What are foraminifera?

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Foraminifera are heterotrophic amoeboid protists. They are present in almost all marine biotopes around the world, from the surface waters to the greatest depths. Some foraminifera live in the plankton but most live on the sea floor. Their reticulating pseudopods are used for numerous purposes, e.g. locomotion, anchoring, reproduction and in capturing food.

Test (shell)

Their test morphology is extremely varied. Chambers may be single or multiple, arranged in rows or spirals, or in a range of complex patterns. Three main types of wall composition are found:

• Organic.
• Calcareous (composed of CaCO3) including porcelaneous and hyaline forms.
• Agglutinated (composed of foreign particles, e.g. sand grains and sponge spicules), held together with cement. The cement can be organic, calcareous or made of ferric oxide.

The quantitative and economic importance of foraminifera

The quantitative importance of foraminifera is large and they may constitute a major portion of the biomass in many marine ecosystems. They must therefore be considered as one of the most significant organism groups living today.

Some recent studies indicate that foraminifera are not only a group of great ecological importance as food organisms for fish and invertebrates, but also play an important role in the turnover of nutrients and energy in the sea. The foraminifera also constitute one of the most abundant groups of fossils with an evolutionary history extending back to the Cambrian. The tests constitute a major, sometimes the dominant, part of many sediments since the Palaeozoic. They are extremely useful in applied geology, such as in history of climate, stratigraphy and in oil prospecting. In spite of their quantitative and economic importance, they are often ignored by marine biologists and little is known about their biology, but the few species that have been studied indicate a considerable diversity in habits.

Advantage of using foraminifera in environmental studies

• Foraminifera are small (usually <500µm) and abundant in most marine environments so only small sediment samples (a few grams) are needed to obtain statistically significant numbers of microfossils to perform environmental analyses.
• They are sensitive to environmental change and their mineralized shells normally get preserved in the sediment after the death of the organism.
• Foraminiferal analyses of dated sediment cores represent a quick and cost efficient way to evaluate possible environmental differences between present and pre-impact (reference) conditions without previous knowledge of the area being examined.

Suggested reading

• Murray, J.W., 2006. Ecology and Applications of Benthic Foraminifera. Cambridge: Cambridge University Press, 426 pp. (ISBN-10: 0521828392)
• Sen Gupta, B.K. (ed), 1999. Modern Foraminifera. Kluwer Academic Publishers, 371 pp. (ISBN 0-412-82430-2)