Responses of freshwater invertebrate fauna to the abrupt 8.2 ka paleoclimatic event: evidence from a small mountain lake in the Czech Republic
Abstrakt
The 8.2 kiloyear cooling is one of the most abrupt climatic events to occur throughout the Holocene. Several studies from central Europe describe widespread ecological changes associated with the event, however, few studies document the response of freshwater invertebrate fauna.
Here, we present a detailed paleoecological record from a sediment profile from Prášilské Lake, a small tarn in southern Czech Republic (1080 m asl, 3.7 ha, max. depth 15 m). Using XRF data and radiocarbon dating, we identified a disturbance sequence correlated with the 8.2 ka event (ca. 6300 years BC).
A multi-proxy approach using lake fauna remains (chironomids, alderflies, bryozoans and in less detail caddisflies, mayflies, and cladocerans) supported by an analysis of aquatic and terrestrial plant macrofossils, pollen, charcoal and terrestrial insects was used to evaluate the ecosystem response on the event. Our results document an increase in both abundance and the number of species of macrozoobenthos (namely profundal chironomids), and changes in catchment vegetation cover during the event.
A synchronous increase in Rubidium suggest increased erosion and more pronounced influence of tributaries which could have supported water column mixing in the humic brown-water lake generally affected by bottom anoxia. Plant macrofossils, pollen, charcoal and terrestrial insect communities also document an increase in humidity.
This change in the hydrology, leading to higher oxygen concentrations near the bottom because of the mixing of the lake, would explain the observed expansion of macrozoobenthos. Our results thus indicate a strong indirect effect of the 8.2 ka event on the lake fauna.