The dynamics of the benthic foraminiferal microhabitat: recovery after experimental disturbance

We report the results of a microcosm experiment in which we studied the effect of disturbance on the occupation of microhabitats by benthic foraminifera. After destruction of the original microhabitat patterns through homogenization of the sediment, two experimental situations were established characterized by different population density regimes. The aim was to observe the rapidity and mode of recovery of microhabitat patterns within an experimental period of 22 days. Relative abundance patterns in the field, twice monitored as control, showed that the experiment reasonably reflected the natural situation. No significant difference was found between the two experimental situations; this suggests that density-dependent processes did not affect the vertical microhabitat distribution. Based on the way the assemblages recovered from the disturbances, two groups of taxa could be identified. The first group consisted of epifaunal to shallow-infaunal, opportunistic taxa: Hopkinsina pacifica, Nonionella turgida and Stainforthia fusiformis. After the onset of the experiment especially H. pacifica and N. turgida migrated rapidly to the uppermost sediment layer, but displayed a high net mortality. The second group consisted of deep infaunal taxa: Acostata mariae, Eggerella scabra/advena and Caronia silvestrii. During the experimental period, these taxa did not display significant net upward or downward change of the distribution patterns. Apparently, they survived successfully or even increased their standing stock, in deep sediment layers. Our data suggest that especially the so-called epifaunal taxa are able to recover rapidly after physical disturbance, but that complete restoration of microhabitat patterns including the deep taxa might take a considerable time.