Introduction:
The Barents Sea is relatively shallow, with an average depth of 230 m. The oceanographic conditions are strongly affected by the variable inflow from the Norwegian Sea. Recent water temperatures have been the highest levels observed. Pollution levels in the sea are generally very low, but toxic substances, which are transported into the area by currents, are found to accumulate in some top predators such as birds and mammals.
Zooplankton production is high, but variable. A wide variety of benthic organisms are also an integral component of the ecosystem. Important pelagic fish species are capelin, polar cod, herring, and blue whiting. Capelin is a key species in the ecosystem, and undergoes large fluctuations in abundance (0.1–7.0 million tons). These fluctuations largely are due to recruitment failure caused by the predation of strong herring year classes on capelin larvae.
Cod is the most abundant demersal fish species, while haddock, redfish, Greenland halibut and long rough dab are also abundant. The most important marine mammals in the Barents Sea ecosystem are minke whales and harp seals.
Oceanography and Climate
Temperatures in the Barents Sea reached record high levels in February 2008, but anomalies decreased throughout the year, and by autumn temperatures were colder than during the year before. Considering annual means, temperatures were a bit lower and ice cover a bit more extensive than in 2007. This was primarily due to a strongly reduced inflow of Atlantic water relative to previous years.
Water masses in the Barents Sea have been extraordinary warm since 2000. Temperatures during 2008, however, were slightly cooler than during 2007. This is likely due to strong reductions in the transport of Atlantic water into the Barents Sea. Ice cover in the Barents Sea during 2008 was low.
Contaminants
Although wind and ocean currents transport various contaminants into the Barents Sea, levels observed in marine organisms were generally low. The major exception is observed in top predators, such as polar bears, where contaminants from persistent organic pollutants (POPs) aggregate.
IMR routinely carries out monitoring of contaminant levels in the Barents Sea. This includes sampling sea water, sediments, and marine biota. Substances analyzed include: a range of hydrocarbons; POPs; and radio-nuclides. The 2009 report presents examples of radio-nuclide levels found in seawater, sediments, marine biota, and selected POPs (PCB, DDT, HCH, HCB) in cod liver. These studies indicate that contaminant levels in the Barents Sea are generally low.
