Taxonomy, stratigraphy, and palaeoecology of chrysophyte cysts from a Late Glacial sediment core section of Längsee, Austria

Chrysophyte resting stages (cysts) were analysed in a sediment core from Langsee, a small lake in the Carinthian lowland (Austria) with climate-driven meromixis, spanning the Late Glacial Interstadial (= Greenland Interstadial 1, ca. 14.7 to 12.7 ky BP). Of the 32 cyst types occurring at least once with a minimum of > 1%, six were related to chrysophyte taxa so far. Nine cyst types were described as new to science. Aiming to define ecological preferences, we compared the cyst stratigraphy with pollen and diatom stratigraphies, diatom-inferred total phosphorus (Di-TP) and diatom-inferred mean summer epilimnetic water temperatures (Di-SEWT). Two significant cyst zones corresponded with the two main pollen zones (Betula followed by Pinus), and a change from meso-eutrophic (dominance of Cyclotella ocellata) to oligotrophic conditions (C. comensis dominance). Secondary changes in cyst assemblages may have been triggered by climate fluctuations.In sum, we classified three groups of cyst types: (1) cysts related to meso-eutrophic conditions; (2) cysts related to oligotrophic conditions and/or cold water; (3) cysts with unknown ecological preferences.