Benthic Foraminifera: Inhabitants of Low-Oxygen Environments

Benthic foraminifera, single-celled eukaryotes, constitute a significant part of the living community in low-oxygen or even oxygen-depleted marine environments. Although the diversity is typically low and the dominance high, selected species appears to thrive in such “hostile” environments. In this chapter, the spatial distribution of modern benthic foraminifera, inhabiting the low-oxygen environments from the eutrophic, hypoxic continental shelf settings to the deep ocean oxygen minimum zones (OMZs), is discussed and typical assemblage composition outlined. Furthermore, the in-sediment distribution, or foraminiferal microhabitat, is summarized, and focus is given on species encountered in the deeper hypoxic and anoxic sediment units. Finally, current laboratory experiments and survival strategies including nitrate storage and the physiological role of chloroplasts and bacterial husbandry of foraminifera living in low-oxygen environments are discussed. Recent advances in our understanding of the foraminiferal role in the marine N-cycle and future directions in foraminiferal ecology studies are also addressed