Ostrakoden und Foraminiferen aus athalassischen Gewässern und deren Anwendung für die Rekonstruktion quartärer Ökosysteme
Athalassic waters are characterised by elevated salinity and continental location with full separation from the sea. Faunal assemblages of athalassic waters are individually distinct and characteristic for specific salinity ranges. They are never, however, identical to fully marine assemblages. Athalassic taxa derive from the marginal marine, intertidal zone, where instable ecological conditions require a high adaptability of species. The present thesis identifies, documents and classifies athalassic foraminifer and ostracod associations and applies them for palaeoenvironmental reconstructions. The classification of athalassic waters based on ostracod and foraminifer assemblages needs a specialised methodology because of generally low diversity and high ecological tolerances of typical species, especially towards salinity. Additional methods allow to compensate for this weakness; morphological features as malformations in foraminifer tests as well as noding and sieve pore variability in Cyprideis torosa are applicable for reconstructing salinity changes of the past. Athalassic waters of the low salinity range are characterised by brackish water and tolerant freshwater taxa, dominance of brackish water species, however, is typical for higher salinities. Hypersaline waters are inhabited by a few euryhaline species only, often occurring in very high numbers because of lacking competing species. Some species of marginal marine origin, often associated with salinity-tolerant freshwater species, are typical for athalassic waters, as a generally low diversity as well. If Foraminifera occur, a high proportion of their tests is malformatted. Climatically generated athalassic waters are located in arid climate zones while those with geogenic salinity are typical for humid climate zones because of a high precipitation/evaporation ratio. Hypersaline waters are of climatogenic type and characterised by very low diversity and the exclusive occurrence of euryhaline taxa.
Use and reproduction:
All rights reserved