This dataset provides chironomid abundance data for a Mid Weichselian sediment sequence retrieved from the Reichwalde mine situated in the Niederlausitz area (Germany) in 1999. Percent-abundances of individual chironomid taxa are presented against relative core depth (m). The lake deposit was encountered in an exposure of Weichselian sediments and was sampled using a box core. The material was dated to the early Mid Weichselian (ca 50ka BP) using 14C dating. A total of 18 samples were analysed for their chironomid content. Samples were taken from the box core, weighted, and subsequently processed in the laboratory (Vrije Universiteit Amsterdam, the Netherlands) using standard protocols - this involved 20min treatment with warm KOH (10%) and sieving over a 100µm mesh. Chironomid head capsules were subsequently handpicked from the residue, mounted on permanent microscope slides, and identified using the literature. This dataset provides chironomid percent-abundances relative to the total count of chironomid head capsules per sample. The chironomid dataset provides insight in the natural evolution of the lake ecosystem and was used to produce a chironomid-inferred July air temperature record.
This dataset provides counts of diatom valves for the Lateglacial sediment sequence retrieved from Lake Hämelsee (Germany) in 2013. Counts per taxon are presented against both depth (m) and age (cal yr. BP). The diatom data provides information on Lateglacial ecosystem dynamics and the dataset was used to interpret changes in aquatic diversity as well as in palaeolimnological conditions. A total of 78 samples were selected for diatom analysis using 2-5 cm sample intervals throughout the Lateglacial section of the core sequence, with a higher sampling resolution (1 cm intervals) around key transitions. Organic matter was removed from the samples (ca. 0.01 grams dried sediment) by oxidation using 5 ml of H2O2 (30%) and heating in a water bath at 70 °C for 24-28 hrs. Subsequently, a few drops of HCl (50%) were added to remove residual H2O2 and carbonates. Samples were washed by adding distilled water, shaking vigorously, centrifuging at 1200 rpm for 4 minutes, and removing the liquid using a pipette. This process was repeated 5 times, and a few drops of ammonia (NH3) were added to the solution prior to the final wash to prevent clumping of diatoms. Diatom slides were mounted using Naphrax and diatoms were identified using Krammer and Lange-Bertalot (1986–1991) and Camburn and Charles (2000). For several samples the target count sum of 300 diatom valves could not be reached due to low concentrations or poor diatom preservation. Prior to analysis and interpretation, and where possible, neighbouring samples with a low count sum were amalgamated until a count of at least 100 valves was reached; if this was not possible the samples were deleted from our dataset prior to subsequent analysis (note that these samples are still included in the dataset provided here). All analyses were performed in the laboratories of University College London, UK.
This dataset provides glycerol dialkyl glycerol tetraethers (GDGTs) concentrations for the Lateglacial sediment sequence retrieved from Lake Hämelsee (Germany) in 2013. GDGTs concentrations (ng/g) are presented against both depth (m) and age (cal yr. BP). The GDGTs dataset was used to calculate the GDGT-0/crenarchaeol ratio, which was interpreted to represent lake water oxygenation, which, given the local settings, was likely driven by changes in windiness. Additionally, the GDGT dataset was used to calculate the degree of methylation of 5-methyl brGDGTs (MBT'5me), which can be used to reconstruct past temperature change through translation MBT'5me into mean temperature of the months above freezing. As such, the GDGT data provides information on LGIT climate dynamics at lake Hämelsee. Of the 167 samples used for lipid extraction (see https://doi.pangaea.de/10.1594/PANGAEA.964524), the alcohol/fatty acid fraction of 94 samples was further processed to analyse glycerol dialkyl glycerol tetraethers (GDGTs), which are membrane lipids of certain archaea and bacteria (Schouten et al., 2013). In short, a known amount of internal standard was added to each fraction, which was then redissolved in hexane:isopropanol 99:1 and passed over a 0.45 µm PTFE filter prior to injection on a Agilent 1260 Infinity ultra-high performance liquid chromatograph coupled to an Agilent 6130 single quadrupole mass spectrometer following the settings and elution protocol of Hopmans et al. (2016). A minimum peak area of 3000 and a signal-to-noise ratio of >3 was maintained as detection limit. Quantification of the GDGTs is based on the assumption that the mass spectrometer equally responds to the GDGTs and the internal standard. All analyses were performed in the laboratories of Utrecht University, the Netherlands.
This dataset provides counts of chironomid head capsules for the Lateglacial sediment sequence retrieved from Lake Hämelsee (Germany) in 2013. Counts per taxon are presented against both depth (m) and age (cal yr. BP), and the total amount of material used for analysis (in g) is provided as well. The chironomid data provides information on Lateglacial ecosystem dynamics and were used to interpret changes in aquatic diversity as well as in local climate conditions. A total of 123 samples from the Lateglacial section of the core were treated with warm KOH (10%) to de-flocculate the material and subsequently rinsed through a sieve with a 100-µm mesh. Chironomid head capsules (HCs) were hand-picked from the residue using a Bogorov sorting tray and mounted on permanent microscope slides using Euparal mounting medium. HCs were identified using Brooks et al. (2007) and the dataset presented here has been matched to the taxonomy of the merged Norwegian/Swiss chironomid-climate calibration dataset. Several samples had low chironomid concentrations and for these we amalgamated adjacent samples (within lithological boundaries) to reach a minimum count sum of 50 head capsules per sample. This process resulted in the final chironomid dataset that is presented here, containing 97 samples. All analyses were performed in the laboratories of the University of Amsterdam, the Netherlands.
This dataset provides concentrations of n-alkanes for the Lateglacial sediment sequence retrieved from Lake Hämelsee (Germany) in 2013. Concentrations of n-alkanes (ug/g), the Carbon Preference Index (CPI) and the Average Chain Length C21-C33 (ACL) are all presented against both depth (m) and age (cal yr. BP). The n-alkane concentration data provides information on the Lateglacial dynamics of local plant productivity, whereas the ACL and CPI of the sediment samples were determined to estimate origin and preservation condition. A total of 167 samples from the Lateglacial section of the core were processed using a Dionex 350 accelerated solvent extraction (ASE) system. Solid phase extraction (SPE) was used to separate the extracts into an aliphatic, aromatic and alcohol/fatty acid fraction. Separation was achieved by loading the extracts on activated silica columns and eluting each fraction with hexane, hexane/DCM (1:1 v/v) and DCM/MeOH (9:1 v/v) successively. The aliphatic fraction, containing the n-alkanes, was analyzed by gas chromatography-mass spectrometry (GC/MS). The peak areas for each n-alkane homologue were compared to the peak areas from an internal standard (5α-androstane) and an external n-alkane standard mixture for absolute quantification. We refer to Rach et al. (2020) for further details on the exact analytical setup. All measurements were performed in the laboratories of GeoForschungsZentrum Potsdam.
This dataset provides delta-Deuterium data for the Lateglacial sediment sequence retrieved from Lake Hämelsee (Germany) in 2013. Compound-specific hydrogen isotope ratios (expressed as δD) normalized to the Vienna Standard Mean Ocean Water (VSMOW) as well as measurement uncertainties (expressed as SD) are presented against both depth (m) and age (cal yr. BP). The data provides information on the Lateglacial development of local climate dynamics: the plant-wax derived δD signal is typically considered to reflect the hydrogen-isotopic composition of plant leaf water and, by extension, precipitation. We therefore interpret the trends in δD record here as an indicator of past hydrological change (cf Sachse et al., 2012). A total of 167 samples from the Lateglacial section of the core were processed using a Dionex 350 accelerated solvent extraction (ASE) system. Solid phase extraction (SPE) was used to separate the extracts into an aliphatic, aromatic and alcohol/fatty acid fraction. Prior to isotope ratio measurement, the aliphatic fraction was further fractionated on a Pasteur pipette column containing activated AgNO3 (10%) coated silica gel. Compound-specific hydrogen isotope ratios (expressed as δD) were subsequently measured on an isotope ratio mass spectrometer. All δD values are normalized to the Vienna Standard Mean Ocean Water (VSMOW) scale using a linear regression function between measured and certified δD values of a standard mix. We refer to Rach et al. (2020) for further details on the exact analytical setup. All measurements were performed in the laboratories of GeoForschungsZentrum Potsdam.
This dataset provides the sedimentological, palaeoecological and geochemical data for the Lateglacial sediment sequence retrieved from Lake Hämelsee (Germany) in 2013. Loss-on-ignition, XRF, n-alkane, delta-Deuterium and GDGT measurements as well as counts of chironomids, diatoms and Pediastrum are presented against both depth (m) and age (cal yr. BP). The data provides information on the Lateglacial development of the landscape around lake Hämelsee, the local climate dynamics, and the changes in the lake ecosystem itself and has been used to identify the effects of external drivers on biodiversity parameters (alpha diversity, compositional turnover and productivity). Cores were retrieved from the lake using a 3-m long UWITEC piston corer deployed from a floating coring platform during field work in July 2013. Following LOI analysis, ITRAX core scanning and sampling for thin section analysis, core segments spanning between 1325-1687 cm sediment depth were subsampled into contiguous 1-cm-thick subsamples. These subsamples formed the basis for the subsequent chronological, sedimentological and palaeoecological analyses and were processed in various laboratories as specified below. Where appropriate, datasets are processed through amalgamation of consecutive samples to e.g. ensure high count sums or concentrations.
Etude de la composition faunistique des larves de Chironomides (dipteres) des lacs de Suisse romande, de la repartition bathymetrique, de l'evolution des peuplements depuis le debut du siecle et de l'utilisation de ces larves comme bioindicateurs. (FRA)
This dataset provides chironomid percent-abundance data for an Early Weichselian sediment sequence retrieved from the Nochten mine (Niederlausitz area, Germany) in 2004. Percent-abundances of individual chironomid taxa are presented against relative core depth (m). The lake deposit was encountered in an exposure of Weichselian sediments and was sampled using a box core. The material was dated to the Early Weichselian (ca 80ka BP) using a combination of OSL and 14C dating. A total of 13 samples were analysed for their chironomid content. Samples were taken from the box core, weighted, and subsequently processed in the laboratory (Vrije Universiteit Amsterdam, the Netherlands) using standard protocols – this involved 20min treatment with warm KOH (10%) and sieving over a 100µm mesh. Chironomid head capsules were subsequently handpicked from the residue, mounted on permanent microscope slides, and identified using the literature. This dataset provides chironomid percent-abundances relative to the total count of chironomid head capsules per sample. The chironomid dataset provides insight in the natural evolution of the lake ecosystem and was used to produce a chironomid-inferred July air temperature record.
Während des 'Joint Danube Survey 2 wurden von zwei Mitarbeitern der Arbeitsgruppe Benthische Fließgewässerökologie der Universität für Bodenkultur Wien an 30 Stellen nahe der Donau Lichtfänge durchgeführt. Die (?) Imagines der Zuckmücken aus diesen Lichtfängen werden bestimmen. Es geht dabei nicht nur um die Erfassung einer wenig bekannten Fauna, unter der eine psammorheophile Gruppe (mit Arten wie Beckidia zabolotzskyi, Chernovskiia orbicus, Ch. macrocera, Lipiniella moderata, Paratendipes 'intermedius, P. 'connectens, Polypedilum acifer, Polypedilum aegyptium, Robackia demeijerei und Telopelopia fascigera) besonders typisch für Teile des Mittel- und Unterlaufes der Donau ist. Es geht auch darum, die erwähnten Arten und andere - in Zusammenschau mit den JDS2-Larvenproben - zumindest saprobiologisch und längenzonal einzustufen. Sehr wahrscheinlich ist es, dass unter den Tieren der Lichtfänge noch weitere Donauarten auftreten werden - etwa Uferbewohner oder Arten aus Augewässern. Es ließe sich, vor allem für Länder, in denen die Donauchironomidae noch weniger bekannt sind (z.B. Kroatien, Moldawien und die Ukraine), eine Erweiterung des Arteninventars anstreben. Die Lichtfänge könnten auch eine Antwort auf die Frage geben, ob in den meisten Teilen der Donau die Chironomidae tatsächlich von Neozoa ('Technoneozoa) und diversen Mollusca und Oligochaeta verdrängt worden sind, oder ob einige Arten im Spätsommer und Frühherbst schwärmen und von ihnen die überwinternden Generationen abstammen. Junglarven von (z.B.) Beckidia zabolotzskyi und Chernovskiia orbicus sind fast so klein und schlank wie Nematoda oder manche jungen Gnitzenlarven, so dass ein Massenfang solcher Arten in einer Lichtfalle zwar kaum zu quantifizieren ist (das gilt allgemein), aber doch Hinweise auf Verluste beim Sieben und Schlämmen böte. Belege einzelner Arten im Oberlauf (etwa von Cladotanytarus conversus, C. 'sexdentatus, Lipiniella moderata, Paratendipes 'intermedius) könnten - im Vergleich mit älterer Literatur (was die ersten 3 betrifft: CURE 1975, JANKOVIÆ 1975) durchaus als Neozoa unter den Chironomidae aufgefasst werden.
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