The microphytobenthos of Königshafen — spatial and seasonal distribution on a sandy tidal flat

A microphytobenthic species composition of a tidal flat in the northern Wadden Sea was analysed regarding cell numbers and biomass (in carbon units). The three sampling sites differed in tidal inundation from 15 cm to about 90 cm water depth at high tide. The sediment was sandy at all three stations. A cluster analysis revealed a separation of the benthic diatoms into three areas: aNereis-Corophium-belt, a seagrass-bed and theArenicola-flat. Small epipsammic diatoms were most abundant and dominated the microalgal biomass. A microphytobenthic “spring bloom” even started beneath the ice cover of the flat in January. Lowest 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 microalgae found. Further cluster analysis within each of the three areas 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 investigatio

Diel variations in some important phytoplankton parameters during a 24 hours sampling period in Balsfjorden, Tromsø and Skjomentfjorden, Nordland, North Norway

Every fourth hour in 24 h periods measurements were made of temperature, salinity, plant nutrients, incident radiation at three m depth, sub-surface light extinction, chlorophyll a, phaeophytin, particulate carbon and nitrogen, cell counts, zooplankton dry weight biomass, in situ primary production (14C), incubator carbon assimilation (14C), heterotrophic activity (14C glucose assimilation), and horizontal variation in chlorophyll a over one nautical mile. The marked variations in all parameters were probably generated by the combined effects of wind-driven circulation of water masses in the fjord and phytoplankton patches. This study stresses the presence of spatial and temporal changes in fjords, and that data conducted from one or few stations should be interpreted with care