Investigations on the seasonal succession of Wadden Sea inhabiting diatoms at Dangast (North Sea, German bight) over a one year period

The subject of the study was the diatom flora of the tidal flat sediments at Dangast (Wadden Sea, German Bight). Special attention was paid to the seasonal succession of diatoms inhabiting the tidal flat sediments over a growing season (March/April to November). Results of the light microscopic analyses, concerning the relative abundance of diatoms during 8 sampling periods, were treated by means of multivariate mathematical techniques including analyses of similarity (Ranked similarity matrix based on the Bray-Curtis similarity index), biodiversity, and ordination. The results clearly show the succession pattern of the diatom assemblages over a vegetation season. The groupings distinguished corresponded to early spring, late spring, mid-summer, late summer and autumn. Although the number of the taxa is relatively high (over 250), the major component of the diatom assemblages included a group of only 33. However, only several taxa out of the latter group were responsible for diversification of the similarity and the MDS diagrams.