Recolonization by deep-sea benthic foraminifera: possible substrate preferences

To understand substrate preferences of benthic foraminifera, I have conducted in situ recoIonization experiments at a permanent deep-sea station, OBB No. 2 (1445 m depth) in Sagami Bay, central Japan since 1991. Substrates, prepared in culture bottles, include defaunated natural sediment, defaunated sediment enriched with dried Chlorella, defaunated sediment covered with plankton netting, and artificial substrate made of silt-size glass beads. Sediment for the experiments was collected by box corer from another deep-sea station and frozen at −80 °C for sterilization. Stained benthic foraminifera occurred in both the defaunated natural sediment and the artificial substrate after one year in both 1992 and 1993. Most species of the natural community colonized the defaunated sediment, although population sizes were 50 times smaller than natural populations. In the artificial substrate, stained foraminifera were only found in the 5–10 mm thick fluffy layer that had been newly deposited upon the artificial sediment. Shallow infaunal and opportunistic species colonized this layer.