The Arctic Ocean
European Environment Agency
Europe's biodiversity - biogeographical regions and seas
Biogeographical regions in Europe
The Arctic Ocean
- home of the walrus
The sea area treated in this chapter is referred to as the Arctic Ocean, and it is identical with OSPAR region I (boundaries are indicated in Map 1). Roughly, it is the sea area between Scandinavia, Greenland, Novaya Zemlya and the North Pole, including the European part of the Arctic Ocean, the Barents Sea, the Norwegian Sea, the Greenland Sea and the Icelandic Sea.
Table 1: Statistics for the European part of the Arctic Ocean
Source: OSPAR 2000
Warm, high-salinity surface water from the Atlantic enters the European Arctic Ocean, where it is cooled and sinks to great depth. The cold water penetrates southwards at great depths and contributes to the oxygenation of the world’s deep oceans. This is a simplified description of the formation of deep and intermediate waters in the European Arctic Ocean, one of the most important features of the global oceanic circulation. Variability of temperature in cold Arctic waters is small but important. The Arctic Ocean alternates between warm and cold states. The length of these states may vary, but fluctuations with periods of 3–5 years are most frequent and the variations appear to be generated by cyclic events rather than to represent progressive changes. The huge Russian rivers Pechora and Northern Dvina have great impact on the Barents Sea with their annual input of ca. 246 km3 of freshwater (AMAP web site).
The Greenland-Scotland Ridge forms a barrier between the deep-water masses north and south of it (Map 1). A shelf extending northward from Iceland forms the floor of the Iceland Sea. The mid-ocean ridge forms the boundary between the deep basins in the Greenland and Norwegian Seas. These basins have relatively open connections to the Arctic Ocean. The shallow Barents and White Seas are the widest ocean shelf areas in the world. The Barents Sea is linked to the Nordic Seas through the gap between Norway and Svalbard, and is also open northwards to the wider Arctic Ocean.
Map 1: Arctic Ocean physiography (depth distribution and main currents in the European part)
Note: The sea area between Greenland
and Norway is often called the Nordic Seas.
The area includes many fjords with rivers flowing into them. In Norway, the coast is uneven with a number of bays, coves, inlets, islands and islets. The Norwegian fjords are relatively long, narrow and deep, normally with a sill that greatly affects circulation and contributes to making fjords sensitive to a build-up of contaminants from the land. The coast east of the Kanin Peninsula in the Russian Federation is low and temporarily flooded. North-western shores of the White Sea are rocky while south-eastern shores are flat and low. The coast of Iceland consists mainly of rock or sand, with fjords that are often more open and funnel-like than the Norwegian ones. The Faeroe Islands have mainly vertical cliffs rising directly from the sea, a result of intensive erosion by waves. The eastern coast of Greenland is mostly similar to the Norwegian coast. Icebergs, mainly from huge calving glaciers in the Greenland fjords, follow the coastal current along the Greenland coast and into the Atlantic Ocean. Much of the central Arctic drift ice forms in winter in the marginal seas. The main exit for Arctic Ocean ice is through the Fram Strait between Greenland and Svalbard.
The main influences on the biodiversity of the Arctic Ocean are:
The cold, the extreme variation in light conditions and the extensive ice cover in the area create unique marine ecosystems. The strong gradients in environmental parameters result in marked differences in the geographical distribution of different types of living organisms. Some of these live on the border of their tolerance. Melting and freezing of ice form rich habitats close to the sunlit sea surface. The wide continental shelves provide large shallow areas, such as the Barents Sea, where freshwater from north-flowing rivers creates estuarine conditions. Arctic marine food webs can be very complex, but with only a few key species connecting the different levels (OSPAR 2000). Bottom-dwelling communities can be very rich along the ice-free coasts, where kelp forests and seaweed become nursing grounds for many fish species (AMAP 1998).
The primary producers of the European Arctic Ocean are 200–300 species of microscopic plants called phytoplankton; half of these are diatoms (Zenkevitch 1963). When the phytoplankton bloom is in phase with the grazing from plankton animals (the zooplankton), most of the bloom is grazed. When out of phase, most of it is lost and not utilised in the pelagic food web because it sinks to the bottom. The spring phytoplankton bloom starts when stratification of the water masses is established and the light level is sufficient.
The zooplankton is characterised by a few dominant species. Crustaceans form the most important group, among which the copepods of the genus Calanus play a key role in the sub-Arctic and Arctic ecosystems. The 3–4 mm long Calanus finmarchicus is the most important contributor to the biomass and has a unique ecological position as the main food for herring, capelin, Arctic cod and other plankton-feeders. Krill is another group of crustaceans playing a significant role in the pelagic ecosystem as food for both fish and sea mammals.
Some organisms, such as ice algae, live in crevices in the snow and ice and can quickly take advantage of the light in spring. Among the ice-living forms are colony-building diatoms and blue-green algae that utilise the scant light that penetrates the ice. In addition to the prominent algal component, sea-ice biota also include other life forms such as bacteria, colourless flagellates, foraminifers, ciliates, nematodes, copepods, amphipods, krill and fish (Horner 1990, Horner et al. 1992).
Sediments in shallow seas and along coasts teem with life. There are, as an example, ca. 2 500 benthic species in the Barents Sea. Crustaceans, sponges and molluscs take advantage of dead plankton and other organic material falling to the sea floor from the productive surface waters. Some fish, eider ducks, bearded seals and walrus feed mostly on this benthic fauna. The benthic food chain is shorter than the one at the ice edge (AMAP 1998). The shallow communities are divided in two main biogeographic regions: the Arctic region and the east Atlantic temperate sub-region, both containing several biogeographic provinces and sub-provinces (see sea introduction chapter). The deep-sea fauna belongs biogeographically to the Atlantic region, but is separated into two sub-regions by the Greenland-Scotland Ridge: warm-water benthic species in the Atlantic sub-region and cold-water species in the Arctic sub-region.
Coral communities associated with the Lophelia coral are now recognised as important benthic features in the deeper waters of the Nordic Seas (Fosså and Mortensen 1998). L. pertusa has been recorded from the north-east Atlantic more frequently than anywhere else in the world. L. pertusa reefs have been identified as an ecosystem of particular importance which is diverse and very sensitive, but which has poor recoverability and is declining in extent, declining in quality, threatened and in need of action (see Map 2 in north-east Atlantic Ocean chapter). The deep-living Lophelia reefs can grow to 35 m high, be hundreds of metres wide, and reach 13 km length off Norway. Some reefs in Norway are found to be 8 000 years old. Studies of Lophelia reefs in the north-east Atlantic revealed a total of 744 associated species, but the number is probably far higher.
The macroalgae are dominated by large brown algae (Table 2). The diversity of macroalgae and the maximum depth to which they grow is generally lower at high latitudes than in temperate regions (Lüning 1990).
Table 2: Characteristic macroalgae of the eastern and western part of the European Arctic Ocean
The continental shelves along the Nordic countries are the spawning area of many fish species. The larvae spread from the spawning grounds into the open ocean. Some of the species perform long annual migrations between the feeding and the wintering areas. A selection of the fish species in the European part of the Arctic Ocean is briefly described in Table 3.
Table 3: Information on selected fish species in the Arctic Ocean
The European flying squid (Todarodes sagittatus) occurs irregularly near the Norwegian coast where it feeds on migrating herring. It has been commercially exploited since 1993 and catches have fluctuated between 0 and 352 tonnes/year (ICES in prep). Another abundant species, the Boreal-Atlantic gonate squid (Gonatus fabricii), lives in the deep North Atlantic after spending the first year in the surface layers. It is an important prey for the bottlenose and sperm whales, and is also consumed by cod, herring and salmon. Squids are used as bait as well as food for humans. Generally, understanding of squid stock dynamics remains poor.
The European Arctic Ocean is one of the most important seabird regions in the world. The breeding population of seabirds in this area exceeds 25 million individuals having major impact on the region’s ecosystem. Species may be grouped into surface feeders and pursuit diving sub-surface feeders. The prey species of Arctic seabirds is dominated by a limited number of key species, which makes the birds vulnerable to variations in the abundance of prey species. Many seabirds are specialised top predators and their sensibility to changes in the lower trophic levels makes them suitable as indicators of changes in the marine environment. The numerous and widespread guillemots are examples of such species.
There are two main groups of whales, both represented in the Arctic Ocean: Baleen whales are primarily plankton feeders, while toothed whales prey on fish, squid and seals (Table 4). Many baleen whales perform long and regular breeding migrations to warm and temperate waters during the winter, and migrate to cold water at higher latitudes to feed on the rich zooplankton supplies during the summer season.
Photo: White whale or beluga
Note: The white whale, or beluga, is the most common of the Arctic whales. It was commercially harvested in Svalbard up to 1960, and in the period 1945–1960 approximately 3 300 white whales were caught. Today these whales are totally protected.
Table 4: Population status of some species of whales occurring in the Arctic Ocean; abundance estimates are uncertain
Source: Isaksen et al. 1998b with references, OSPAR 2000
In addition to the walrus, seal species found in the northern Atlantic north of 62°N are harbour seal, grey seal, harp seal, hooded seal, ringed seal and bearded seal. All seals are carnivorous, feeding on fish, krill, amphipods or bottom animals.
During the spring most seals collect in large aggregations to breed and mate, and they usually also gather during the moulting period. Harp seals, in particular, are very concentrated during breeding and moulting periods and have traditionally been extensively hunted. The pups, 'white coats', have been particularly important economically.
Note: The walrus is a giant among seals in the Arctic Ocean. It has a disjunct circumpolar distribution and has been heavily exploited for its ivory tusks, blubber and thick skin. It has long considered endangered in the European part of the Arctic Ocean, but is now protected under the Bern Convention, Appendix II.
Polar bears are found in ice-covered areas and they have a circumpolar distribution. The Svalbard-Barents Sea population suffered from over-harvesting until 1973, but is now believed to have fully recovered. This population is unique in that it is the only one not currently hunted. The main food of polar bears is seals, which they catch on the ice. The distribution of bears is therefore highly dependent on the distribution of the ice and the seals. The polar bear is protected by Norwegian law and also under the Bern Convention, Appendix II.
The largest and economically most important fish populations in the Arctic Ocean are cod, herring, capelin and blue whiting. The largest fisheries for the deep-water shrimp (Pandalus borealis) are in Icelandic waters. Squids are being fished for use as bait as well as for consumption by humans.
*Norwegian spring spawning; ** autumn/winter 1996-97; ***1998
Source: OSPAR 2000
Hunting for ringed and harp seal, together with whaling for fin and minke whale, is part of the hunting tradition and of great importance to the population of Greenland, but the International Whaling Commission (IWC) has agreed on catch limits of stocks subject to aboriginal subsistence whaling. Hunting for small cetaceans like the narwhale and the beluga is regulated bilaterally with Canada. In the Faeroe Islands, non-commercial whaling for long-finned pilot whales has been carried out for more than a thousand years although recent regulations have banned some traditional practices and equipment. In the Barents Sea limited hunting for bearded seal is permitted to the native people. The Norwegian minke whale quota for 1999 was 753 animals. Norway has entered a formal reservation against the 1982 IWC moratorium on commercial whaling.
Seabirds have traditionally been caught in the Faeroe Islands, and also in Iceland and the Barents Sea, but the catch is now partly regulated.
In some areas various types of gastropods and mussels, like Iceland scallop (Chlamys islandica) and ocean quahog (Artica islandica), are harvested for human food and bait in long-line fisheries. Kelp and other brown seaweed are harvested for alginate production along the coast of Iceland and the west coast of Norway.
Fish farming in the Arctic area is limited, but production is expected to increase significantly. Norway is the biggest producer with 220 000 tonnes in 1997. Farming of shellfish includes only limited amounts of blue mussels, scallops and oysters.
Many species in the northern regions live and spawn at the limits of their distribution. Even moderate changes in temperature will have a pronounced effect on the distribution, growth, and success of spawning to a number of organisms. The results of scientific research and indigenous knowledge have increasingly documented climatic changes that are more pronounced in the Arctic region than in other regions of the world or are critical to our understanding of global-scale climatic processes (ACIA 2000):
So far, there is no consensus of scientific opinion on whether these changes are due to anthropogenic influences or to natural variation.
Most fish stocks in remote areas of the open sea are nowadays being exploited, and fish catches doubled several times during the last century. The collapse in commercial fish stocks is due to the combined effect of poor recruitment, increased natural mortality, reduced growth and over-exploitation. The problems increase when the exploited species are food for other commercial species.
The three most important fish populations in the Barents Sea are herring, cod and capelin and these three species are biologically strongly linked: young herring feeds on capelin larvae, while young cod eats the mature capelin. Thus, years with good recruitment of herring and cod have resulted in poor capelin recruitment and subsequently a low capelin stock, which severely shrinks the young cod’s diet. After the collapse of the Norwegian spring spawning herring stock in 1969, capelin recruitment was high and the interest in capelin fishery increased. Fishery was large until the mid 1980s when the stock collapsed. The consequences of this collapse are described in the case study below.
The second largest shark, the basking shark, is threatened by overfishing because of low to very low productivity. Documented fisheries in several regions have usually been characterised by rapidly declining local populations as a result of short-term fisheries exploitation, followed by very slow or no recorded population recovery (Froese and Pauly 2001). In the Arctic Ocean, Norway and Iceland have a small harpoon fishery for this species. Fishbase has listed it as a vulnerable species (Froese and Pauly 2001), and it is now protected in some territorial areas but not in the Arctic Ocean. The FAO (Food and Agricultural Organization of the United Nations) is leading a plan to establish international shark fishery management strategies for a number of species, including the basking shark.
Illustration: Basking shark
Source: Petter Wang
Figure 1: Norwegian catches of basking shark
Source: Froese and Pauly 2001
Other major impacts of fishery activities on biodiversity are as follows.
Bycatch is thought to be the primary mortality factor for several seabird species in the Barents Sea region (Follestad and Runde 1995). The common guillemot population on the Norwegian coast has shown a marked decline in population, which can be accounted for by mortality in fishing nets. In some areas breeding colonies have decreased by more than 95 % since they were first counted in the 1960s. This may, to a large extent, be explained by drowning in cod and salmon nets (see Anker-Nilssen et al. 2000). Little is known about the bycatch of seabirds in the Barents Sea region, but the problem is probably most relevant for populations breeding at the Norwegian coast.
Offal and discards from fishing provide food for scavengers. It is difficult to obtain exact figures on the extent of discards and therefore difficult to assess the effects on the biological communities. The dramatic population increase of the fulmar is, however, at least partly due to the rapid increase in food available from discards (Ollason and Dunnet 1988).
• Effects on benthos
The extent of damage from trawling within the Arctic Ocean is not well known. Effects of disturbance on vulnerable species and habitats, e.g. deep-water coral reefs, have been identified; further assessment of these effects along the Norwegian coast will be carried out. The extensive sponge communities in the Barents Sea are affected by trawling, but the wider consequences of this are still unknown (OSPAR 2000).
Whaling from the 17th century up to the 19th century led to the depletion of several whale species in the Arctic region. The recovery of the over-exploited species has been very slow for some species, such as the bowhead and the blue whale. Elements of the ecosystems have probably been permanently altered by intense whaling.
There is today very limited commercial whaling. Aboriginal subsistence whaling is permitted from Greenland for fin and minke whales. A major area of discussion has been the killing of whales for scientific purposes; Iceland carried out a four-year research programme between 1986-89, killing 292 fin and 70 sei whales. Norway carried out a seven-year research programme starting in 1988 to study and monitor minke whales in the north-east Atlantic; 289 whales were killed.
• Fish farming
In some local areas emissions from fish farms represent the largest anthropogenic input of organic matter, but no wider effects of this have been reported. One of the most serious current problems of fish farming is the spread of salmon lice from farmed to wild fish. Generally, lice infection on salmon seems to have increased, but how much of this is contributed by the spread of lice from farmed to wild salmon has not been identified. The most effective strategy for controlling lice infections in salmon farms appears to be the use of several species of the small fish wrasse (Labridae) together with chemicals. Wild salmon stocks are currently falling while salmon farming is growing rapidly. Escaped farmed salmon could pose a threat to the genetic diversity of the Atlantic salmon.
Photo: Goldsinny wrasse (Ctenolabrus rupestris)
Note: The small Goldsinny wrasse (Ctenolabrus rupestris) is used to remove salmon lice from farmed fish: 1 wrasse per 50 salmon is recommended.
Pollution from offshore oil and gas activity is primarily related to accidental oil spills and operational discharges of oil and chemicals. In the Arctic, environmental conditions increase the general risk and the consequences of accidents. The south-western part of the Barents Sea was formally opened for exploratory drilling for oil in 1989, but to date there is no oil or gas production north of the Arctic Circle (66° 33Ž N). Drift ice, and in particular the marginal ice edge, is important for Arctic marine life. An oil spill entering such an area can cause significant harm to animal populations. The potential effects on seabirds and marine mammals of petroleum activity in the Barents Sea have been evaluated (e.g. Isaksen et al. 1998a) and birds like auks and ducks, and marine mammals such as the polar bear, are especially vulnerable to such activity. It is, due to the great potential for oil exploration, likely that oil will pose a much more serious threat to marine life in the Barents Sea in the future (Anker-Nilssen et al. 2000).
Shipping in the Arctic poses a greater risk of accident than shipping further south, because of the extreme climatic conditions of ice, darkness and fog; these also complicate clean-up work and thus increase the risks of environmental damage. Ships are themselves point sources for long-time/low-level emissions to air as well as discharges to sea. Oil films are frequently detected on the surface in areas of intense shipping. Other possible impacts of shipping include the introduction of non-indigenous species, noise and physical disturbance, and the biological effects of antifoulants. Constructions of harbours and industrial installations will destroy habitats in the coastal zone. The environmental impact of increased shipping in the Arctic has recently been thoroughly evaluated in relation to the opening of the Northern Sea Route from Europe to Japan along the Siberian coast (e.g. Brude et al. 1998).
Many organisms in the Arctic Ocean are under stress as a result of environmental characteristics such as low temperatures and extreme seasonal variations in light. Such conditions also make them especially vulnerable to environmental contaminants. For example, since the ability to gather and store energy is a prime requirement for survival during the dark and cold winter, fat plays a more important role in animal metabolism in the Arctic than in temperate regions, and this, in turn, increases the importance of biomagnification of fat-soluble contaminants. Bioaccumulation of contaminants is also accentuated in many Arctic animals by long lifespans.
So far, there is no evidence that contaminants are causing effects on population levels in the Arctic (Knutzen 1999). Recent investigations within the area are, however, indicating that contaminants can have effects on biological communities. There is evidence of:
The Sellafield reprocessing plant on the north-west coast of England, the Tsjernobyl accident in 1986 and trial blasting of nuclear weapons are the most important sources of the anthropogenic radionuclides found in the Arctic marine environment (Strand et al. 1997). The mobility of radionuclides accumulated in sediment is, however, low and levels of radionuclides in fish, seals and whales collected in Greenland waters and in the Barents Sea since the early 1960s are very low (AMAP 1998) and pose a minor threat to marine biodiversity.
Significant threats to the environment from radionuclides in the Arctic are today mainly associated with the potential for accidents in the civilian and military nuclear sectors.
The most significant ecological effects of non-indigenous species are competition with indigenous and/or commercially important species for food, space or light, and pathogenic effects. Introduction of harmful planktonic algae is considered a major global problem, but problems in the Arctic are not serious compared with the more southern areas. Only a limited number of non-indigenous organisms have been reported in the European Arctic Ocean (Table 6).
Table 6: Non-indigenous marine species in the Arctic Ocean
Source: Hopkins 2001, JNCC 2001, OSPAR 2000
There are few quantitative estimates of ecological or economic impacts from these species. The bay barnacle, introduced as fouling on ships, may change the habitat and compete for space with indigenous species. About 12 500 king crabs, a commercially important shellfish in the northern Pacific, were introduced to the Barents Sea in the 1960s. This big crab (>10 kg) has now migrated westwards to the coasts of northern Norway where the population is increasing. Studies have been made of the yearly output in northern Norway (Olsvik 1996), but not of the effects on or interactions with native species which have no economic significance. There is concern that the crab may have a negative ecological impact on the native species (see Hopkins 2001).
Figure 2: King crab (Paralithodes camtschatica) in Norway, stock abundance estimates
Source: Toresen 1999
Photo: King crab
Source: Stein Johnsen/www.uvfoto.no
Polar bear, walrus, harbour seal, otter, 11 species of whales and 14 seabird species are the marine Arctic animals on the Norwegian Red List. Five of the whale species are internationally (IUCN–The World Conservation Union) listed as endangered or critically endangered (the Svalbard stock of bowhead whales moved from endangered to critically endangered on the 2000 List). The only fish species listed as critically endangered by IUCN in the European Arctic is the common sturgeon. No fish species are listed as endangered. Blue skate, Atlantic halibut and acadian redfish are, however, considered endangered in European Arctic waters by Fishbase (Froese and Pauly 2001). Generally, the status of non-commercial fish stocks is not well known. In addition, loggerhead and leatherback turtles are listed as endangered and critically endangered, respectively, by IUCN. No marine invertebrates are found on the IUCN Red List for this area. Lack of knowledge about this huge group of animals makes evaluation of the status of most marine invertebrates very difficult.
Nature protection is mostly land based, and the Arctic countries have identified gaps in their protected area systems and have proposals for additional protected areas. Among the most poorly covered are marine areas, coasts and fjords. However, even with all the proposals implemented there would still be major gaps in coverage of critical habitats and representative ecosystems (CAFF 2000a). Habitat conservation is a declared priority in CAFF’s Work Plan.
National legal instruments for marine conservation in the Arctic have been summarised by CAFF (2000b).
International nature protection conventions and programmes extend protection to several marine species in the Arctic Sea on the basis of international and national Red Lists. Gaps in species protection have been identified by CAFF. As an example, 16 marine mammals in Russia are considered endangered, but the ranges of these mammals are basically unprotected (CAFF 2000a). Most Red-Listed species in the Arctic are protected under the Bern Convention (Appendix II or III), which is ratified by Iceland, Greenland (Denmark) and Norway, but not Russia.
Commercial hunting and fishing is generally strictly regulated in the European Arctic marine areas. There is a common understanding that an optimal and sustainable development of the marine resources must include regulations. The size of quotas is mainly based on previous scientific stock estimates and international agreements. ICES (International Council for the Exploration of the Sea) and IWC (International Whaling Commission) are in this context important providers of scientific information and advice on living resources and their harvesting.
Since 1997, AMAP has had a ministerial mandate to continue to carry out 'monitoring, data collection, exchange of data on impacts, assessment of the effects of contaminants and their pathways, increased ultraviolet-B (UV-B) radiation due to stratospheric ozone depletion, and climate change on Arctic ecosystems'. CAFF developed a 'Strategic plan for the conservation of Arctic biological diversity' in 1998, and the plan identifies monitoring as one of the key objectives. Early in 2000 CAFF/AMAP arranged a workshop to advance the work on biodiversity and monitoring of climate change in the circumpolar Arctic region.
The International Arctic Science Committee (www.iasc.no/) is a non-governmental organisation, which advises the Arctic Council and promotes several programmes of direct relevance to biodiversity. The Arctic Ocean Sciences Board (www.aosb.org) is another non-governmental body that supports multinational and multidisciplinary natural science and engineering programmes, e.g. the International Arctic Polynya Programme.
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For references, please go to http://www.eea.europa.eu/publications/report_2002_0524_154909/regional-seas-around-europe/page111.html or scan the QR code.
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