Life in the open waters – Trap Greenland

Krill (*Meganyctiphanes norvegica*) is an important link in the food chain in the southern marine areas east and west of Greenland.
ØYSTEIN PAULSEN/MAR-ECO, CREATIVE COMMONS, 2005

When the ice disappears during spring, and the light can once again penetrate the water, a cascade of production begins in the water column. The melting of the sea ice has left a thin layer of fresh water on the surface, and here the phytoplankton exploits the rays of the sun for an intensive production. Nutrients are supplied from the deeper saltier water, but during summer the surface water becomes so mixed up that the primary production decreases in intensity and moves to greater depths. The periodicity of the ice and light means that production in the seas around Greenland has a distinct seasonal rhythm, which differs from lower latitudes. This rhythm is of great importance for zooplankton, which constitutes the next link in the food chain. The daphnia, which overwinter in deep water, migrate up through the water column in spring to graze on the intense production of phytoplankton. The fatty daphnia are eaten by fish larvae and certain birds and whales and are thus a vital link in the transport of energy, in the form of, e.g. omega-3 fatty acids, up through the food chain and thus also for the recruitment of new fish for the fishing industry.

To the south of East and West Greenland, in slightly warmer waters without ice cover in winter, the North Atlantic species of krill can be found, which primarily graze on the phytoplankton. Krill, in turn, is prey for a wide variety of boreal fish, birds and marine mammals, which head to the northern regions to forage on the concentrations of krill.

Rising ocean temperatures will affect the composition of zooplankton communities, and this will have consequences for the entire food chain in the ocean.

Further reading