Editing Norwegian Sea (section)

== Flora and fauna ==
The Norwegian Sea is a transition zone between [[Boreal ecosystem|boreal]] and Arctic conditions, and thus contains flora and fauna characteristic of both climatic regions.<ref name=b366>[[#refBlindheim|Blindheim, 1989]], pp. 366–382</ref> The southern limit of many Arctic species runs through the North Cape, Iceland, and the center of the Norwegian Sea, while the northern limit of boreal species lies near the borders of the Greenland Sea with the Norwegian Sea and Barents Sea; that is, these areas overlap. Some species like the [[scallop]] ''[[Chlamys islandica]]'' and [[capelin]] tend to occupy this area between the Atlantic and Arctic oceans.<ref name="Skreslet103">[[#refSkreslet|Skreslet & NATO, 2005]], pp. 103–114</ref>

=== Plankton and sea bottom organisms ===
Most of the aquatic life in the Norwegian Sea is concentrated in the upper layers. Estimates for the entire North Atlantic are that only 2% of biomass is produced at depths below 1,000 metres and only 1.2% occurs near the sea floor.<ref name="Schäfer81">Andrea Schröder-Ritzrau ''et al.'', ''[https://books.google.com/books?id=iVAzudOPt1kC&pg=PA81 Distribution, export and alteration of plankton in the Norwegian Sea Fossiliziable]''. [[#refSchaefer|Schaefer, 2001]], pp. 81–104</ref>

The blooming of the [[phytoplankton]] is dominated by [[chlorophyll]] and peaks around 20 May. The major phytoplankton forms are [[diatoms]], in particular the genus ''[[Thalassiosira]]'' and ''[[Chaetoceros]]''. After the spring bloom the [[haptophytes]] of the genus ''[[Phaecocystis pouchetti]]'' become dominant.<ref name="ICES5">[[#refICES|ICES, 2007]], pp. 5–8</ref>

<gallery class="center" widths="160px" heights="130px">
File:Hyperia.jpg|[[Hyperiidea]]
File:Pandborealisind.jpg|Shrimp ''[[Pandalus borealis]]''
File:Lophelia pertusa.jpg|''[[Lophelia pertusa]]''
File:Meganyctiphanes norvegica.jpg|''[[Northern krill|Meganyctiphanes norvegica]]''
</gallery>

Zooplankton is mostly represented by the [[copepods]] ''Calanus finmarchicus'' and ''Calanus hyperboreus'', where the former occurs about four times more often than the latter and is mostly found in the Atlantic streams, whereas ''C. hyperboreus'' dominates the Arctic waters;<ref name="ICES5"/> they are the main diet of most marine predators.<ref name="Skreslet103" /> The most important krill species are ''[[Northern krill|Meganyctiphanes norvegica]]'', ''[[Thyssanoessa inermis]]'', and ''[[Thyssanoessa longicaudata]]''.<ref name="ICES5"/> In contrast to the Greenland Sea, there is a significant presence of [[calcareous]] plankton ([[Coccolithophore]] and [[Globigerinida]]) in the Norwegian Sea.<ref name="Schäfer81"/> Plankton production strongly fluctuates between years. For example, ''C. finmarchicus'' yield was 28 g/m<sup>2</sup> (dry weight) in 1995 and only 8 g/m<sup>2</sup> in 1997; this correspondingly affected the population of all its predators.<ref name="ICES5"/>

Shrimp of the species ''[[Pandalus borealis]]'' play an important role in the diet of fish, particularly cod and [[blue whiting]], and mostly occur at depths between 200 and 300 metres. A special feature of the Norwegian Sea is extensive coral reefs of ''[[Lophelia pertusa]]'', which provide shelter to various fish species. Although these corals are widespread in many peripheral areas of the North Atlantic, they never reach such amounts and concentrations as at the Norwegian continental slopes. However, they are at risk due to increasing [[trawling]], which mechanically destroys the coral reefs.<ref name="ICES5"/>

=== Fish ===
[[File:Clupea harengus.png|thumb|Atlantic herring]]

The Norwegian coastal waters are the most important spawning ground of the [[Atlantic Herring|herring populations]] of the North Atlantic, and the hatching occurs in March. The eggs float to the surface and are washed off the coast by the northward current. Whereas a small herring population remains in the fjords and along the northern Norwegian coast, the majority spends the summer in the Barents Sea, where it feeds on the rich plankton. Upon reaching puberty, herring returns to the Norwegian Sea.<ref name="Blindheim382">[[#refBlindheim|Blindheim, 1989]], pp. 382–401</ref> The herring stock varies greatly between years. It increased in the 1920s owing to the milder climate and then collapsed in the following decades until 1970; the decrease was, however, at least partly caused by overfishing.<ref name="Wefer"/> The biomass of young hatched herring declined from 11 million tonnes in 1956 to almost zero in 1970;<ref name="Skreslet103"/> that affected the ecosystem not only of the Norwegian Sea but also of the Barents Sea.<ref name="Stokke">Olav Schram Stokke ''Governing High Seas Fisheries: The Interplay of Global and Regional regime,'' Oxford University Press, 2001 {{ISBN|0-19-829949-4}}, pp. 241–255</ref>

[[File:Mallotus villosus.gif|thumb|[[Capelin]] is a common fish of the Atlantic-arctic transitional waters]]
Enforcement of environmental and fishing regulations has resulted in partial recovery of the herring populations since 1987.<ref name="Wefer"/><ref name="Skreslet103"/> This recovery was accompanied by a decline of capelin and cod stocks. While the capelin benefited from the reduced fishing, the temperature rise in the 1980s and competition for food with the herring resulted in a near disappearance of young capelin from the Norwegian Sea.<ref name="Helfman321">Gene S. Helfman ''Fish Conservation: A Guide to Understanding and Restoring Global Aquatic Biodiversity and Fishery Resources'', Iceland Press, 2007 {{ISBN|1-55963-595-9}}, pp. 321–323</ref> Meanwhile, the elderly capelin population was quickly fished out. This also reduced the population of cod – a major predator of capelin – as the herring was still too small in numbers to replace the capelin in the cod's diet.<ref name="Helfman321"/><ref name="NRC">National Research Council (U.S.). Committee on Ecosystem Management for Sustainable Marine Fisheries: Sustaining Marine Fisheries, National Academies Press, 1999, {{ISBN|0-309-05526-1}}, p. 46</ref>

[[File:Micromesistius poutassou Gervais.jpg|thumb|Blue whiting]]

[[Blue whiting]] (''Micromesistius poutassou'') has benefited from the decline of the herring and capelin stocks as it assumed the role of major predator of plankton. The blue whiting spawns near the British Isles. The sea currents carry their eggs to the Norwegian Sea, and the adults also swim there to benefit from the food supply. The young spend the summer and the winter until February in Norwegian coastal waters and then return to the warmer waters west of Scotland.<ref name=b366/> The Norwegian Arctic cod mostly occurs in the Barents Sea and at the [[Svalbard]] Archipelago. In the rest of the Norwegian Sea, it is found only during the reproduction season, at the Lofoten Islands,<ref name="Blindheim382"/> whereas ''[[Pollachius virens]]'' and [[haddock]] spawn in the coastal waters.<ref name=b366/> [[Mackerel]] is an important commercial fish. The coral reefs are populated by different species of the genus ''[[Sebastes]]''.<ref name="ICES5"/>

=== Mammals and birds ===
[[File:Gonatus fabricii 600.jpg|thumb |Armhook squid ''[[Gonatus fabricii]]'']]
Significant numbers of [[minke whale|minke]], [[Humpback whale|humpback]], [[Sei whale|sei]], and [[orca]] whales are present in the Norwegian Sea,<ref name="Hoyt">Erich Hoyt: ''Marine Protected Areas for Whales, Dolphins, and Porpoises'' Earthscan, 2005 {{ISBN|1-84407-063-8}}, pp. 120–128</ref> and [[white-beaked dolphin]]s occur in the coastal waters.<ref name="Dolphins138">[[#refKlinowska|Klinowska, 1991]], p. 138</ref> Orcas and some other whales visit the sea in the summer months for feeding; their population is closely related to the herring stocks, and they follow the herring schools within the sea.<ref name="ICES5"/> With a total population of about 110,000, minke whales are by far the most common whales in the sea. They are hunted by Norway and Iceland, with a quota of about 1,000 per year in Norway. In contrast to the past, nowadays primarily their meat is consumed, rather than fat and oil.<ref>[https://web.archive.org/web/20061001084616/http://www.norway.org.uk/policy/environment/whaling/whaling.htm Norwegian minke whaling]. the Norwegian Ministry of Foreign Affairs. norway.org.uk</ref>

The [[bowhead whale]] used to be a major plankton predator, but it almost disappeared from the Norwegian Sea after intense whaling in the 19th century,<ref name="Skreslet103"/> and was temporarily extinct in the entire North Atlantic. Similarly, the [[blue whale]] used to form large groups between Jan Mayen and Spitsbergen, but is hardly present nowadays.<ref name="Johnson95">[[#refJohnson|Johnson, 1982]], pp. 95–101</ref> Observations of [[northern bottlenose whale]]s in the Norwegian Sea are rare.<ref name="Dolphins320">[[#refKlinowska|Klinowska, 1991]], p. 320</ref> Other large animals of the sea are [[hooded seal|hooded]] and [[harp seal]]s and [[squid]].<ref name="Skreslet103" />

Important waterfowl species of the Norwegian Sea are [[puffin]], [[kittiwake]] and [[guillemot]]. Puffins and guillemots also suffered from the collapse of the herring population, especially the puffins on the Lofoten Islands. The latter hardly had an alternative to herring and their population was approximately halved between 1969 and 1987.<ref name="Jennings">Simon Jennings ''et al.'' [https://books.google.com/books?id=_J_E8O33E2gC&pg=PA297 Marine Fisheries Ecology], Blackwell Publishing, 2001 {{ISBN|0-632-05098-5}}, p. 297</ref>