Editing North Sea (section)

== Ecology and environment ==

The North Sea contains open shelf water, shallow banks, muddy depressions, estuaries, salt marshes, and tidal flats. Mixing brings nutrients into the upper water column and supports high plankton production. Coastal shallows and offshore banks serve as spawning or nursery grounds for many fish species.

Herring and mackerel form large pelagic shoals. Cod and haddock occupy deeper water close to the seabed, while plaice and sole are common over sand and mud. Sandeel are especially important because they transfer energy from plankton to larger fish, seabirds, and marine mammals.

Harbour porpoises are widespread across the basin. Grey seals and harbour seals breed around several coasts and islands. Estuaries and tidal flats provide feeding areas for migratory birds, while cliffs and offshore islands support major seabird colonies.

Human activity has altered much of the marine environment. Bottom trawling disturbs seabed habitats, and dredging changes local sediment movement. Nutrient pollution has caused eutrophication in some coastal waters. Industrial chemicals and oil have entered through rivers, shipping, and offshore operations, although regulation has reduced several older sources of contamination.

Ports, pipelines, platforms, and wind farms occupy an increasing part of the sea. Their construction changes local habitats and requires restrictions on navigation or fishing. Rising temperatures are also shifting the distribution of plankton and fish. Sea-level rise increases the long-term flood risk along low-lying coasts.