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Living Marine Resources

Phytoplankton

The monitoring of phytoplankton biomass, density and species composition as well as nutrient dynamics in the North Sea and Skagerrak provides information about the effects of human activity and climatic changes. IMR carries out detailed monitoring along transects ― Hanstholm–Aberdeen, Utsira–Start Point and Torungen–Hirtshals ― and during a regional covering in April/May. The divergences in 2008 from the long-term means, as seen on the Torungen–
Hirtshals transect, were a much smaller (time and amount) spring bloom, lower overall chlorophyll concentration during the summer, and the absence of autumn bloom on the Norwegian side of the Skagerrak. On the Danish side of the Skagerrak, the spring bloom in 2008 occurred later than normal (approximately 1 month). The chlorophyll concentrations were lower during summer, and there was an autumn bloom in October, two months later than normal. On the Hansholm–Aberdeen transect, 2008 was more or less similar to 2007. The average annual modeled primary production in 2008 in the North Sea was well above the average for the period 1985–2008.

Zooplankton

Zooplankton is an essential link between the base of the food web and higher level consumers. Thus, the zooplankton monitoring program provides information that improves our understanding of ecological processes in the North Sea. In 2008, the plankton monitoring in the North Sea and Skagerrak included sampling along three fixed transects (Utsira–Start Point, Hanstholm–Aberdeen and Torungen–Hirtshals), and one regional covering of Skagerrak and the central and northern areas of the North Sea. In April 2008, the average zooplankton biomass in the northern North Sea was dominated by the large herbivorous copepod Calanus finmarchicus, but with an increasing proportion of C. helgolandicus west- and southward in the area. The average biomass of zooplankton in coastal waters in Skagerrak in 2008 was close to the mean value for 1994–2008.

In Skagerrak, the divergences in 2008 from the long-term means were a much smaller (time and amount) spring bloom, lower overall chlorophyll concentration during the summer, and the absence of autumn bloom on the Norwegian side of the Skagerrak. On the Danish side, the spring bloom in 2008 occurred later than normal (approx. one month). The chlorophyll concentrations were lower during summer, and there was an autumn bloom in October, two months later than normal. The average annual modeled primary production in 2008 in the North Sea was well above the average for the period 1985–2008. Higher temperatures have extended the distribution of several zooplankton species northwards and more southern species have increased survival in the North Sea. The cold-water copepod Calanus finmarchicus is in retreat and is only partially being replaced by the more southern C. helgolandicus. In April 2008, the average zooplankton biomass in the northern North Sea was dominated by the large herbivorous copepod Calanus finmarchicus, but with an increasing proportion of C. helgolandicus west- and southward in the area. The average biomass of zooplankton in coastal waters in Skagerrak in 2008 was close to the mean value for 1994–2008. Mnemiopsis leidyi was observed along the cost from Skagerrak to Møre.

Marine Mammals

Harbor porpoise, minke whale and white beaked dolphins are the three dominant cetaceans. Influx of warm water into the North Sea often brings more exotic guests, species such as common dolphin, striped dolphin and Risso’s dolphin. Sandeel, mackerel, herring and gadoids are important prey items for marine mammals.

Bottom fauna

IMR has had no activity on bottom fauna in the North Sea since 2005. New projects are planned. They will be focusing on the effects climate changes have on benthic species, the inventory and biodiversity and ecological functioning of the benthic ecosystem.
 

North Sea Facts

Size: Approximately 750,000 km2
Depth: 94 m on Average
Important Fisheries: North Sea herring; saithe; mackerel; cod; anglerfish; sand lance; shrimp; and Norway lobster
Special Features

  • The most shallow of our seas: two-thirds of which is less than 100 m deep. The Norwegian trench can extend to depths greater than 700 m
  • One of the worlds’ most heavily trafficked ocean areas with large harbors, extensive fisheries, developing oil and gas industries, extraction of sand and gravel, and sediment dumping. Approximately 184 million human inhabitants reside along the coast of this ecosystem which leads to harmful inputs from urban development, agriculture, and industrial land use.
     

What is an ecosystem?

Ecosystems are often described in terms of energy transfer between levels of the food chain. Behind the energy transfer, however, a life or death struggle between predators and prey is taking place. This struggle, in which every individual tries to make the most of itself by spreading its genes, results in what we call the “interplay of nature”. This interplay is fascinating, both as a field of study and as a management problem.

More about ecosystem