Coastal habitats with brackish waters often host benthic
foraminiferal species from the agglutinated Trochammina,
Jadammina, and Miliammina and calcareous Elphidium,
Miliolidae, and Ammonia genera (Boersma et al., 1998).
In the brackish Baltic Sea, carbonate preservation is limited and foraminiferal assemblages are largely dominated
by the calcareous Elphidium and Ammonia and agglutinated Miliammina, Trochammina, and Reophax genera.
Intertidal-subtidal lagoons and estuaries often host foraminifera adapted to extreme daily salinity fluctuations from
35 to 0.5 psu (Murray, 2006). In the Mediterranean Sea,
during dry seasons brackish lagoons become hypersaline
but still hold foraminiferal species, which tolerate salinities of >45 psu (Murray, 2006).
Substrate determines foraminiferal microhabitats, and,
based on substrate preferences, benthic foraminifera can
be epifaunal (e.g., Cibicidoides wuellerstorfi) and shallow
to deep infaunal (e.g., Melonis barleeanum, Uvigerina
peregrina, Globobulimina affinis, Chilostomella
ovoidea). Epifaunal species live at the sediment surface,
while shallow and deep infaunal taxa dwell at 2–4 cm
and below 4 cm in the sediments, respectively (Gooday,
2001).
Shell geochemistry
Calcareous benthic foraminifera incorporate aspects of the
chemical elements prevailing in seawater as they precipitate their shells. Hence, these organisms record environmental information – being preserved as fossils serves as
a signal carrier for climate and ocean changes taking place
during their life cycle. This makes foraminifera important
paleoproxies (indicators of past changes).
The pioneering work of Cesare Emiliani, using stable
oxygen isotopes from planktonic foraminifera as a proxy
for temperature change, fundamentally changed our view
on past climates (Emiliani, 1955). This paleothermometer
can be applied to benthic foraminifera: depending on bottom water temperatures and glacial-interglacial cycles,
benthic foraminifera incorporate more or less
16
O or
18
O
into their shells, in much the same way as planktonic species in the upper water column. Changes in
18 O/
16
O ratios
have been widely considered as indices of climate cycles
during the Pleistocene and Quaternary (Ravelo and
Hillaire-Marcel, 2007). Oxygen isotopic records also mirror ice volume fluctuations and, hence, allow estimation of
past sea-level changes (Mix and Ruddiman, 1984; Shackleton, 1987). The application of oxygen isotopes
improved our understanding of glacial-interglacial stages
in the North Atlantic during the Pleistocene (Shackleton
et al., 1988).
Another approach increasingly used in paleoclimate
studies is magnesium/calcium ratios measured in foraminiferal shells. The Mg/Ca is used as a paleotemperature
proxy and can be used to constrain the salinity and temperature components of the oxygen isotope records with
respect to seawater (Kristjansdottir et al., 2007). The
Mg/Ca ratios measured on benthic foraminifera proved
glacial-interglacial temperature shifts in the deep ocean
during the Quaternary, as well as deep water mass temperature oscillations (Martin et al., 2002). Additionally, other
trace element ratios (Cd/Ca and Ba/Ca) in benthic foraminiferal shells can be analysed to study seawater nutrient
content (Lea, 1999).
Conclusions
Benthic foraminifera are an important component of
marine habitats. Due to their high fossilization potential,
worldwide occurrence, high abundances, high reproduction rates and rapid response to environmental changes,
benthic foraminifera are used in numerous studies from
biostratigraphy and reconstructions of past climate, ocean
and sea-level changes, to bio-monitoring and ocean acidification (Horton et al., 1999; Murray, 2006; Schönfeld
et al., 2012; Haynert et al., 2012; Dolven et al., 2013).
The uniformitarian principle “the present is a key to the
past” has been widely applied in paleoenvironmental
interpretations based on foraminiferal assemblages, with
reference to their present ecological preferences. These
marine organisms show enormous potential - providing
interdisciplinary knowledge linking biology, geosciences
and industry. This potential will undoubtedly expand to
other subjects in years to come.
Bibliography
Almogi-Labin, A., Perelis-Grossovicz, L., and Raab, M., 1992. Living Ammonia from a hypersaline inland pool, Dead Sea area,
Israel. Journal of Foraminiferal Research, 22, 257–266.
Boersma, A., 1998. Foraminifera. In Haq, B. U., and Boersma,
A. (eds.), Introduction to Marine Micropaleontology. Singapore:
Elsevier, pp. 19–78.
Boltovskoy, E., and Wright, R., 1976. Recent Foraminifera. The
Hague: W. Junk.
Bradshaw, J. S., 1955. Preliminary laboratory experiments on ecology of foraminiferal populations. Micropaleontology, 1,
351–358.
Bradshaw, J., 1957. Laboratory studies on the rate of growth of the
foraminifera Streblus beccarii (Linne) var. tepida (Cushman).
Journal of Paleontology, 31, 1138–1147.
Dolven, J., Alve, E., Rygg, B., and Magnusson, J., 2013. Defining
past ecological status and in situ reference conditions using benthic foraminifera: a case study from Oslofjord, Norway. Ecological Indicators, 29, 219–223.
Emiliani, C., 1955. Pleistocene temperatures. Journal of Geology,
63, 538–578.
Frew, R. D., Dennis, P. F., Heywood, K. J., Meredith, M. P., and
Boswell, S. M., 2000. The oxygen isotope composition of water
masses in the northern North Atlantic. Pergamon, I 47, 2265–
2286.
Goldstein, S. T., 2003. Foraminifera: a biological overview. In Sen
Gupta, B. K. (ed.), Modern Foraminifera. London: Kluwer,
pp. 37–55.
Gooday, A. J., 2001. Benthic foraminifera. In Turekian, K. K. (ed.),
Climate and Oceans. Princeton: Elsevier, pp. 425–436.
Haynert, K., Schönfeld, J., Polovodova Asteman, I., and Thomsen,
J., 2012. The benthic foraminiferal community in a naturally
CO 2 -rich coastal habitat of the Southwestern Baltic Sea.
Biogeosciences, 9, 4421–4440.
Haynes, J. R., 1981. Foraminifera. London: Macmillan.
254
FORAMINIFERS (BENTHIC)
foraminiferal species from the agglutinated Trochammina,
Jadammina, and Miliammina and calcareous Elphidium,
Miliolidae, and Ammonia genera (Boersma et al., 1998).
In the brackish Baltic Sea, carbonate preservation is limited and foraminiferal assemblages are largely dominated
by the calcareous Elphidium and Ammonia and agglutinated Miliammina, Trochammina, and Reophax genera.
Intertidal-subtidal lagoons and estuaries often host foraminifera adapted to extreme daily salinity fluctuations from
35 to 0.5 psu (Murray, 2006). In the Mediterranean Sea,
during dry seasons brackish lagoons become hypersaline
but still hold foraminiferal species, which tolerate salinities of >45 psu (Murray, 2006).
Substrate determines foraminiferal microhabitats, and,
based on substrate preferences, benthic foraminifera can
be epifaunal (e.g., Cibicidoides wuellerstorfi) and shallow
to deep infaunal (e.g., Melonis barleeanum, Uvigerina
peregrina, Globobulimina affinis, Chilostomella
ovoidea). Epifaunal species live at the sediment surface,
while shallow and deep infaunal taxa dwell at 2–4 cm
and below 4 cm in the sediments, respectively (Gooday,
2001).
Shell geochemistry
Calcareous benthic foraminifera incorporate aspects of the
chemical elements prevailing in seawater as they precipitate their shells. Hence, these organisms record environmental information – being preserved as fossils serves as
a signal carrier for climate and ocean changes taking place
during their life cycle. This makes foraminifera important
paleoproxies (indicators of past changes).
The pioneering work of Cesare Emiliani, using stable
oxygen isotopes from planktonic foraminifera as a proxy
for temperature change, fundamentally changed our view
on past climates (Emiliani, 1955). This paleothermometer
can be applied to benthic foraminifera: depending on bottom water temperatures and glacial-interglacial cycles,
benthic foraminifera incorporate more or less
16
O or
18
O
into their shells, in much the same way as planktonic species in the upper water column. Changes in
18 O/
16
O ratios
have been widely considered as indices of climate cycles
during the Pleistocene and Quaternary (Ravelo and
Hillaire-Marcel, 2007). Oxygen isotopic records also mirror ice volume fluctuations and, hence, allow estimation of
past sea-level changes (Mix and Ruddiman, 1984; Shackleton, 1987). The application of oxygen isotopes
improved our understanding of glacial-interglacial stages
in the North Atlantic during the Pleistocene (Shackleton
et al., 1988).
Another approach increasingly used in paleoclimate
studies is magnesium/calcium ratios measured in foraminiferal shells. The Mg/Ca is used as a paleotemperature
proxy and can be used to constrain the salinity and temperature components of the oxygen isotope records with
respect to seawater (Kristjansdottir et al., 2007). The
Mg/Ca ratios measured on benthic foraminifera proved
glacial-interglacial temperature shifts in the deep ocean
during the Quaternary, as well as deep water mass temperature oscillations (Martin et al., 2002). Additionally, other
trace element ratios (Cd/Ca and Ba/Ca) in benthic foraminiferal shells can be analysed to study seawater nutrient
content (Lea, 1999).
Conclusions
Benthic foraminifera are an important component of
marine habitats. Due to their high fossilization potential,
worldwide occurrence, high abundances, high reproduction rates and rapid response to environmental changes,
benthic foraminifera are used in numerous studies from
biostratigraphy and reconstructions of past climate, ocean
and sea-level changes, to bio-monitoring and ocean acidification (Horton et al., 1999; Murray, 2006; Schönfeld
et al., 2012; Haynert et al., 2012; Dolven et al., 2013).
The uniformitarian principle “the present is a key to the
past” has been widely applied in paleoenvironmental
interpretations based on foraminiferal assemblages, with
reference to their present ecological preferences. These
marine organisms show enormous potential - providing
interdisciplinary knowledge linking biology, geosciences
and industry. This potential will undoubtedly expand to
other subjects in years to come.
Bibliography
Almogi-Labin, A., Perelis-Grossovicz, L., and Raab, M., 1992. Living Ammonia from a hypersaline inland pool, Dead Sea area,
Israel. Journal of Foraminiferal Research, 22, 257–266.
Boersma, A., 1998. Foraminifera. In Haq, B. U., and Boersma,
A. (eds.), Introduction to Marine Micropaleontology. Singapore:
Elsevier, pp. 19–78.
Boltovskoy, E., and Wright, R., 1976. Recent Foraminifera. The
Hague: W. Junk.
Bradshaw, J. S., 1955. Preliminary laboratory experiments on ecology of foraminiferal populations. Micropaleontology, 1,
351–358.
Bradshaw, J., 1957. Laboratory studies on the rate of growth of the
foraminifera Streblus beccarii (Linne) var. tepida (Cushman).
Journal of Paleontology, 31, 1138–1147.
Dolven, J., Alve, E., Rygg, B., and Magnusson, J., 2013. Defining
past ecological status and in situ reference conditions using benthic foraminifera: a case study from Oslofjord, Norway. Ecological Indicators, 29, 219–223.
Emiliani, C., 1955. Pleistocene temperatures. Journal of Geology,
63, 538–578.
Frew, R. D., Dennis, P. F., Heywood, K. J., Meredith, M. P., and
Boswell, S. M., 2000. The oxygen isotope composition of water
masses in the northern North Atlantic. Pergamon, I 47, 2265–
2286.
Goldstein, S. T., 2003. Foraminifera: a biological overview. In Sen
Gupta, B. K. (ed.), Modern Foraminifera. London: Kluwer,
pp. 37–55.
Gooday, A. J., 2001. Benthic foraminifera. In Turekian, K. K. (ed.),
Climate and Oceans. Princeton: Elsevier, pp. 425–436.
Haynert, K., Schönfeld, J., Polovodova Asteman, I., and Thomsen,
J., 2012. The benthic foraminiferal community in a naturally
CO 2 -rich coastal habitat of the Southwestern Baltic Sea.
Biogeosciences, 9, 4421–4440.
Haynes, J. R., 1981. Foraminifera. London: Macmillan.
254
FORAMINIFERS (BENTHIC)