Ecological Changes in the North Sea as a consequence of biological globalisation and climate change
Long-term monitoring studies at the ‘Biologische Anstalt Helgoland’ (BAH), part of the Alfred Wegener Institute for Polar and Marine Research, document rapid ecological changes in the North Sea. Scientists explain these changes primarily with the introduction of non-native species and global climate change. Investigations that have been carried out continually since 1962 provide evidence for this notion. The nearly unbroken record of physical, chemical and biological parameters, collected regularly on work days by the ‘Biologische Anstalt Helgoland’, represents one of the most valuable marine long-term data sets worldwide. Using up-to-date methods for long-term data collection, scientists on Helgoland, in close cooperation with other institutes, contribute in a major way to the analysis of ecological changes and hence provide decision making tools for management of marine resources and for development of environmental policies. The current issue (Volume 58, issue 4) of the scientific journal ‘Helgoland Marine Research’ (published by Springer) is dedicated to ecological long-term research on Helgoland.
More than 150 years of research on the North Sea island of Helgoland have produced an invaluable data set, the analysis of which will keep science busy for a long time to come. “Regular measurements and observations extending over decades are the most important tool for detecting historical changes of ecological conditions. This is the only way to evaluate the present state of our ecosystems and to develop models which will allow predictions about their future”, explains Dr Karen Wiltshire of the ‘Biologische Anstalt Helgoland’.
The data document a rise of 1.1 °C in sea water temperature over the past 40 years, concurrent with a slight increase in salinity. The formation of sea ice at Helgoland, a phenomenon which, until the 1940s, used to occur approximately every ten years on average, was observed only once (in 1963) during the past 60 years. The North Sea shows clear changes regarding the abundance of species, both in terms of seasonal patterns of occurrence, as well as in terms of species composition. Since the closely linked components of species communities do not all respond uniformly to alterations, the ecosystem undergoes change. For the first time, it was possible to demonstrate a link between the change in timing and magnitude of a diatom bloom and the trend in sea water temperature. In the ocean, diatoms represent the basis of the food web. Because diatom population growth largely determines the seasonality of species communities in the water column and on the sea floor, researchers expect major alterations of the whole ecosystem in the future.
Helgoland scientists found that several native species, such as lobster and cod, have become rarer. Other organisms, e.g. various seaweeds and the European oyster have completely disappeared from the region. Some species, e.g. the edible crab, have increased in abundance and others are new to the region. The vast majority of species newly found in the area over the past 15 years are ‘southern’ species originating from the Atlantic region, which have been able to expand further north as a consequence of the rise in temperature. Hence, they represent indicators of this trend. Other new species have been introduced by humans and, locally, have already led to significant changes in habitats and species communities.
Back in 1873, the first regular measurements on the North Sea island of Helgoland began. The establishment of the ‘Biologische Anstalt Helgoland’ in 1892 created an institution which, right from the beginning, was committed to long-term research. Since 1998, the ‘Biologische Anstalt Helgoland’ has been part of the Alfred Wegener Institute for Polar and Marine Research.
Bremerhaven, January 31, 2005
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The Alfred Wegener Institute pursues research in the polar regions and the oceans of mid and high latitudes. As one of the 18 centres of the Helmholtz Association it coordinates polar research in Germany and provides ships like the research icebreaker Polarstern and stations for the international scientific community.