8 Grid-Based Modelling of Macrozoobenthos in
the Intertidal of the Wadden Sea: Potentials
and Limitations
Volker Grimm, Carmen-Pia Gunther, Sabine Dittmann, Hanno Hildenbrandt
Abstract: Grid-based ecological models are a valuable tool in terrestrial ecology
which have considerably improved the understanding of many terrestrial systems.
Therefore an attempt is made here to apply the grid-based approach to marine
benthic soft bottom communities. The concept of patch-dynamics and the theory of
mosaic-cycles are the theoretical background which motivated this attempt. Both
these concepts are based on the notion of a spatially structured landscape whose
spatial and temporal dynamics is ecologically significant. Using two grid-based
models we try to find out whether in the intertidal of the Wadden Sea the spatial
and temporal dynamics of dominant macrozoobenthic species meet the criteria of
the patch-dynamics concepts and the mosaic-cycle theory. The first model takes
into account the processes settlement, succession, disturbance events (storms, ice
winters) and the dispersal of mussels (Mytilus edulis) into adjacent areas. This first
model demonstrates that the frequency of disturbance events and dispersal of
M. edulis are the major factors which determine the spatial distribution of the
model species. However, the first model has four main methodological deficiencies: (I) the results of the model indicate that the spatial scale to which the model
may apply must be rather small « I OOx 100m 2 ). (2) For the same reason the model
does not reproduce large-scale zonation patterns of benthic communities. (3) Abiotic factors apart from disturbance events which are known to be decisive in the
Wadden Sea, e.g. topography, are not taken into account. (4) Interactions between
neighbouring spatial units ("cells") are all but neglected in the model. Thus, based
on the topography of a selected part of the Wadden Sea (sandtlat "Swinnplate" and
surroundings), an advanced second model is developed (TOPOGRID) which only
considers the two species Lanice conchi/ega and M. edulis. This model demonstrates elements of a future model of macrozoobenthos in the intertidal in the
Wadden Sea which would be supported by much more expert knowledge than
TOPOGRID, more field studies which are designed parallel to the model, and
oceanographic models of the current regime. With respect to the theoretical concept which was to be tested with the two models presented here, we conclude that
neither the concept of patch-dynamics nor the theory of mosaic cycles are applicable to the Wadden Sea in their original, full meaning.
the Intertidal of the Wadden Sea: Potentials
and Limitations
Volker Grimm, Carmen-Pia Gunther, Sabine Dittmann, Hanno Hildenbrandt
Abstract: Grid-based ecological models are a valuable tool in terrestrial ecology
which have considerably improved the understanding of many terrestrial systems.
Therefore an attempt is made here to apply the grid-based approach to marine
benthic soft bottom communities. The concept of patch-dynamics and the theory of
mosaic-cycles are the theoretical background which motivated this attempt. Both
these concepts are based on the notion of a spatially structured landscape whose
spatial and temporal dynamics is ecologically significant. Using two grid-based
models we try to find out whether in the intertidal of the Wadden Sea the spatial
and temporal dynamics of dominant macrozoobenthic species meet the criteria of
the patch-dynamics concepts and the mosaic-cycle theory. The first model takes
into account the processes settlement, succession, disturbance events (storms, ice
winters) and the dispersal of mussels (Mytilus edulis) into adjacent areas. This first
model demonstrates that the frequency of disturbance events and dispersal of
M. edulis are the major factors which determine the spatial distribution of the
model species. However, the first model has four main methodological deficiencies: (I) the results of the model indicate that the spatial scale to which the model
may apply must be rather small « I OOx 100m 2 ). (2) For the same reason the model
does not reproduce large-scale zonation patterns of benthic communities. (3) Abiotic factors apart from disturbance events which are known to be decisive in the
Wadden Sea, e.g. topography, are not taken into account. (4) Interactions between
neighbouring spatial units ("cells") are all but neglected in the model. Thus, based
on the topography of a selected part of the Wadden Sea (sandtlat "Swinnplate" and
surroundings), an advanced second model is developed (TOPOGRID) which only
considers the two species Lanice conchi/ega and M. edulis. This model demonstrates elements of a future model of macrozoobenthos in the intertidal in the
Wadden Sea which would be supported by much more expert knowledge than
TOPOGRID, more field studies which are designed parallel to the model, and
oceanographic models of the current regime. With respect to the theoretical concept which was to be tested with the two models presented here, we conclude that
neither the concept of patch-dynamics nor the theory of mosaic cycles are applicable to the Wadden Sea in their original, full meaning.