Seasonal variability of Holocene climate: a palaeolimnological study on varved sediments in Lake Jues (Harz Mountains, Germany)

Abstract

Studies combining sedimentological and biological evidence to reconstruct Holocene climate beyond the major changes, and especially seasonality, are rare in Europe, and are nearly completely absent in Germany. The present study tries to reconstruct changes of seasonality from evidence of annual algal successions within the framework of well-established pollen zonation and 14 C-AMS dates from terrestrial plants. Laminated Holocene sediments in Lake Jues (10°20.7 0 E, 51°39.3 0 N, 241 m a.s.l.), located at the SW margin of the Harz Mountains, central Germany, were studied for sediment characteristics, pollen, diatoms and coccal green algae. An age model is based on 21 calibrated AMS radiocarbon dates from terrestrial plants. The sedimentary record covers the entire Holocene period. Trophic status and circulation/ stagnation patterns of the lake were inferred from algal assemblages, the subannual structure of varves and the physico-chemical properties of the sediment. During the Holocene, mixing conditions alternated between di-, oligo-and meromictic depending on length and variability of spring and fall periods, and the stability of winter and summer weather. The trophic state was controlled by nutrient input, circulation patterns and the temperature-dependent rates of organic production and mineralization. Climate shifts, mainly in phase with those recorded from other European regions, are inferred from changing limnological conditions and terrestrial vegetation. Significant changes occurred at 11,600 cal. yr. BP (Preboreal warming), between 10,600 and 10,100 cal. yr. BP (Boreal cooling), and between 8,400 and 4,550 cal. yr. BP (warm and dry interval of the Atlantic). Since 4,550 cal. yr. BP the climate became gradually cooler, wetter and more oceanic. This trend was interrupted by warmer and dryer phases between 3,440 and 2,850 cal. yr. BP and, likely, between 2,500 and 2,250 cal. yr. BP.

Postglacial history of vegetation, human activity and lake-level changes at Jezioro Linówek in northeast Poland, based on multi-proxy data

“…was a general trend in the whole of Europe. It was recorded in the Netherlands (Van Geel et al 1996), Switzerland (Holzhauser et al 2005), Northern Ireland (Swindles et al 2007), Finland ), Germany (Voigt et al 2008) and Sweden (Andersson and Schoning 2010). It corresponds to a widespread climate reversal identified at the Sub-boreal to Sub-atlantic transition (Van Geel et al 1996).…”

Determining the responses of vegetation to natural processes and human impacts in north-eastern Poland during the last millennium: combined pollen, geochemical and historical data

“…In varved sediments it is possible to assess yearly flux rates of pollen, to define rates of palaeoenvironmental changes and to describe them on decadal and even subdecadal scales (Birks and Birks 2006). Holocene palaeoecological reconstructions including pollen studies from varved sediments were obtained for several European areas, for instance in Scandinavia (Anderson et al 1996;Haltia-Hovi 2010;Ojala et al 2008), Germany (Kerig and Lechterbeck 2004;Kubitz 2000;Leroy et al 2000;Litt et al 2001;Voigt et al 2008), Switzerland (e.g. Haas et al 1998;Lotter 1999;Tinner et al 2003) and France (e.g.…”

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“…This species was also found in a lagoon (Colombia) (Montoya- Moreno et al, 2013) and in Animas river (USA), where heavy metals loading is present (Sgro, Poole, & Johansen, 2007). Otherwise, it is a fossil species found in some sediment core samples (Voigt, Grüger, Baier, & Meischner, 2008;Loakes, 2015). We found this species at H003 station of Lake Hazar in Elazığ (Turkey).…”

“…Also, this species was recorded as a new taxon for Bulgarian algal flora in a study in Boyanska River (Isheva & Ivanov, 2014). Otherwise, in some studies it was found in sediment cores (Voigt et al, 2008;Loakes, 2015). Ludwig and Schnittler (1996) reported that this taxon is also in red list category (endangered species) for Germany.…”