Younger Dryas Cladocera assemblages from two valley mires in central Poland and their potential significance for climate reconstructions

This paper presents a palaeoenvironmental reconstruction of the Wilczków fen (central Poland). The fen developed in an inactive valley at the onset of the Holocene (~11 ka BP) and peat accumulation lasted until 5.7 ka BP. Multi‐proxy reconstructions were made on the basis of palaeobotanical, cladoceran, chironomid, beetle and geochemical analyses. A Kohonen self‐organizing map (SOM, unsupervised artificial neural network) of the biotic sequence distinguished four stages of fen history. Stage X1 (11.0–10.7 ka BP) was relatively wet and cool. Organic matter started to accumulate but the habitat conditions remained unstable. Moss, sedge and fern communities then developed. Sedimentary changes reveal an intensive groundwater supply at that time. Numerous and diverse chironomid and cladoceran subfossils indicate nearly permanent aquatic conditions. During stage Y1 (10.6–9.2 ka BP) conditions were dry and the upper peat layer desiccated. Cladocera nearly disappeared whereas chironomids were represented by semi‐terrestrial and predatory (Tanypodinae) species. Conditions started to be more reducing. All the remaining samples belonged to the interweaving stages X2 and Y2. Stage Y2 (mostly 9.1–7.3 and 6.0–5.7 ka BP) was also dry but humidity increased towards the top. Oxidizing conditions occurred and the pH became more alkaline, favouring Cladium mariscus. The basin received mostly allochthonous matter input at that time. Stage X2 (mostly 6.8–6.1 ka BP) was humid and warm. The groundwater supply remained low but there was an increase in precipitation, changing local conditions to ombrotrophic. Species‐rich chironomid and cladoceran communities were associated with temporary pools. Finally, conditions returned to those characteristic of stage Y2. The presented reconstruction documents long‐term abiotic and biotic changes determined by water supply, including groundwater outflow, which have rarely been detected at a multi‐proxy scale. We show that inactivated valley fens are sensitive to climate‐driven hydrological fluctuations. Kohonen neural networks appear to be a promising method for analysing variability in multi‐proxy data.

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“…). In turn, the species diversity of Cladocera in the Wilczków fen was low, similar to other Polish sites (Pawłowski ,b; Pawłowski et al . ).…”

Section: Discussionsupporting

confidence: 84%

Fen ecosystem responses to water‐level fluctuations during the early and middle Holocene in central Europe: a case study from Wilczków, Poland

Płóciennik

Kruk

Forysiak

et al. 2015

Boreas

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“…sphaericus and Daphnia spp. populations are not only compatible with the presence of zooplanktivorous fish but also with nutrients, waterlevel increase, an influence of floods and, indirectly, even climate change (Pawłowski 2012). Additionally, changes in predator-prey relationships might have caused changes in the reproductive strategies of Cladocera (Sarmaja-Korjonen 2003).…”

Section: Limitations Of Palaeohydrological Reconstructions Based On Fmentioning

confidence: 99%

A reconstruction of the palaeohydrological conditions of a flood‐plain: a multi‐proxy study from the Grabia River valley mire, central Poland

Pawłowski

Kowalewski

Milecka

et al. 2015

Boreas

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This study investigated the Grabia River valley mire in central Poland to reconstruct its palaeoenvironmental conditions from the Younger Dryas to the present. We analysed sedimentological, biological and geochemical data from the palaeo-oxbow lake and valley mire to identify the principal hydrological trends, especially episodes of high water level. During the Lateglacial and Holocene, the Grabia River had a meandering channel, and its hydraulic parameters and the channel dimensions changed in response to climatic oscillations and vegetation development. We identified phases of high flood intensity and high groundwater level that correlate with regional and supraregional climatic events. The frequency and timing of palaeohydroclimatic oscillations show strong similarities to records from other sites in Poland and the rest of Europe. We show that various analytical methods, namely, pollen, plant macrofossils, Cladocera, Chironomidae, sedimentological, geochemical and radiocarbon data, can be effective tools for reconstructing past hydroclimatic changes in palaeo-oxbow lakes and investigating the effects of past climate changes on river environments. The high sensitivity of the biota, especially Cladocera, to changes in water level permits the reconstruction of palaeoecological changes, especially flood episodes that occurred in the river valley. In particular, the increase in the proportion of sediment-associated Cladocera and pelagic taxa was closely correlated with floods. Through comparisons with the palaeobiological data, geochemical data allowed the identification of humid phases within the fen associated with a rising groundwater table, direct fluvial activity (floods) and alluvial deposition. We also discuss the limitations of palaeohydrological reconstructions based on these proxies, especially on fossil aquatic invertebrates.

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“…The study sites have previously undergone Clado cera analysis (Pawłowski 2012a(Pawłowski , 2012bDzieduszyńska et al 2014;Pawłowski et al 2015aPawłowski et al , b, 2016a. However, the cladoceran-inferred paleotemperature estimates from most study sites -Żabieniec, Rąbień, Korzeń, Ługi, Kolonia Bechcice, and Koź-min -have not yet been presented.…”

Section: Methodsmentioning

confidence: 99%

The usefulness of subfossil Cladocera remains in Younger Dryas climatic reconstructions in central Poland

Pawłowski

2017

Acta Geologica Polonica

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ABSTRACT:Pawłowski, D. 2017. The usefulness of subfossil Cladocera remains in Younger Dryas climatic reconstructions in central Poland. Acta Geologica Polonica, 67 (4), 567-584. Warszawa.Cladoceran-based paleotemperature estimates for the Younger Dryas for ten sections of paleo-oxbow lakes, valley mires, and lacustrine sediments from central Poland are presented, and their potential usefulness to climatostratigraphy is described. Most of the changes observed in the cladoceran assemblages are responses to climate changes. The cladoceran-based temperature reconstructions reflect cold conditions during the Younger Dryas (YD) and allow a division of this period into two phases: an older colder phase, between 12,800 and 12,000 cal yrs BP, and a younger, warmer phase, between ca. 12,000 and 11,500 cal yrs BP. The geomorphological features of the study sites and local environmental forces are also taken into consideration. The cladoceran-inferred summer temperature estimates from all of the study sites correspond closely with the available climate reconstruction for the YD in central Europe.

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Younger Dryas Cladocera assemblages from two valley mires in central Poland and their potential significance for climate reconstructions

Cited by 18 publications

References 37 publications

Fen ecosystem responses to water‐level fluctuations during the early and middle Holocene in central Europe: a case study from Wilczków, Poland

Fen ecosystem responses to water‐level fluctuations during the early and middle Holocene in central Europe: a case study from Wilczków, Poland

A reconstruction of the palaeohydrological conditions of a flood‐plain: a multi‐proxy study from the Grabia River valley mire, central Poland

The usefulness of subfossil Cladocera remains in Younger Dryas climatic reconstructions in central Poland

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