The Barents Sea is a shelf sea of the Arctic Ocean. Being a transition area between the North Atlantic and the Arctic Basin, it plays a key role in water exchange between them. Atlantic waters enter the Arctic Basin through the Barents Sea and the Fram Strait (Figure 3.1.1). Variations in volume flux, temperature and salinity of Atlantic waters affect hydrographic conditions in both the Barents Sea and the Arctic Ocean and are related to large-scale atmospheric pressure systems.

The Barents Sea is a shelf sea of the Arctic Ocean. Being a transition area between the North Atlantic and the Arctic Basin, it plays a key role in water exchange between them. Atlantic waters enter the Arctic Basin through the Barents Sea and the Fram Strait (Figure 3.1.1). Variations in volume flux, temperature and salinity of Atlantic waters affect hydrographic conditions in both the Barents Sea and the Arctic Ocean and are related to large-scale atmospheric pressure systems.

During 2013, the NAO index changed from negative values in January–March to slightly positive values which lasted the rest of the year. During winter (2012 –2013) northerly, northwesterly and northeasterly winds prevailed over the Barents Sea; during summer (April–August) southerly, southwesterly, and southeasterly winds prevailed. During autumn (September–October) wind direction shifted to easterly and northeasterly.

Air temperature data from the NOMADS (NOAA Operational Model Archive Distribution System http://nomad2.ncep.noaa.gov) website were averaged over the western (70–76°N, 15–35°E) and eastern (69–77°N, 35–55°E) Barents Sea. During 2012, positive air temperature anomalies prevailed in the Barents Sea, with the largest values (4–7°C) in the eastern part of the sea from January to April (Figure 4.2.2).

Volume flux in the Barents Sea varies within periods of several years, and was significantly lower during 1997–2002 than during 2003–2006 (Figure 4.2.3). During winter 2006, volume flux was at a maximum throuhout 1997-2013; whereas, during fall volume flux was anomalously low. After 2006, volume flux has been relatively low, particularly during spring and summer. During 2013, volume flux was generally larger than the 1997–2013 average.

Throughout 2013, positive surface water temperature anomalies prevailed in the Barents Sea. The largest anomalies (up to 4.0°C) were found in the eastern sea. Compared to 2012, the surface temperatures were much higher (by 1.3–2.7°C) in most of the Barents Sea, especially in its central and southern parts. In August–September 2013, during the joint Norwegian-Russian ecosystem survey, the surface temperatures were the highest since 1951 in about 50% of the surveyed area (ICES AFWG, 2014).

3.8.1 Marine mammals

During the 20 June to 14 August 2017 period, a sighting survey was conducted in the Barents Sea east of 28°E as part of a six-year mosaic survey of the Northeast Atlantic to estimate the regional abundance of minke whales and other cetaceans during summer. Coverage was adequate, except in the southeastern area where military restrictions re-stricted survey activity. The most often observed species was minke whale, followed by white-beaked dolphins, harbour porpoises, humpback whales, and fin whales. A few observations were also made of bowhead whales and beluga whales. Data have not yet been analysed but the qualitative impression was that minke whales were abun-dant in northern and eastern areas (Figure 3.8.1.1). Harbour porpoises were observed mostly in the southern parts of the area covered, and they are associated with the coastal areas along Kola and fjord systems. Humpback whales were sighted in the northwest, which is considered an early appearance in waters where they usually occur later in autumn in association with capelin distribution. White-beaked dolphins were, as usual, observed in southern and central parts of the survey area, especially over the Central Bank. It is noteworthy that a considerable number of harp seal observations — single animals and groups — were made in open waters north of about 74°N. During summer, ime harp seals are usually closely associated with the ice edge in the north.

Zoogeographical groups of fish species are associated with specific water masses. Rel-ative distribution and abundance of fish species belonging to different zoogeographic groups are of interest because these fish will respond differently to climate variability and change. Since they are not commercial species, fishing does not directly contribute to changes in abundance and distribution of these species. Different zoogeographic groups also tend to differ in their trophic ecology: many of the Arctic species are small, resident, and feed mainly on invertebrates; whereas, most boreal and mainly boreal species are migratory and piscivorous. Therefore, the relative abundance of these spe-cies should influence foodweb structure and dynamics. Comparing changes in relative abundance and distribution of species classified into zoogeographical groups based on established criteria from the literature, is relatively simple and does not rely on sophis-ticated statistical methods — like those used to study changes in the Barents Sea fish community, e.g. Fossheim et al., 2015 and Frainer et al., 2017.

Mesozooplankton biomasses

Mesozooplankton play a key role in the Barents Sea ecosystem by transferring energy from primary producers to animals higher in the food web. Geographic distribution patterns of total mesozooplankton biomass show similarities over time, although some inter-annual variability is apparent. Challenges in covering the same area each year are inherent in such large-scale monitoring programs, and inter-annual variation in ice-cover is one of several reasons for this. This implies that estimates of average zooplankton biomasses for different years might not be directly comparable.

In 2017, relatively high biomass (> 10 g m^-2) was observed in the Bear Island Trench (southwestern region), north of Svalbard/Spitsbergen; south of Franz Josef Land, and in large parts of the easterly survey-region including the South-eastern Basin. Relatively low biomass (< 3 g m^-2) was observed: in the westernmost area bordering the Norwegian Sea; in regions both south and east of Svalbard/Spitsbergen, and in the south-eastern corner of the survey area (Fig. 3.3.1). Relative to 2016, the most notable difference in 2017 was enhanced biomass in easterly parts of the Barents Sea. However, a large area just north of the Kola Peninsula was not covered in 2016, which complicates comparison.

Benthos

Benthos is an essential component of the marine ecosystems. It can be stable in time, characterizing the local situation, and is useful to explain ecosystem dynamics in retrospect. It is also dynamic and shows pulses of new species distribution, such as the snow crab and the king crab, and changes in migrating benthic species (predatory and scavenger species such as sea stars, amphipods and snails with or without sea anemones). The changes in community structure and composition reflect natural and anthropogenic factors. There are more than 3000 species

of benthic invertebrates registered in the Barents Sea (Sirenko 2001), but here we only present the megafaunal component of the benthos collected by trawl and registered (species, abundance and biomass) during the BESS survey. This includes mainly large bodied animals with long life spans. This includes mainly large-bodied animals with long life spans. This investigation was initiated in 2005 - only a short timeline relative to investigations related to plankton and fish. Accordingly, interpretation of long-term trends for megabenthic data must be pursued with caution.

Total biomass

Zero group fish are important consumers on plankton and are prey of other predators, and, therefore, are important for transfer of energy between trophic levels in the ecosystem. Estimated total biomass of 0-group fish species (cod, haddock, herring, capelin, polar cod, and redfish) was 1.92 million tonnes during August-September 2017; slightly above the long term mean of 1.76 million tonnes (Fig 3.5.1). Biomass was dominated by cod and haddock, and mostly distributed in central and northern-central parts of the Barents Sea.

Capelin, polar cod, young herring, and blue whiting constitute the bulk of pelagic fish biomass in the Barents Sea. Note that the acoustic target strength for blue whiting has been changed recently, and the time series has been recalculated. Total biomass of the main pelagic species (age 1 and older fish) in the Barents Sea in 1986-2017 has fluctuated between 0.5 and 9 million tonnes; mainly driven by fluctuations of the capelin stock. In 2017, cumulative biomass of capelin, herring, polar cod, and blue whiting was close to the long-term mean (Fig. 3.5.2).

Most Barents Sea fish species are demersal (Dolgov et al., 2011); this fish community consists of about 70-90 regularly occurring species which have been classified into zoogeographical groups. About 25% are Arctic or mainly Arctic species. The commercial species are all boreal or mainly boreal (Andriashev and Chernova, 1995), except for Greenland halibut (Reinhardtius hippoglossoides) that is classified as either Arcto-boreal (Mecklenburg et al., 2013) or mainly Arctic (Andriashev and Chernova, 1995).

Distribution maps for cod, haddock, long rough dab, Greenland halibut, redfish, and six other demersal fish species can be found at: http://www.imr.no/tokt/okosystemtokt_i_barentshavet/utbredelseskart/en, and are based on data from the BESS.

Mercury is the single most toxic element for seabirds. Mercury, along with Cadmium and lead, is one of the heavy metals that are of environmental concern as it can be toxic at levels only moderately elevated above natural ambient levels.

The surface sediments, i.e. the predominant sediment type of the upper ~ 50 cm of the seabed, form the uppermost part of a sediment sequence covering the rocks of the Barents Sea. This sediment sequence varying in thickness from a few to several hundred meters and was mainly deposited during the Quaternary (the last 2.6 million years), a time period where glaciations took place repeatedly.

The map service shows the grain size of seabed surface sediments of the Barents Sea. The map has been compiled in cooperation between the Geological Survey of Norway, Trondheim (Aivo Lepland), and OAO "SEVMORGEO", St. Petersburg (Aleksandr Rybalko), in the frame of the Norwegian-Russian Environmental Commission Workplan 2013-2014, OECEAN 5. Existing maps produced by various organizations served as a basis for the compilation.

This biotope map, covering the entire Barents Sea, has been compiled in collaboration between the Geological Survey of Norway, the Norwegian Institute of Marine Research (IMR) and the Russian Polar Research Institute of Marine Fisheries and Oceanography (PINRO) in the frame of the Norwegian-Russian Environmental Commission Workplan for 2011-2013 and 2013-2015.

The protected areas in Northwest Russia are divided into different categories of protection and management. In strict nature reserves (zapovednik) no economic activities are permitted. National parks are designated to nature conservation, research, educational and cultural purposes as well as controlled recreational activities. In national parks there are restrictions to the management of natural resources. Nature parks (prirodnyi park) are the equivalent of the Norwegian

Scientists, managers and commercial fishermen from Northern Norway, Finland and north-west Russia, White Sea area combined their efforts in the Kolarctic salmon project (2011-2013), with the aim of providing a better knowledge-base for the countries salmon management. Within this joint and unique effort bio-specimen were sampled along the North-Norwegian coast and in Russian Barents and White Seas generating the most comprehensive ecological and genetic datasets for Atlantic salmon (Salmo salar).