Diatom assemblage responses to environmental change during the Holocene from a mountain lake (Prášilské jezero, Czech Republic)
Abstrakt
Mountain lake sediments are invaluable recorders of environmental change. Here, we present the thorough paleolimnological analysis of glacial lake in the Bohemian Forest, which aims to supplement our knowledge about paleoenvironmental development of Prášilské jezero (49.07519°N, 13.39976°E), Central Europe.
Diatom analysis was conducted as a part of the multi-proxy study (pollen, plant macrofossils, chironomids, charcoal, sediment geochemistry). Specifically, diatom analysis will be used to reconstruct pH and trophic state of the lake basin to determine timing and behaviour of major shifts in the lacustrine ecosystem.
Diatom valve concentration, relative abundances of species and the stomatocyst-to-diatom ratio were examined in order to observe diatom assemblage development in detail. Preliminary results show two distinct shifts in diatom species composition in the Holocene record.
The first shift corresponded to an erosional event in association with the 8.2 ky cal. BP event.
The second shift was accompanied by the establishment of Asterionella ralfsii W. Sm. around 4 ky cal.
BP and corresponded with the decline of quillworts (Isoëtes). This suggests substantial changes of the water chemistry, most likely the pH decline, weakened the population of quillworts.
These results affirmed that the diatom record in Prášilské jezero was able to elucidate the factors affecting changes in lacustrine ecosystem, specifically the changing abundance of quillworts. Further diatom analysis may potentially explain the cause of quillworts' extinction in constituent basins from the Bohemian Forest.