Ostracoda as proxies of anthropogenic impacts in fluvial systems – new actualistic studies and perspectives from Central Germany

Ostracoda (Crustacea) are widely used and approved proxies for lacustrine palaeoenvironments, but are rarely applied for characterising river sediments. Their densities are generally lower in rivers and overbank sediments, the latter often show dissolution of the calcitic ostracod shells. We think, however, that ostracods have a much higher potential for palaeoecological analysis of river sediments, especially when combined with molluscs, but this needs additional research. For further exploring their potential, we analysed recent ostracod associations from several river systems in Germany: The Saale and its tributaries around Jena (37 samples), streams in the Thuringian Forest (26), as well as two smaller rivers in southwestern Germany; Echaz and Eger (18). Almost all samples contained ostracods, most of them in high numbers, allowing detailed statistical analyses. We found 32 ostracod species in total. Most abundant are Candona candida, Cavernocypris subterranea, Cypria ophthalmica, Eucypris pigra, Ilyocypris inermis, I. bradyi, Limnocythere inopinata Prionocypris zenkeri, Psychrodromus olivaceus and Potamocypris zschockei. Water quality assessment based on recent or fossil associations, similar to the saprobia index, is possible and can be improved by combining ostracod with mollusc data. Water turbulence, phytal zones and non-permanent water cover are indicated. Special attention has to be paid to taphonomical effects, like transport, disarticulation, fragmentation, abrasion and dissolution.