100 million visitors every year. This influx of people increases the waste discharges from domestic and industrial sources.
The Mediterranean Sea has an average depth of 1.5 km, though more than 20 per cent of the total area is covered by water less than 200 m deep (UNEP, 1989). The sea consists of two major basins, the eastern and the western. There are also smaller regional seas within the Mediterranean: the Ligurian, Tyrrhenian, Adriatic and Aegean seas. It is linked to the Atlantic by the Strait of Gibraltar, with the Black Sea and Sea of Azov by the Dardanelles, the Sea of Marmara and the Bosporus, and with the Red Sea by the Suez Canal. The Mediterranean Sea is characterised by low precipitation, high evaporation, high salinity, low tidal action and relatively low nutrient concentrations outside the inner coastal zone and parts of some regional seas.
The coasts of the northwestern Mediterranean are the most affected by pollution because of the concentration of urban populations, industrial activities and discharges of major rivers including the Ebro and the Rhone. The Adriatic receives the discharge of the River Po. The North African coast, in contrast, is for most part arid with little urbanisation or industrialisation. Pressures on the marine environment therefore vary widely depending on the local or regional situation.
Countries bordering the Mediterranean Sea met in Barcelona in 1975, under the auspices of UNEP, to draw up a programme of action to protect the Mediterranean this became the Barcelona Convention for the Protection of the Mediterranean Sea against Pollution. The UNEP Regional Seas programme had been initiated in 1974 when the Mediterranean had been selected as a 'concentration' area where coastal states would be assisted in the implementation of an action plan.
The Mediterranean Action Plan (MAP) consists of three main components: legal; environmental assessment; and environmental management. The legal component is contained within the Barcelona Convention. The long-term Mediterranean Pollution Monitoring and Research Programme (MEDPOL) was launched in 1975 under MAP, Phase 1 lasting until 1980. Phase II, endorsed in 1981, foresees monitoring at four levels: sources of pollution; nearshore areas; offshore areas; and transport of pollutants from the atmosphere. MEDPOL monitoring started in 1983 through the implementation of National Monitoring Programmes and at present 16 countries have ongoing programmes and are submitting data. The Blue Plan, which forms a part of the environmental management component of MAP, was launched in 1979 to assist the Mediterranean countries in making appropriate practical decisions for the protection of their marine and coastal environment.
Physical features |
Surface water, entering the Mediterranean from the Atlantic, migrates generally towards the east (Map 6.2). Evaporation processes transform this surface water into denser, deep water which flows east to west back into the Atlantic. In fact, water loss by evaporation exceeds the water input from runoff and precipitation, resulting in the Mediterranean's characteristic high salinity (average 38.5 per thousand, ranging from 37 in the west to 39 in the east). Strong vertical currents in winter ensure mixing of the water column and oxygenation of the deep waters. It takes on average about 80 years for the water in the Mediterranean to be completely exchanged.
Biological features |
The Mediterranean Sea has a high species diversity but its biological productivity, while being extremely varied, is among the lowest in the world due to extremely low nutrient concentrations (UNEP, 1989). The total number of species of animals and plants has been estimated to be around 10 000 (Boudouresque, 1993). Its fauna includes many endemic species and is notably richer than the fauna of the Atlantic coasts. The eastern and western Mediterranean, separated by the relatively shallow straits between Sicily and Tunisia, show differences in resident fauna and flora, indicating a degree of isolation between the two regions (Clark, 1986). The biodiversity of the western Mediterranean is also greater than that of the eastern (Boudouresque, 1993).
The most threatened species in the Mediterranean is the monk seal, Monachus monachus, which is one of the ten most threatened species of mammals in the world (IUCN, 1988) (see Chapter 9).
The loggerhead turtle, Caretta caretta, and the green turtle, Chelonia mydas, nest regularly and in significant numbers in the Mediterranean (COE, 1990a) both are recognised by the IUCN as globally threatened species, the former being ranked as 'vulnerable' and the latter as 'endangered' (IUCN, 1988). There are on average 2000 female loggerhead turtles nesting annually in the Mediterranean, the majority in Greece and Turkey. Green turtles, as far as is known, nest only in the extreme southeast of Turkey and in Cyprus (COE, 1990a).
There are around nine species of whales and dolphins regularly found in the Mediterranean (Tethys Research Institute, 1991). The biggest populations are found in the particularly rich pelagic zone of the western Ligurian Sea.
The extensive seagrass beds of Posidonia oceanica are an important part of the Mediterranean marine ecosystem, often occupying a considerable part of the littoral zone. A characteristic feature is the formation of Posidonia seagrass beds parallel to the shore in sheltered and shallow bays, isolating a coastal lagoon (Augier, 1982). These beds have suffered greatly from physical modifications of the coast (see Chapter 9). Posidonia plays an important role in the ecosystem: through the production of organic material at the base of the food-chain; as a primary oxygen producer; as a feeding and nursery area for numerous species of fish (many commercially important); through the stabilisation of sediments; and through attenuation of wave and swell (protection of beaches) (Boudouresque, 1993).
A tropical, non-indigenous alga, Caulerpa taxifolia, has been observed in the Mediterranean since 1984. First seen in the Monaco area (perhaps as a result of an accidental release from an aquarium in Monaco (Meinesz and Hesse, 1991)), this alga had, by 1990, been found up to 150 km from Monaco at Toulon. At some locations it inhabits a wide range of substrates, including rock, mud and sand, and a wide range of depths, 3 to 35 m, and has achieved 100 per cent coverage in some places. Wherever it becomes established it considerably modifies the vegetal communities in the infralittoral zone. It also contains a toxin which may inhibit some other organisms such as grazers, epiphytes and competitors. It appears to be consumed by only a few fish species.
There are important fisheries in the Mediterranean, with fish such as mullet (Mugilidae) and hake (Merluccius spp) being in most demand (see Chapter 24). Other fish such as anchovy (Engraulis encrasicolus), sardines (Sardina pilchardus) and mackerel (Trachurus spp) in the northwest are also intensively fished. Oil pollution in some parts of the sea has led to tainting of a variety of fish and bivalves.
Inputs |
Contaminants enter the Mediterranean from rivers, direct discharges (land-based and offshore), atmospheric deposition, and through water exchange primarily with the Atlantic Ocean and Black Sea. A major assessment of land-based inputs into the Mediterranean, reported by UNEP et al (1984), relied upon data collected by national monitoring networks. More recent work, such as that undertaken within the CEC EROS 2000 project, has indicated that these earlier estimates are too high (eg, CEC, 1992; Martin et al, 1989 and Dorten et al, 1991). In particular, when non-conservative processes, which reduce gross loads passing through estuaries, are taken into account, and when the partitioning of contaminants between the dissolved and particulate phase are considered, the net riverine loads of metals, such as mercury, copper, lead and zinc, entering the main body of the sea are now calculated (Dorten et al, 1991; Martin et al, 1989) to be much lower than estimated in the earlier compilation. In Figure 6.2(ae) both the UNEP and the more recent estimates of loads for some heavy metals are illustrated.
The Mediterranean basin is unusual in that it is rich in mercury deposits, for example cinnabar and metallic mercury (Zafiropoulos, 1986) 65 per cent of the world's mercury mineral resources are located in the region (Scoullos, 1993). Natural inputs of mercury (via rivers) can be locally very significant, for example into the Tyrrhenian Sea (Baldi, 1986), compared to anthropogenic sources. Dissolved mercury riverine inputs to the Mediterranean are now estimated to be between 1.7 and 20 tonnes per year (Dorten et al, 1991), compared with the original estimate of 120 tonnes per year (UNEP et al, 1984) from rivers.
Recent work in the northwestern basin has assessed the relative contributions of atmospheric and river inputs of about 40 elements including heavy metals, radionuclides and nutrients. For the majority of the elements analysed the proportion of atmospheric deposition relative to total deposition (from rivers and atmosphere) did not exceed 20 per cent (CEC, 1992). However, for heavy metals atmospheric input generally appears to predominate: this derives from both the heavily industrialised northern boundary and dust loads originating in the Sahara region (Dorten et al, 1991). For cadmium, lead and copper (in the dissolved phase) atmospheric inputs are much greater than riverine (50, 200 and 5 times respectively) (Martin et al, 1989). For inorganic nitrogen, atmospheric and riverine inputs are roughly equivalent, and in the case of inorganic phosphorus, riverine inputs are most important. Major anthropogenic contaminant loads are discharged from the rivers Nile, Rhone, Ebro and Po.
There is also an exchange of dissolved trace metals between the Mediterranean and the Atlantic Ocean through the Strait of Gibraltar, and also with the Black Sea via the Bosporus. Recent mass balance calculations (Martin et al, 1993) indicate that in the case of dissolved copper, nickel and cadmium there may be a net export to the Atlantic.
Inputs of oil to the sea are estimated at 635 000 tonnes per year (UNEP, 1989). Of this, around half is spilt from tankers during ballasting and loading operations and during the washing of the bilge and tanks. Land-based sources account for 42 per cent of total oil loads, and the atmosphere accounts for 6 per cent (Figure 6.6). Natural seeps have also existed over geological time-scales, particularly in the northeastern parts of the sea (UNEP, 1989). The coastal area off Libya receives the highest oil input. Oil spills are also a problem, but are infrequent and generally localised.
Nuclear power stations are operating in three countries on the Mediterranean: Spain, France and Slovenia. However, it is the nuclear reprocessing plant at Marcoule in France that represents the most important source of artificial radioactivity in the sea (see Figure 5.32). It is also apparent that atmospheric inputs are a significant proportion of the total input load of some radionuclides such as Cs-137 (Martin et al, 1989).
Contaminant levels |
In the Mediterranean Action Plan status report of 1989, it was reported that the concentrations of trace metals and chlorinated hydrocarbons in sea water and sediment should be considered (at that time) with caution, and typical concentrations could not be identified this was because of inadequate analytical quality control and different analytical methods. However, concentrations in biota were considered to be more reliable because extensive laboratory intercalibration had been carried out (UNEP, 1989). Over the last five years the CEC has funded research through a number of projects implemented in the western Mediterranean and some regional seas (eg, EROS 2000) as reported by Scoullos (1993).
Only a few data have been found on the open-sea metal concentrations in the Mediterranean (Fowler, 1990). For mercury these concentrations are similar to concentrations in the adjacent North Atlantic, whereas for cadmium the concentrations (1 to 7 ng/l in the open sea), while still being well below accepted values for pollution, are generally higher than in the Atlantic. Recent analyses of cadmium show some relatively high values for certain coastal areas of Spain and Italy (5 and 10 ng/l, respectively). Lead values are also slightly higher than for Atlantic water between 20 and 40 ng/l in the northwest Mediterranean, compared with oceanic levels of 5 to 15 ng/l. Offshore concentrations of zinc are reported to range between 150 and 240 ng/l (Morley and Burton, 1991); higher levels of 410 ng/l are found in the north Adriatic (Scoullos, 1993). A gradient of increasing concentrations of cadmium, lead, copper and zinc from the south to the north of the Adriatic Sea is also reported.
Elevated concentrations of mercury, cadmium, zinc and lead in sediments are found at 'hot-spots', which are generally in the coastal zones receiving industrial effluents, solid waste and domestic sewage. For example, concentrations of up to 37 mg/kg dry weight of mercury have been reported, compared with a typical background of 0.05 to 0.1 mg/kg dry weight (Fowler, 1990). Zinc concentrations are reported to be as high as 6480 µg/g, 5930 µg/g and 2550 µg/g (dry weight) at 'hot spots' along the coasts of Spain, at Venice and at Marseilles, respectively (Scoullos, 1993).
Sea gooseberry |
The MEDPOL programme has used two indicator species for monitoring contaminants, the mussel (Mytilus galloprovincialis) and the red mullet (Mullus barbatus). Mercury has been given special attention because recent data show that Mediterranean fish (eg, bluefin tuna, Thunnus thynnus, sardines, Sardina pilchardus, anchovy, Engraulis encrasicolus, and scads, Trachurus spp) and other marine animals generally have higher levels than those of the North Atlantic (Figure 6.7) (FAO, 1986). However, results are very variable and are available mainly for the northern parts of the sea.
A three-fold decrease in PCBs has been detected in coastal waters of the northwestern Mediterranean between the mid-1970s and the period 1978 to 1982. This trend has also been confirmed by measurements made along the French coast in 1984.
The limited number of measurements of organochlorines in sediments in the Mediterranean show a few 'hot spots'. For example, elevated sediment concentrations of PCBs have been found near the Athens sewage outfall; in the Bay of Naples; near the Marseilles outfall; and offshore from Nice (UNEP, 1989).
Measurements on biota are scattered and variable, but again the industrialised regions and major estuaries stand out. Mussels containing elevated levels of PCBs have been observed at Toulon and Marseilles near the Rhone estuary (UNEP, 1989). Levels of PCBs and other organochlorines in red mullet and mussels show a general decrease from the more northern parts of the sea to the south and east. There are as yet not enough reliable data for trend analysis.
Oil pollution in the Mediterranean Sea is associated mainly with shipping routes, ports and oil and gas exploration activities. Data on concentration levels of hydrocarbons show increases over recent years, especially with regard to concentrations in water and on beaches. In general, concentrations of dissolved/dispersed petroleum hydrocarbons in open waters are between 0 and 5 µg/l, and values above 10 µg/l have been observed near the shore, particularly near industrialised areas and river mouths (UNEP, 1989).
The amounts of petroleum hydrocarbons in marine organisms and sediments in the area are poorly known. The available data cover mainly the coastal zone, and thus the contamination of the open waters is less well known. Results also show an increased level of petroleum hydrocarbons in sediments compared with the concentrations in water, which indicates that they may be accumulating in the sediments. Aliphatic and aromatic petroleum hydrocarbon concentrations in sediments range from 1 to 62 µg/g, and 2 to 66 µg/g, respectively, along the Spanish coast outside harbours, oil terminals and river mouths (Scoullos, 1993). Polycyclic aromatic hydrocarbons (PAHs) in the northwest Mediterranean range from 0.4 to 0.7 µg/g in the deep sea basin, from 0.3 to 0.5 µg/g on the continental shelf, and from 0.4 to 5 µg/g off Barcelona (Tolosa et al, 1993).
Almost no observations exist about the effect of petroleum hydrocarbons on Mediterranean marine organisms (UNEP 1989).
The results from the 1992 bathing season (CEC, 1993) indicate that 97 per cent of the designated bathing waters around Greece complied with the mandatory standard of 2000 faecal coliforms per 100 ml, as specified in the EC Directive on the quality of bathing water, and 95 per cent were within the guideline value of 100 per 100 ml. The bathing water quality around the Italian coastline was also reported to be of relatively high quality, with 92 per cent complying with the mandatory standard and 85 per cent with the guideline value. The main areas of non-compliance included the Naples and Caserta districts, around Genoa in northern Italy and along the north coast of Sicily around Palermo. Along the Spanish Mediterranean coastline, approximately 95 per cent of bathing waters complied with the mandatory standard: non-compliant waters included those around the Granada, Malaga and Valencia areas. In France, 95 per cent of bathing waters complied with the Directive.
The open Mediterranean Sea is nutrient-depleted. Typical 'background' concentrations of nitrate nitrogen are 7 µg N-NO3/l, in moderately eutrophic areas 21 µg N-NO3/l, and in heavily eutrophic, 70 to greater than 110 µg N-NO3/l (GESAMP, 1990). Corresponding values for phosphate are 0.93, 4.7 and 9.3 µg P-PO4/l, respectively. It is generally Mediterranean shores adjacent to urban agglomerations and tourist resorts (such as the Adriatic coast) which show the highest nutrient concentrations.
Immediately following the Chernobyl accident, the surface water and sediment concentrations of caesium (Cs)-137 increased by one to two orders of magnitude and by a factor of 2 to 4, respectively (UNEP, 1989). The distribution of the fall-out was very heterogeneous due to variations in local conditions and, in particular, was concentrated around river discharges, reflecting the fall-out that occurred within the drainage catchments. Areas of higher concentrations included the Rhone estuary and the Italian coast. The high concentrations decreased again relatively rapidly and were close to pre-Chernobyl values by the end of 1989. It has been estimated that the Chernobyl accident resulted in a 25 to 40 per cent increase of the total amount of Cs-137 in the Mediterranean Sea (UNEP, 1989). The effects of artificial radionuclides on living organisms in the Mediterranean are considered to be negligible.
Biological effects |
The Mediterranean Sea is generally considered to be oligotrophic (poor in nutrients) and does not have widespread problems arising from nutrient enrichment. However, coastal areas which receive anthropogenically enhanced nutrient loads from rivers and the direct discharge of untreated domestic and industrial wastewater are most susceptible to eutrophication. Examples can be observed in many coastal lagoons, estuaries and semi-enclosed bays, particularly in northern areas (eg, bays of the Ebro delta, the Albufera of Valencia, the coastal lagoons of southeastern France, the lagoon of Tunis, the Kastela Bay in Croatia and the Izmir Bay in Turkey (Estrada, 1993). This is clearly illustrated in the satellite image in Map 6.3.
Monitoring in the Mediterranean |
Two areas show extensive cultural eutrophication: the Gulf of Lions and the Northern Adriatic Sea. In the Northern Adriatic extensive dinoflagellate and diatom blooms occur in the spring and autumn: on occasions massive quantities of mucilage are produced (Estrada, 1993). However, the species responsible for this mucilage or gel production or the trigger mechanism is not yet fully known (Barth and Fegan, 1990). The key features of the North Adriatic which make it vulnerable to gel production are believed to be: shallowness (under 35 m); low turbulence during the summer and the high riverine nutrient input (Estrada, 1993). Studies in the Emilia-Romagna coastal waters of the northwest Adriatic
(to the south of the River Po delta) have indicated that phosphorus rather than nitrogen is the prevailing limiting nutrient (Vollenweider et al, 1992). However, in some circumstances in this area, such as in the summer and when nitrogen supply is low, nitrogen may also become limiting. The most severe eutrophic conditions are restricted to semi-enclosed bays and to the areas within the estuarine plume of the Po, which dominates the freshwater inputs. Numerous point sources are also important nutrient inputs. In response to the increased nutrient load, primary productivity increases with a maximum in the Emilia-Romagna area. During summer this area has suffered from persistent heavy algal blooms whose eventual decomposition causes anoxic conditions and mass kills of fish and benthic fauna. In 1990 the accumulation of gelatinous material produced by Phaeocystis spp on the beaches of Benicasim (Spain) had an adverse effect on the tourist trade.
'Red' tides also occur in the Mediterranean, often associated with the dinoflagellate Noctiluca scintillans (eg, frequently along the Catalan coast since the 1970s) (Estrada, 1993). Toxic algal episodes are also reported, for example, paralytic shellfish poisoning (from Alexandrum minutum and Gymnodinium catenatum) and diarrhetic shellfish poisoning (from Dinophysis spp). There is increasing evidence to suggest that mass development of toxin-producing unicellular algae is related to eutrophication. However, a cause­effect relationship between increased productivity and toxin production has not been proven (Barth and Fegan, 1990).
There has been a marked reduction in the Posidonia oceanica (seagrass) beds over the last decades. The reduction has been particularly noticeable around large industrial ports (eg, Barcelona, Marseilles, Toulon, Nice, Genoa, Naples, Athens and Algiers). The depths at which Posidonia is able to grow has also decreased. This has been associated with an increase in water turbidity reducing the amount of light exposure on the sea bed. Because of the role Posidonia plays in the Mediterranean ecosystem (see above, on biological features), its reduction is considered to have severe economic consequences (Boudouresque, 1993).
Conclusions |
THE BLACK SEA AND THE SEA OF AZOV |
General situation |
The Black Sea, the world's largest land-locked and anoxic sea, is located in a semi-arid climatic zone (see Map 6.1). It is bordered by Bulgaria and Romania to the west, Ukraine to the north, the Russian Federation and Georgia to the east and Turkey to the south. Although only these six countries surround it, the total catchment area draining into the Black Sea is over five times the size of the actual sea and includes parts of 21 countries. The northwestern basin receives the heaviest impact from human activities because, of the 171 million people living in the Black Sea catchment, 81 million live in the River Danube basin alone. The human activities in the catchments have had major effects, not only on the rivers, but also on the receiving water body, the Black Sea. The Black Sea coasts are important tourist areas, with up to 40 million visitors during the summer.
The Black Sea has until recently been unprotected by any common policy or legal regime. In 1992 a legal Convention for the Protection of the Black Sea, based on the Barcelona Convention, was signed by Bulgaria, Georgia, Romania, the Russian Federation, Turkey and Ukraine. The Global Environment Facility (GEF co-managed by the World Bank and UNEP) is assisting the countries in drawing up an action plan for implementation of the Convention. A recent common policy declaration (the Odessa Declaration, April 1993) by all six environment ministers of the Black Sea Convention calls for improved assessment and monitoring of contaminants, and the 'development of comprehensive and co-ordinated plans for the restoration, conservation and management of living natural resources'. A project for environmental management of the Black Sea was recently approved by GEF. This project should provide the urgently needed short-term support for environmental assessments, institutional capacity building, pre-investment feasibility studies and an emergency investment portfolio of actions to complete unfinished key pollution control projects such as sewage treatment works.
There is also a Convention on Fishing in the Black Sea implemented in 1959 by Bulgaria, Romania and the former USSR. However, it was not signed by Turkey, an important Black Sea fishing nation. Also of direct relevance to the Black Sea is the Bucharest Declaration which was signed by eight countries in 1985 and under which Danube water quality data are collected and the information exchanged. The control of pollution in the Danube catchment is very important as it is a major source of contaminants to the Black Sea. Building on this Declaration, the riparian states decided in February 1991 to elaborate a convention on the protection and management of the river Danube and an ecological agreement for the entire basin (signed in Sofia in June 1994).
The main sources of information for the following sections have been Balkas et al (1990), Dechev (1990), Mee (1991 and 1992) and Mnatsakanian (1992). Additional sources are identified in the text where appropriate.
Physical features |
The Black Sea has a surface area of 461 000 km2 and an average depth of 1240 m. About 25 per cent of its area is occupied by its northwestern continental shelf which is less than 200 m deep. This northwestern area is subject to the discharge of the largest rivers (the Danube, Dnepr, Dnestr and Yuzhnyy (Southern) Bug see Map 5.11) entering the Black Sea. The sea's only link to other seas is with the Mediterranean through the Bosporus, the Sea of Marmara and the Dardanelles. In the north the Kerch Strait connects the Black Sea to the shallow Sea of Azov. This latter sea has an area of 39 000 km2, an average depth of 8 m and a maximum depth of 12 m. The major rivers flowing into the Sea of Azov are the Don and the Kuban.
The link of the Black Sea to the Mediterranean Sea via the Dardanelles is shallow (50 m) and narrow, and the inflow of salty water from the Mediterranean is outweighed by the outflow of surface water from the Black Sea. This water deficit is compensated by freshwater discharge. These two inflow sources have resulted in a stratification of the water column with fresher water (salinity 17.5 to 19 per thousand) at the surface and denser water (salinity average about 22 per thousand) at depth. This permanent halocline (change in salinity) located between 100 and 200 m is a distinguishing characteristic of the Black Sea. The difference in density between these two water masses, coupled with the absence of well-defined vertical currents, prevents the mixing of these two water layers and the subsequent penetration of oxygen from the surface to the bottom. Over the years organic matter has been sinking and decomposing in the deep waters of the Black Sea. For this reason the Black Sea is permanently anoxic below a depth of 150 to 200 m, and 90 per cent of its total water volume is anoxic.
Under these anoxic conditions, further degradation of organic matter takes place using oxygen bound in nitrates and especially in sulphates. The latter chemical reduction results in the formation of hydrogen sulphide. Hydrogen sulphide has been produced for millennia and has contaminated 90 per cent of the total waterbody of the Black Sea, making it fit only for anaerobic bacteria. The depth of the aerobic and anaerobic layers in the water column reflects the steady-state balance of the flows of organic matter and oxygen that has been established in the past centuries. The depth of the oxygenated layer varies spatially. It is greatest near coasts and less over the deeper basin. Whether the oxygenated layer is still decreasing is currently a question of scientific debate.
The surface water temperature varies on both a seasonal and a regional basis, with a range from 0°C in the northwestern coastal and shelf area during winter up to 25°C in the west during summer. The deep water remains constant at 9°C at 1000 m depth all year round.
The main feature of the water currents is an anti-clockwise boundary current which runs approximately parallel to the shore, two cyclonic gyres (spiral flows) that almost divide the basin in two and a series of smaller and anti-clockwise eddies originating from the larger features (see Map 6.2). The freshwater input and its associated contaminants from the large rivers on the northwestern shelf are transported by gyres throughout the Black Sea.
During the last 30 years the damming of the Danube and other major rivers, particularly in the former USSR, has resulted in an estimated decrease of freshwater input to the Black Sea of up to one fifth. This reduction in freshwater and associated sediment load has resulted in coastal erosion, particularly of the Romanian coasts, and an increase in salinity. Some Romanian beaches have been eroded at a rate of 12 m per year. Partly because of this erosion, extensive coastal engineering work has been carried out along the Romanian coast to protect the shoreline and to enlarge Constant,a harbour. As a consequence a large amount of material has been dumped in the coastal waters, reducing the water quality. The most severely affected biota have been filter feeding organisms and rocky zone macroflora.
Heavy pollution and increased agricultural activity coupled with limited mixing results in oxygen depletion in the coastal waters, especially during summer, further exacerbating the naturally anoxic nature of the Black Sea.
Biological features |
The most biologically productive areas of the Black Sea include the northwestern and northeastern parts of the basin, including the Azov Sea. This is because these areas receive enhanced nutrient loads from the inflowing rivers as well as being subject to efficient vertical mixing.
There are 180 species of fish in the Black Sea, more than half of which are also present in the Mediterranean Sea. There are three species of dolphin. The brackish nature of the Black Sea restricts the number of species of organisms present. Because the water below about 150 m contains no oxygen it is largely devoid of life, except for anaerobic bacteria.
The Ukrainian part of the Black Sea has four conservation/nature reserves which comprise extensive marine areas (COE, 1990b). The Danube Delta Protected Area has a rich and varied marine fauna, with 92 fish species including salmon, sturgeon and Clupeidae (including many endemic species). The area also has great ornithological value with 225 species of aquatic birds. Chernomosk National Reserve includes large marine areas (11 000 ha) of the Black Sea and Sea of Azov: its waters are productive with extensive mats of Zostera and Phyllophora. Its rich fauna includes the very rare Black Sea herring. Karadag Park in the Crimea (809 ha) also has extensive beds of Zostera, rocky shores and many nesting sea-birds. Mys Martjan Park, Crimea, holds many species that have disappeared from other areas.
Inputs |
The nutrient load to the Black Sea has increased markedly in recent decades, probably as a consequence of the widespread use of phosphate detergents and intensification of agriculture. This has been reflected in an increase in the concentrations of nitrogen and phosphorus compounds. Between 1970 and 1991 a two- to three-fold increase in the nitrate maximum, just above the halocline, has been reported. During the same period a seven-fold increase in phosphate concentration was observed along the Romanian shelf (Mee, 1992).
A recent study (Ludikhuize, 1992) commissioned by UNEP (for the Global Environment Facility) gave a preliminary assessment of inputs to the Black Sea. It suggests that 65 per cent of the nitrogen input to the Black Sea is via rivers, 40 per cent alone from the Danube River (that is, 340 kilotonnes total inorganic nitrogen). This study also estimated the inputs of nitrogen from different sources (Figure 6.8a) of which agriculture and domestic wastewater contributed the largest share (31 and 26 per cent, respectively). Other important inputs were from industry and atmospheric deposition. However, data about the different sources were very limited in this study and values are rough estimates. There are few data on phosphorus inputs but the same study estimates that the Danube River is again the most imporant source, contributing some 60 kilotonnes of total phosphorus input to the Black Sea (Figure 6.8b).
Even though nutrient loads may be reduced in the future, release of sediment-bound nutrients (particularly from the continental shelf areas) would fuel eutrophication for many years or decades with gradually diminishing intensity.
There is limited information available on the loads of heavy metals being discharged into the Black Sea: it is, however, reported that the Danube alone (based on the Bucharest Declaration's 1989 figures) is responsible for discharging annually up to 280 tonnes of cadmium, 60 tonnes of mercury, 900 tonnes of copper, 4500 tonnes of lead, 6000 tonnes of zinc and 1000 tonnes of chromium (Mee, 1992). More recent water quality data on the rivers Danube, Dnepr, Don, Kuban and Belaya were obtained during the collection of data for inclusion in Chapter 5 on inland waters (EEA-TF questionnaire). These indicate generally similar total loads (to the Danube) from these rivers 87 tonnes of cadmium, 1500 tonnes of copper, 825 tonnes of lead, 2600 tonnes of zinc, 207 kilotonnes of nitrate and 47 kilotonnes of total phosphorus. There appear to be no recent data from other Black Sea rivers though loads for three Turkish rivers have been quoted (Balkas et al, 1990). These data indicate that in 1984 between 300 and 1200 tonnes of cadmium, 30 to 300 tonnes of copper and up to 3000 tonnes of lead were discharged. Heavy metal loads must be considered to be minimum values, as additional sources such as direct discharges and atmospheric deposition have not been quantified.
The annual oil load of the Danube River in the period 1988 to 1989 has been estimated at 50 000 tonnes. Few data exist about sea-based sources, which are expected to account for the oil pollution along shipping lanes and in ports. Oil drilling along the Romanian coastline may be another potential source of oil pollution. However, several active oil rigs have been subject to protective measures and monitoring has not yet detected adverse effects (Balkas et al, 1990). Inadequate port reception facilities and deballasting activities add further inputs of oil.
There are also 16 official waste disposal sites within the western Black Sea on the continental shelf: dredging spoils are disposed of at these sites and these would add an unquantified load of contaminants to the offshore zone of the sea.
Contaminant levels |
There are few published data on heavy metals in the Black Sea, and those available reflect high and very variable concentrations. This is probably due to analytical difficulties caused by their low concentration in sea water. Concentrations of metals in water are generally higher in the nearshore zones than further offshore and in the open sea. In particular, high levels of cadmium are found along the coastline of Romania (up to 1.6 µg/l compared with open sea levels of 0.05 µg/l), and high levels of mercury and copper along the Bulgarian coast (up to 2.6 µg/l mercury and 83 µg/l copper, compared with open sea levels of 0.1 µg/l and 0.5 µg/l, respectively (Dechev, 1990)).
There are generally no validated data on pesticides in the Black Sea, though levels of up to 200 to 300 ng/l total organochlorine pesticides have been reported in the River Don, compared with general levels of 10 to 30 ng/l in water of the Sea of Azov, and 5 ng/l in the open Black Sea. In addition, mean and maximum water column concentrations of *HCH and *HCH (lindane) are reported to be 5 ng/l and 23 ng/l, and 1 ng/l and 5 ng/l, respectively.
Total DDT water concentrations in the Kerch Strait range from 8 to 20 ng/l, approximately two orders of magnitude higher than in the Mediterranean Sea (Mee, 1992). Measurements made in 1981 and 1982 indicated DDT water levels of 32 to 486 ng/l in the region of the Danube delta and 20 to 550 ng/l of lindane. Total DDT levels in two fish species were reported to be in the order of 1 µg/g (dry weight) for Gobius spp and 4.6 µg/g (dry weight) for Sprattus spp.
Surfactants (synthetic detergents) are reported to be widespread in the surface waters of the Black Sea and Sea of Azov, ranging from 0.6 mg/l around Odessa to 0.1 mg/l in the open waters of the Black Sea, and 1.2 mg/l in the coastal zone to 0.1 mg/l in open waters of the Sea of Azov (Mnatsakanian, 1992). There are also 'hot spots' of phenol in water, such as up to 14 ng/l in the Odessa area and 18 ng/l in other northern coastal areas. Levels of phenol in water up to 3 ng/l have been found along the western shores around the Danube, along eastern shores and in the Sea of Azov.
Areas of the Black Sea are severely polluted with oil, particularly those areas subject to river discharge and ports. Sevastopol Bay, which serves as the major port for the Black Sea navy, is the most polluted, with an average annual concentration of 5 mg/l, over 100 times higher than the maximum permissible concentration (MPC) allowed by the Russian Federation water standards. Even the average open sea oil concentration of 0.1 mg/l exceeds the MPC by a factor of two, and is two orders of magnitude higher than oil concentrations in the open North Sea (1 to 3 µg/l). Oil pollution along shipping lanes is especially heavy (typically around 0.3 mg/l) and is suggested to be caused by deballasting and bilge discharges. Some ports (Odessa and Novorossiysk) have facilities for this but others do not (eg, Varna, Burgas and Sevastopol).
Associated with the increasing loads of nutrients into the Black Sea over the last 25 years, there has been a long-term change in nitrogen and phosphorus concentrations. For example, between 1960 and 1975 the nitrate and phosphate concentrations along the Romanian coast have increased between 5-fold and 10- to 20-fold respectively (Mee, 1991). Ammonia and phosphate concentrations increase, and nitrate decreases, with depth in the Black Sea; this is caused by the decomposition of organic matter under anoxic conditions. Mean surface water concentrations of ammonia, nitrate and phosphate were reported to be 2.8 mg N/l, 0.8 mg N/l and 0.4 mg P/l, respectively (Dechev, 1990). At 500 m nitrate is no longer present but ammonia concentrations are some 21 times greater (58.5 mg N/l) than at the surface, and phosphate some 14 times greater (5.6 mg/l).
There are few data on the bacterial level of municipal wastewater and the level of bacteriological pollution of coastal waters, but a large number of beaches have been known to suffer from bacteriological contamination. This led to the closing of many Ukrainian beaches during the summer of 1989. The beaches of the easternmost part of the Sea of Azov and Taganrog Bay were also closed in 1989 because of alleged bacterial contamination.
Deposition of Chernobyl radionuclides occurred in the Black Sea, but there are limited data on the resultant concentrations within sea water, sediments and biota. Available information indicates that sea water concentrations in the Crimea area ranged between 190 and 650 Bq/m3 Cs-137, and 79 and 320 Bq/m3 Cs-134 during 1986: these had decreased to between 90 and 120 Bq/m3 Cs-137 and to between 20 and 55 Bq/m3 Cs-134 during 1987 at the same place (Stepanets et al, 1992). Other sources of information report that Cs-137 concentrations in the Black Sea ranged from 41 to 165 Bq/m3, and Cs-134 from 17 to 78 Bq/m3, following the Chernobyl accident (Balkas et al, 1990).
Biological effects |
The evidence is overwhelming that a major part of the Black Sea is critically eutrophic (Mee, 1992). Eutrophication is especially apparent in the northwestern shelf area because of the heavy anthropogenic nutrient load carried by the rivers. Other areas suffering from eutrophication include Crimea, Kavka and near Batumi. The consequences of eutrophication in the Black Sea and Sea of Azov include:
Eutrophication has caused the base of the food-chain to change, resulting in an increase in the development of monospecific blooms of plankton. Higher levels within the food-chain have subsequently also been changed with massive basin-wide biomasses of jellyfish (Aurelia aurita) and a predatory comb jelly (Mnemiopsis leidyi). The decomposition of the massive quantities of these two species has resulted in widespread hypoxia and has caused a large reduction in the number of macrobenthic marine species. These changes to the marine ecosystem of the Black Sea have contributed to the demise of the fisheries and reduced its tourist potential.
A number of opportunistic species, brought into the Black Sea in the ballast water of ships, have found ecological niches in which they thrive. Some of these species have had important ecological consequences for the Black Sea and Sea of Azov:
The combination of reduced river discharge, increased water pollution, recruitment failure and overexploitation has adversely affected fish stocks in the Black Sea and Sea of Azov. Commercial fishing in the Dnepr and Dnestr estuaries has been much reduced and some valuable species such as pike (Esox lucius), perch (Perca fluviatilis), roach (Rutilus rutilus), bream (Abramis brama) and vimba (Vimba vimba) have disappeared altogether. In fact, of the 26 commercial fish species abundant in 1970, only five are left in commercial quantities today: the anchovy (Engraulis encrasicolus), sprat (Sprattus sprattus and Clupeonella cultriventris) and horse mackerel (Trachurus mediterraneus and Trachurus trachurus). Depletion of the stocks of the dominant predators such as bonito (Sarda sarda), bluefish (Pomatomus saltatrix) and dolphins in the 1970s coupled with the increase in primary productivity and zooplankton biomass has resulted in this increase in biomass of small pelagic fish.
Conclusions |
THE CASPIAN SEA |
General situation |
The Caspian Sea is situated in an arid and semi-arid zone and is surrounded by the Russian Federation, Azerbaijan, Kazakhstan, Turkmenistan and Iran (see Map 6.1). It is the largest relatively low-salinity, land-locked body of water in the world. The main ports along the coasts of the Caspian Sea are Baku (Azerbaijan), Astrakhan and Makhachkala (Russian Federation), Krasnovodsk (Turkmenistan), Shevchenko (Kazakhstan), and Bandar Anzalï in Iran. The Caspian Sea is an important source of oil and gas and extensive drilling operations are located at the Baku Archipelago and Neftyanyye Kamni Fields in the Baku district.
Physical features |
The Caspian Sea has a surface area of 436 000 km2 and is structurally divided into three parts: northern, middle and southern. The major rivers flowing into the Caspian are the Volga, the Ural, the Kura, the Terek and the Samur. Of these, the Volga, to the north of the sea, is alone responsible for three-quarters of the riverine freshwater input. Salinity varies little with depth but widely from north to south. In the north it ranges from 2 per thousand close to the mouth of the Volga, to 5 to 10 per thousand elsewhere; the whole of this part of the sea is like a gigantic estuary inhabited by fresh and brackish-water organisms. The north is also very shallow, with a depth of 10 to 12 m. In contrast, the middle and southern Caspian are deep waterbodies with maximum depths of 788 m and 1025 m, respectively, divided by the pronounced Aspheron Ridge, with a marine type of water circulation and a salinity of 12 to 13 per thousand.
The Caspian Sea has been influenced by long-term sea level variations. In the early 1930s the level of the sea was 26 m lower than the world ocean. By 1977 this level had dropped to 29 m, from where it started to rise to its present level of 27.5 m. The reasons for these sea-level changes are presently unknown but one could be the Volga drainage rate. Dams constructed on the Volga and Kura rivers for hydroelectric plants and irrigation schemes have reduced the flow of freshwater into the Caspian. This has been only partly mitigated by the construction of canals to divert water from the Siberian rivers, which discharge into the Arctic, into the Volga catchment. This sea-level rise has caused a problem for beaches and cities in the North Caucasus region. The construction of large reservoirs on the Syr-Dar'ya and Amudar'ya rivers to support rice and cotton growing has also seriously depleted the water in the Aral Sea. Between 1965 and the late 1980s the Aral Sea had lost two thirds of its volume and its water level fell by 17 m (Tursunov, 1989). Because it is situated in Asia, a discussion of the serious environmental problems concerning the Aral Sea is beyond the scope of this report.
In summer, the surface temperature of the Caspian Sea is 24 to 27°C and in winter it falls to 9°C in the south and to 0°C in the north, where sea-ice forms. Vertical water circulation is limited, resulting in serious oxygen depletion at depth. This is particularly significant below 200 to 300 m and results in the production of hydrogen sulphide in deep sediments (Clark, 1986).
Rivers add 350 km3 of freshwater per year into the Caspian Sea and a further 100 km3 comes from direct precipitation onto the sea; all of this volume (450 km3) is lost by evaporation. The eastern side of the sea receives little precipitation and negligible river input; there is also a high rate of evaporation. This results in some bays and semi-enclosed areas of the sea having very high salinities, for example up to 200 per thousand in the Kara-Bogaz-Gol Bay, which is almost completely separated from the Caspian proper. The bay is shallow and joined to the main sea through a very narrow channel which was closed off by a dam at the end of the 1970s. This area was used for the evaporation of water for the collection of several sea-water minerals.
Biological features |
Lack of oxygen at depth has resulted in an impoverished benthic fauna in the central and southern parts of the Caspian Sea; in some parts it is completely missing (Clark, 1986). The northern Caspian benthic fauna is dominated by molluscs and there was a previously conspicuous absence of polychaetes (bristleworms). Between 1939 and 1941 some 65 000 Hediste diversicolor, a polychaete, were introduced to restructure the benthic ecosystem (Clark, 1986). This has become the dominant food for sturgeon, of which there are two main species: the Russian sturgeon, Acipenser gueldenstaedti, and the stellate sturgeon, Acipenser stellatus. However, the sturgeon population has been much reduced and is still diminishing rapidly. There is a reported trend of decreasing species diversity of phytoplankton, zooplankton and macrobenthos; for example, the latter showed a decrease in species numbers from 90 in 1980, to 63 in 1990 (Izrael and Tsyban, 1992). This trend towards a decrease in benthic biomass and species diversity is more strongly marked in the central and southern regions than in the northern Caspian Sea. The species diversity has been reduced to almost the minimal level in some stretches of water.
Inputs |
About 12 km3 of wastewater per year is discharged into the Caspian Sea from the Volga basin and 8 km3 comes from the coastal towns: 2.5 km3 out of that is discharged without any treatment, a further 7.5 km3 is partially treated. The Volga is the largest European river in terms of catchment area (1 360 000 km2), mean discharge (230 km3 per year) and length (3530 km), and, with 15 major cities and major industry in its catchment, represents the principal source of pollution in the northern Caspian. There is also major oil industry along the Azerbaijan coast with numerous offshore oil wells with associated refineries and petrochemical plants. In addition, there is a large urban population around Baku.
An estimate of the minimum gross load of some contaminants entering the Caspian has been made from water quality data from the River Volga obtained from the EEA-TF's inland waters questionnaire (see Chapter 5). No data have been found on the loads from other sources such as other rivers and direct inputs. From the available data it has been calculated that 98 kilotonnes (kt) of nitrate, 126 kt of total nitrogen and 5 kt of phosphates entered the Caspian from the Volga in 1991. In addition, there are some limited data on metal concentrations in Volga river water (Karpinsky, 1992). These have been used, with the flows provided by the Hydrochemical Institute, Rostov-on-Don, to estimate the annual load of cadmium (114 tonnes (t)), copper (1600 t), lead (297 t) and zinc (5100 t).
Contaminant levels |
The concentrations of copper, zinc, lead and cadmium in Volga water are reported to be 7 µg/l, 22.5 µg/l, 1.3 µg/l and 0.5 µg/l, respectively, and all are reported to have increased significantly over the last 15 years, exceeding maximum permissible pollutant levels designated by the former USSR (Karpinsky, 1992). There are apparently no other data reported or available.
Organochlorine pesticide concentrations in water are reported to be as high as 27 ng/l around the Volga delta compared with 1.8 to 1.9 ng/l in more open sea locations (Mnatsakanian, 1992). The average annual concentration of phenol in 1988 in the northern Caspian and in the Dagestan and Far Eastern coastal areas were 4 to 6 µg/l. There were, however, high phenol contamination levels, 5 to 16 µg/l, along the Azerbaijan coast.
Oil pollution has a very long history in the Caspian Sea. Natural benthic oil springs have long caused some contamination, but it was not until the middle of the twentieth century that the threat of oil pollution increased from offshore oil production. Oil pollution is also associated with petroleum extraction operations, river runoff and along shipping routes. The level of oil in coastal and open sea waters of the Caspian is relatively high, with coastal waters having in general reported concentrations of between 100 and 300 µg/l (Mnatsakanian, 1992). However, some coastal waters are even more polluted. The average annual concentration of oil compounds in 1988 in the northern Caspian region and in the Dagestan and Far Eastern coastal areas were between 100 and 150 µg/l. Higher levels of 200 to 600 µg/l were also found along the Azerbaijan coast, caused not only by the runoff from large cities but also from offshore oil rigs.
Turkmenistan also has many oil wells in the Krasnovodsk-Cheleken region, where frequent accidents at wells and pipelines have occurred. In the region of oil fields the oil concentrations along Turkmenistan coasts is between 100 and 200 µg/l. The highest observed concentrations in the Turkmenistan coastal region are in the Kara-Bogas-Gol Bay, with concentrations of up to 750 µg/l.
In 1989 four accidents were recorded which resulted in more than 300 tonnes of oil being discharged into the sea. One accident alone resulted in oil being spread over more than 200 km2. These spillages have had extremely adverse effects for the marine environment because the Caspian Sea has no official organisation which is responsible for cleaning up spilled oil. In 1989 the Azerbaijan government decided to stop all new deep sea drilling until new equipment was available to prevent these oil spillages.
There were no available data on the levels of nutrients in the Caspian Sea.
In the North Caucasus region there is a problem due to a lack of sufficient wastewater treatment facilities in the cities (Mnatsakanian, 1992). For example, in Makhachkala all of the sewage goes into the sea without any treatment. In 1990 no seasonal fluctuations were observed in the bacterial populations in the west, middle and south Caspian: total numbers of bacteria varied from 0.5 to 3.5 million per ml (Izrael and Tsyban, 1992). In the Bay of Bakinsky the numbers of bacteria were a little lower than in the other regions.
It has been recently reported that surface water concentrations of Sr (strontium)-90 in the Caspian Sea in 1990 and 1991 were 15 Bq/m3, and from 12 to 87 Bq/m3, respectively (Yablokov et al, 1993).
Biological effects |
It is reported that there is a trend of decreasing ecological quality of the Caspian Sea, with the middle and southern parts being the most impacted (Izrael and Tsyban, 1992). In 198889 hundreds of thousands of sturgeon were found dead with gross changes in their bodies (destruction of muscles): overall the stocks of sturgeon are believed to be falling (Mnatsakanian, 1992). A phenomenon first recorded in 1984 and observed on a mass scale in 198788 (in up to 90 per cent of the stock) is the lamination of the muscle tissue and egg membrane in the sturgeon, which was given the name 'myopathy' (Karpinsky, 1992). Associated with this is metabolic disturbance, atrophy and adiposity of muscle fibres, blood changes, and elevated content of heavy metals and organochlorine pesticides in the blood and tissues ­ a possible cause of this disease is cumulative toxicosis.
Significant declines have been observed in the breeding and nursery grounds for sturgeon, bream, pike, crucian carp (Carassius carassius) and other commercial fish species. The decrease in fish catches has been linked with the variations in sea level, increased salinities and pollution levels, and is possibly compounded by overfishing. The total fish catch from the Caspian was 0.3 million tonnes per year in the mid-1930s; this had dropped to 0.1 million tonnes by 1970.
Conclusions |
THE WHITE SEA |
General situation |
The White Sea is a semi-enclosed inland sea of the Arctic Ocean situated on the northern coast of the Russian Federation between the Kanin and Kola peninsulas. In the north it joins the Barents Sea. The coastline topography varies, with predominantly high, rocky outcrops along the northwest coasts and flat low-lying land along the southeast coasts. The sea has a number of gulfs or bays: the Gulf of Mezen, the Gulf of Onega, the Gulf of Kandalaksha and the Gulf of Dvina. In winter the sea is completely covered with ice, thus limiting its use for shipping. The main coastal cities are Arkhangelsk, Onega, Kem and Kandalaksha. A large nuclear submarine shipyard is located in the city of Severodvinsk, near Arkhangelsk.
At a Ministerial Conference in Rovaniemi, Finland, in June 1991, the ministers from the eight arctic countries, including the Russian Federation, agreed to develop an Arctic Monitoring and Assessment Programme (AMAP), which will be implemented by an Arctic Monitoring and Assessment Task Force (AMAP, 1993). The initial priorities are work on persistent organic contaminants, selected heavy metals and elements, and radionuclides. The White Sea is included within the programme.
Physical features |
The White Sea surface covers 90 000 km2 and is comparatively shallow, with a maximum depth of 350 m. There are three major rivers discharging into the White Sea (see Map 5.11): the Severnaya (northern) Dvina; the Mezen and the Onega. These three rivers are all within the 30 largest European rivers in terms of catchment area. The largest, the Severnaya Dvina, has a catchment of 358 000 km2, a mean annual discharge of 148 km3 and a length of 740 km. These catchments are relatively sparsely populated.
Biological features |
The formerly rich White Sea fisheries, numerous seal herds and natural seagrass mats have become depleted due to overexploitation and pollution (Mnatsakanian, 1992). Seagrass is very intensively used for the production of agar and iodine. It has been estimated that the amount of seagrass in the White Sea in 1989 was only half of that present in 1975 (Mnatsakanian, 1992). The population of Greenland seals is also thought to have halved in the four years between 1985 and 1989.
Inputs |
Floating logs can create |
Very few data have been found on the input loads of contaminants entering the White Sea. In 1989 it was estimated that 2600 tonnes of oil, 107 tonnes of phenol and 382 tonnes of surfactants were discharged into the White Sea (Mnatsakanian, 1992).
Loads of some other contaminants have been estimated from 1991 data on river water quality and flow obtained by the EEA-TF inland waters questionnaire (Chapter 5). The data relate to the three major rivers discharging into the White Sea: the Severnaya Dvina, Mezen and Onega. From these data it was estimated that, in 1991, 187 tonnes (t) of copper, 314 t of lead, 1656 t of zinc, 276 t of nickel, 8.8 kilotonnes (kt) of nitrate nitrogen, 17.2 kt of total nitrogen and 1.5 kt of orthophosphate were discharged from these rivers. These values must be considered as minima, since no data are available on direct discharges into the sea, other riverine inputs or atmospheric deposition.
Radioactive waste has also been discharged into the White Sea. According to a recent report, between 1959 and 1984, a total of 3.7 TBq of liquid waste was discharged (1 TBq = 1012 Bq or 27 Curies). In 1984 the Murmansk Marine Shipping Line (the organisation responsible for radioactive waste disposal) ceased dumping liquid waste (Yablokov et al, 1993).
A considerable problem in the White Sea is the effect of the large number of logs transported down river. Not all of the logs are successfully collected from the rivers and as a result log jams are sometimes formed in the river mouths. All shores along the White Sea often resemble timber stock yards.
Contaminant levels |
There are limited data published or available on the levels of contaminants in water, sediment and biota of the White Sea:
Biological effects |
In the spring of 1990 there was a massive death of starfish, crabs, mussels and marine mammals, which the Soviet Inter-governmental Commission attributed to sulphuric compounds (such as mustard gas) or the leakage of missile fuel from a submarine (Izrael and Tsyban, 1992).
Conclusions |
THE BARENTS SEA |
General situation |
The Barents Sea is a marginal sea of the Atlantic Ocean and is situated at the outermost bounds of the polar ocean between the coasts of Europe and Svalbard, Franz Josef Land and Novaya Zemlya (see Map 6.1). It reaches the coasts of the Russian Federation and Norway. The hydrological characteristics of the Barents Sea are strongly affected by its location between the Atlantic Ocean and the arctic basin. In the northwest region which is under the influence of the warm Atlantic waters the sea never freezes, whereas in the northern area it is partially covered by polar ice for part of the year. The coastline of the Barents Sea is strongly indented with gulfs and fjords. The most important river flowing into the Barents Sea is the Pechora.
The Barents Sea is relatively unpolluted as it is situated a long way from dense human populations and industrialised areas. The coastal areas of the Barents Sea are not heavily populated. The largest town is Murmansk (the Russian Federation) which has a large naval base and heavy industry. Apart from that there are just a few small Norwegian towns and fishing villages. The most important industry is fishing.
The Barents Sea is included within the area covered by the Paris Convention, and, as Norway is a signatory to the Convention, input and quality data are submitted annually to the Paris Commission for the Norwegian sector of the Barents Sea. However, as the Russian Federation is not a signatory to the Convention, comparable data for the Russian Federation sector of the sea are not available. More details on the Paris Convention are given below in the section on the North Sea. The Barents Sea and the Kara Sea (the sea to the east of Novaya Zemlya) are also included in the Arctic Monitoring and Assessment Programme, with both Norway and the Russian Federation being signatories ­ for more details on AMAP see the section on the White Sea.
This section on the Barents Sea has been compiled largely from the following references (specific points are referenced as appropriate): Gjosaeter (1992), Loeng (1989 and 1991), Northern Europe's Seas (1989), and Saetre et al (1992).
Physical features |
The Barents Sea covers an area of 1 425 000 km2 and has an average and maximum depth of 230 m and 600 m, respectively. More than 20 per cent of its area is shallower than 100 m, but troughs deeper than 400 m enter the area from the west and northeast. The deepest waters are found in the western part, between Norway and Bear Island; the shallowest water is on Svalbard Bank and in the southern part where depths are less than 50 m. The bottom topography strongly influences the current conditions.
There are large long-term variations in the properties of the Atlantic inflow into the Barents Sea which may influence the properties of locally formed water masses. In the Barents Sea there is warm Atlantic water in the south and cold Arctic water in the north. The transition zone between the Atlantic and Arctic water masses is called the polar front, and is formed by the mixing of these two water masses. During winter strong vertical mixing gives rise to a water column with very low stability. Nutrient concentrations are therefore homogeneously distributed with depth during winter, and so are available for phytoplankton utilisation in spring. During spring and summer vertical stability develops differently in ice-covered and ice-free areas. In ice-covered areas, the vertical stability in the surface layers increases as soon as the ice starts to melt and a surface layer of low salinity water is formed. In ice-free areas, that is in areas with Atlantic water, vertical stability is formed through heating of the surface layers by the sun. The vertical mixing during winter and the formation of layered surface water during spring and summer are important for primary production. Maximum ice coverage occurs between March and May, and minimum in August to September.
There are three main current systems linked to the three different water masses (see Map 6.2). The Norwegian coastal current flows along the whole Norwegian coast, bringing relatively low salinity and high temperature water from the Baltic, the North Sea and the Norwegian fjords. The Atlantic current has a high salinity (over 35 per thousand) and temperature (between 3.5 and 6.5°C) at its inflow area between Norway and Bear Island. Atlantic water flows north along the western coast of Svalbard and also into the Barents Sea. The influx of Arctic water occurs through two main routes: between Svalbard and Franz Josef Land, and, more importantly, through the opening between Franz Josef Land and Novaya Zemlya.
Biological features |
The Barents Sea is an arctic sea with high biological production and relatively low species diversity. During the six summer months the Barents Sea experiences almost optimal conditions for life, with intense summer sunlight and adequate nutrient supply. One of the most important production areas is the edge of the polar ice cap. Phytoplankton grow very rapidly and in large quantities and these are eaten by the zooplankton which are the staple food of herring (Clupea harengus) and capelin (Mallotus villosus). This high density of phytoplankton and zooplankton and plankton-eating fish forms the basis for the rich fauna of the area. The sea contains some of the world's largest sea-bird populations, and is also an important area for fisheries and sea mammals. As the biological production is very limited in space and time the ecosystem is potentially vulnerable to the influence of human activity.
The Barents Sea contains some of the world's largest fish stocks of capelin, cod (Gadus morhua) and the Norwegian spring-spawning herring (Clupea harengus). There are strong interactions between these stocks, and variations in the year-class sizes have a marked influence on other components of the ecosystem. The capelin stock reached a maximum biomass in 1975 of 7.3 million tonnes. Since then it has generally declined, with the lowest estimate of 0.02 million tonnes in 1987. The Barents Sea is a nursery area for several fish species including the herring, cod, haddock (Melanogrammus aeglefinus) and saithe (Pollachius virens). The Norwegian spring-spawning herring stock was the largest fish stock in European waters until its collapse in the 1960s. The total fish biomass landed over the last 40 years was 2 to 3.5 million tonnes, which is the same as from the North Sea. However, the proportion of fish of the cod family in total catches has decreased from about 50 per cent in the 1950s to around 30 per cent in the 1980s. Pelagic species like capelin and herring have increased to about 60 per cent of total catch.
The Barents Sea contains several species of migratory whales: the minke whale (Balaenoptera acutorostrata) is the most important species during the summer and autumn. There is also the humpback (Megaptera novaeangliae) and fin whale (Balaenoptera physalus). In addition there are populations of grey seal (Halichoerus grypus), common seal (Phoca vitulina) and harp seal (Pagophilus groenlandicus). Walrus (Odobenus rosmarus) and polar bears (Ursus maritimus) are also common.
Practically all of the Barents Sea's shores are ice-bound from late autumn onwards, and during the summer thaw the shores are scoured by drift ice. As a result few animals and plants inhabit the shore and nearshore environment, but brown and red algae flourish from a depth of 5 to 10 m.
Inputs |
Direct and riverine inputs of contaminants to the Barents Sea from Norway are reported annually to the Paris Commission. Information on discharges from the Russian Federation into the Barents Sea have been obtained from two sources: the Knipovich Polar Research Institute of Marine Fisheries and Oceanography (PINRO), Murmansk, and from information obtained from the EEA-TF inland waters questionnaire (Chapter 5). The estimates of loads are gross values and do not take into account estuarine processes which might reduce the net loads discharged to coastal waters. Compared with some other European seas, such as the North Sea, the load of contaminants to the Barents Sea is relatively low. A comparison of the data from Norway and the Russian Federation indicates that loads from Russian rivers can greatly exceed riverine and direct discharges from Norway; for example, the zinc load is 26 times greater, copper 18 times, and total nitrogen 5 times. In addition, some 3840 tonnes of oil and 3.4 tonnes of synthetic organic compounds (eg, DDT, HCH and PCBs) are discharged annually from rivers of the Russian Federation.
In addition to local sources, there are chemical contaminants transported by ocean currents and by long-range atmospheric transport. The atmospheric southnorth poleward transport of contaminants from more urbanised and industrialised areas plays an important role in the Barents Sea.
A limited part of the Norwegian coast was opened to oil exploration in 1980: between 1980 and 1992, 54 exploratory wells were drilled in the Norwegian sector. In addition, there are approximately 17 wells in the Russian Federation sector. The main impacts from drilling are: seismic activity; pollution; and area conflicts. Seismic testing can lead to the death of larval fish, and can frighten adult fish away (for example, adult cod can be affected 20 nautical miles away). Though not reported in other sections, the effects of seismic testing could also be relevant to other European seas where oil exploration is undertaken.
Radioactive inputs to the Barents Sea arise from a number of sources, including:
The first two sources are predominant, as demonstrated by a recent assessment of the anthropogenic radionuclide inventory of the Barents and Kara seas over the period from 1961 to 1990 (Yablokov et al, 1993). This indicated that, in the Barents Sea, 63 per cent of anthropogenic radioactivity originated from surrounding seas, 31 per cent from atmospheric fall-out, 4 per cent from the dumping of solid and liquid radioactive waste and 2 per cent from river runoff.
Inputs from surrounding seas arise principally from the nuclear reprocessing plant at Sellafield in the Irish Sea (UK), with smaller contributions from the reprocessing plant at Cap de la Hague (France) and the nuclear power stations discharging to Northern European waters.
There is an exchange of water between the Barents and Kara seas through the Kara Gate or north of Novaya Zemlya. The present levels of radioactivity in the Kara Sea are, in addition to the sources mentioned for the Barents Sea, also attributed to runoff from Russian rivers, in particular the Ob and Yenisey, as well as to a potential release from dumped radioactive solid waste, especially in bays at the eastern part of Novaya Zemlya. The potential future importance of this latter source is indicated by an inventory of anthropogenic radioactivity in the Kara Sea (Yablokov et al, 1993). This indicates that the major contribution (95 per cent) is from the sinking of solid radioactive waste contained within nuclear reactor chambers. The remaining inputs have arisen from atmospheric fall-out (3 per cent), river runoff (1.3 per cent), and the dumping of liquid and other solid radioactive waste (0.7 per cent).
The discharge of liquid radioactive waste into the Barents and Kara seas from the former USSR began in 1960, and, by 1991, 450 TBq had been discharged into the former and 315 TBq (Sr-90 equivalent) into the latter. Five main disposal areas were used in the Barents Sea, the largest quantity being discharged at three sites to the west of Novaya Zemlya. Smaller amounts were disposed of at the two sites closest to the mainland coast of the Russian Federation. There was one main disposal site in the Kara Sea off the southern part of the east coast. The dumping of liquid waste by the Murmansk Marine Shipping Line was stopped in 1984. The naval fleet continued the dumping of low-level liquid waste until 1991.
Solid radioactive waste dumped in the Kara Sea has arisen from the Russian Federation nuclear powered naval and ice-breaking fleets, and from ship-repairing and shipbuilding factories. Solid, low - and medium-level radioactive waste was contained in metallic containers; large sized waste was sunk separately or inside vessels such as barges and tankers. According to available data the total activity of the low and medium solid radioactive waste sunk between 1957 and 1991 in the Kara Sea was 574 TBq (Sr-90 equivalent) and in the Barents Sea 1.5 TBq (Sr-90 equivalent). This waste was disposed of at eight sites along the eastern coast of Novaya Zemlya in the Kara Sea, with the largest volume in the deep trench (380 m deep) of Novaya Zemlya and the largest radioactive quantity in the Gulf of Sedov (13 to 33 m deep).
In addition to the solid radioactive waste, seven reactors with spent nuclear fuel and ten reactors without fuel have been dumped in the Ambrosimov, Tsivolki and Stepovogo bays, along the eastern coast of Novaya Zemlya, as well as in the Kara Sea trench. It is estimated that there could be up to 85 000 TBq of radioactivity within this waste. These reactors are considered by the Russian Federation to represent the greatest radiological risk to the Kara Sea (Yablokov et al, 1993). The potential future impact on the Barents Sea would depend on a number of factors, including water currents and the exchange of water between the Kara and Barents seas. As a result the relevant areas are being closely monitored by the Norwegian and Russian Federation authorities.
Contaminant levels |
There are few data on trace metals in sea water and sediment: concentrations are generally at natural 'background' levels, and generally lower than those found in the North and Baltic seas.
Levels of metals in fish are generally found to be at background levels (Saetre et al, 1992). However, measurements of mercury in the liver and kidney of harbour porpoises showed a decreasing mercury concentration gradient from south to north along the Norwegian coast: concentrations ranged from 0.26 to 9.9 µg/g in liver samples and from 0.15 to 3.5 µg/g in kidney. Polar bear livers were found to have concentrations between 0.4 and 6.0 µg/g mercury, from less than 0.1 to 1.2 µg/g cadmium and from less than 0.5 to 1.6 µg/g lead. Levels of copper and zinc were at normal physiological levels.
There are limited data on trace organic compound concentrations in sea water. In 1985, HCH (* and *) concentrations ranged from 4.8 to 6.2 ng/l in the North Sea, from 2.3 to 3.8 ng/l along the coast of Norway and from 1.2 to 1.8 ng/l in the Barents Sea. Other chlorinated organics are usually at lower concentrations than HCH.
The analysis of sediments is part of the AMAP programme (see the section on the White Sea). Preliminary results indicate that aromatic hydrocarbons are present in sediments from all the sampling stations, indicating that they are influenced by anthropogenic inputs (Saetre et al, 1992). Mean concentrations of NPD (sum of naphthalene, phenanthrene, dibenzothiophenes) and PAHs (polycyclic aromatic hydrocarbons) were found to be 0.14 and 0.26 µg/g dry weight, respectively: these are 4 to 5 times lower than in the Skagerrak and 2 to 3 times lower than sediment in parts of the Norwegian Sea. Mean PCBs concentration was found to be 0.5 ng/g dry weight, which is 8 to 10 times lower than found in the Skagerrak.
Persistent organic compounds have been measured in a range of different biota, and results indicate that fish, sea-birds, marine and terrestrial mammals accumulate persistent organic compounds from different sources (Saetre et al, 1992). For example, the levels of PCBs in ringed seal (Phoca hispida) blubber from Svalbard ranged from 0.39 to 9 µg/g wet weight. With a few exceptions, birds from the Barents Sea region contain low levels of chlorinated hydrocarbons compared with more southerly populations; the highest concentrations of PCBs were found in the predatory glaucous gull (Larus hyperboreus).
In recent years there has been an increase in oil and gas exploration on the continental shelf of the Barents Sea by both Norway and the Russian Federation. In 1988 the Kola Gulf was the most polluted of the gulfs in the Barents Sea. Murmansk is located in Kola Bay and the bay is especially polluted near the mouth of the Severomorsk River and the settlement of Roslyakovo. In this bay concentrations of oil and phenol were up to 0.05 mg/l and 0.007 mg/l, respectively (Bruggeman et al, 1991). Petroleum product concentrations in sea water of up to 0.5 mg/l have been recorded in areas of petroleum and gas exploration off the sea shelf.
Oil exploration |
The most widely measured artificial radionuclide in the coastal waters of North Europe is Cs-137. Before Chernobyl its source was largely the reprocessing activities at Sellafield in the UK together with a smaller contribution from fall-out due to weapons testing (Camplin and Aarkrog, 1989). The most pronounced radioactive contamination in the Barents Sea was detected during atmospheric nuclear weapon tests (Saetre et al, 1992). The highest concentrations in fish were observed in the early 1960s, followed by a rapid decrease from about 80 Bq/kg wet weight in 1963, to below 10 Bq/kg wet weight by 1968. More recent levels are reported to be in the range of 0.5 to 1 Bq/kg wet weight, compared with levels of 30 Bq/kg in the Irish Sea and Baltic Sea (NRPA, 1993): both the latter values are well below the Norwegian action level for human consumption of 600 Bq/kg. Based on a joint NorwegianRussian expedition in 1992 to the Barents and Kara seas, the concentrations of Cs-137 in surface waters were within 3 to 8 Bq/m3, with the highest concentrations of 20 Bq/m3 in bottom waters (Foyn and Semenov, 1992). The results indicate a significant decrease in the concentration of Cs-137 during the last ten years. A significant contribution of Sr-90 from the Ob and Yenisey rivers was also identified.
Biological effects |
In general there are no major problems of nutrients and eutrophication in the Barents Sea, although locally increased nutrient levels may be found (eg, in some fjords).
The Barents Sea is a marginal area for several fish species. Changes in climatic conditions influence the distribution of fish, recruitment and growth. Global changes in climate may, therefore, have drastic biological consequences regardless of whether a warming or cooling takes place (Saetre et al, 1992).
The greatest human impact on the Barents Sea is from fishing, for example:
Conclusions |
THE NORWEGIAN SEA |
General Situation |
The Norwegian Sea is bordered to the east by the coast of Norway between 61°N and North Cape (of Norway), 25° 45'E, to the northeast along a line from North Cape over Bear Island to the south point of West Svalbard (see Map 6.1). Its western limit extends from this point along a line to Jan Mayen and further to Gerpir, the easternmost point of Iceland. The southern limit extends from there to the Faeroe Islands and on to the position 61°N, 00° 53'W. The coastal areas of the sea are scantily populated and the major occupations are fishing, aquaculture, mining and some heavy industry. The port of Narvik is especially subject to shipping of ore vessels. Freight vessels and fishing boats are also important in the area, as is transit traffic from the Russian harbours in the north. The Norwegian Sea continental shelf is a site of oil and gas exploration activities.
Norway is a signatory to the Paris Convention, which covers the Norwegian Sea. The part of the Norwegian Sea north of the Arctic Circle is also included in the Arctic Monitoring and Assessment Programme (AMAP), to which Norway is a signatory (for more details on AMAP see the section on the White Sea).
This section on the Norwegian Sea has been compiled largely from the following references (specific points are referenced as appropriate): Aksnes et al (1993), Blindheim (1989) and Northern Europe's seas (1989).
Physical features |
The Norwegian basin has two main depressions separated by a ridge between the Voring Plateau and Jan Mayen, through which only a narrow passage is deeper than 3000 m. The larger basin to the south contains wide areas with depths between 3500 and 4000 m. The Norwegian Sea is separated from the North Atlantic Ocean by the ScotlandIceland ridge: the deepest passage is the channel to the southwest of the Faeroes with a depth of 850 m; the channel between the Faeroes and Iceland is shallower than 500 m. To the north the connection to the Greenland Sea is deeper than 2500 m off the Barents Sea shelf, which forms the northeastern margin of the basin.
There are four major water masses within the Norwegian Sea. The warm and saline Atlantic water (temperature higher than 8°C and salinity greater than 35 per thousand) flowing in from the North Atlantic is confined to the upper layers over most of the area. Arctic water from the east Icelandic current (temperature less than 3°C and salinity between 34.7 and 34.9 per thousand) occupies upper layers in the southwestern part of the sea: at intermediate depths its distribution is much wider. Bottom water (salinity close to 34.92 per thousand and temperature below 0°C) originating from the Greenland Sea and the Arctic Ocean fills the deeper layers and represents the largest water volume. Within the area these three different water masses are continuously being mixed and modified. Coastal water along the coast of Norway is the fourth major water mass in the Norwegian Sea. It is made up of a mixture of freshwater from land and more oceanic water, and is generally of low salinity. Locally salinity can be very variable, reaching a minimum in spring when runoff is at a maximum due to snow-melt. As a result the coastal waters are strongly stratified, and their temperature may be subject to large seasonal variations, particularly in surface layers. Most of the Norwegian Sea is ice-free during winter, with sea-ice occurring only in the border areas between Bear Island and West Svalbard, and along the borderline between West Svalbard and the island of Jan Mayen.
Biological features |
In the Norwegian Sea winter convection currents extend to about 300 m depth, varying somewhat in different areas. Thus waters with high concentrations of nutrients are brought into the surface layer. In early spring the waters of this layer are rich in nutrients and have a large potential for primary production. As a result the Norwegian Sea is amongst the most productive seas in the world. Phytoplankton production starts along the Norwegian coast, where the wide salinity range in the coastal waters maintains some stratification throughout the year. In the open sea the mixed layer in early spring is too deep to support primary production and consequently the spring bloom occurs one to two months later than in coastal waters. The spring bloom consists mainly of diatoms but there are considerable yearly variations in the qualitative and quantitative aspects of the bloom in all parts of the Norwegian Sea. Summer production is relatively poor but there is more diversity with regard to species.
Herring (Clupea harengus) has traditionally been the most commercially important pelagic fish in the Norwegian Sea. Herring spawn along the Norwegian coast, mainly in March. The hatched larvae are carried northward by the coastal current and most are transported into the Barents Sea, which is the main nursery area. The herring return to the Norwegian Sea when sexually mature. By the end of the 1960s the herring stock was almost depleted. Since then the blue whiting (Micromesistius poutassou), which feeds in the Norwegian Sea and spawns west of the British Isles, has formed the largest pelagic plankton-consuming fish population in the area. Three species of redfish (Sebastes marinus, Sebastes mentella and Sebastes viviparus) are also found in the Norwegian Sea, the first two having commercial value. In addition, cod (Gadus morhua), saithe (Pollachius virens) and haddock (Melanogrammus aeglefinus) are found along the continental shelf.
Seals and whales are important components of high latitude ecosystems. Bowhead (Balaena mysticetus), blue (Balaenoptera musculus), fin (Balaenoptera physalus), sei (Balaenoptera borealis), humpback (Megaptera novaeangliae), sperm (Physeter catodon), and minke (Balaenoptera acutorostrata) whales all use the Norwegian Sea as an important feeding area. The bowhead, blue, sei and minke whales have a more or less clear seasonal migration pattern with a northward movement in the spring and a return to more southern areas in autumn. It has been estimated that up to 10 000 individual whales live in the area during the summer season, with fin and sperm whales being the most common. The world population of minke whale has been estimated to represent about 86 000 individuals.
Hundreds of fish farms are located along the Norwegian coasts between Sogn og Fjordane and Tromsø. These farms have produced increasing quantities of organic matter, resulting in local nutrient and eutrophication problems (see below).
Inputs |
Norway submits data to the Paris Commission on direct and riverine inputs into the Norwegian Sea. It is considered that discharges to the Norwegian Sea from riverine and direct sources are amongst the lowest when compared with those to other seas in the Convention's area (OSPARCOM, 1992a). For example, in 1990, cadmium loads to the Norwegian Sea were estimated to be 8.9 tonnes, compared with 55 tonnes to the North Sea and 70 tonnes to the North Atlantic. In the case of total nitrogen the loads were 31 kilotonnes (kt), 920 kt and 314 kt, respectively. No data were available on the contribution of other sources of contaminants, for example atmospheric deposition. There are also inputs of contaminants via ocean currents flowing into the Norwegian Sea.
The largest scale salt-water fish farming industry in the Nordic region is located in the fjords of the west coast of Norway, including the Norwegian Sea coastline. Such operations have marked effects on the nutrient status of the waters where exchange with the open sea is limited (eg, in some fjords). It has been estimated that at present aquaculture releases some 13.5 kt of nitrogen and 2.7 kt of phosphorus into Norwegian coastal waters annually, equivalent to the nutrient load in untreated sewage from a population of 2 million people (Bernes, 1993).
Contaminant levels |
The concentrations of trace metals in sea water in the Norwegian Sea are reported to range from 12 to 23 ng/l cadmium, 88 to 120 ng/l copper, 187 to 195 ng/l nickel and 25 to 35 ng/l lead. There are very limited data available on trace organic compound concentrations in sea water. For example, mean concentrations of *HCH and *HCH in the Norwegian Sea were reported to be 0.2 to 1.0 ng/l, respectively. Levels of synthetic surface active substances and hydrocarbons in sea water were reported to be very low, and concentrations of chlorinated hydrocarbons did not exceed 1 ng/l (Izrael and Tsyban, 1992).
Data were submitted from two coastal sites along the Norwegian Sea for inclusion in the Oslo and Paris Commissions' 1990 supplementary baseline study of contaminants in fish and shellfish. Neither showed 'elevated concentrations' of metals in tissues or 'higher concentrations' of organochlorines in one or more species (OSPARCOM, 1992a). The concentration of PCBs in zooplankton in the southern part of the sea have been found to be up to 55.6 µg/kg, and HCH levels were between 0.3 and 1 µg/kg in molluscs and 2.2 µg/kg in zooplankton these concentrations were considered to be very low (Izrael and Tsyban, 1992).
Biological effects |
It has been postulated that the ecosystem of the Norwegian Sea has been affected by climatic variability and, in particular, variability in temperature and salinity (Blindheim, 1989). For example, during the years 196568 waters of below 0°C in the East Iceland current extended further eastward into the Norwegian Sea than previously observed. This change is believed to have brought about a complete alteration in the feeding migrations of herring. In addition, a succession of several poor year classes of blue whiting during the late 1970s is also a possible effect. Even though the herring stock was subject to heavy fishing pressure in the 1960s, it is likely that the climatic variability was also an important factor for the depletion of stock around 1970. The biomass of the herring is at present estimated to be 2 million tonnes compared with 1950s values of 10 million tonnes (Aksnes et al, 1993).
Conclusions |
THE BALTIC SEA |
General situation |
The Baltic Sea (see Map 6.1) is a shallow, relatively young and sheltered inland sea, created after the last ice age some 10 000 years ago. It is the largest brackish-water area in the world. The present salinity conditions have remained largely unaltered for the last 3000 years. The sea is surrounded by Germany, Poland, the Russian Federation, Lithuania, Latvia, Estonia, Finland, Sweden and Denmark. The drainage basin of the Baltic Sea is over 1 800 000 km2, which is more than four times larger than the entire sea surface area. It is densely populated (77 million people) and heavily industrialised, and there are large areas of intensive agriculture.
The area of the Baltic Sea is 412 560 km2, and the volume is 21 000 km3; the mean depth is only 55 m although the maximum depth is 459 m (the Landsort Deep). Roughly 17 per cent of the area is shallower than 10 m. The Baltic Sea consists of a series of basins, most of them separated by shallow areas or sills, except for the Gulf of Finland which is a direct continuation of the Baltic proper. The Belt Sea, including the Danish Straits and the Sound, forms together with the Kattegat a transition zone and the only link between the Baltic Sea and the North Sea.
Due to its location in high latitudes, relative poor mixing and low salinity, ice-cover is a characteristic feature of the Baltic Sea. The Bothnian Bay (the north part of the Baltic) can be ice-covered for up to 6 months a year. Therefore, the productive season in northern parts of the Baltic Sea is only 4 to 5 months, compared with that of 8 to 9 months in southern sounds and the Kattegat.
There is high river discharge into the Baltic Sea, giving it a positive freshwater balance. The rivers Neva, Wisla and Oder are the largest rivers discharging to the Baltic Sea (see Map 5.11). Together they constitute about 23 per cent of the total freshwater inflow. The river discharges vary seasonally, the maximum runoff generally occurring in the spring during the snow-melting period.
The fact that the Baltic Sea is a land-locked basin with a relatively small water volume and a long residence time of water (30 years) makes it very susceptible to any kind of pollution load. The Baltic Sea ecosystem is subject to severe natural fluctuations as well as anthropogenic disturbances. During the recent decades there has been a clear tendency towards eutrophication.
Concern about the environmental problems of the Baltic Sea led in 1974 to the signing of the Baltic Marine Environment Protection Convention (Helsinki Convention) by the states surrounding the sea, and also resulted in the formation of the Helsinki Commission (HELCOM). A new Convention, revising the 1974 version, was signed in April 1992 in Helsinki and adds the states within the catchment area of the Baltic Sea: the Czech Republic, Norway (though not a member of HELCOM), the Slovak Republic and Ukraine. The Baltic Republics (Estonia, Latvia and Lithuania) also acceded. Today, monitoring is coordinated in all the Baltic Sea countries and periodic evaluations of the state of the sea are carried out. There have been two pollution load compilations, in 1987 and 1990. In the Ministerial Declaration of 1988 it was agreed that loads of nutrients, persistent organic substances and heavy metals should be reduced by 50 per cent. In 1991 the first periodic assessment of all coastal waters was undertaken by an expert group of HELCOM. The 14 states in the Baltic Sea catchment area, together with international financial institutions, have (in 1992) started the implementation of the Baltic Sea Joint Comprehensive Action Programme in order to improve the state of the sea during the next two decades.
The main contribution to this report on the Baltic Sea was made by the National Board of Waters and the Environment, Helsinki, and, unless otherwise stated, the main sources of information for this section were HELCOM (1987, 1990, 1991, 1992), Saxén et al (1989) and Voipio (1981).
Physical features |
The three important factors regulating the characteristics of the Baltic Sea ecosystem are salinity, temperature and oxygen concentration. The variation in salinity is large in the Kattegat, between 15 and 30 per thousand, but much smaller in the Baltic Sea itself. In the open areas of the Bothnian Sea the salinity is almost stable. In the Baltic proper the surface salinity varies between 6 and 8 per thousand, in the Gulf of Finland, between 2 and 7 per thousand, in the Bothnian Sea, between 4 and 6 per thousand and, in the Bothnian Bay, between 1 and 3 per thousand.
The surface temperature of the Baltic Sea shows a strong annual cycle. A spring and summer thermocline is developed over most of the Baltic Sea at depths between 15 and 20 m. The summer thermocline may be very sharp, and the stability at the thermocline layer can thus effectively suppress vertical mixing. During autumn and early winter the surface layers become uniform in temperature because of thermohaline convection and wind-induced mixing.
A clear natural trend of decreasing oxygen content of deep and bottom waters in the Baltic Sea basins has been demonstrated. The oxygen content of these waters is influenced by weak mixing across the halocline, by stagnant periods and by oxidation of organic matter. The lack of oxygen in the bottom is accompanied by a deterioration of the benthic community and a disappearance of higher forms of life. In the Baltic Sea, a continuous oxygen deficiency exists occasionally below the permanent halocline, except in the Bothnian Bay. The area of bottom water and sediments with reduced conditions for life varies naturally and was largest during 1968 and 1969, the current area being about 100 000 km2.
The freshwater supply to the Baltic Sea generates a brackish surface layer of outflowing water, and incoming subsurface flow from the North Sea forms layers of more saline deep and bottom waters. A dominating feature of the Baltic oceanography is, therefore, the marked permanent salinity stratification at approximately 60 m. The salt water inflow from the North Sea is made up of two principal components: a frequently occurring deep-water stream, and an irregular, intensive inflow connected with prevailing southwesterly winds. Usually the intensive inflows cause a successive renewal of the bottom water in the deep basins. A large inflow occurred in 1975 and 1976, followed by a period of stagnation which lasted until January 1993, when the last inflow of high saline water into the Baltic Sea occurred.
Biological features |
The Baltic Sea has a flora and fauna very poor in species due to its brackish-water. Most of the species are immigrants from neighbouring regions. Three different types of immigrants can be distinguished: marine organisms from estuaries and shallow coastal areas in the North Sea and the Atlantic, freshwater organisms from lakes, and glacial relicts. The genuine brackish-water species are also characteristic to the Baltic Sea. The number of marine species decreases steeply as one goes through the Danish Straits into the Baltic proper, and continues to decrease further up to the Gulf of Finland, and finally to the Bothnian Bay.
Of the 1500 macroinvertebrate species on the adjacent Norwegian coast, only some 70 species are found in the central Baltic Sea, and of the several hundred marine macroalgal species on the Norwegian coast, only 24 are found on the Finnish coast. Several organisms originating from freshwater or marine areas are reduced in size or altered in their morphology in the Baltic Sea.
Among the most threatened species in the Baltic Sea area are the three resident species of seals, the grey seal (Halichoerus grypus), the ringed seal (Pusa hispida), and the harbour seal (Phoca vitulina). The populations of these species have greatly reduced during the last decades, although some recovery of grey seal populations has been found recently. The number of white-tailed eagles (Haliaeetus albicilla) has also decreased. Today, only about 200 nesting pairs live in the Baltic Sea. As top predators, the seals and the sea eagles have been affected by organic micropollutants such as PCBs and other organochlorine compounds. The populations of seals have also been affected by hunting and modern fishing gear.
Inputs |
Contaminants enter the Baltic Sea from many sources: domestic sewage from about 77 million people; industrial and agricultural effluents; traffic; atmospheric deposition; and inflow from neighbouring seas.
The most significant industrial inputs come from: the paper and pulp processing industry; mining; steel and metal manufacture; and fertiliser production. Paper and pulp production in the Russian Federation and Sweden takes place mainly along the coastline, whereas it is more widespread throughout Finland and Poland. This area is responsible for 25 per cent of the world's total production of pulp, paper and board. The pulp mills were formerly major sources of mercury discharges, and the associated bleaching plants are the dominant source of organochlorine compounds arising from Sweden and Finland. Nitrogenous and phosphate fertilisers are produced in large quantities, leading to major discharges of nutrients and cadmium. In addition, Sweden is a major producer of iron and zinc ore, Poland of copper, lead and zinc, and Finland of iron, zinc and some silver.
Atmospheric deposition of some heavy metals to the Baltic Sea accounts for over 50 per cent of the total load. The upper sediment layers of the Baltic Sea have been found to contain concentrations of cadmium, mercury, lead, zinc, arsenic, copper and cobalt, several times higher than the pre-industrial layers. It is evident from data submitted to HELCOM that the dominating portion of the river-borne metal emissions originate in the Russian Federation, the Baltic States and Poland. The atmospheric deposition of many synthetic organic compounds is a more important source than riverine discharges, runoff or wastewaters. It is also believed that the acidification of freshwaters has increased the quantity of some metals entering the Baltic Sea.
The use of DDT has been banned in most industrialised countries since the 1970s. Now the main source of input of DDT into the Baltic Sea is through the atmosphere from areas where it is still in use. The manufacture and use of PCBs have decreased markedly since the 1970s because of regulatory action.
Petroleum hydrocarbons enter the Baltic Sea environment in many different ways. The total amount of oil products released into the Baltic Sea has been estimated to range from 21 kt to 660 kt per year. There are no natural seeps of oil. Transportation of oil and intensive shipping activities may be a larger source of petroleum hydrocarbons (10 per cent of total) than in other seas, but the highest input figures are from land (62 per cent) and atmospheric deposition (14 per cent) (Figure 6.9). As in other seas, oil spills in the Baltic are a danger to ecosystems, the effects depending, among other things, on the magnitude and location of the spill.
The major nutrient inputs are from runoff from agricultural land, from domestic and industrial wastewaters and from atmospheric deposition. This results in nutrient concentrations being higher in the coastal waters than in the open sea. About 40 per cent of the nitrogen load comes from atmospheric inputs, and about 90 per cent of the phosphorus input is from land areas. The total input of nutrients to the Baltic Sea from land-based sources, including the Danish Straits and the Kattegat, is estimated to be 46 kt of phosphorus per year, and 630 kt of nitrogen per year. The total loads of nitrogen and phosphorus into the Baltic have increased two-fold and four-fold, respectively, since 1950. It has also been estimated that 75 per cent of the total nitrogen load and 90 per cent of the total phosphorus load from land-based sources is anthropogenic in origin. Of the total nitrogen load arising from land-based sources (in 1990), it was calculated that approximately 43 per cent arose from the former USSR, 17 per cent from Poland, 15 per cent from Sweden and 11 per cent from Denmark. The corresponding figures for total phosphorus loads were 43 per cent from the former USSR, 27 per cent from Poland, 11 per cent from Denmark and 9 per cent from Sweden.
Agriculture is important in all the Baltic countries: generally high amounts of artificial fertilisers are used, and surplus amounts of by-products, such as manure, are produced. These are diffuse sources of pollution which are now recognised as a significant component of the total load entering the Baltic Sea.
Contaminant levels |
It has been estimated that even if all the riparian countries of the Baltic were immediately to reduce their discharges of contaminants by 50 per cent, it would still take 10 to 15 years before a measurable reduction in the concentration of some contaminants occurred in the marine environment.
According to the Second Periodic Assessment of the State of the Baltic Sea, the area most affected by pollution is the eastern part of the Gulf of Finland, which is heavily polluted by the city of St Petersburg and the Neva River. For example, 50 to 70 per cent of the wastewater load of the city is estimated to be discharged into the Neva River or the Neva Bay without any purification whatsoever. Other areas heavily affected by pollution are the Belt Sea and the Kattegat, where heavy blooms of diatoms and dinoflagellates, with subsequent oxygen deficiency in the deep water, have been reported.
In the northern and western riparian countries of the Baltic the application of modern technology has significantly reduced the emissions from industries over the last 10 to 15 years. On the other hand, in Central and Eastern European countries, many industrial plants are technologically outdated, and need to be rebuilt to meet the present environmental demands (see Chapter 12).
Investigations show that mercury concentrations increase from north to south in the Baltic, which supports the assumption that sources on the European continent are important contributors to the atmospheric mercury emissions in the Nordic countries. Total mercury content in water samples ranges from 2 to 630 ng/l in various sub-regions of the Baltic Sea, being the highest in the Bay of Gda´nsk (277­630 ng/l). The concentrations in Baltic fish (cod and plaice) normally range from 20 to 500 µg/kg wet weight.
In general, the regional variations in the cadmium content of water are fairly small. The mean concentration is approximately 30 ng/l, with some higher values reported from nearshore regions. The concentrations in fish (cod and herring) and in shellfish (mussels) have been reported to range from 2 to 200 µg/kg wet weight and 1300 to 10 800 µg/kg wet weight, respectively.
The concentrations of lead in fish and blue mussels in the Baltic Sea have shown a decreasing trend since the early 1980s. The concentration of lead in fish (cod and herring) from the Baltic Sea has been found to range from 50 to 1300 µg/kg wet weight. These findings are supported by decreasing dissolved lead concentrations in Baltic Sea water.
Typically the concentrations of copper and zinc in muscle tissue of fish are below 1 mg/kg and 10 mg/kg wet weight, respectively, whereas the corresponding liver concentrations are about 5 to 10 times higher. The levels of copper and zinc are not significantly different in the Baltic Sea from those in the North Sea.
The decreased use of PCBs is reflected by a clear downward trend in their concentrations in biota from the 1970s to the 1980s, and the concentrations now seem to have stabilised at approximately one third of the maximum level of the 1970s. The highest values of PCBs have been recorded in the northern part of the Baltic proper. Between 1980 and 1988 the mean levels of PCBs in liver of cod collected from the Baltic proper declined from approximately 8.5 mg/kg (lipid weight) to less than 2.5 mg/kg.
Investigations in 1983 revealed quantifiable concentrations of DDT in the water of the western Baltic proper and the Belt Sea. Since then the concentration in water has fallen below detection limits. There was also a clear downward trend for DDT concentration in biota of the Baltic Sea from the 1970s to the 1980s, but during the last decade the levels in biota have remained almost unchanged.
Toxaphene was introduced as a substitute after the use of DDT was prohibited. Today, the concentration of toxaphene in the Baltic Sea environment is of the same magnitude as that of DDT. Lindane (*HCH) has also been used as a substitute for DDT and today it can be found in all parts of the Baltic Sea environment. In 1983 the concentration of lindane in surface water from different parts of the Baltic Sea varied between 1.9 and 7.2 ng/l, compared with between 1.5 and 3.2 ng/l in 1988. This indicates a decline in surface water concentrations of lindane in the Baltic Sea.
The various control systems used for determination of the microbiological conditions, standards and categories applied differ between the countries in the Baltic Sea area.
The relative number of beaches where bathing is temporarily or frequently prohibited is markedly higher in the southern and eastern parts of the Baltic Sea than in the northern parts. For example, in Estonia the internationally known beaches in the Pärnu Bay have been closed because of microbiological pollution. In summer, values exceeding 100 000 E. coli per 100 ml have been recorded. Bathing was also banned from 25 bathing areas along the Baltic coast of Denmark in 1992 (CEC, 1993). However, overall in 1992 Denmark achieved compliance with the EU mandatory standard of 2000 faecal coliforms per 100 ml in 93 per cent of its designated bathing waters. Along the Baltic coast of Germany, 74 per cent of designated bathing waters were found to comply with the mandatory standard in 1992: this represented a marked improvement over 1991, when 63 per cent complied. In 1992, 15 bathing waters along the German Baltic coast were also closed for swimming.
The petroleum content in the surface water is at about the same level in all parts of the Baltic Sea but, compared to the North Sea and the North Atlantic, the levels are two and three times higher, respectively.
The Baltic Sea was for a long time considered to be an oligotrophic sea (nutrient poor), but lately that opinion has changed. In the Baltic proper, the Gulf of Finland and the Kattegat, nitrogen plays a key role as a limiting nutrient, whereas phosphorus is the limiting nutrient in the Bothnian Bay. In many areas of the Baltic Sea, the strong increase of phosphorus and nitrogen concentrations observed in the 1970s has stopped, with the exception of the Kattegat, the Gulf of Riga and the eastern Gulf of Finland, where the nitrogen concentrations are still increasing. Phosphorus and nitrogen concentrations have been at such high levels that the increasing biological production and sedimentation, followed by the microbial decomposition of the biogenic organic material, cause further deterioration of the oxygen conditions in basins of the Baltic Sea.
The areal radionuclide fall-out from the Chernobyl accident was unevenly distributed. In 1988 the surface water concentrations of Cs-137 were about 150 to 170 Bq/m3 in the Baltic proper, 120 to 230 Bq/m3 in the Gulf of Finland, 220 to 320 Bq/m3 in the Bothnian Sea, and about 120 Bq/m3 in the Bothnian Bay. In the gulfs of Finland and Bothnia the total amounts of Cs-137 were about five to six times higher in 1988 than before the Chernobyl accident, but only three times higher in the Baltic proper. The post-Chernobyl values of Cs-137 in pike were in 1988 about 10 to 40 times higher than the pre-Chernobyl values.
Biological effects |
Regardless of whether anthropogenic activities or natural variations play the dominating part in the nutrient increase, eutrophication has been identified as one of the most serious problems in the Baltic Sea area. Phytoplankton primary production seems to have doubled within the last 25 years in the area from the Kattegat to the Baltic proper. Today, unusually intensive algal blooms appear to occur more frequently in the Kattegat, in the Gulf of Finland and in the Belt Sea. Signs of eutrophication are also evident in the pelagic ecosystem of the Baltic Sea, although no drastic changes in species or population numbers have occurred there.
The increase in primary production and the subsequent increase in algal sedimentation and decomposition in the benthic system have decreased the oxygen content of the deep water. The decrease is no longer restricted to the deep basins but increasingly affects the shallower parts, and has resulted in drastic changes in the composition of benthic communities below the halocline. The phytoplankton composition has not changed drastically, but there is a tendency towards more frequent, and sometimes toxic, algal blooms.
The mass development of microscopic algae over large areas of the Baltic Sea drastically reduces the water transparency and sometimes also creates surface scums and odours. The present transparency shows pronounced decrease (by 2 to 3 m, generally) in the open coastal waters compared with that during the first half of the century. The depth at which Fucus vesiculosus, the bladder wrack, occurs has also decreased since the 1940s, apparently due to the increased turbidity of the waters. In addition, an increased dominance by filamentous benthic algae has been reported from the Swedish coast, leading to local adverse effects on the hatching of herring eggs.
Within the southern Kattegat, mortality of benthic macrofauna, mainly bivalves, has been observed in most seasons and years. This has been attributed to oxygen deficiency from the degradation of algal biomass. In 1988 the area of the Kattegat affected was 5600 km2 over which fish and the Norway lobster, Nephrops norvegicus, were either absent or found only in low numbers.
The Baltic fish stocks are a major living resource, with herring (Clupea harengus membras), sprat (Sprattus sprattus) and cod (Gadus morhua) representing about 90 per cent of the total catch. The catch of fish has increased steadily during the last 50 years, due mainly to increased fishing efforts and improved techniques. The annual yield has grown to about one million tonnes.
The environmental conditions in the Baltic influence the fish stocks considerably. For example, the stocks of cod are hampered by the increasing frequency of oxygen depletion and water containing hydrogen sulphide. The hatching of cod is affected by the gradually decreasing salinity in the spawning areas in the Bornholm Sea, the Gotland Deep, and the Gda´nsk Deep. Pelagic fish, like herring and sprat, benefit from moderate eutrophication.
Conclusions |
THE NORTH SEA |
General situation |
The North Sea is situated on the continental shelf of northwest Europe. It is open to the Atlantic Ocean in the north, to the English Channel in the south and to the Baltic Sea in the east (see Map 6.1). The climate of the North Sea is dominated largely by the Atlantic Ocean, and is therefore characterised by a large variety of wind directions and speeds, a high rate of cloudiness, and relatively high precipitation compared with other marine areas (425 mm on average per year for the North Sea proper). Its coastlines are shared between the UK, Norway, Sweden, Denmark, Germany, The Netherlands, Belgium and France. The catchment area of the rivers that flow into the North Sea (including the English Channel, Skagerrak and Kattegat) is about 850 000 km2 (165 million people). The catchment areas of the rivers Elbe, Weser, Rhine, Thames, Humber and Seine are densely populated, highly industrialised and farmed intensively. As a consequence these river systems are among the largest sources of contaminants and nutrients flowing from land into the North Sea.
The Oslo Convention (Convention for the Prevention of Marine Pollution by Dumping from Ships and Aircraft) and the Paris Convention (Convention for the Prevention of Marine Pollution from Land-Based Sources) provide the regulatory framework for the protection of the maritime area of the northeast Atlantic (including the North Sea) against pollution. The Oslo Convention came into force in 1974 and has been ratified by 13 European states; the Paris Convention came into force in 1978 and has also been ratified by 13 states. Finland has ratified only the Oslo Convention and Luxembourg has signed only the Paris Convention. The commissions established by the Conventions carry out programmes to assess the state of the marine environment and formulate policy to eliminate or reduce existing pollution and prevent further contamination of coastal waters and open seas. The commissions adopt appropriate measures to implement these policies, and assess their effectiveness on the basis of reports on their implementation and on the results of monitoring, thus adapting their policies and introducing new measures as appropriate.
In 1984, the perceived slow progress in reducing pollution of the North Sea resulted in a series of ministerial conferences on the North Sea attended by the environment ministers of all riparian countries. There have been three conferences to date; the last was in The Hague in 1990. At the end of each conference the ministers from the participating countries agreed objectives by way of declaration. These declarations are not legally binding and it is up to each government to decide how to achieve the stated objectives. Following the London Ministerial Conference Declaration, the North Sea Task Force (NSTF) was set up during 1988 with the following membership: Belgium, Denmark, France, Germany, The Netherlands, Norway, Sweden, the UK, the Commission of the European Communities and the International Council for the Exploration of the Sea (ICES). The NSTF set up an extensive monitoring master plan, providing the various countries bordering the North Sea with a responsibility for specific areas. The primary objective of the NSTF was to produce a new quality status report by the end of 1993, and to achieve this objective a monitoring master plan was drawn up in 1989 for implementation during 1990/91 (Portman, 1991). Each North Sea riparian state was to carry out a field monitoring programme at sea and in coastal waters for an agreed list of substances using agreed techniques.
Ministers from 15 European countries agreed in September 1992 a new Convention for the Protection of the North East Atlantic. Together with its action plan (which is subject to annual review) and the accompanying Ministerial Declaration, the new Convention will provide a comprehensive framework for the protection of the Convention's area. The Convention covers pollution from vessels, offshore installations, dumping, monitoring and assessment. The Convention's area is the North Sea and the North Atlantic Ocean.
Those North Sea states which are members of the European Union have also to comply with relevant directives aimed at controlling and eventually eliminating the discharge of the most toxic substances to the aquatic environment.
Unless otherwise stated, the source of information and contribution on the North Sea is from the secretariat of the North Sea Task Force (Ducrotoy, personal communication).
Physical features |
Together with the English Channel, the Kattegat and the Skagerrak, the North Sea covers 750 000 km2 for a volume of 94 000 km3. The sea has an average depth of 85 m, with depths increasing towards the Atlantic Ocean to about 200 m at the edge of the continental shelf. The Norwegian Trench reaches a maximum water depth of 700 m. The English Channel is shallow and deepens gradually from about 30 m in the Strait of Dover to about 70 m in the west. In the shallow North Sea, the entire waterbody derives from North Atlantic water and freshwater runoff in different admixtures. Most of the North Sea water flows through the Skagerrak before leaving through the Norwegian Coastal Current. The flow from the English Channel is from west to east, feeding a salty core of Atlantic water through the Strait of Dover.
Tidal currents are the most energetic feature in the North Sea, stirring the entire water column in most of the southern North Sea, and the English Channel. Tidal energy from the Atlantic Ocean also forces a persistent current with an anti-clockwise circulation (see Map 6.2). Tidal heights are greatly amplified in the bays of the French coast of the Channel, where they can reach 12 m.
Most areas of the North Sea are vertically well mixed in winter. In late spring, a thermocline is established over large areas; this separates the lower from the upper layer and a self-stabilising stratification develops (50 m in the northern North Sea, 20 m in the western English Channel). The deeper parts (Norwegian Trench and Kattegat) are permanently stratified. A coastal strip along the southern part of the North Sea, stretching from northern France to the German Bight, remains vertically mixed during the whole year.
Residence times vary greatly between areas and layers in the North Sea. In the Skagerrak, the residence time is much longer for the deeper water (one to three years) than for the near surface water (one month), and times of up to 3.9 years are observed along the British coast (Reid et al, 1988).
Biological features |
The distribution patterns of macroalgae and shore animals show that the North Sea is a transition area between the warm region in the southwest and the cold boreal region in the east and the north. A number of saltmarsh plants reach their northern limit of distribution in the Firth of Forth (Scotland) and their eastern limit in The Netherlands. In some coastal areas several types of plant populations have been reported to have declined, such as the seagrass Zostera marina in the 1930s and during the 1960s. Other plants, on the contrary, have dramatically increased in biomass in recent years. Green algae have developed on many tidal flats, for example Enteromorpha and Ulva species in the Wadden Sea and on the French Channel coast and in some British and Danish estuaries and lagoons.
In 1988, the phytoplankton bloom of the toxic flagellate Chrysochromulina polylepis resulted in the massive kill of epibenthic fauna along the Kattegat and Skagerrak coasts of Sweden and Norway. Phaeocystis has also caused nuisance foams on beaches of Germany, The Netherlands, Belgium and France. An increase of macrofauna in the Wadden Sea has been observed; for example, on tidal flats, the biomass doubled between 1990 and 1991.
The fish communities today reflect the impact of more than a century of intensive utilisation by the fisheries industry. In general, smaller, short-lived plankton-feeding species dominate; for example, sand eel (Ammodytes tobianus), dab (Limanda limanda), Norway pout (Trisopterus esmarki), herring (Clupea harengus) and mackerel (Scomber scombrus).
Many of the sea-birds in the North Sea are present in numbers that represent substantial proportions of their world population. Counts of bird populations breeding on British coasts indicate an increase in numbers during the last decades, and, in some cases, expansion of range; for example fulmar (Fulmarus glacialis), gannet (Sula bassana), lesser black-backed gull (Larus fuscus), guillemot (Uria aalge), great skua (Stercorarius skua), and Arctic skua (Stercorarius parasiticus). Some species, such as roseate tern (Sterna dougallii), herring gull (Larus argentatus) and black-headed gull (Larus ridibundus), have declined.
There is a long-term trend of increasing seal populations, but in 1988, phocine distemper virus caused a major mortality of mainly common seal (Phoca vitulina) and, to a lesser extent, the grey seal (Halichoerus grypus). For example, there was a 50 per cent reduction in the common seal population of the Wash on the east coast of England. Other populations along the UK's North Sea coast were probably less severely affected (Northridge, 1990). These two species of seal are the only ones to breed along the coasts of the North Sea. Since the disease outbreak, the number of seals has remained generally unchanged or has been increasing. At present, current estimates of the North Sea populations give a number of about 40 000 common seals and 47 000 grey seals.
The harbour porpoise (Phocoena phocoena) is the most common coastal water cetacean in the North Sea. Another species, the bottle-nose dolphin (Tursiops truncatus), is found in small resident populations at certain sites such as in the Moray Firth, Scotland. Other cetaceans show varying degrees of migratory behaviour, for the most part dependent on the movement of their food supplies. White-beaked dolphins (Lagenorynchus albirostris), for example, which breed off the Dutch coast in June and July, migrate to British waters to feed on herring and mackerel. Other species, particularly those in the northern and southwestern sectors of the North Sea, such as the minke whale (Balaenoptera acutorostrata) and the common dolphin (Delphinus delphis), visit these waters seasonally from the North Atlantic.
Inputs |
Rivers, the atmosphere and dumping of dredged material are the major input sources of contaminants into the North Sea (Figure 6.10). In 1990 riverine inputs were generally greater than inputs from direct land-based discharges. Where comparable data were available, land-based inputs in general exceeded atmospheric inputs and inputs via dumping, though for several contaminants (eg, cadmium and lead) the atmospheric inputs were of the same order of magnitude as the other land-based inputs. Riverine discharges of heavy metals such as cadmium and mercury into the North Sea are generally lower than those into other European seas; in the case of total nitrogen, loads are close to the highest. Figure 6.11 shows a country-by-country breakdown of riverine and direct inputs in 1990.
It is not yet possible to estimate how much of the riverine and direct loads are retained within estuaries or how much reaches the open sea. It should be noted that riverine loads (metals and nutrients) have both natural and anthropogenic contributions.
An important step towards the reduction and termination of dumping of industrial waste was taken in 1987 when France ceased its dumping of phosphogypsum. A further reduction occurred in 1989/90 when Belgium and Germany phased out the dumping of waste from the production of titanium dioxide. By the end of 1992, the UK had ended the dumping of industrial waste at sea. Disposal of sewage sludge at sea will be terminated by the end of 1998. The metal load of dredged material from estuaries, harbours and navigation channels is considerable. However, this load is made up of generally unquantified contributions from both natural and anthropogenic sources. The anthropogenic metal load from this source is, therefore, overestimated.
Besides the global fall-out from nuclear weapon tests, primarily from the 1960s anthropogenic inputs of radioactivity in the North Sea originate mainly from authorised releases from the reprocessing plants of Sellafield (UK, to the Irish Sea) and Cap de la Hague (France, to the English Channel). Soluble radioactivity from Sellafield is initially transported southwards and then northwards before leaving the Irish Sea via the North Channel between Ireland and Scotland. It then travels northwards along the west coast of Scotland, around the northern coast of Scotland and then southwards into the North Sea. In addition there are 14 other nuclear sites that discharge relatively small amounts of radioactivity into the tidal waters of the North Sea and English Channel. The amount of deposition of radioactivity in North European waters from the reactor accident at Chernobyl in 1986 was highest in the Baltic Sea, though the North Sea, the northwest coast of Scotland and the Irish Sea also received a significant input (Camplin and Aarkrog, 1989). As is the case for routine discharges from the nuclear industry, the dominant radionuclide was found to be Cs-137, accompanied by Cs-134 and other radionuclides.
An estimated maximum of 260 000 tonnes of oil enters the North Sea from all sources annually (GESAMP, 1993). The major source of oil inputs from the activities of the offshore oil and gas industry is the discharge of cuttings arising from the use of oil-based and water-based drilling fluids. Particular concentrations of drilling sites occur in the major production areas of the northern North Sea, in particular in the East Shetland basin (primarily oil-fields) and the south/central North Sea (primarily gas-fields). The annual input of oil from cuttings was in the range of 15 000 to 25 000 tonnes per year over the period 1984 to 1990. There are some indications of a general increase of sediment hydrocarbon levels in the East Shetland basin as a result of the concentration of production platforms in that area, whereas no such general elevations have been observed in the southern gas-field areas. Operational discharges of oil from shipping are estimated at 1000 to 2000 tonnes per year, about 0.5 to 2.0 per cent of the total input to the North Sea.
Dumping of dredged contaminated mud adds |
The cultivation of fish in coastal waters provides a direct input of organic matter, nutrients and other chemicals (eg, therapeutants) to the North Sea. Shellfish cultivation does not normally involve the addition of material such as feed. The main areas of fish farming activities around the North Sea are Shetland and Norway. The inputs of nutrients are small in relation to the natural flux of nutrients through the area by water movements.
Ninety to ninety-five percent of the nutrients entering the North Sea from land (excluding atmospheric deposition) originates from a few main rivers, more than half of them from the river Rhine. Nutrient inputs were maximal in the late 1970s and early 1980s for the Southern Bight, where they reached four times the input levels for total nitrogen and seven times those for total phosphorus, compared with 1930­40 levels. The importance of the second pathway of eutrophication by airborne nitrogen loads is now appreciated and can be in the same order of magnitude as the riverine sources in summer. In the central parts of the North Sea aerial transport is more important than riverine transport. Measurements suggest that atmospheric inputs of ammonia and nitrogen oxides are higher than previously thought.
Contaminant levels |
From sea water monitoring carried out by the North Sea Task Force (NSTF) in 1990 and 1991, the highest average values for lead, mercury and cadmium were in the central North Sea. A periodic or seasonal variation in the concentration of mercury and cadmium in sea water over the Dogger Bank has been described. Stormy conditions have been observed to lead to remobilisation of manganese, iron, cadmium and zinc following disturbance of the sediments. A plume of elevated and variable concentrations to the northeast of the Humber estuary was also described. The high metal concentrations found over the Dogger Bank and off the coast of England have been tentatively ascribed to airborne transport from land. Concentrations of lead in sea water were found to be lower in the eastern part than in the rest of the English Channel in springtime only, possibly due to removal of lead by phytoplankton during the spring blooms but coupled with reduced river inputs.
In 1990 the central parts of the North Sea had sediments with background levels of mercury. This implies that most of the mercury is trapped in estuaries and near coastal waters. Some elevated levels occur in the inner Skagerrak, the Norwegian Trench, the German Bight, to the north of the Dogger Bank and in estuaries surrounding the North Sea. The most notable areas of higher concentrations of lead in sediment are the Hardangerfjord (Norway), the Scheldt area, the Baie de Seine and the northeast coast of England. The northeast coast of England is heavily impacted from old lead mines. The concentrations of chromium are higher near the English coast, in the Skagerrak and in the Norwegian Trench.
The results of the Oslo and Paris Commission's (OSPARCOM) 1990 supplementary baseline study of contaminants in fish and shellfish identified the following areas with 'elevated concentrations' of metals in tissues (OSPARCOM, 1992a):
The highest inferred concentrations of tributyl tin (TBT) in 1991 and 1992 (through the study of abnormalities in the sexual organs of female dogwhelks, Nucella lapillus) were found along the coast from Denmark to Belgium (from 40 to greater than 128 ng/l). These can be compared with the relatively low levels found along the coasts of Sweden and Norway (1 to greater than 4 ng/l). Since controls were instituted, TBT concentrations have decreased markedly at estuarine locations frequented by yachts, but in harbours and dry-dock areas concentrations are variable and still often high.
The occurrence of numerous other compounds even in very remote regions shows that some trace organics are degraded so slowly, if at all, that long-range transport is possible. High concentrations (mainly of PCBs) have been observed in predators. Relatively high DDT concentrations, particularly in biota, still occur. Clear gradients occur in several estuaries (eg, Thames, Western Scheldt, Weser, Elbe, Göta). Work is required to determine the source of these compounds. Determination of the origin and the toxicological significance of relatively high levels of toxaphene observed in river fish and mammals' blubber is also required.
The highest levels of lindane (*HCH) in fish were from the southern North Sea and ranged from 2 µg/kg wet weight in cod muscle to 10 µg/kg wet weight in herring. Corresponding levels in cod liver were higher: between 20 and 50 µg/kg wet weight.
The results of the OSPARCOM 1990 supplementary baseline study of contaminants in fish and shellfish identified the following areas with 'higher concentrations' of organochlorines in one or more species/tissues (OSPARCOM, 1992a):
On different occasions, slicks of alkylphenols (nonylphenols and dodenylphenol), probably originating from ships' illegal discharges, have caused the death of sea-birds on the north coast of the Frisian Isles.
Outflow from chemical plant, |
The North Sea riparian countries who are members of the EU have to submit data annually on the quality of designated bathing waters in terms of microbial contaminants and physico-chemical parameters.
Oil spills can cause |
The highest concentrations of oil hydrocarbons in sediments are found around installations where oil-based drilling muds have been used. The concentrations in the sediments rapidly decline from the platforms out to a distance of about 500 m. High concentrations of polycyclic aromatic hydrocarbons (PAHs) in sediments were found in the Skagerrak and the Norwegian Trench. But PAHs appear to be widespread in sediments, including offshore areas such as the Dogger Bank and the Oyster Ground (off the Dutch coast).
Winter background concentrations of total inorganic nitrogen (TIN) (NO3+NO2+NH4) and soluble reactive phosphorus (SRP) in the central North Sea are around 0.14 mg N/l and 0.019 to 0.022 mg PO4-P/l, respectively, and in the Kattegat 0.056 mg N/l and 0.013 mg PO4-P/l, respectively (OSPARCOM, 1992b). Between 1985 and 1990, relatively high winter TIN and SRP concentrations were found along many coasts of the North Sea, including those of The Netherlands, Belgium, Germany, Denmark, Norway (in the Skagerrak and Oslofjord) and the UK (southeast coast). In these areas winter nutrient concentrations could be up to 11 times and 5 times greater than background levels of TIN and SRP, respectively.
The concentration of most of the artificial radionuclides shows a declining trend in sea water and biota in the North Sea. A number of different radionuclides have been detected in biota during recent years. The radionuclide of greatest (though still small) radiological significance is Cs-137. In cod liver, Co (cobalt)-60, Ag (silver)-110m and Ag-108m have been detected in extremely low concentrations. Elevated concentrations of Po (polonium)-210 have recently arisen in some localities from the phosphate ore processing industry. The concentration of the Chernobyl derived nuclides Cs-134 and Cs-137 were almost negligible in biota in 1990.
Biological effects |
Enhanced nutrient concentrations are associated with the large continental European rivers, and their areal extent depends on the influence of river water. The areas of concern are the continental coastal waters from France to Denmark, where the river water influence is confined to a narrow coastal water zone with water exchange offshore limited by hydrographical fronts. The major extension of the coastal water and hence of eutrophication is found in the German Bight and the Kattegat. Also, estuaries, fjords and bays with reduced water exchange may be showing signs of eutrophication. However, transport of nutrients bound to organic particles can reach further out into the sea, accumulating in sedimentation areas, such as the Norwegian Trench.
Potential effects of eutrophication include the enhancement of growth of phytoplankton with its consequences for the food-chain, including the zooplankton and the benthos. The dominance of certain species of Phaeocystis, with increasing cell numbers and duration of blooms, has become an issue of concern in some parts of the North Sea. For example, massive blooms of Phaeocystis gelatinous colonies are observed each year during spring in the area extending from the Strait of Dover to the German Bight. Dinoflagellates, like Dinophysis and Alexandrium species, which can cause shellfish poisoning, have developed large blooms since 1980. In 1988 a bloom of Chrysochromulina polylepis gave rise to serious fish kills in the Kattegat and Skagerrak. The 1988 bloom was a result of a specific combination of biological, physical and chemical conditions which could happen again in the future, although the probability is low.
Deficits in oxygen have been reported as a consequence of eutrophication in areas with a temporal density stratification of the water column which reduces turbulent water (and oxygen exchange): the Oyster Ground (temporarily), the German Bight, the Danish Jutland current, some Norwegian fjords (others are naturally anoxic) and Danish bays, and the southeastern Kattegat. Oxygen deficiencies have also been found in large areas in the bottom waters of the southeastern North Sea and in deep waters in the Kattegat.
The most obvious direct effect of fishing is the removal of fish from the ecosystem (for details see Chapter 24). At present, between 30 and 40 per cent of the total biomass of commercially exploited fish is caught in the North Sea each year; the stocks are therefore heavily exploited. The effect of fishing on such a complex ecosystem as the North Sea is, however, difficult to define with respect to the inherent natural variability.
In the course of the past century, a number of alien species have found their way into the North Sea. The accidental spreading of exotic species due to aquaculture or by ballast water from ships causes a potential environmental hazard. Some species, such as the slipper limpet, Crepidula fornicata, and the brown macroalga, Sargassum muticum, can be a threat (eg, by out-competing) to native species and can cause problems (eg, to boat users, through excessive growth).
Conclusions |
THE NORTH ATLANTIC OCEAN |
General situation |
For the purpose of this report the North Atlantic Ocean is defined as the area of the ocean lying between Europe's western seaboard and 42°W, and between 36°N and the Arctic Circle (see Map 6.1). It therefore includes the southeast coastline of Greenland, the coast of Iceland, the Faeroe Islands and the western coasts of the UK, Ireland, France, Spain and Portugal. It also includes the relatively shallow coastal waters of the semi-enclosed Irish Sea, the Celtic Sea, the Bay of Biscay and the Gulf of Cadiz. The Irish Sea in particular is subject to extensive monitoring by the UK and Irish authorities, and an overview of its current status has been recently compiled by the Irish Sea Study Group (ISSG, 1990).
The continental shelf ends at varying distances off the mainland, being relatively close to the northern shores of Spain and Portugal (less than 10 km in places) and more distant from the southwest peninsula of England (300 km). Within the continental shelf, water depths are generally less than 200 m; within the main body of the ocean, depths of 5700 m are found.
Major rivers discharging into the North Atlantic (see Map 5.11) include: the Guadiana and Guadalquivir in southwest Spain (Gulf of Cadiz); the Douro and Tajo on the west coast of Portugal; the Garonne and Loire on the west coast of France (Bay of Biscay); the Severn on the southwest coast of Britain (Celtic Sea); the Mersey (Irish Sea) and Clyde on the west coast of Britain; and the Shannon on the west coast of Ireland. The rivers on the mountainous north coast of Spain have relatively small catchments, though many are heavily industrialised. Major cities along the coastal zone include: Seville, Lisbon, Oporto, Bilbao, Bordeaux, Nantes, Dublin, Liverpool and Glasgow. Many river catchments are heavily industrialised, for example the River Mersey and the River Oria, whereas others have largely rural or agricultural catchments, for example the Shannon and the Loire. Human influence on the North Atlantic is most readily detectable within the relatively shallow coastal zone.
The Oslo Convention and the Paris Convention provide the regulatory framework for the protection of the maritime area of the northeast Atlantic against pollution (for details see the section on the North Sea). As for the North Sea, those EU countries with Atlantic coastlines have to comply with the requirements of the relevant EU Directives (76/464/EEC with six 'daughter directives') that concern the discharge of dangerous substances to surface waters and the subsequent quality of those waters.
Physical features |
The North Atlantic exchanges water with: the Arctic Ocean; the Norwegian Sea; the North Sea through the English Channel and to the north of the UK; and the Mediterranean through the Strait of Gibraltar. Surface water movements in the north of the ocean are dominated by the relatively warm and saline water from the main body of the Atlantic, flowing in the North Atlantic Current. This current flows on both sides of the Faeroes, directly and indirectly towards the Norwegian Sea with its lower water temperature. Here a sharp front is formed with the colder and less saline water from the East Iceland Current. Warm water moves along this front into the Norwegian Sea while the colder water from the north passes into the deep Atlantic troughs and flows southwards. Around Iceland the Arctic Current branches off from the warmer Gulf Stream. Iceland's northern and northwestern coasts are occasionally blocked by drift-ice from the north. The warmer Atlantic water moves west, beneath and outside the polar water. To the east, the Arctic water gives way to the East Iceland Current which flows in the direction of the Faeroes.
Open ocean salinity remains relatively constant at between 35 to 36 per thousand, any variation reflecting regional precipitation and evaporation patterns and the effects of ocean currents. Salinity of the water around Iceland, the UK and the Bay of Biscay is generally between 34 and 35 per thousand.
Biological features |
Extensive fisheries exist in the northern part of the ocean. The waters around Iceland are particularly productive, with the total annual catch of fish being approximately 1.5 million tonnes. The most important species caught are cod (Gadus morhua), redfish (Sebastes spp), haddock (Melanogrammus aeglefinus) and saithe (also known as coalfish) (Pollachius virens). There is growing concern over the deteriorating state of fish stocks in Icelandic waters and around the Faeroes. The reasons for the deterioration are not fully understood but could include fishing and periodic climatic variability. Aquaculture (eg, of salmon, Salmo salar, and trout species), is becoming more important in Iceland. Fisheries are also generally important within the other parts of the ocean, for example off the coasts of Spain, Portugal, France and the UK.
Inputs |
The atmospheric inputs of many metals (excluding mercury) to the North Sea, Baltic Sea and Mediterranean Sea are three to ten times higher than those to the open North Atlantic. In open ocean basins, however, the atmospheric flux of man-made contaminants is generally more important than the net input from rivers; this is partially because riverine materials are generally captured within the coastal zone. An estimate of the direct and riverine inputs into the northeast Atlantic Ocean during 1990 can be obtained from data submitted to the Paris Commission by the riparian Atlantic states. It was considered, however, that the loads are underestimates (OSPARCOM, 1992a) as, most significantly, there were no data from the Atlantic coasts of France and Spain, and, less significantly, none from Iceland and Greenland. (There is very little marine pollution arising from Iceland and Greenland.) Direct and riverine loads of metals to the North Atlantic are generally of the same order of magnitude as those to the North Sea, although the impact of the loads away from the coastal zone is generally very small compared with that of other seas, because of the North Atlantic's very large volume and energetic mixing and dispersion characteristics.
The disposal of solid, low-level radioactive waste in the North Atlantic ceased in 1982, by which time some 54 PBq (1.5 million Curies) of radioactive waste in 140 000 tonnes of packaged material had been disposed of at ten sites around 46°N, 17°W (Camplin and Aarkrog, 1989). The present and future risk to individuals from past oceanic dumping is considered to be extremely small. Nuclear waste reprocessing plants are sited at Sellafield (UK, on the Irish Sea) and Cap de la Hague (France, on the English Channel). In 1990, it was reported that 71 TBq (1900 Curies) of total beta radioactivity, 2 TBq of total alpha and 23 TBq of Cs-137 were discharged from the Sellafield site (Kershaw et al, 1992). Discharges from Sellafield have decreased significantly in recent years because of a progressive introduction of more advanced treatment measures (ISSG, 1990). Overall, this trend is expected to continue into the future. In addition, there are a total of ten nuclear power stations bordering the northeast Atlantic: one in France and nine in the UK. They generally discharge smaller amounts (than Sellafield) of radioactivity into the Atlantic.
Contaminant levels |
The areas considered by the Oslo and Paris Commissions in their 1990 quality report (OSPARCOM, 1992a) to be generally more contaminated were: the Gironde and Loire estuaries (France); the Spanish coast near Santander, La Coruna and the Navia estuary; and the Portuguese rias de Arosa, Pontevedra and Vigo.
Lead concentrations in the open North Atlantic are between 5 to 50 ng/l in surface samples that is, eight to ten times greater than in deeper water layers. Lead concentrations in sea water may have decreased over the last few years because of the increasing use of unleaded petrol. Cadmium and mercury concentrations in the open ocean are reported to range from 1.1 to 11.2 ng/l, and 0.6 to 1.2 ng/l, respectively (UNEP, 1990).
The results from the 1990 supplementary baseline study of contaminants in fish and shellfish (OSPARCOM, 1992a) identified the following areas with 'elevated' concentrations of metals:
'Higher' concentrations of organochlorines (PCBs) in one or more species were found by OSPARCOM along the west coast of France and the north coast of Cornwall (UK) . Neither of the two criteria, 'elevated' and 'higher' concentrations, however, implied any hazard to human health or the environment.
Chlorinated hydrocarbon concentrations in water are in the order of a few ng/l and are fairly uniformly distributed at all depths (UNEP, 1990), but with highest concentrations occurring in surface microlayers naturally enriched with lipids.
The only areas of the North Atlantic that are contaminated with microbial contaminants are along the coastal zone.
Within the North Atlantic Ocean the highest concentrations of Cs-137 (one of the most widespread and abundant artificial radionuclides arising from the nuclear industry) in sea water are found in the Irish Sea. Between 1980 and 1985 the average sea water concentration of Cs-137 in the Irish Sea was 730 Bq/m3 (arising from the Sellafield reprocessing plant), with relatively high levels off the west coast of Scotland (190 Bq/m3) and the North Sea (10 to 49 Bq/m3). Average concentrations in the open Atlantic, and for comparison, the Norwegian Sea, Barents Sea and Baltic proper, were 3.3 Bq/m3, 23 Bq/m3, 27 Bq/m3 and 18 Bq/m3, respectively (Camplin and Aarkrog, 1989). More recent surveys indicate lower levels of Cs-137 in the surface waters of the Barents and Kara seas: 7 and 6 Bq/m3, respectively (NRPA, 1993). As a comparison, the usual content of naturally occurring radionuclides in sea water is about 12 000 Bq/m3 mainly due to K (potassium)-40 but also from the uranium and thorium radionuclide decay series. The mean concentration of radionuclides arising from Sellafield in the Irish Sea is about 2000 Bq/m3 (Camplin and Aarkrog, 1989).
It has been estimated that the average annual radiation dose arising from natural sources in the UK is 1.87 mSv a year (Hughes and Roberts, 1984). As a comparison, the radiation doses to the most exposed groups of people are estimated to be: from six times less to twice 'natural' levels for the Sellafield discharges; 20 times less for Cap de la Hague; from 20 000 times less to six times less from the other nuclear sites; and 90 000 times less from the previous solid waste disposal in the northeast Atlantic Ocean (Camplin and Aarkrog, 1989) (see also Chapter 16).
Biological effects |
Most of the North Atlantic ecosystem is relatively unpolluted, and any adverse biological effects are limited to the coastal zones, often in semi-enclosed areas and bays, and estuaries bordering the main ocean. For example, there are concerns about the possible effects of eutrophication along the Irish Sea coasts, and the destruction of coastal habitats along the eastern coasts of the Atlantic.
Conclusions |
CONCLUSIONS AND THE WAY FORWARD |
This chapter has reviewed the current quality and status of Europe's seas. It has introduced and highlighted some problems common to Europe's seas and these have been expanded upon in the detailed description of each sea.
The review has established, as far as possible, the current status of the individual seas within Europe. It is clear that some of the seas have environmental problems associated with human activities. However, for many seas, the scale of the problems has not been fully quantified or understood. In order to improve this situation, detailed quality and status assessments are required. These are already periodically undertaken in many seas, for example the North and Baltic seas. Such assessments establish the scope of any environmental impacts and effects, and provide a quantitative baseline against which future quality can be compared and progress monitored. In other seas very few baseline data exist, or if they do exist they have not been collated in a coordinated way. Thus, for some of Europe's seas, establishing a baseline of quality in terms of input loads, contamination levels and biological status and effects would be a useful starting point for improvement. Indeed the Action Plan of the new Convention of the north east Atlantic requires a quality assessment of the Convention area by the year 2000, and for reports on constituent parts of the area before 2000.
As described in the introduction to this chapter, a comparison of riverine (or for some seas, land-based, if separate riverine data are not available) loads of contaminants has been made from available information. It is re-emphasised here that this should be considered as only approximate as there are likely to be differences in methodologies by which the data were derived, and, for some seas, data were unavailable for some of the different sources, or did not exist at all. Also for some seas, riverine or land-based sources may not necessarily be the most important in terms of total loads. The comparison undertaken is of gross loads, as it does not take into account non-conservative estuarine processes which would remove a proportion of the riverine loads before reaching the main body of the sea. Studies to quantify this loss are under - way, for example in the Mediterranean and North seas. In addition, no attempt has been made to separate the dissolved component from the particulate component of the load. This distinction has been defined for some seas, particularly for the Mediterranean Sea. The effect of allowing for non-conservative estuarine processes and the form of the contaminant on the assessment of loads reaching any sea is illustrated by the pink-shaded areas for the Mediterranean Sea in Figures 6.2b (mercury), 6.2d (lead) and 6.2e (zinc). It can be clearly seen that net riverine loads are potentially considerably less than gross loads.
Bearing in mind all the qualifying statements made above, it would appear from the available information (Figure 6.2ag) that:
The keystone to the collection of baseline data is the application of appropriate standard methods and quality control procedures. To help improve the situation, a joint initiative taken by marine institutes of EU and EFTA countries has, in 1993, led to the launching of QUASIMEME, a programme for quality assurance of information for marine environmental monitoring in Europe (Wells, 1993). This is essential for the provision of quantitative and comparable data on which judgements and decisions can be based with some confidence. It is evident that such baseline data have not been collected, or are not available, for many of Europe's seas, thus making quantitative comparisons of, for example, contamination levels between seas very difficult and somewhat qualitative.
To achieve quality improvements, there is a clear need for international collaboration and agreement, not only among the riparian states around a particular sea, but also involving the states within the catchment, and even those upwind in the case of atmospheric transport of contaminants. As has been described in the text, such international cooperation has been formalised in a number of conventions which cover a number of Europe's seas, for example, the Barcelona and Helsinki conventions.
The quality assessments presented here, based on the available information, indicate that the seas most at risk, or most affected by human activities, are the Black Sea and the Sea of Azov, and the Caspian Sea; and those least affected are the North Atlantic Ocean, the Norwegian Sea and the Barents Sea.
The key environmental issues and problems facing Europe's seas identified in this review are:
Problems of the coastal zone are identified here as a prominent environmental problem of concern for Europe, and discussed in Chapter 35. Marine eutrophication is linked to similar problems in freshwaters, and discussed in Chapter 33. Climate change is discussed in Chapter 27.