13 Summary
What are the processes and mechanisms relevant for stability properties in the
Wadden Sea ecosystem? As part of the "Ecosystem Research Wadden Sea", the
interdisciplinary project ELA WAT ("Resilience of the Wadden Sea Ecosystem")
was carried out from 1993 to 1997 to increase the understanding of processes essential for regeneration and ecological relations within this ecosystem. Temporal
and spatial distribution patterns of abiotic and biotic components were investigated
as well as the regeneration following natural and experimentally induced disturbances. The main study area was the backbarrier system of the island of Spiekeroog in the East Frisian Wadden Sea and two tidal flat areas therein, the Groninger
Plate and Swinnplate, were studied in detail. This book covers a synthesis of the
results of this project and provides a case study on the ecology of an intertidal
backbarrier system.
The approach taken in ELA W AT put stability properties into the centre of the
conceptual framework for this ecosystem analysis. Special attention was given to
resilience, i.e. the ability to return to a reference state or reference dynamic following a temporary disturbance. In most cases the results revealed a high variability which made it difficult to specify reference states for this ecosystem. Instead, it
became apparent that the state of the Wadden Sea is its dynamic.
Based on the results of the investigations and experiments, stability properties
were enumerated for several abiotic and biotic components. The analysis of relevant processes for regeneration after disturbance events also lead to recommendations for the protection of processes in the Wadden Sea. In the following, some
results of this research project are summarized.
• The backbarrier system of Spiekeroog covers an area of 73.5 km 2 with more
than 80 % tidal flats. The water volume related to mean sea level amounts to
110 Mill m', whereof 70 % are exchanged at each low tide through the tidal inlet of the Otzumer Balje between the islands of Spiekeroog and Langeoog.
Mesotidal conditions prevail in the backbarrier system of Spiekeroog with a
tidal range of 2.7-2.9 m. The current velocities were higher on the Swinnplate
than on the Groninger Plate and while the first area was dominated by ebb currents, flood currents prevailed on the latter.
• The majority of the tidal flats in the backbarrier system of Spiekeroog were
muddy sand or sandflats, mudflats were subordinate. The deficit of fine particles is seen as a consequence of coastal engineering. The two tidal flats studied
in detail showed little variation in their grain size distribution, but biodeposition
by blue mussels contributed to > 50 % of the mud content over the summer
months on the SWinnplate. In the winter months, the mud content was as low as
10 0/0, as the mud fraction was resuspended or had been exported in suspension.
• The meteorological situation during the three study years was characterized by a
high variability. Whi Ie 1994 and 1995 were warmer than average, 1996 was
What are the processes and mechanisms relevant for stability properties in the
Wadden Sea ecosystem? As part of the "Ecosystem Research Wadden Sea", the
interdisciplinary project ELA WAT ("Resilience of the Wadden Sea Ecosystem")
was carried out from 1993 to 1997 to increase the understanding of processes essential for regeneration and ecological relations within this ecosystem. Temporal
and spatial distribution patterns of abiotic and biotic components were investigated
as well as the regeneration following natural and experimentally induced disturbances. The main study area was the backbarrier system of the island of Spiekeroog in the East Frisian Wadden Sea and two tidal flat areas therein, the Groninger
Plate and Swinnplate, were studied in detail. This book covers a synthesis of the
results of this project and provides a case study on the ecology of an intertidal
backbarrier system.
The approach taken in ELA W AT put stability properties into the centre of the
conceptual framework for this ecosystem analysis. Special attention was given to
resilience, i.e. the ability to return to a reference state or reference dynamic following a temporary disturbance. In most cases the results revealed a high variability which made it difficult to specify reference states for this ecosystem. Instead, it
became apparent that the state of the Wadden Sea is its dynamic.
Based on the results of the investigations and experiments, stability properties
were enumerated for several abiotic and biotic components. The analysis of relevant processes for regeneration after disturbance events also lead to recommendations for the protection of processes in the Wadden Sea. In the following, some
results of this research project are summarized.
• The backbarrier system of Spiekeroog covers an area of 73.5 km 2 with more
than 80 % tidal flats. The water volume related to mean sea level amounts to
110 Mill m', whereof 70 % are exchanged at each low tide through the tidal inlet of the Otzumer Balje between the islands of Spiekeroog and Langeoog.
Mesotidal conditions prevail in the backbarrier system of Spiekeroog with a
tidal range of 2.7-2.9 m. The current velocities were higher on the Swinnplate
than on the Groninger Plate and while the first area was dominated by ebb currents, flood currents prevailed on the latter.
• The majority of the tidal flats in the backbarrier system of Spiekeroog were
muddy sand or sandflats, mudflats were subordinate. The deficit of fine particles is seen as a consequence of coastal engineering. The two tidal flats studied
in detail showed little variation in their grain size distribution, but biodeposition
by blue mussels contributed to > 50 % of the mud content over the summer
months on the SWinnplate. In the winter months, the mud content was as low as
10 0/0, as the mud fraction was resuspended or had been exported in suspension.
• The meteorological situation during the three study years was characterized by a
high variability. Whi Ie 1994 and 1995 were warmer than average, 1996 was