MICROHABITAT PREFERENCES OF BENTHIC FORAMINIFERA - A STATIC CONCEPT OR A DYNAMIC ADAPTATION TO OPTIMIZE FOOD ACQUISITION

In situ observations of microhabitat preferences of living benthic foraminifera are presented from sediments of the Norwegian-Greenland Sea, the upwelling area off northwestern Africa and the shallow-water Kiel Bight (Baltic Sea). Certain foraminiferal species (e.g. Cibicidoides wuellerstorfi and Rupertina stabilis) can be regarded as strictly epibenthic species, colonizing elevated habitats that are strongly affected by bottom water hydrodynamics. Large epibenthic foraminifera (e.g. Rhabdammina abyssorum and Hyperammina crassatina) colonize the sediment surface in areas where strong bottom currents occur and might have by virtue of their own size an impact on the small-scale circulation patterns of the bottom water. Motile species changing from epifaunal to infaunal habitats (e.g. Pyrgo rotalaria, Melonis barleeanum, Elphidium excavatum clavatum, Elphidium incertum, Ammotium cassis and Sphaeroidina bulloides) are regarded here as highly adaptable to changes in food availability and/or changing environmental conditions. This flexible behaviour is regarded as a dynamic adaptation to optimize food acquisition, rather than a static concept leading to habitat classification of these ubiquitous rhizopods.