THE MICROPHYTOBENTHOS OF KONIGSHAFEN - SPATIAL AND SEASONAL DISTRIBUTION ON A SANDY TIDAL FLAT

A microphytobenthic species composition of a tidal flat in the norther n Wadden Sea was analysed regarding cell numbers and biomass (in carbo n units). The three sampling sites differed in tidal inundation from 1 5 cm to about 90 cm water depth at high tide. The sediment was sandy a t all three stations. A cluster analysis revealed a separation of the benthic diatoms into three areas: a Nereis-Corophium-belt, a seagrass- bed and the Arenicola-flat. Small epipsammic diatoms were most abundan t and dominated the microalgal biomass. A microphytobenthic ''spring b loom'' even started beneath the ice cover of the flat in January. Lowe st values of cell numbers and biomass of benthic microalgae were found in summer. Highest values were measured in the uppermost area (Nereis -Corophium-belt), and only here was an autumnal increase of benthic mi croalgae found. Further cluster analysis within each of the three area s revealed seasonal differences although the majority of species were present all year round. Many species were most abundant in spring, and some showed a bimodal distribution (spring-autumn) in the year of inv estigation.