Foreign species in North Sea and Wadden Sea
Pacific oysters cover areas of several hectars of the Wadden Sea since the turn of the millenium
Commodity flows and shipping traffic are increasing worldwide. Along with the ships more and more organisms from foreign coasts enter the North Sea and Wadden Sea. They survive a transcontinental journey lasting weeks across the seven seas in the ballast water or attached to the shell plating of ships. On average one exotic species a year establishes itself in the southeast North Sea, in some cases with far-reaching impacts on the native communities of organisms. Pacific oysters, for instance, overgrow native mussel banks, as a result of which food for mussel-eating crabs and birds may become scarce.
Japanese brown seaweed form new habitat
On the other hand, algae introduced from Japan form dense forests under water. This additional structure is utilised by an impressive variety of native species that form entirely new communities there. Thus, the impacts of exotic species are diverse and the change they cause is revolutionary. This anthropogenically caused ecological change on the North Sea coast is a central topic of the North Sea environmental research conducted by the Alfred Wegener Institute. The tasks include investigating the ecological impacts of foreign organisms, forecasting future developments in view of the invasion of species and providing public advisory services on how to deal with the immigrant species.
