Tomasz Goslar

Correlation and synchronisation of Lateglacial continental sequences in northern central Europe based on annually laminated lacustrine sediments

Abstract The present study focusses on correlation and synchronisation of Weichselian Lateglacial varved lake sediments from western Germany (Meerfelder Maar, Eifel region), northern Germany (Hamelsee, Lower Saxony), central Poland (Lake Gości a z) and eastern Poland (Lake Perespilno) by using varve chronology, tephrochronology, palynostratigraphy and stable isotopes. Comparison of the several independent time scales shows that biotic and abiotic parameters respond abruptly and quasi-synchronously, within the errors of the different chronologies, during the Younger Dryas/Preboreal transition. Moreover, there is a consensus about the length of the Younger Dryas cold stage of 1100–1150 varve years. In the Allerod the prominent Laacher See tephra (12,880 varve years BP) can be used to fix floating varve chronologies. The relative duration of this biozone has been determined in Meerfelder Maar and Hamelsee at between 625 and 670 varve years. In the Meerfelder Maar a combination of continuous varve counting and biostratigraphy has been possible for the almost entire Lateglacial. The comparison between continental limnic sequences and Greenland ice-core records should be made on the basis of independent chronologies in both archives. It is more practicable to develop regional stratotypes on the continental regions instead of simply using ice cores as stratotypes for the Lateglacial for terrestrial European records. In this respect, annually laminated lacustrine sequences have a great potential.

Fifty thousand years of Arctic vegetation and megafaunal diet

Although it is generally agreed that the Arctic flora is among the youngest and least diverse on Earth, the processes that shaped it are poorly understood. Here we present 50 thousand years (kyr) of Arctic vegetation history, derived from the first large-scale ancient DNA metabarcoding study of circumpolar plant diversity. For this interval we also explore nematode diversity as a proxy for modelling vegetation cover and soil quality, and diets of herbivorous megafaunal mammals, many of which became extinct around 10 kyr bp (before present). For much of the period investigated, Arctic vegetation consisted of dry steppe-tundra dominated by forbs (non-graminoid herbaceous vascular plants). During the Last Glacial Maximum (25–15 kyr bp), diversity declined markedly, although forbs remained dominant. Much changed after 10 kyr bp, with the appearance of moist tundra dominated by woody plants and graminoids. Our analyses indicate that both graminoids and forbs would have featured in megafaunal diets. As such, our findings question the predominance of a Late Quaternary graminoid-dominated Arctic mammoth steppe.

DNA from soil mirrors plant taxonomic and growth form diversity

Ecosystems across the globe are threatened by climate change and human activities. New rapid survey approaches for monitoring biodiversity would greatly advance assessment and understanding of these threats. Taking advantage of next-generation DNA sequencing, we tested an approach we call metabarcoding: high-throughput and simultaneous taxa identification based on a very short (usually <100 base pairs) but informative DNA fragment. Short DNA fragments allow the use of degraded DNA from environmental samples. All analyses included amplification using plant-specific versatile primers, sequencing and estimation of taxonomic diversity. We tested in three steps whether degraded DNA from dead material in soil has the potential of efficiently assessing biodiversity in different biomes. First, soil DNA from eight boreal plant communities located in two different vegetation types (meadow and heath) was amplified. Plant diversity detected from boreal soil was highly consistent with plant taxonomic and growth form diversity estimated from conventional above-ground surveys. Second, we assessed DNA persistence using samples from formerly cultivated soils in temperate environments. We found that the number of crop DNA sequences retrieved strongly varied with years since last cultivation, and crop sequences were absent from nearby, uncultivated plots. Third, we assessed the universal applicability of DNA metabarcoding using soil samples from tropical environments: a large proportion of species and families from the study site were efficiently recovered. The results open unprecedented opportunities for large-scale DNA-based biodiversity studies across a range of taxonomic groups using standardized metabarcoding approaches.

High-resolution lacustrine record of the late glacial/holocene transition in central Europe

Abstract In this paper we present the high-resolution record of proxy climatic data in central Europe during the final stages of the last deglaciation, derived from the annually laminated sediments of Lake Gościaz (central Poland). The isotopic, palynological and other microfossil data confirm sudden changes of climate at the onset and termination of the Younger Dryas (completed within 150 and 70 years, respectively), in close agreement with the previous estimates derived from the polar ice cores and marine sediments. In the upper YD some amelioration of climate took place already about 600 years before the main YD/Preboreal transition. Counting of annual varves in the lake sediments allows a direct estimate of the duration of the Younger sDryas in central Europe; it lasted approximately 1640 years, substantially longer than suggested by previous estimates derived from laminated lake sediments and glacial varves, but agreeing with the radiocarbon calibration data obtained for Barbados corals. The calendar ages of the boundaries of the YD, 12,920 and 11,280 cal BP, are tentatively set.

Fossil akinetes of Aphanizomenon and Anabaena as indicators for medieval phosphate-eutrophication of Lake Gosciaz (Central Poland)

Records of fossil akinetes of Aphanizomenon and Anabaena (Cyanobacteria) in the laminated sediments of Lake Gosciaz are interpreted. Increasing human impact in the catchment area of the lake (as can be interpreted from the pollen records of human impact indicators) apparently had its effect on the trophic conditions of the lake water: from ca. 1000 AD on fosil akinetes of Aphinizomenon and Anabaena are present in enormous quantitites in the sediment. The increases of the Cyanobacteria are interpreted as the effect of an intensiication of farming and land fertilization in the area around Lake Gosciaz, causing eutrophication of the lake. Phosphorus enrichment form effluent and excreta in the catchment area of the lake at times will have become so high that N-limited growth conditions occurred. In such conditions Cynoobacteria capable of nitrogen fixation (namely Alphanizomenon and Anabaena) could bloom. The deposits of the last ca. two centuries are characterised by the successive appearance of Pediatrum boryanum, Tetraedron minimum, Coelastrum cf. reticulatum, Botryococcus, Scenedesmus, Spirogyra, Gloeotrichia and Staurastrum manfeldtii, whereas Cyanobacteria show a decline. This phytoplankton succession could be interpreted in terms of competition for nutrients and light: higher eutrophication levels and higher turbidity caused a decline of available light, and as a consequence less enegry was avilable for the energyu consuming process o nitrogen fixation by Aphanizomenon and Anabaena.

Very fast environmental changes at the Pleistocene/Holocene boundary, recorded in laminated sediments of Lake Gościż, Poland

Abstract This paper presents a reconstruction of the climatic changes at the Pleistocene/Holocene transition, recorded in the annually laminated sediments of Lake Gości a z, Poland. This reconstruction is based on pollen, stable isotope, mineralogical and chemical analyses of sediments, made with a time resolution of 1–4 yr. It reveals a sequence of abrupt climatic changes which preceded and followed the major warming around 11 500 cal BP. Our data show that the warming period was preceded by a 30-yr-long phase of increased winter and decreased summer precipitation (11 550–11 520 cal BP). About 11 520 cal BP, a very brief period of wetter conditions occurred, simultaneously with the beginning of the major warming. However, most of the first phase of the major warming (11 520–11 500 cal BP) was characterised by a generally dry climate, presumably due to lowered winter precipitation. Our records suggest that in this phase the warming concerned winter seasons mostly. In the second phase (11 500–11 460 cal BP) the warming also concerned summer seasons. Also, a distinct increase of humidity is noted in this period, which caused moistening of soils and, despite enhanced evaporation and evapotranspiration, inhibited the process of lake-level drop. The following 70 years (11 460–11 390 cal BP) were rather dry, which caused a distinct lowering of the lake (and probably also of groundwater) level. In this period, maximum biological productivity (per unit area) in the lake is noted. The whole sequence of phases of rather different climates was completed within a time interval (160 years) spanning two human lifes only. One should stress that the transitions between the consecutive phases were rather abrupt, lasting no longer than 10 years.

Preparation of Graphite Targets in the Gliwice Radiocarbon Laboratory for AMS 14C Dating

A line for preparation of graphite targets for accelerator mass spectrometry (AMS) radiocarbon dating has been built in the Gliwice (super 14) C Laboratory. The AMS (super 14) C measurements of our targets are performed in the Leibniz-Labor fur Altersbestimmung, Kiel, Germany. The quality of our line has been tested in two series of AMS (super 14) C measurements of background and Ox-II standard samples and by measurements of the amount of CO (sub 2) released during combustion of sample-free quartz tubes. Most background contamination in the first series was introduced during combustion, which has been greatly reduced by baking quartz tubes vacuum-sealed with CuO and Ag. The residual contamination (ca. 1.5 mu g C) seems to come mostly from the quartz tubes themselves. At present, most of the contamination of the background is introduced during graphitization. The reproducibility of background preparations is satisfactory, especially for samples larger than 1.5 mg, when it is better than + or -0.09 pMC. Despite still significant contamination with low- (super 14) C carbon during the graphitization process (corresponding to 1.2+ or -0.2% of (super 14) C-free carbon), the good reproducibility of the results allows us to use our line in routine (super 14) C dating.

THE YOUNGER DRYAS COLD EVENT-WAS IT SYNCHRONOUS OVER THE NORTH ATLANTIC REGION?

Determined independently from annually laminated ice cores and lake sediments, and German pines, the calendar ages of Younger Dryas (YD) boundaries significantly disagree with one another. 14C dates, plotted vs. calendar ages for samples from different sediments, also reveal distinct offsets. The adjustment of varve chronologies to synchronize the boundaries of the YD nearly cancels the discrepancies between 14C data, and supports the synchronism of the YD cold period over the North Atlantic region. However, the exact timing of the event cannot be estimated in this way.

Anthropogenic changes in the sediment composition of Lake Gości& aogon;ż (central Poland), during the last 330 yrs*

According to historical sources, the development of settlement around Lake Gości& aogon;ż during the last 330 yrs was intense at two time periods: the second half of the 1700s, and from ca. 1880 until 1944. The small farms were then abandoned, following which the lake surroundings were planted with forest trees. The presented study of human influence on the lake ecosystem and surrounding vegetation has been based on analyses of general sediment composition and its chemistry, pollen, Cyanobacteria, Chlorophyceae, Rotatoria, Cladocera, and a preliminary diatom survey. The history of human impact has been divided into four phases: 1. Phase of small local hamlets (before ca. 1770): The human impact was rather moderate then, but the cultivation of Canabis sativa, Secale cereale and later of Fagopyrum is evidenced from that time. 2. Phase of ‘Hollandii’ settlement (ca. 1770-1863). Its influence is indicated first by the recession of deciduous wood (Corylus, Carpinus) stands, which triggered drastic drop of calcium in sediments. The development of rural economy in the area, including, an extension of agriculture (Secale and other cereals, crucifers, potatoes), and animal breeding based partly on grazing in the forest, is evidenced only after 1820. 3. Phase of German colonization (1863-1944): In the early periods (before 1910) the pollen spectra do not document any essential change in the type of farming, however, a serious disturbance of the lake ecosystem and sediment chemistry is evidenced by the blooms of Araphidinae diatoms and Tetraedron minimum, a maximum frequency of Bosmina longirostris, disturbances of the regular spring blooms of Chrysophyceae, appearance of vivianite, distinct maxima of organic matter, potassium, and iron concentration in sediments and an increase of the sedimentation rate. An intensification of agricultural activities commenced around 1910; woods, including also pinewoods, were then heavily devastated, and farming extended on poor soils, what was symptomatic for the general poverty of population. Coincidently in the lake, Centriceae showed blooms, Araphidinae diatoms and Tetraedron minimum developed, and the content of potassium, iron and phosphorus increased substantially, indicating altogether rising eutrophication. 4. Phase of restoration of the natural landscape (after 1945): The farm degradation from ca. 1944 is very weakly expressed in pollen data, which show a substantial fall of farming indicators from 1953/6 only, when the whole area was used for forest plantation. It was accompanied by a certainly spontaneous development of Betula and Alnus woods, this process progressing till recent time. The gradual extinction of farming activity near Lake Gościąż was accompanied by abrupt changes in the lake ecosystem, expressed by the restored blooms of Chrysophyceae expansion of planktonic Cladocera, rapid decline of phosphorus and extinction of vivianite from sediments. As documented by the drop of Cu/Zn ratio, lake hypolimnion has been weakly oxidized since 1949, what was probably responsible for the drop of Fe and Mn content in sediments. Increasing strength of overturns affected preservation of laminae in sediments, which almost completely disappeared after 1966.

Problematic 14C-AMS dates of pollen concentrates from Lake Gosciaz (Poland)

Pollen concentrates and macrofossils of mid-Holocene age from the annually laminated sediments of Lake Gosciaz (Poland) are dated by 14C AMS. Dating the sediment by matching to the radiocarbon calibration curve is possible for the macrofossils. The 14C ages of the pollen concentrates, however, do not support the varve chronology, probably due to an as yet not fully explained reservoir effect.