Foraminifera in marginal marine environments

9.6 Summary

Hundreds of known benthic foraminifer species live in coastal marine environments. Most of them are rare. The dominant species are widely distributed, many across major biogeographic barriers. The transoceanic distribution of some abundant marsh and estuarine species is hard to explain, except by accidental transport and high tolerance to environmental variables. The transition from a brackish to a normal-marine nearshore fauna is generally marked by increases in species diversity and the proportion of calcareous species in the community. A few calcareous genera are represented by the same or sibling species on the soft, clastic substrates of many inner continental shelves, spanning large latitudinal and longitudinal ranges. Hard substrates and marine vegetation in the tropics support a large variety of taxa, including nearly all living species of larger Foraminifera. With a few exceptions, the biogeographic imprint on nearshore, open-marine faunas is best seen in the composition of the entire assemblage, rather than in the presence or absence of a few dominant species.