Effects of the Laacher See Eruption and the Younger Dryas cosmic impact / airburst on mountain lake biota in central Europe
Abstrakt
Sudden environmental catastrophes pose a considerable threat to the human society. In Central Europe, the Late Glacial period (⁓14700-11650 cal.
BP) was characterized by abrupt climatic changes. It ended with the Greenland Stadial 1 (12850-11650+-99 cal.
BP; ⁓Younger Dryas biozone) whose onset is associated with identification of cosmic impact-related proxies pointing to a possible cause of this event. Another catastrophic event, the Laacher See volcanic eruption, occurred a hundred years earlier (⁓12920 cal.
BP) in western Germany. It was the largest late Quaternary eruption in continental Europe north of the Alps (VEI = 6).
The aim of our study is to describe possible damaging effects of these two events on lake communities and compare them with long-term development during the Late Glacial and the Early Holocene. We performed diatom, chironomid, and cladoceran analyses using lacustrine sediment profiles from a central European paleolake (Stara Jimka, Czech Republic).
The results were compared with the lake-catchment system history (pollen and charcoal analyses, geochemical and geophysical characterization of the lake sediment), a record of volcanic glass, and a record of glassy microspherules often considered as impact/airburst related proxy. We identified clear evidence of the Laacher See tephra shards presence (deposition in the distance of 470 km from the volcanic crater) and a distinct peak of glassy microspherules at the onset of the Younger Dryas climatic cooling.
Both events correspond with changes in diatom, chironomid, and cladoceran species composition and abundances. However, all these shifts don't show any drastic reduction of the lake biota.
Additionally, the most significant change is not associated with these events but with the later Younger Dryas-Holocene transition. Our data show effects of the long-range atmospheric transport of "contaminants" on a sensitive lake ecosystem during the two transient events.
The project is supported by the Czech Grant Foundation (17-05935S - LAYERS).