not severely depressed, making it difficult for paleooceanographers to disentangle the influence of these
two variables. Finally, biological factors such as
microhabitat preferences and the exploitation of
phytodetrital aggregates (‘floc’) influence the stable
isotope chemistry of foraminiferal tests.
There are many examples of the use of benthic
foraminiferal faunas to interpret the geological history of the oceans. Only one is given here. Cores
collected at 50141
0 N, 21152
0 W (3547 m water depth)
and 58137
0 N, 19126
0 W (1756 m water depth) were
used by E. Thomas and colleagues to study changes
in the North Atlantic over the past 45 000 years. The
cores yielded fossil specimens of two foraminiferal
species, Epistominella exigua and Alabaminella
weddellensis, both of which are associated with
seasonal inputs of organic matter (phytodetritus) in
modern oceans. In the core from 511N, these ‘phytodetritus species’ were uncommon during the last
glacial maximum but increased sharply in absolute
and relative abundance during the period of deglaciation 15 000–16 000 years ago (Figure 9). At the
same time there was a decrease in the abundance of
Neogloboquadrina pachyderma, a planktonic foraminifer found in polar regions, and an increase in the
abundance of Globigerina bulloides, a planktonic
species characteristic of warmer water. These changes were interpreted as follows. Surface primary
productivity was low at high latitudes in the glacial
North Atlantic, but was much higher to the south of
the Polar Front. At the end of the glacial period, the
ice sheet shrank and the Polar Front retreated
northwards. The 511N site was now overlain by
more productive surface water characterized by a
strong spring bloom and a seasonal flux of phytodetritus to the seafloor. This episodic food source
favored opportunistic species, particularly E. exigua
and A. weddellensis, which became much more
abundant both in absolute terms and as a proportion
of the entire foraminiferal assemblage.
Conclusions
Benthic foraminifera are a major component of deepsea communities, play an important role in ecosystem
functioning and biogeochemical cycling, and are
enormously diverse in terms of species numbers and
test morphology. These testate (shell-bearing) protists
are also the most abundant benthic organisms preserved in the deep-sea fossil record and provide
powerful tools for making paleo-oceanographic reconstructions. Our understanding of their biology has
advanced considerably during the last two decades,
although much remains to be learnt.
See also
Anthropogenic Trace Elements in the Ocean.
Cenozoic Oceans – Carbon Cycle Models. Ocean
Carbon System, Modeling of. Radiocarbon. Stable
Carbon Isotope Variations in the Ocean. Tracers of
Ocean Productivity.
Further Reading
Fischer G and Wefer G (1999) Use of Proxies in
Paleoceanography: Examples from the South Atlantic.
Berlin: Springer-Verlag.
Gooday AJ, Levin LA, Linke P, and Heeger T (1992) The
role of benthic foraminifera in deep-sea food webs and
carbon cycling. In: Rowe GT and Pariente V (eds.)
Deep-Sea Food Chains and the Global Carbon Cycle,
pp. 63--91. Dordrecht: Kluwer Academic.
Jones RW (1994) The Challenger Foraminifera. Oxford:
Oxford University Press.
Loeblich AR and Tappan H (1987) Foraminiferal Genera
and their Classification, vols 1, 2. New York: Van
Nostrand Reinhold.
Murray JW (1991) Ecology and Palaeoecology of Benthic
Foraminifera. New York: Wiley; Harlow: Longman
Scientific and Technical.
SenGupta BK (ed.) (1999) Modern Foraminifera.
Dordrecht: Kluwer Academic.
Tendal OS and Hessler RR (1977) An introduction to the
biology and systematics of Komokiacea. Galathea
Report 14: 165--194, plates 9–26.
Van der Zwan GJ, Duijnstee IAP, den Dulk M, et al. (1999)
Benthic foraminifers:: proxies or problems? A review of
paleoecological concepts. Earth Sciences Reviews 46:
213--236.
BENTHIC FORAMINIFERA 401
two variables. Finally, biological factors such as
microhabitat preferences and the exploitation of
phytodetrital aggregates (‘floc’) influence the stable
isotope chemistry of foraminiferal tests.
There are many examples of the use of benthic
foraminiferal faunas to interpret the geological history of the oceans. Only one is given here. Cores
collected at 50141
0 N, 21152
0 W (3547 m water depth)
and 58137
0 N, 19126
0 W (1756 m water depth) were
used by E. Thomas and colleagues to study changes
in the North Atlantic over the past 45 000 years. The
cores yielded fossil specimens of two foraminiferal
species, Epistominella exigua and Alabaminella
weddellensis, both of which are associated with
seasonal inputs of organic matter (phytodetritus) in
modern oceans. In the core from 511N, these ‘phytodetritus species’ were uncommon during the last
glacial maximum but increased sharply in absolute
and relative abundance during the period of deglaciation 15 000–16 000 years ago (Figure 9). At the
same time there was a decrease in the abundance of
Neogloboquadrina pachyderma, a planktonic foraminifer found in polar regions, and an increase in the
abundance of Globigerina bulloides, a planktonic
species characteristic of warmer water. These changes were interpreted as follows. Surface primary
productivity was low at high latitudes in the glacial
North Atlantic, but was much higher to the south of
the Polar Front. At the end of the glacial period, the
ice sheet shrank and the Polar Front retreated
northwards. The 511N site was now overlain by
more productive surface water characterized by a
strong spring bloom and a seasonal flux of phytodetritus to the seafloor. This episodic food source
favored opportunistic species, particularly E. exigua
and A. weddellensis, which became much more
abundant both in absolute terms and as a proportion
of the entire foraminiferal assemblage.
Conclusions
Benthic foraminifera are a major component of deepsea communities, play an important role in ecosystem
functioning and biogeochemical cycling, and are
enormously diverse in terms of species numbers and
test morphology. These testate (shell-bearing) protists
are also the most abundant benthic organisms preserved in the deep-sea fossil record and provide
powerful tools for making paleo-oceanographic reconstructions. Our understanding of their biology has
advanced considerably during the last two decades,
although much remains to be learnt.
See also
Anthropogenic Trace Elements in the Ocean.
Cenozoic Oceans – Carbon Cycle Models. Ocean
Carbon System, Modeling of. Radiocarbon. Stable
Carbon Isotope Variations in the Ocean. Tracers of
Ocean Productivity.
Further Reading
Fischer G and Wefer G (1999) Use of Proxies in
Paleoceanography: Examples from the South Atlantic.
Berlin: Springer-Verlag.
Gooday AJ, Levin LA, Linke P, and Heeger T (1992) The
role of benthic foraminifera in deep-sea food webs and
carbon cycling. In: Rowe GT and Pariente V (eds.)
Deep-Sea Food Chains and the Global Carbon Cycle,
pp. 63--91. Dordrecht: Kluwer Academic.
Jones RW (1994) The Challenger Foraminifera. Oxford:
Oxford University Press.
Loeblich AR and Tappan H (1987) Foraminiferal Genera
and their Classification, vols 1, 2. New York: Van
Nostrand Reinhold.
Murray JW (1991) Ecology and Palaeoecology of Benthic
Foraminifera. New York: Wiley; Harlow: Longman
Scientific and Technical.
SenGupta BK (ed.) (1999) Modern Foraminifera.
Dordrecht: Kluwer Academic.
Tendal OS and Hessler RR (1977) An introduction to the
biology and systematics of Komokiacea. Galathea
Report 14: 165--194, plates 9–26.
Van der Zwan GJ, Duijnstee IAP, den Dulk M, et al. (1999)
Benthic foraminifers:: proxies or problems? A review of
paleoecological concepts. Earth Sciences Reviews 46:
213--236.
BENTHIC FORAMINIFERA 401