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.

Figure 3.8.1.1. The survey area summer 2017. Black lines are transects conducted in primary search mode and black dots are minke whale sightings.

Although an estimate of minke whale abundance from the 2017 summer survey is not yet available, we have a series of abundance estimates from earlier surveys, which can be compiled to illustrate the status over a time of nearly 30 years (Figure 3.8.1.2). The summer abundance of minke whales in the Barents Sea is now about 50 000 animals and has been quite stable or increasing over the period. The sighting rate from the 2017 survey is the highest recorded which may confirm the apparent increasing trend at present.

Figure 3.8.1.2. Summer abundance of minke whales in the Barents Sea over the past nearly 30 years.

During the ecosystem surveys in the Barents Sea in August–October 2017 marine mam-mal observers were on all vessels. In total, 1518 individuals of 9 species of marine mam-mals were observed and an additional 46 individuals were not identified to species. The observations are presented in Table 3.8.1 and distributions in the Figures 3.8.1.3 (toothed whales) and 3.8.1.4 (baleen whales).

As in previous years, white-beaked dolphins were most common (more than 50% of all registrations). This species was widely distributed in the research area. Most records of white-beaked dolphin overlap with distribution of capelin and cod in the central area, and herring in the coastal area. The largest groups of white-beaked dolphin in-cluded up to 20–40 individuals.

In addition to white-beaked dolphins, other observed species of toothed whales in-cluded: sperm whale (Physeter macrocephalus); harbour porpoise (Phocoena phocoena); and killer whale (Orcinus orca). Sperm whales were observed in deeper waters along the continental slope in the western part of the survey area. Harbour porpoises were mainly observed in the southeastern area between 70° and 73°13'N; their distribution overlapped with recorded herring aggregations. Killer whales were only observed in the western part of the 2017 survey area.

Table 3.8.1.1. Number of marine mammal individuals observed from the RV “Johan Hjort”, “G.O. Sars”, “Vilnyus” during the ecosystem survey in 2017.

Baleen whales — minke (Balaenoptera acutorostrata), humpback (Megaptera novaean-gliae), and fin whales (Balaenoptera physalus) — were also abundant in the Barents Sea, and comprised 39% of all marine mammals observed. Minke whales were widely dis-tributed in the survey area; dense concentrations in the northwestern areas overlapped with capelin aggregations. In southern areas, minke whales overlapped with herring and juvenile cod aggregations. In 2017, minke whale abundance exceeded levels ob-served during the 2012–2015 period.

Figure 3.8.1.3. Distribution of toothed whales in August–October 2017.

Figure 3.8.1.4. Distribution of baleen whales in August–October 2017.

In 2017, humpback whale abundance was lower than observed in 2013 and 2015. Most humpback whales were observed — in groups of up to 12 individuals or as single spec-imens — on Great Bank and at White Island, and overlapped with dense concentra-tions of capelin. Minke whales and fin whales were recorded in the same area. More fin whales were observed during the 2017 survey; mostly in capelin areas east of Sval-bard Archipelago and Great Bank.

In 2017, the only pinnipeds observed were harp seals and bearded seals (Erignathus barbatus). Harp seals were recorded on Great Bank, while bearded seals occurred north-ward of White Island. Polar bears (Ursus maritimus) were not observed during the 2017 survey, most likely due lack of the ice in the surveyed area.

3.8.2 Seabirds

About six million pairs from 36 seabird species breed regularly in the Barents Sea (Bar-rett et al. (2002), Table 3.8.2.1). Allowing for immature birds and non-breeders, the total number of seabirds in the area during spring and summer is about 20 million individ-uals. 90% of the birds belong to only 5 species; Brünnich’s guillemot, little auk, Atlantic puffin, northern fulmar and black-legged kittiwake. The distribution of colonies is shown in Figure 3.8.2.1. Colonies in the high-Arctic archipelago are dominated by little auks, Brünnich’s guillemots and kittiwakes. These birds utilize the intense secondary production that follows the retreating sea ice. Little auks feed mainly on lipid rich Calanus species, amphipods and krill while Brünnich’s guillemots and black-legged kittiwakes feed on polar cod, capelin, amphipods and krill. The seabird communities, as well as their diet change markedly south of the polar front. In the Atlantic part of the Barents Sea, the seabirds depend more heavily fish, including fish larvae, capelin, I-group herring and sandeels. The shift in diet is accompanied by a shift in species composition. In the south, Brünnichs’ guillemots are replaced its sibling species, the common guillemot. Large colonies of puffins that largely sustain on the drift of fish larvae along the Norwegian coast, are found in the southwestern areas.

Figure 3.8.2.1. Major seabird colonies in the Barents Sea. Data compiled from SEAPOP (www.seapop.no), Fauchald et al. (2015), Anker-Nilssen et al. 2000 and The Seabird Colony Registry of the Barents and White Seas.

Table 3.8.2.1. Seabirds in the Barents Sea sorted by breeding population size in decreasing number. Breeding pairs are from Strøm et al. (2009). Observations on BESS 2017 are the ob-servations from Norwegian and Russian vessels during the ecosystem survey in 2017.

Population monitoring in Norway and Svalbard has revealed a marked downward trend for several important seabird species the last 30 years, including puffin, Brünnich’s guillemot and kittiwake (Figure 3.8.2.2). The population of common guil-lemot was decimated in the 1980s mainly due to a collapse in the capelin stock com-bined with low abundance of alternative prey. The population has increased steadily since then. The status and trends of the large populations of seabirds in the Eastern Barents Sea is less known.

Figure 3.8.2.2: Size and trends of puffin, guillemots and kittiwake populations in the Western Barents Sea (Norway and Svalbard incl. Bjørnøya). Data from Fauchald et al. (2015).

Recent tracking studies (see www.seatrack.no) show that after the breeding season, parts of the adult populations of kittiwakes, puffins and common guillemots from col-onies along the Norwegian coast migrate into Barents Sea to feed, possibly increasing the number of birds in the area in August and September. However, during September and October the populations of Brünnich’s guillemots and little auks from colonies in West-Spitsbergen and Bjørnøya start their migration westward, crossing the Norwe-gian Sea to reach their wintering grounds in the Northwest Atlantic. The large eastern populations (birds breeding in East Spitsbergen, Franz Josef Land and Novaya Zem-lya), however, seem to over-winter in the southern Barents Sea. Kittiwakes do also mi-grate out of the Barents Sea during winter, while common guillemots stay in the south-eastern part of the Barents Sea throughout the non-breeding period. Finally, only a few puffins from the eastern colonies over-winter in the southern Barents Sea, while the rest of the population roam over large areas in the central North Atlantic. Most seabird populations return to the colonies in late winter or early spring.

Broadly, the spatial distribution of seabirds during the ecosystem survey reflects the climatic gradient from a boreal Atlantic climate with common guillemots, puffins, her-ring and black-backed gull in the south and west, to an Arctic climate with little auks, Brünnich’s guillemots and kittiwakes in the north and east (Figure 3.8.2.3). Seabirds have been surveyed uninterruptedly on Norwegian vessels in the western part of the Barents Sea since 2004. Based on the minimum annual survey extent, the abundance (Figure 3.8.2.4) of different species and the centre of gravity of the spatial distribution (Figure 3.8.2.5) was calculated for each year.

Figure 3.8.2.3. Density of seabirds during the Barents Sea ecosystem surveys in 2016 (top) and 2017 (bottom). Left panel is the distribution of auks (little auk, Bünnich’s guillemot, puf-fin and common guillemot). Right panel is the distribution of shipfollowers (fulmar, glaucous gull. Kittiwake, black-backed gull and herring gull).

Note the large fluctuations in the abundance estimates from the at-sea surveys (Figure 3.8.2.4). These fluctuations do not necessarily reflect the observed population trends from the colonies (cf. Figure 2). This discrepancy could be related to the fact that the at-sea abundances are influenced by annual differences in migration pattern which would mask the general population trends. There is not yet an evidence for a wide-spread “borealization” (Fossheim et al. 2015) of the seabird communities in the Barents Sea, although there is a tendency for a slight northward displacement of puffins, kitti-wakes and glaucous gull (Figure 3.8.2.5). During the last 14 years, the different seabird species seem to stay relatively fixed within their respective geographic niche.

Figure 3.8.2.4. Abundance of auks (left) and shipfollowers (right) in the Western Barents Sea during the ecosystem surveys 2004-2017.

Figure 3.8.2.5. Center of gravity in the north direction of the distribution of auks (left) and shipfollowers (right) in the Western Barents Sea during the ecosystem surveys 2004-2017. Black line indicates the position of Bjørnøya.

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.

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

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.

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).

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).