The use of benthic foraminifera in environmental studies

KEY QUESTIONS:

How are foraminifera related to the environment in which they live?

• Foraminiferal assemblages, with their species diversity, abundance and species composition vary with the environment.
• In "good" environments (well oxygenated, stable) the diversity and presence of generalist species are high.
• In "bad" environments (e.g., highly polluted, oxygen depleted, unstable) the foraminiferal diversity is low and one or a few opportunistic species dominate.

How can they tell us something about changes in the environment back in time?

• Most foraminifera have a mineralized shell (test). When these organisms die their soft tissues are degraded, but their tests are preserved in the sediment on the sea floor as microfossils.
• As time proceeds new sediment (including fossils) is accumulated on top of older sediment. Normally, the age of the sediments therefore gets older the deeper into the sediment we get. Sediment layers can be dated by various methods (like ¹³⁷Cs, ²¹⁰Pb, ¹⁴C).
• The foraminiferal assemblages in sediment cores can tell us whether the environment has changed through time or not.

How is this knowledge useful for our society?

• Establishment of long biological time series based on foraminifera is an easy and cost-efficient way to evaluate changes in the environment through time.
• Essential for coastal management, this record can be used to distinguish natural conditions (e.g. in “pre-human impact times”) from human induced environmental changes.
• As required by EU’s Water Framework Directive, benthic foraminiferal analyses can provide quantitative data on biologically defined environmental status (i.e., define reference conditions) in marine coastal waters. This even applies for areas were no previous monitoring has been carried out.