SYNOPTIC PATTERNS OF MEIOFAUNAL AND MACROFAUNAL ABUNDANCES AND SPECIFIC COMPOSITION IN LITTORAL SEDIMENTS

During recent years, many investigations on small zoobenthos have been performed at the island of Sylt. As these studies were carried out sporadically over many years and as different extraction methods were used, comparisons of the results have been hampered. Therefore, in August/September 1986, 24 sites were sampled and evaluated using one quantitative method throughout. Sites range from mud to exposed sand and from the sublittoral to the supralittoral. Macrofauna and the taxa Platyhelminthes, Polychaeta, and Oligochaeta are determined to species level. Macrofaunal (> 0.5 mm) abundance is highest in mud and continuously decreases with increasing exposure to wave action. Meiofaunal (< 0.5 mm) abundance is less variable. Nematoda dominate in mud and muddy sand, Copepoda in sheltered and exposed sand, other taxa only intermittently. Related to surface area, no correlation between macro- and meiofaunal abundance is apparent. Platyhelminthes and Copepoda reach highest abundance per surface area in sand but their per volume density is higher in mud and muddy sand. Related to sediment volume instead of surface area, the meiofaunal abundance pattern is very similar to the macrofaunal pattern. The faunal composition changes gradually along the tidal gradient without general faunal boundaries. On an averange, the faunal similarity of neighbouring sites is highest in Oligochaeta and lowest in Platyhelminthes. Presumably, Oligochaeta tolerate wider ranges of environmental factors. This may explain the low number of oligochaete species. On the other hand, Platyhelminthes seem to adapt to relatively narrow ranges of factors and their species richness is highest. Because of macrofauna-meiofauna interaction it is suggested that the meiofaunal assemblage will be least stable in mud and muddy sand, and most stable in exposed sand.