Arctic Ice Shelves and Ice Islands by Luke Copland & Derek Mueller

Author:Luke Copland & Derek Mueller
Language: eng
Format: epub
Publisher: Springer Netherlands, Dordrecht

8.3.3 Foraminifera

Foraminifera are a group of single-celled marine organisms that are typically present in virtually all habitats of the world’s oceans (Sen Gupta 1999). Below extant ice shelves they have, however, been observed to be either absent or present in greatly reduced abundances (Bentley et al. 2005; Domack et al. 2005, Antoniades et al. 2011). Consequently, changes in foraminiferal abundances in the sedimentary record can provide information about past ice shelf characteristics. An absence of foraminifera in the sedimentary record often indicates the existence of ice shelves, while their presence implies a seasonally open marine environment and thus ice shelf absence (Bentley et al. 2005; Domack et al. 2005; Hillenbrand et al. 2005; Smith et al. 2006), although these scenarios may be complicated somewhat by the advection of material beneath ice shelves (e.g., Hemer and Harris 2003). Changes in foraminiferal concentrations may also be indicative of the nearby advance or retreat of ice shelves (Domack et al. 1995).

Foraminiferal community composition can also be a useful tool for inferring environmental differences, as foraminiferal diversity and morphology are related to ocean conditions (Ishman and Szymcek 2003; Pudsey et al. 2006). Increases in calcareous benthic and planktonic forms have been taken to indicate open marine conditions (Domack et al. 1995), as well as productivity increases caused by ice shelf retreat (Brachfield et al. 2003). Arenaceous forms (those with tests (shells) formed of clay particles cemented with calcium carbonate) were suggested to be indicative of cold, saline bottom waters (Brachfield et al. 2003), while those with tests formed from agglutinated sediments implied ice shelf conditions (Domack et al. 1995). In certain regions calcite dissolution may occur; it has been suggested that in such circumstances paleoenvironmental inferences are best drawn from agglutinated forms (Murray and Pudsey 2004), although the taxonomy and ecology of agglutinated foraminifera are less well known relative to other groups.

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