Abstrakt
In the Czech Republic, there are unfortunately just several lakes of natural origin which limits the possibilities of using the information preserved in their sediments. Lake biotopes have never been especially common in the Czech Republic, not even during their maximal occurrence in the Late Glacial and Early Holocene.
Furthermore, if lakes appeared in the periglacial landscape, their biotopes were usually in-filled during the Holocene climatic optimum at the latest. Except for 5 mountain-glacial lakes (Southern Bohemia), only one lowland lake persisted until the 20th century, 25 km2 of Komořanské Lake (the Most basin, Northern Bohemia).
However, its sediments were totally removed in the second half of the last century due to the brown coal surface mining. Several archived sediment profiles are now analyzed.
In contrast to former paleobotanical studies, fossil chironomid assemblages indicate that Komořanské Lake was mesotrophic or eutrophic shallow water body as early as the time of its presumable creation in the Bolling period. The aim of the present research (chironomids, diatoms, plant macrofossils, coccal green algae, pollen; geochemistry, sedimentology) is complex evaluation of the last remains of this lost natural archive.The second studied locality, Stará jímka Lake (the Bohemian Forest, Southern Bohemia), is a former mountain lake which was dammed by slope movements in a paraglacial phase after local deglaciation.
Subsequent infilling of lake basin was finished ca. 3 kyr cal. BP.
Chironomid assemblages from the base of the sediment profile (LG origin) show dynamic changes although they are always dominated by taxa of cold/oligotrophic lentic waters. It has probably a good potential for climate reconstructions.
The main objectives of our future work are quantitative reconstruction of LG chironomid mean July air temperature, reconstruction of chironomid δ18O and their comparison.