Influence of temperature, oxygen and food availability on the migrational activity of bathyal benthic foraminifera: evidence by microcosm experiments

Foraminifera are a dominant group of amoeboid protists in the deep-sea and play possibly a significant role in decomposition processes of incoming org anic matter. In order to study the poorly known ecology of these protozoans , microcosm experiments with living bathyal benthic foraminifera have been conducted. Foraminifera from 2880 m and shallower water depths were success fully maintained and their movement patterns investigated. By video documen tation, high mean migration speed of 20,02 (N = 22) and 24,48 mu m min(-1) (N = 10) at 4 degrees C were found for species such as Hoeglundina elegans and Quinqueloculina seminula from 1847 m and 1921 m water depth, respective ly. The results demonstrate that some bathyal foraminifera have migration s peeds comparable to those of shallow water species. Environmental factors s uch as temperature, food concentration and oxygen content showed a marked i nfluence on the migration of some species. An increase in temperature from 10 degrees C to 15 degrees C resulted in an increase of 35% in the migratio n speed of Allogromia spp. However, other species reacted differently. High er food concentration resulted in a decrease in speed of some species. Whil e in Quinqueloculina lamarckiana speed was not greatly affected by a low ox ygen content in the sediment, other foraminifera responded to oxygen deplet ion by migration to the surface layers. Observations of benthic foraminifer a in the laboratory microcosms are discussed in relation to microhabitats a nd the fate of organic matter on the sea floor and in the sediment.