Benthic Foraminifera and Diatoms as Ecological Indicators

Ecology can be defined as the study of causes that govern the distribution and abundance of organisms and their relation to the environment. Among benthic microorganisms (10 μm–500 mm), diatoms and foraminifera are of great importance in aquatic ecosystems worldwide because (1) their species react in a rapid and sensitive way to environmental changes in water bodies, and (2) they preserve in sediments for a long time due to their shells, which are made of silica (diatoms) or calcium carbonate or cemented detrital material (foraminifera). In shallow coastal ecosystems (coastal lagoons, marshes), these attributes make foraminifera and diatoms extremely valuable for both ecology and geology because modern communities indicate the dynamic transition between terrestrial and marine habitats, and fossil assemblages record past sea-level changes. While many other works provide specific information on the taxonomy, biology, and ecology of foraminifera and diatoms independently, this chapter aims to provide a comprehensive joint perspective of the applications and uses of these two groups of organisms for environmental studies in coastal habitats. Given the ongoing and future threats associated with sea-level rise and water scarcity, and the lack of long-term monitoring data to assess ecosystems' deviation from natural baseline conditions, palaeoecological applications of foraminifera and diatoms are also discussed in the context of environmental and restoration policies.