Climate variability and ecosystem response in the German Bight
To cope with a changing earth one needs to develope strategies and information for a sustainable development of our habitat. The ulimate gap is that regional climate or climate impact research is still rather fragmented by discipline, in particular, oceanography, meteorology and ecology. A challenge is to understand how climate variability impact the functioning of the marine ecosystem. It is still under debate how and on what time scales the marine biology react to physical and chemical forcings. There have been previous regime shift studies of the whole North Sea. I downscale to a smaller part closer to the coast for occurrence of such shifts. Thus, the aim of my study is to understand the interactions of the physical, chemical and biological compartments and to understand the functioning of the marine ecosystem under a changing climate by focusing on the long-term developement on key organisms and the environmental conditions in the region of the German Bight. A set of advanced statistical tools is used to clarify the impact of the physical variability on the German Bight ecosystem.
A regime shift in 1987/88 in the German Bight area can be detected according to my definition. Results of statistical analysis suggest a major change in 1987/88 of all components spanning the width of the German Bight and relating disparate measurements, physical parameters such as SST, nutrients and the abundances of biological populations. The shift is mainly explained by hydrophysical forcing linked to larger scale northern hemispheric climate. The strength of the association is widespread among the different biological species. The connection is not of the same sign across a range of trophic levels giving much implications for a replacement of one species by another. Analysing the three different compartments shows that they are dissimilar. There is much more variability in the physics which is not seen in the biology. I find that the magnitude and shape of response to seasonal warming trends differs among trophic levels. The temporal responses of gelatinous zooplankton are abrupt in realation to small abrupt temperature changes. Consequently, the phenological changes in secondary consumers lead to changes in primary consumers.