In the Barents Sea, the general pattern of circulation is strongly influenced by large-scale atmospheric circulation, inflow of waters from adjacent seas, bottom topography, tides, and other factors — all of which make it rather complicated and variable (Figure 2.3.1).

Climate conditions in the Barents Sea are determined by both Atlantic and Arctic climate systems, and the winter North Atlantic Oscillation (NAO) explains about 15-20% of the inter-annual variability in air and sea temperatures in the southern region. The climate oscillates between warm and cold states. The warm state is characterized by low air pressure over the Sea giving southwesterly winds which cause increased Atlantic inflow, higher seasonal temperatures, and more northward positioning of the Polar Front. 

Recent data indicate that more than 200 fish species representing 70 families occur in the Barents Sea (Dolgov 2004; Bogstad et al., 2008). Predominant families are: eelpout (Zoarcidae), snailfish (Liparidae), codfish (Gadidae), sculpin (Cottidae), flatfish (Pleuronectidae), and rockling, ling, and tusk (Lotidae). These families account for nearly 80% of the species regularly occurring in the Barents Sea, and more than 40% of the species recorded in this region (Dolgov et al., 2011).

Benthic ecosystems in the Barents Sea have considerable value, both in direct economic terms, and in their ecosystem functions. Benthic fauna are an integral component of the ecosystem, and benthic processes are tightly linked to total system dynamics. A total of 3,245 faunal taxa have been recorded — of this total, benthic macrofauna (60%) and meiofauna (34%) make up the majority — and more than 3,050 species of benthic invertebrates inhabit the Sea (Sirenko, 2001).

In this chapter we handle species of particular conservation concern due to their population status. These are the species present in the Barents Sea area and listed on the Global Red List (IUCN, 2008), the Russian Red Data book (Danilov-Danilyan et al., 2001 -  Russia is preparing a new edition of the Red Book of the Russian Federation, in which will change the lists and categories of the rarity of certain species, subspecies and populations of animals. But while the book is not published,

At present, fish are the best indicators of the health of the aquatic environment and of changes due to anthropogenic stressors.  The frequency of occurrence of diseases is a valuable indicator of the actual state of the Barents Sea ecosystem and can be useful to identify factors causing negative impacts. Monitoring long-term changes in the prevalence of diseases is needed to determine if/how they correlate with human activities and impacts (Karasev et al., 2011).

The Barents Sea has a number of water masses with the relatively warmer and more saline (>35) Atlantic Water which flows through the southern part of the Barents Sea, and the colder, less saline (34.4-35) Arctic Water to the north.  The boundary between these two water masses is marked by the Polar Front, and the different physical and chemical properties of these water masses influence the growth and development of the resident phytoplankton species (Loeng and Drinkwater, 2007).

The Barents Sea Region supports some of the largest concentrations of seabirds in the world. A total of 33 species breed regularly in the region, and about 20-25 million seabirds harvest approximately 1.2 million tonnes of biomass annually from the area.Seabirds spend most of the year at sea, visit land only to breed and find all their food in the marine environment (Schreiber and Burger, 2002). Typically, they form large breeding colonies on inaccessible places along the coast or on remote islands.

In the Barents Sea ecosystem, zooplankton forms a link between phytoplankton (primary producers) and fish, mammals and other organisms at higher trophic levels. The most abundant zooplankton species — calanoid copepods, krill, and hyperiid amphipods — form the major diet of herring, capelin, polar cod, and juveniles of other fish species. The Arctic front in the Barents Sea marks the boundary between the mainly Arctic zooplankton species (Calanus glacialis and Themisto libellula) and the Atlantic/subarctic species (C. finmarchicus, Meganyctiphanes norvegica, Thysanoessa spp and Themisto spp).

Typical of other oceans, 6 types of microbes (single-celled microorganisms) occur in the Barents Sea: Archaea, Bacteria, Viruses, Fungi, Protista, and Microbial Mergers. In biogeochemical cycles of the ocean, a multitude of processes are catalyzed by Bacteria and Archaea; functioning of these cycles in the Barents Sea do not differ qualitatively from those at lower latitudes. The carbon cycle serves well as an example of a biogeochemical cycle (Figure 2.4.1).

During the last half century, 2 major crab species were introduced to the Barents Sea: red king crab Paralithodes camtschaticus in the 1960s; and snow crab Chionoecetes opilio in the 1990s. Early this century(2000), species from the southern boreal areas have expanded northward to appear in the Barents Sea, including the snake pipefish Entelurus aequoreus, snail ray Dipturus linteus, whiting Merlangius merlangus, grey gurnard Eutrigla gurnardus, and megrim Lepidorhombus whiffiagonis.

Polar bears, seven pinniped species and five cetacean species reside full-time in the Barents Sea region. Eight additional whale species are regular seasonal migrants that come into the Barents Sea to take advantage of the seasonal, summer-time peak in productivity as the ice retreats northward. Three additional dolphin species are occasionally observed in the southern Barents Sea and sei whales (Balaenoptera borealis) have been observed north of 79° off the west coast of Spitsbergen, but these

According to the decree of the Murmansk regional government from December 25, 2013 № 768-PP / 20 "On the Strategy of socio-economic development of the Murmansk region till 2020 and for the period up to 2025", the role of tourism in economic and socio-cultural development of the region should be increased. The cruise tourism is recognized as a key area for further development. In order to develop the infrastructure to ensure regular and marine passenger transport, the investment project "Arctic harbor" will be implemented.

The Barents Sea is split by a natural geological border along the midline between Norway and Russia. This border separates a number of enormous gas fields identified on the Russian side from modest discoveries on the Norwegian side.Oil and gas exploration in the Barents Sea has developed slowly due to the costs and political risks involved. Approximately 0.3 billion Sm3 o.e. (standard cubic meters of oil equivalents) of extractable oil have been identified on the Norwegian side mainly as gas, with an estimated 1 billion m3 unidentified.

A wide range of shipping activities take place throughout the Barents Sea, involving merchant vessels, cruise ships, research and fishing vessels, ice-breakers, and naval and coast-guard vessels. Industries involved include ports and harbors, passenger transport, tourism, and offshore petroleum and mining operations. Shipping of oil and gas (and other hazardous cargo) was relatively stable with approximately 250 vessel transits per year between 2005 and 2008 (Stiansen et al., 2009).

Harvested demersal stocks in the Barents Sea and adjacent waters (ICES areas I and II) include cod, haddock, saithe, and shrimp. In addition, redfish, Greenland halibut, anglerfish, wolffish, and flatfishes (e.g. long rough dab, plaice) are common on the shelf and at the continental slope, and ling and tusk at the slope and in deeper waters. In 2012, catches of about 1,300 thousand tonnes are reported from the stocks of cod, haddock, saithe, redfish, Greenland halibut and anglerfish.

Physical conditions in the Barents Sea are largely determined by three main water masses: Coastal Water, (North) Atlantic Water, and Arctic Water. These three water masses are linked to three different current systems: the Norwegian Coastal Current, the Atlantic Current, and the Arctic Current. Climatic variability is determined by their properties and the activity of inflowing Atlantic Water. Variations in activity of these currents may be explained by external forcing, but may also be a result of processes

The composition and migratory habits of living organisms in the Barents Sea are determined by the contrast of the environmental conditions between the Atlantic and the local water masses (Matishov 1986a). The food web has 5-6 trophic levels: phytoplankton → zooplankton → pelagic fish → demersal fish → sea birds → marine mammals (including polar bear Ursus maritimus). Species diversity is relatively high compared to other Arctic seas. A total of 3,245 faunal taxa have

The Barents Sea is strongly influenced by human activity: historically, involving the fishing and hunting of marine mammals. More recently, human activities also involve marine transport of goods, oil and gas, tourism, aquaculture, and bioprospecting. Fishing is believed to have the largest human impact on the fish stocks in the Barents Sea, and thereby on the functioning of the whole ecosystem. However, observed variations in both fished species and the ecosystem as a whole are also the effect