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The archaeological sites in the open‐cast mine of Schöningen, Germany, represent outstanding archives for understanding Middle Pleistocene interglacial–glacial transitions and human adaption. Aquatic microfossil and pollen assemblages from the ‘Reinsdorf sequence’, likely correlated to Marine Isotope Stage 9, document environmental changes from a thermal maximum to succeeding glacial conditions recorded in two sequences of excavation sites 12 II and 13 II. Multi‐proxy analyses enable detailed reconstruction of lake‐shore and landscape developments despite variable microfossil preservation in changing carbonate‐ and organic‐rich deposits. Rich aquatic vegetation with abundant charophytes suggests repeated phases with water depths of 0.5–2 m at site 13 II, while even greater temporary depths are deduced for 12 II DB. Mesorheophilic and mesotitanophilic ostracod species indicate stream inflows with medium–low calcium contents of >18 mg Ca L–1 originating from nearby springs. Diatoms point to meso‐eutrophic conditions and an alkaline pH of the lake water. Interglacial conditions with thermophile forests but no aquatic microfossils preserved, suggesting a dry or only temporarily flooded site, mark the beginning of the sequence. Continuous presence of aquatic organisms and overall dominance of small tychoplanktonic diatoms during a subsequent cool steppe phase provide evidence for increased water depths and unstable habitats characterized by erosion and probably prolonged periods of lake ice cover. During the succeeding boreal forest‐steppe phase, surface runoff into the productive, shallow lake decreased due to a more extensive vegetation cover. Concurrently, intensified groundwater input in contact with the nearby salt wall caused elevated salinities. Following a lake level drop, stream inflows and lake levels increased again towards the end of the Reinsdorf sequence and promoted development of a diverse fauna and flora at the lake shore; thereby maintaining an attractive living and hunting environment for early humans during a phase of generally cooler temperatures and landscape instability at the transition into a glacial period., Niedersächsisches Ministerium für Wissenschaft und Kultur http://dx.doi.org/10.13039/501100010570, Deutsche Forschungsgemeinschaft http://dx.doi.org/10.13039/501100001659

Three new needle-shaped Fragilaria species from freshwater lake Apastepeque in El Salvador (Fragilaria salvadoriana sp. nov., F. maarensis sp. nov.) and subsaline lake Nam Co on the Tibetan Plateau (F. huebeneri sp. nov.) are described and compared based on light and scanning electron microscopy observations and morphometric analyses. Fragilaria salvadoriana sp. nov. is characterized by narrowly linear-lanceolate, sometimes centrally constricted valves, subcapitate to rarely capitate apices, and a distinct, dented appearing central area. Striae are composed of 2−5 occluded areolae. It can be differentiated from similar needle-shaped species by the valve outline, relatively low striae density, and shark fin-shaped spines. Characteristic of F. maarensis sp. nov. are a very narrowly lanceolate valve outline and subcapitate apices. The apical pore field is composed of 2–3 rows of poroids and acute, irregularly oriented spines are present at the junction between valve face and mantle. This taxon is clearly different from other Fragilaria species, displaying a high length-to-width ratio and a low number of areolae per stria. The Tibetan species, F. huebeneri sp. nov., forms long ribbon-like colonies linked together by spatula-shaped spines. Valves have subcapitate apices, a spindle- to needle-shaped outline and an indistinct central area. Striae are alternate and composed of 3–5 areolae per stria. Teratological forms of F. huebeneri sp. nov. were commonly observed in the sediment trap samples. Fragilaria salvadoriana sp. nov. and F. maarensis sp. nov. were found in a warm, tropical crater lake characterized by low conductivity and dissolved oxygen content, medium alkaline pH, and magnesium-calcium-bicarbonate-rich waters. Fragilaria huebeneri sp. nov. was frequent in a large, high elevation lake with increased specific conductivity, alkaline pH and sodium-bicarbonate-rich waters. The new species are compared to morphologically similar species from the genus Fragilaria Lyngbye and ecological preferences are discussed.

Permafrost as a climate-sensitive parameter, its occurrence and distribution plays an important role in the observation of global warming. However, field-based permafrost distribution data and information on the subsurface ice content at the large area of the southern mountainous Tibetan Plateau (TP) is very sparse. Existing models based on boreholes and remote sensing approaches suggest permafrost probabilities for most of the Tibetan mountain ranges. Field data to validate permafrost models are generally lacking because access of the mountain regions in extreme altitudes is limited. The study provides geomorphological and geophysical field data from a north-orientated high-altitude catchment in the western Nyainqentanglha Range. Our multi-method-approach combines (A) geomorphological mapping data, (B) subsurface ice-occurrence derived from electrical resistivity tomography (ERT) data, and (C) multi-annual displacement rates from Interferometric Synthetic Aperture Radar (InSAR) analysis to assess the lower occurrence of the probable permafrost around 5400 m a.s.l. in the Qugaqie basin. Periglacial landforms such as rockglaciers and protalus ramparts are located in the periglacial zone from 5300–5600 a.s.l. The altitudinal periglacial landform distribution is supported by ERT data detecting ice-rich permafrost in a rockglacier at 5500 m a.s.l. and ice lenses around the rockglacier (5450 m a.s.l.). The highest, multiannual displacement rates up to 150 mm/y are observed typically on these rockglaciers. However, seasonality of rockglacier surface displacement like in other high mountain areas is missing. This study closes the gap of unknown state of periglacial features and potential permafrost occurrence in a high-elevated basin at the western Nyainqentanglha Range (Tibetan Plateau) and suppose – compared to other high mountain regions – a higher-elevated permafrost occurrence.

Dwelling in a variety of aquatic habitats, one of the most abundant groups of microcrustaceans, ostracodes, are widely used indicator organisms in paleolimnological research. Typically, they are identified via traditional methods using morphological features but this may be excessively time‐consuming and prone to inter‐investigator variation. DNA barcoding and metabarcoding have become important tools for specimen identification, with a great impact in the field of taxonomy, (paleo‐)ecology and evolution. Despite its potential, metabarcoding has been rarely used to analyze the community structure of ostracodes. Here, we evaluate the performance of a metabarcoding approach for ostracode identification in surface sediment samples collected from Lake Nam Co on the Tibetan Plateau. We tested six different primer pairs amplifying fragments of three different genes, and compared their success in inferring ostracode communities, coupled with morphological identification of ostracodes from the same sediment samples. In total, depending on the primer pair used, seven to nineteen ostracode amplicon sequence variants (ASVs) were identified. Via microscopy, eight morphospecies were identified. We found considerable differences between primer pairs in yielding ostracode sequences via metabarcoding. In general, the highest proportions of ostracode reads and ASVs were found with primers amplifying fragments of the 18S rRNA gene, whereas primers for COI gene had the highest in silico amplification success and highest sequencing depth per sample but only contained

The western Nyainqêntanglha Range on the Tibetan Plateau reaches an elevation of 7,162 m and is characterized by an extensive periglacial environment under semi-arid climatic conditions. Rock glaciers play an important part of the water budget in high mountain areas and recent studies suggest that they may even act as climate-resistant water storages. In this study we present the first rock glacier inventory of this region containing 1,433 rock glaciers over an area of 4,622 km. To create the most reliable inventory we combine manually created rock glacier outlines with an automated classification approach. The manual outlines were generated based on surface elevation data, optical satellite imagery and a surface velocity estimation. This estimation was generated via InSAR time series analysis with Sentinel-1 data from 2016 to 2019. Our pixel-based automated classification was able to correctly identify 87.8% of all rock glaciers in the study area at a true positive rate of 69.5%. In total, 65.9% of rock glaciers are classified as transitional with surface velocities of 1–10 cm/yr. In total, 18.5% are classified as active with higher velocities of up to 87 cm/yr. The southern windward side of the mountain range contains more numerous and more active rock glaciers. We attribute this to higher moisture availability supplied by the Indian Monsoon.

Understanding Earth’s response to climate forcing in the geological past is essential to reliably predict future climate change. The reconstruction of continental climates, however, is hampered by the scarcity of universally applicable temperature proxies. Here, we show that heterocyte glycolipids (HGs) of diazotrophic heterocytous cyanobacteria occur ubiquitously in equatorial East African lakes as well as polar to tropical freshwater environments. The relative abundance of HG26 diols and keto-ols, quantified by the heterocyte diol index (HDI26), is significantly correlated with surface water temperature (SWT). The first application of the HDI26 to a ~37,000 year-long sediment record from Lake Tanganyika provides evidence for a ~4.1 °C warming in tropical East Africa from the last glacial to the beginning of the industrial period. Given the worldwide distribution of HGs in lake sediments, the HDI26 may allow reconstructing SWT variations in polar to tropical freshwater environments and thereby quantifying past continental climate change., Understanding the past is necessary to comprehend Earth’s response to present climate change, but past climate reconstruction is hampered by a lack of temperature proxies. Here the authors develop the HDI26, a proxy using cyanobacterial glycolipids to reconstruct water temperatures of lakes worldwide.

The modern basin of trinational Lake Constance, between Switzerland, Germany, and Austria, represents the underfilled northern part of a glacially overdeepened trough. It is over 400 m deep and reaches well into the Alps at its southern end. The overdeepening was formed by the numerous glacial advance-retreat cycles of the Rhine Glacier throughout the Middle to Late Quaternary. A seismic survey of Lake Constance revealed a Quaternary sediment fill of over 150 m thickness under the modern lake floor in a maximal water depth of >250 m. This sedimentary sequence represents at least the last glacial cycle with ice-contact deposits at the base on top of the Molasse bedrock overlain by glaciolacustrine to lacustrine sediments. During the successful field test of a newly developed mid-size coring system ("HIPERCORIG"), the longest core ever taken in Lake Constance was recovered with an overall length of 24 m. The drill core, taken in a water depth of 200 m, consists of a nearly continuous succession of lacustrine sediments including over 12 m of pre-Holocene sediment at the base. The entire core was petrophysically and geochemically analyzed, sedimentologically described, and 14 lithotypes were identified. In combination with a 14C- and OSL-based age-depth model, the core was divided into three main chronostratigraphic units. The basal age of ~13.7 ka BP places the base of the section back into the Bølling-Allerød interstadial whereas the overlying strata represent a complete Younger-Dryas and Holocene section.The sediments offer a high-resolution insight into the evolution of Paleolake Constance from a cold postglacial to a more productive warm Holocene lake. The Late Glacial sections are dominated by massive, m-thick sand beds reflecting episodic sedimentation pulses. They are most likely linked with a subaquatic channel system that is still apparent in today's lake bathymetry despite the Holocene drape. This channel system was fed from a Late Glacial river from the north; provenance analysis of the initially unexpected sands together with hydrologic considerations will document whether this inflowing high-discharge river represented a local catchment (i.e. northern lake shore) or an Alpine signal (i.e. from the south) provided by the Rhine glacier. Tentative pore water hydrogeochemical and isotope analyses indicate a still active flow system at depth. The overlying Holocene section reveals a prominent, several cm-thick double-turbiditic event layer representing the most distal impact of the "Flimser Bergsturz", the largest known rock slide of the Alps that occurred over 100 km upstream the Rhine River at ~9.5 ka BP. Furthermore, lithologic variations in the Holocene section document the varying sediment load of the Rhine and of the endogenic production representing a multitude of environmental changes.

Seasonally laminated lacustrine sediments of Lake Stadtsee, located in the city of Bad Waldsee (Southern Germany), offer a continuous archive that allows a unique and yearly correlation of sedimentary signals and historic documents since medieval times. Comparison of the economic and environmental history of an urban centre will provide detailed insight into how the history of a city and its periphery region affected lake development and water quality, and how fast water quality and aquatic ecosystem recovered from human impact and activities. An interdisciplinary research team consisting of geologists, biologists, and historians from various universities and institutions has been established and started its work recently. The common goal of the different working groups and disciplines is to investigate temporally highly resolved sediment records of diatom and pollen spectra, geochemical proxies, and sediment facies of profundal sediment cores from Lake Stadtsee and to compare and calibrate these results with historic documents, stock books, archive records, dendrochronology records, and maps. So far, continuous geochemical sediment records of Lake Stadtsee were acquired non-destructively using X-ray fluorescence (XRF) core scanning. These element intensity records of the major elements (e.g. Al, Si, K, Ca, Ti, Fe) were measured every 2 mm. Sampling and subsequent analyses (e.g. pollen, PAH, isotopes) are ongoing.Overall, the environmental impact of socio-economic development for the preindustrial development phase of a city from AD 1200 to 1800 will be assessed for the first time. The research will focus on the effects of population growth or decrease, farming intensity, economic production, trade activity in relation to environmental, and climate change, including catastrophic events such as fires and floods. The results will provide important insights about the response of urban surface waters to changing emissions of the city and the long-term behaviour of persistent pollutants on lakes. The project will thereby contribute to the knowledge of historic human impact on the environment in Germany, pre-medieval reference conditions, and the limits of resilience of aquatic systems. Thus, it will target the past environmental footprint of anthropogenic induced events on urbanized lake ecosystems and help to understand the mechanism behind such processes in the future.

The western Nyainqêntanglha Range on the Tibetan Plateau (TP) reaches an elevation of 7162 m and is characterized by an extensive periglacial environment. Here, we present the first rock glacier inventory of the central TP containing 1433 rock glaciers over an area of 4622 km². The rock glaciers are identified based on their surface velocity. The surface velocity is derived from Sentinel-1 satellite data of 2016 to 2019 via InSAR time series analysis. 16.4 % of the inventoried rock glaciers are classified as active with a surface velocity above 10 cmyr-1 and 80.0 % are classified as transitional with 1 to 10 cmyr-1. The western Nyainqêntanglha Range forms a climate divide between the dry continental climate brought by the Westerlies from the north-west and the Indian Summer Monsoon to the south. 89.7 % of all active rock glaciers and 74 % of the free ice glacial area are located on the southern side. The higher moisture availability on the southern (windward) side of the mountain range is likely the cause of a higher rock glacier occurrence and the greater activity.Manually identifying and outlining rock glaciers is time consuming and subjective. To ensure a high reliability and comparability of our inventory, we therefore combined a manual approach with an automated classification. Three analysts worked in tandem to generate the manual outlines according to the guidelines of the IPA action group on ‘Rock glacier inventories and kinematics’. A subset of these outlines acted as training areas for a pixel-based maximum likelihood classification. Both the manual and the automated classification were performed based on DEM parameters (elevation, slope etc.), optical datasets (Sentinel-2 and NDVI) and surface velocity (generated with InSAR). 87.8 % of all manually outlined rock glaciers were identified successfully at a true positive rate of 69.5 %. 18 additional rock glaciers were added to the inventory based on the automated classification. This combined approach is therefore beneficial to generate a complete inventory. The automated classification can, however, not replace the expertise of an analyst as it greatly overestimates the actual rock glacier area.

During the last four decades, sediment cores were collected from the deepest zones of >30 small lakes in south-west Germany to investigate archaeological questions about settlement and land use history in Central Europe. The primary aim was to establish well-dated pollen profiles with very high temporal resolution. A major focus was to reconstruct the extent and intensity of land clearing during the Neolithic, the Iron Age, the Roman Period as well as through the Medieval timeframe in context with intermittent recovery periods during political and economic crises. In southwestern Germany, lake sites are not evenly distributed, but rather restricted to the formerly glaciated landscapes of the Northern Alpine foreland, including Lake Constance and the Black Forest. The most important results are as follows: 1. Central basinal sediments of small lakes are the best archives to study environmental change, past human impact, and vegetation. 2. The lakes reflect the environment and its change, triggered by natural and anthropogenic factors. 3. Lakes in areas with silicic bedrock have much lower sedimentation rates than lakes in the carbonate-rich North Alpine foreland in Germany. 4. Human impact causes sedimentation rates to increase by different rates, depending on the magnitude of impact and system sensitivity; in most cases, lamination disappears from the sedimentary record. 5. The small lakes integrate local landscape history, whereas the larger lakes integrate over larger catchments and record regional signals. 6. During the Late Weichselian and early Holocene, the landscape history of Southwestern Germany was rather uniform on a regional scale. 7. Landscape history from the middle Holocene onwards was more and more impacted by man, resulting in a variety of local and regional effects that are recorded in these lakes. 8. Overall, climate and natural factors determined the environmental settings, and people preferred regions with fertile soils and warm climate for settling and farming.

Two of the largest and deepest endorheic lakes on the Tibetan Plateau, Nam Co and Tangra Yumco, were targeted to infer Late Quaternary (24 ka) responses of their hydrological balance to environmental dynamics. For this purpose, high-resolution multi-proxy records were used to obtain information on lake level variations and how these are related to direct precipitation proxies. Allochthonous minerogenic input as reflected by potassium (K), is directly linked to precipitation driven by variations in Indian Summer Monsoon. Negatively correlated elements such as Ca, Sr and Mg and associated carbonate mineral phases represent autochthonous sediment production, which is coupled to evaporation in these closed systems. δ13C and δ18O of bulk carbonates represent lake water conditions, i.e., salinity and lake water volume, interpreted as precipitation-evaporation (P/E) balance. In combination with geomorphological features, i.e., lake level terraces and paleo-shorelines, the multy-proxy data set from Nam Co is used to reconstruct lake level dynamics. Low lake levels of >90 m below the recent one between 20 and 16 ka cal BP are associated with most enriched δ18Ocarb values and the precipitation of aragonite and high-Mg calcite in a shallow lake with highly dynamic allochthonous minerogenic input. Similar conditions are observed between 13.1 and 11.4 ka cal BP matching the Younger Dryas chronozone. Between 15.5 and 13.1 ka cal BP as well as during the Early Holocene (11.4 to 8.0 ka cal BP) distinctly depleted δ18Ocarb and δ13Ccarb coupled with high rates of allochthonous minerogenic input suggest substantial strengthening in precipitation. After 9.4 ka cal BP, the terrigenous input and thus precipitation is significantly reduced, whereas δ18Ocarb reveals only a slight enrichment trend and thus a slowly but steady decrease in lake level througout the Mid- to Late Holocene. The decoupling of this relation between precipitation and lake level suggest that lake level terraces of large endorheic lakes on the TP and also δ18Ocarb records are not a direct indicator of (monsoonal) precipitiation, whereas the allochtonous minerogenic input can be directly linked to precipitation dynamics. This is supported by the comparison to regional archives from the Arabian Sea and the northern Bay of Bengal, showing the very same pattern in precipitation variability. The presented monsoon precipitation record from Nam Co additionally reveals a link to supra-regional atmospheric circulation components as it is oscillating in- and anti-phase to El-Nino strength and frequency. A distinct precipitation change at 2 ka cal BP seems to have affected all archives, however leaving space for future studies to find the cause of this Late-Holocene climatic shift.

While there is substantial evidence for art and symbolic behaviour in early Homo sapiens across Africa and Eurasia, similar evidence connected to Neanderthals is sparse and often contested in scientific debates. Each new discovery is thus crucial for our understanding of Neanderthals’ cognitive capacity. Here we report on the discovery of an at least 51,000-year-old engraved giant deer phalanx found at the former cave entrance of Einhornhohle, northern Germany. The find comes from an apparent Middle Palaeolithic context that is linked to Neanderthals. The engraved bone demonstrates that conceptual imagination, as a prerequisite to compose individual lines into a coherent design, was present in Neanderthals. Therefore, Neanderthal’s awareness of symbolic meaning is very likely. Our findings show that Neanderthals were capable of creating symbolic expressions before H. sapiens arrived in Central Europe. The authors report an incised giant deer phalanx (toe bone), directly radiocarbon dated to at least 51,000 years old. The age and context of the object suggests that it was engraved by Neanderthals.

Tipping points can be defined as critical ecosystem thresholds that start self-enforced dynamics pushing systems into new stable states. Many lake ecosystems of arid Central Asia are sensitive to hydrological changes as they are located at the intersection of the influence of the dry Siberian Anticyclone and the relatively humid mid-latitude Westerlies, and their sediment records can be used to study past tipping points. We studied subfossil chironomid remains preserved in a ca. 6000-year-long sediment record from the Central Asian lake Son Kol (Central Kyrgyzstan) to reconstruct past ecosystem dynamics. Our results show abrupt transitions from a chironomid fauna dominated by macrophyte-associated, salinity-indicating taxa, to a vegetation-independent fauna, and subsequently to a macrophyte-associated, freshwater-indicating fauna. A comparison of the chironomid-based environmental reconstruction to other proxy indicators from the same record suggests a phase of increased Westerly strength starting about 4900 cal. yr BP. This increase led to enhanced precipitation and sediment fluxes into the lake, which in turn led to high turbidity levels and consequently to a macrophyte collapse causing abrupt changes in the chironomid fauna. At 4300 cal. yr BP, a weakening of the Westerlies in combination with higher lake levels led to lower turbidity and ultimately to the recovery of the macrophyte population and associated changes in the chironomid assemblage. These two sequences of events show how the occurrence of a gradual change in an external trigger (Westerlies) can trigger a cascade of within-lake processes (turbidity, macrophyte density) and may ultimately lead to an abrupt reorganization of the ecosystem (chironomid fauna), providing models for tipping points.

The present geophysical study was motivated by the need to determine suitable coring locations for paleolimnological studies in two karst lakes (Metzabok and Tzibaná) of the Lacandon Forest in Chiapas, southern Mexico. We used seismic and transient electromagnetic methods to map the sediment thickness below the lake floor. When lakes were filled in March 2018, we collected seismic data with a sub-bottom profiler (SBP) and transient electromagnetic (TEM) data with a floating single-loop configuration. The latter aimed at assessing the TEM method as an alternative to seismic methods for the investigation of lake sediments and geology. After the first campaign, water levels of both studied lakes dropped dramatically by July 2019, leaving Lake Metzabok (maximum depth ~ 25 m) dry and Lake Tzibaná (~ 70 m) with a water level decreased by approx. 30 m. After the sudden drainage of the lakes, we complemented water-borne measurements by a survey carried out on the exposed lake floor in October 2019, when lake levels were still low. During this second campaign, we collected time-domain induced polarization (TDIP), and seismic refraction tomography (SRT) data on the desiccated bed of Lake Metzabok and some dry parts of Lake Tzibaná. By comparing the various data sets, we find that (i) SBP and TDIP phase images consistently resolve the thickness of the fine-grained lacustrine sediments covering the lake floor, (ii) TEM and TDIP resistivity images consistently detect the upper limit of the limestone bedrock and the geometry of fluvial deposits of a river delta, and (iii) TDIP and SRT images suggest the existence of a layer that separates the lacustrine sediments from the limestone bedrock and consists of collapse debris mixed with lacustrine sediments. While our results do not imply that resistivity-based methods could generally replace seismic reflection surveys for lake-bottom reconnaissance, they clearly show that TEM and TDIP surveys can provide important complementary information and resolve additional geological units or bedrock heterogeneities.

The aquifers on the Tibetan Plateau (TP) constitute as origin for major river systems, which are supplying millions of people all over Asia. Increasing population and tourism activities leading to larger water consumption. Hence, water supply is getting increasingly important. The TP is a sensitive system and is noticeable reacting climate change. Past decades are marked with, increasing trends of precipitation, melting of glaciers and degradation of permafrost and have generally lead to rising water levels in lakes on the TP. To ensure future water supply, aquifer characterisation and future prognosis on groundwater behavior are therefore necessary. However, due to the remote character of the TP, knowledge according to hydrogeological parameter is scarce. The aim of this study is therefore to estimate a range for aquifer parameter based on geophysical methods. The Zhagu basin, situated in the Nam Co Lake basin (second largest lake on the TP), is used as a case study. This project is part of the International Research Training Group “Geoecosystems in transition on the Tibetan Plateau” (TransTiP), funded by the DFG.During several field work campaign in July 2018, May 2019 and September 2019 disturbed sediment samples were taken and were analyzed for grain size distribution. Selected sediment layer in the laboratory were tested. Outcome of this analysis is the porosity for each selected sediment layer. Another measurement during field work has been conducted, namely electrical resistivity tomography measurements (ERT). To get better approximation of porosity and sediment characteristics, Archie’s Law is used as model to estimate those properties and later on to compare it to field and laboratory results. Two approaches are implemented (i) calculates the bulk resistivity based on known porosity from the laboratory and known conductivity of pore water measured during field work (ii) calculates the porosity with known conductivity of pore water and the bulk conductivity. For analysis saturated sediment layers were chosen.The investigation shows that both approaches are largely applicable and leading to almost same results and trends of each sediment layer. The best percentage deviation of the modeled bulk resistivity results to the measurement in the field could be achieved by position D11 which is situated near the Nam Co Lake showing a deviation of around 7%. Inside the catchment the percentage deviation is largely increasing. However, the application of Archie’s Law in combination with field and laboratory measurements allows to construct a porosity ranges for future groundwater flow calibration. In addition, the results emphasising the zonation of the subsurface in (un)saturated zones due to the small amount of resistivity.Sediment profiles, ERT measurements, observations, interpretation and conclusion including the comparison of simulated resistivity and simulated porosity to field resistivity and porosity based on laboratory analysis will be shown and discussed in the contribution.

espanolPara entender el registro paleoecologico en el contexto de la ocupacion humana, es necesario examinar la distribucion del polen moderno a lo largo de gradientes climaticos y de impacto humano. Este estudio analiza las respuestas de ensambles de polen moderno de 125 muestras superficiales a la influencia humana de la region Maya, usando tres aproximaciones basicas: i) evaluacion de la habilidad de espectros de polen moderno para distinguir los principales tipos de vegetacion antropogenica y natural, ii) uso del analisis de correspondencia sin tendencia (DCA por sus siglas en ingles) para evaluar los patrones de distribucion del polen a lo largo de gradientes ambientales que incluyen la influencia humana, y iii) evaluacion de las respuestas de taxa individuales a un gradiente de influencia humana a traves del analisis de taxa indicadores de umbral. Las 125 muestras de la interfaz agua-sedimento se dividieron en cuatro grupos que corresponden a los principales tipos de vegetacion de la region Maya (bosque de pino-encino, cultivos y pastizales, bosque estacional tropical, y bosque tropical siempre verde). En terminos de las respuestas a nivel de taxon, nosotros detectamos 20 elementos asociados significativamente con el gradiente de influencia humana. Estos elementos fueron asignados a grupos de respuesta negativos (disminuciones) o positivos (incrementos) dependiendo de la direccion de respuesta. La mayoria de los elementos arboreos de bosques estacionales tropicales disminuyeron, mientras elementos no-arboreos tipicamente de vegetacion antropica aumentaron en respuesta a diferentes niveles de influencia humana. Adicionalmente, fue detectado un cambio abrupto a nivel de comunidad para un indice de influencia humana de 15. Cuando la influencia humana supera este umbral, elementos importantes de la vegetacion natural son afectados negativamente, mientras elementos oportunistas son favorecidos. En general, el estudio de la distribucion del polen a lo largo de gradientes ambientales, asi como la identificacion de taxa indicadores de impacto humano, ofrecen herramientas valiosas para interpretar los registros de polen fosil de la region Maya. EnglishTo understand human occupation in the context of paleoecological records from the Maya region, there is need to explore the distribution of modern pollen along climate and human-impact gradients. In this study, we analyze the responses of pollen assemblages from 125 surface samples to human influence in the Maya region, using three basic approaches: (i) the evaluation of using modern pollen spectra to distinguish the main anthropogenic and natural vegetation types; (ii) the usage of detrended correspondence analysis (DCA) to evaluate the distribution patterns of pollen along environmental gradients including human influence; and (iii) the evaluation of the responses of taxon-specific elements to the human-influence gradient, that expresses on the modern landscape, using threshold-indicator taxa analysis. The 125 locations where mud-water interface samples were retrieved were divided into four groups that correspond to the major vegetation types of the Maya region (coniferous and Quercus forest, croplands and pastures, tropical seasonal forest, and tropical evergreen forest). In terms of individual taxa responses, we detected 20 elements significantly related to the human-influence gradient. These were assigned to negative (decreasing) or positive (increasing) response groups depending on the response direction. Mostly arboreal elements from tropical seasonal forests decreased, while non-arboreal elements typically from anthropogenic vegetation increased in response to different levels of human influence. Also, a community-level abrupt point change is detected at a human influence index of 15. When human influence exceeds this threshold, important elements of the natural vegetation are negatively affected while opportunistic elements become favored. Overall, the study of pollen distribution along environmental gradients and the identification of taxa indicators of human impact provide valuable tools for the interpretation of fossil pollen records from the Maya region.

Enrichment of heavy metals was assessed in the Thi Vai Estuary and in the Can Gio Mangrove Forest (SE, Vietnam). Cd, Co, Cr, Cu, Mn, Ni, Pb and Zn contents in water and in sediments were measured. Total organic carbon, nitrogen, phosphorus and C/N ratios were determined. Cu and Cr values were higher than threshold effect level of toxicity, while Ni exceeded probable effect level, indicating the risk of probable toxicity effects. Enrichment factors (EF), contamination factor (CF) and Geo-accumulation index (I-geo) were determined. CF reveals moderate to considerable pollution with Cr and Ni. EF suggests anthropogenic sources of Cr, Cu and Ni. I-geo indicates low contamination with Co, Cu and Zn and moderate contamination with Cr and Ni. Overall metal contents were lower than expected for this highly industrialized region, probably due to dilution, suggesting that erosion rates and hydrodynamics may also play a role in metal contents distribution.

espanolLos estudios paleolimnologicos requieren de una base amplia de informacion sobre la geometria y la profundidad de los paquetes sedimentarios de las cuencas lacustres antes de la extraccion de nucleos. Comunmente, se emplean metodos sismicos para la caracterizacion indirecta de los sedimentos acumulados en los fondos de los lagos. Sin embargo, en ocasiones el uso de metodos sismicos puede ser limitado debido a las condiciones superficiales, contrastes sismicos reducidos entre las unidades estratigraficas de interes o a una calidad de datos insuficiente para la seleccion de los sitios de perforacion. Las fuentes de ruido cultural son la principal razon por la que metodos sismicos fallan en sitios de estudio ubicados cerca de o dentro de ciudades grandes, como la Ciudad de Mexico. Bajo ciertas condiciones, metodos electricos y electromagneticos pueden sustituir o complementar la exploracion sismica, ya que responden a otras propiedades fisicas del subsuelo. Para evaluar la aplicabilidad de estos metodos, se presentan dos estudios de caso realizados en los antiguos lagos de Chalco y Xochimilco, ambos ubicados en areas urbanas dentro de la Cuenca de Mexico, en los que se realizaron mediciones de tomografia de resistividad electrica (TRE), sondeos electromagneticos por transitorios (TEM) y sondeos magnetoteluricos (MT) para caracterizar el basamento y los sedimentos lacustres. En ambos ejemplos, los resultados de la exploracion geofisica brindaron informacion estratigrafica valiosa para la posterior perforacion y recuperacion de nucleos, lo cual evidencia el potencial de los metodos electricos y electromagneticos para estudios paleolimnologicos EnglishPaleolimnological studies require a broad understanding of the geometry and depth of the sedimentary fill of lake basins prior to coring campaigns. Seismic methods are routinely employed for the indirect characterization of lake-bottom sediments. However, the use of seismic methods might occasionally be limited due to surface conditions or poor seismic contrasts between the stratigraphic units, which lead to data quality that is too poor to provide sufficient information for the selection of drill sites. Sources of cultural noise are one of the main reasons why seismic methods fail in study areas near or within large cities, such as Mexico City. Under certain conditions, electrical and electromagnetic methods might be a suitable substitute or complement to seismic exploration, as they respond to different physical properties of the subsurface. To evaluate the applicability of such methods, here we present two recent case studies from the desiccated lakes Chalco and Xochimilco both located in urban areas within the Basin of Mexico where electrical resistivity tomography (ERT), transient electromagnetic (TEM) and magnetotelluric (MT) soundings were conducted for the characterization of lake basement and lacustrine sediments. In both examples, the results of the geophysical exploration contributed valuable stratigraphic information for the following drilling and core recovery, which highlights the potential of electrical and electromagnetic methods in paleolimnological studies.

High mountain ranges such as the Tibetan Plateau with an average altitude above 4500 m are topographically complex formations. Elevational gradients, physiographic diversity and climatic heterogeneity have led to highly biodiverse ecosystems in these regions. Mountain ranges can be seen as cradles of evolution and harbour, due to their unique characteristics, a high number of highly adapted species. At the same time these areas are hard to access and therefore taxonomic information is limited. Here we describe a new Acricotopus (Diptera: Chironomidae: Orthocladiinae) larval morphotype occurring in lakes and ponds of differing salinity and water depths located on the Southern and Central Tibetan Plateau. The description is based on larvae and their genetics (ribosomal 18S, 28S and mitochondrial COI sequences) collected from a shallow pond in close proximity to the large saline lake Selin Co. Larvae of Acricotopus indet. morphotype incurvatus are characterized by a mentum with a cluster of lateral teeth, partially folded inwards, a mandible with a toothed lobe in addition to four inner teeth and a sclerotized plate positioned behind the mentum. Up to now, these morphological features have only been found in early instars of other Acricotopus species. The proposed morphotype name is inspired by the peculiar form of the mentum.

The discovery of a tusk and a rib of a straight-tusked elephant within layer 13 II-2c3 of the famous Lower Palaeolithic archaeological site Schoningen (district Helmstedt, Lower-Saxony, Germany) provided the reason for studying the climatic and ecological conditions of this part of the Middle Pleistocene Reinsdorf sequence in high resolution in relation to new chronometric data. Sediment, pollen, aquatic microfossil (diatoms, ostracods, gyrogonites of charophytes) and micro mammalian analyses provide evidence for a strong environmental change and landscape opening following the post-temperate boreal forest phase of the Reinsdorf Interglacial. Palynological and palaeontological evidence from this horizon suggest increasing dryness and seasonality. The high proportions of non-arboreal pollen including Poaceae as well as a major decrease of thermophile tree taxa indicate the development of zonal steppe environments. The assemblage of small mammal remains includes indicators of temperate as well as cold climatic conditions. A bone tool together with flint artefacts clearly show the presence of hominins in this context. Based on palaeoecological evidence and new luminescence dating, previous correlations of the Reinsdorf sequence to Marine Isotope Stage (MIS) 9 and thus of the interglacial sediments to MIS 9e are confirmed and the onset of the first post-interglacial steppe phase represented by layer 13 II-2c3 to MIS 9d is proposed.

In order to assess the current ecological status of the tidal Thi Vai Estuary and the Can Gio Mangrove Forest in Southern Vietnam, we evaluated the spatial diatom composition and abundance in surface sediments and their relation to physical and chemical parameters of the water. Major changes in the distribution of diatom assemblages were determined by multivariate statistical analyses. Principal component analysis (PCA) was used to ordinate environmental variables of the water, showing a clear gradient along the estuary, with higher nutrient levels (total phosphorus and total nitrogen) and lower dissolved oxygen (DO) concentrations at upstream sites. Canonical correspondence analysis (CCA) was used to determine the species-environmental relationship. Total phosphorus (TP) and DO (p

The Wadi ad Dawasir fluvial system in central Saudi Arabia is investigated using remote sensing and sedimentology, in combination with bio-proxy analyses (molluscs and ostracods). Age control is provided by radiocarbon as well as luminescence dating, using both quartz and feldspar grains. It is shown that the fluvial system was active from the Asir Mountains across the partially sand-covered interior of the Arabian Peninsula to the Arabian Gulf during the Holocene humid period. Sedimentology and faunal analysis reveal the presence of perennial streams and a permanent freshwater lake in the distal reach of the Dawasir system that are synchronous with fluvial accumulation in the headwaters of its major tributary, Wadi Tathlith. The increased runoff during the Holocene led to a re-activation of streams that largely followed pre-existing Late Pleistocene courses and eroded into older sediments. The absence of Holocene lakes in most of the Rub' al-Khali implies that trans-Arabian rivers were mainly fed by precipitation in the Asir Mountains. Monsoonal rainfall was apparently stronger there as well as in the northern, south-eastern and southern part of the Arabian Peninsula (southern Yemen and Oman), but it apparently did not directly affect the interior during the Holocene. The palaeoenvironmental reconstruction shows a narrow trans-Arabian green freshwater corridor as the result of phases of sustained flow lasting up to several centuries. The permanent availability of water and subsistence for wildlife provided a favourable environment for human occupation as documented by Neolithic stone tools that are found all along Wadi ad Dawasir.

Paleoecological assessment is challenging in highly dynamic environments such as estuaries, where sedimentation of material derived from the catchment interferes with marine processes. In this study we analyzed sedimentary heavy metal contents of the last decades to assess the impact of recent industrialization and changes in land use of the Thi Vai Estuary in Southern Vietnam. Two sediment cores (upstream and downstream) were dated using 210Pb, allowing the environmental reconstruction of the last three decades. Considering the recent and fast economic growth of this region these results are suitable for the evaluation of anthropogenic impacts. Mean sedimentation rates (9.2 cm yr−1 upstream, 4.7 cm yr−1downstream) indicate high land erosion likely due to deforestation and dumping of dredged material. Sediment quality guidelines (SQG's) showed that Cr and Cu levels exceed threshold values (TEL) in both cores. Upstream Ni is above the probable effect level (PEL) suggesting risk of potential adverse biological effects. Geo-accumulation (I-geo), enrichment factor (EF) and contamination factor (CF) indices were calculated based on geogenic background values. Most indices show only moderate contamination for different elements, particularly by Cr and Pb. However, considering the historical land use impacts (such as discharge of untreated wastewater, intense agricultural practices, tanning operations, etc.), pollutant concentrations are lower than expected, presumably due to dilution by high sedimentation rates and tidal hydrodynamics. Nonetheless, heavy metal indices and SQG's indicate the ecological condition in the area is of concern, particularly upstream as corroborated by high metal fluxes, highlighting severe impacts in the region.

International audience; At present, Lake Chad (∼ 13 • N, ∼ 14 • E) is a shallow freshwater lake located in the Sahel/Sahara region of central northern Africa. The lake is primarily fed by the Chari-Logone river system draining a ∼ 600 000 km 2 watershed in tropical Africa. Discharge is strongly controlled by the annual passage of the in-tertropical convergence zone (ITCZ) and monsoon circulation leading to a peak in rainfall during boreal summer. During recent decades, a large number of studies have been carried out in the Lake Chad Basin (LCB). They have mostly focused on a patchwork of exposed lake sediments and outcrops once inhabited by early hominids. A dataset generated from a 673 m long geotechnical borehole drilled in 1973, along with outcrop and seismic reflection studies, reveal several hundred metres of Miocene-Pleistocene lacustrine deposits. CHADRILL aims to recover a sedimentary core spanning the Miocene-Pleistocene sediment succession of Lake Chad through deep drilling. This record will provide significant insights into the modulation of orbitally forced changes in northern African hydroclimate under different climate boundary conditions such as high CO 2 and absence of Northern Hemisphere ice sheets. These investigations will also help unravel both the age and the origin of the lake and its current desert surrounding. The LCB is very rich in early hominid fossils (Australop-ithecus bahrelghazali; Sahelanthropus tchadensis) of Late Miocene age. Thus, retrieving a sediment core from this basin will provide the most continuous climatic and environmental record with which to compare hominid migrations across northern Africa and has major implications for understanding human evolution. Furthermore, due to its dramatic and episodically changing water levels and associated depositional modes, Lake Chad's sediments resemble maybe an analogue for lake systems that were once present on Mars. Consequently, the study of the subsurface biosphere contained in these sediments has the potential to shed light on microbial biodiversity present in this type of depositional environment. We propose to drill a total of ∼ 1800 m of poorly to semi-consolidated lacustrine, fluvial, and eolian sediments down to bedrock at a single onshore site close to the shoreline of present-day Lake Chad. We propose to locate Published by Copernicus Publications on behalf of the IODP and the ICDP. 72 F. Sylvestre et al.: The Lake CHAd Deep DRILLing Project (CHADRILL) our drilling operations onshore close to the site where the geotechnical Bol borehole (13 • 28 N, 14 • 44 E) was drilled in 1973. This is for two main reasons: (1) nowhere else in the Chad Basin do we have such detailed information about the lithologies to be drilled; and (2) the Bol site is close to the depocentre of the Chad Basin and therefore likely to provide the stratigraphically most continuous sequence.

This study focuses on Holocene monsoon dynamics on the central Tibetan Plateau (TP) inferred using a sediment record from Lake Nam Co. A high-resolution (decadal) multi-proxy approach, using geochemical, micropaleontological, and sedimentological methods was applied. Fifteen AMS-14C ages were used to establish the chronology, assuming a reservoir effect of 1,420 years. Our results point to a first strong monsoonal pulse at Lake Nam Co ~11.3 cal ka BP, followed by colder and drier conditions until ~10.8 cal ka BP. A warm and humid climate from ~10.8 to ~9.5 cal ka BP is related to a strong summer monsoon on the central TP, triggering a lake-level highstand at ~9.5 cal ka BP. Declining minerogenic input after ~9.5 cal ka BP indicates less moisture availability until ~7.7 cal ka BP. Following stable conditions between ~7.7 and ~6.6 cal ka BP, a warm and wet climate is inferred for the time span from ~6.6 to ~4.8 cal ka BP. A change towards drier conditions after ~4.8 cal ka BP points to a weakening of the Indian Ocean Summer Monsoon on the central TP, further diminished after ~2.0 cal ka BP. A short-term wet spell occurred from ~1.5 to ~1.3 cal ka BP. By comparing the results derived from Lake Nam Co with several lacustrine records from the central, northern, and eastern TP, a similar but not synchronous pattern of monsoon-driven paleoenvironmental change is observed. Although the general trend of lake and catchment evolution on the TP during the Holocene is also reproduced in this record, pronounced spatial and temporal offsets with respect to distinct climate events were detected, suggesting periods of non-uniform moisture and temperature evolution.

Mechanisms of climatic control on river system development are still only partially known. Palaeohydrological investigations from river valleys often lack a precise chronological control of climatic processes and fluvial dynamics, which is why their specific forces remain unclear. In this multidisciplinary case study from the middle Elbe river valley (northern Germany) multiple dating of sites (palynostratigraphy, radiocarbon- and OSL-dating) and high-resolution analyses of environmental and climatological proxies (pollen, plant macro-remains and ostracods) reveal a continuous record of the environmental and fluvial history from the Lateglacial to the early Holocene. Biostratigraphical correlation to northwest European key sites shows that river system development was partially out of phase with the main climatic shifts. The transition from a braided to an incised channel system predated the main phase of Lateglacial warming (∼14.6 ka BP), and the meandering river did not change its drainage pattern during the cooling of the Younger-Dryas period. Environmental reconstructions suggest that river dynamics were largely affected by vegetation cover, as a vegetation cover consisting of herbs, dwarf-shrubs and a few larger shrubs seems to have developed before the onset of the main Lateglacial warming, and pine forests appear to have persisted in the river valley during the Younger Dryas. In addition, two phases of high fluvial activity and new channel incision during the middle part of the Younger Dryas and during the Boreal were correlated with changes from dry towards wet climatic conditions, as indicated by evident lake level rises. Lateglacial human occupation in the river valley, which is shown by numerous Palaeolithic sites, forming one of the largest settlement areas of that period known in the European Plain, is assigned to the specific fluvial and environmental conditions of the early Allerod.

Highlights • Dating 400 ka paleoclimate record of Neotropics. • Revision and new eruptive volumes for large Central American eruptions. • Age models for Peten Itza sediments. • Linking lacustrine ash inventory to eruptions from Central America and Mexico. Abstract Lake Peten Itza, northern Guatemala, lies within a hydrologically closed basin in the south-central area of the Yucatan Peninsula, and was drilled under the auspices of the International Continental Scientific Drilling Program (ICDP) in 2006. At 16°55′N latitude, the lake is ideally located for study of past climate and environmental conditions in the Neotropical lowlands. Because of its great depth (>160 m), Lake Peten Itza has a record of continuous sediment accumulation that extends well into the late Pleistocene. A key obstacle to obtaining long climate records from the region is the difficulty of establishing a robust chronology beyond ∼40 ka, the limit of 14C dating. Tephra layers within the Lake Peten Itza sediments, however, enable development of age/depth relations beyond 40 ka. Ash beds from large-magnitude, Pleistocene-to-Holocene silicic eruptions of caldera volcanoes along the Central American Volcanic Arc (CAVA) were found throughout drill cores collected from Lake Peten Itza. These ash beds were used to establish a robust chronology extending back 400 ka. We used major- and trace-element glass composition to establish 12 well-constrained correlations between the lacustrine tephra layers in Lake Peten Itza sediments and dated deposits at the CAVA source volcanoes, and with their marine equivalents in eastern Pacific Ocean sediments. The data also enabled revision of eight previous determinations of erupted volumes and masses, and initial estimates for another four eruptions, as well as the designation of source areas for 14 previously unknown eruptions. The new and revised sedimentation rates for the older sediment successions identify the interglacial of MIS5a between 84 and 72 ka, followed by a stadial between 72 and 59 ka that corresponds to MIS4. We modified the age models for the Lake Peten Itza sediment sequences, extended the paleoclimate and paleoecological record for this Neotropical region to ∼400 ka, and determined the magnitude and timing of CAVA eruptions.

Environmental reconstructions based on fossil pollen rely on the understanding of modern pollen distribution along climatic and biogeographic gradients. This study analyses the modern pollen spectra of Central America using three basic approaches: (1) the evaluation of using modern pollen spectra to differentiate the main vegetation types of the region, (2) the usage of non-linear regression to predict individual pollen abundances as a function of climate, and (3) the construction of pollen—climate transfer functions. Standard pollen analysis was carried out on mud—water interface samples from 81 lakes in the Yucatan Peninsula and adjacent mountains of Guatemala and Mexico. Detrended correspondence and cluster analyses were used to evaluate the biogeographic patterns revealed by this modern pollen data set. Non-parametric locally weighted scatterplot smoothing (LOESS) regression was used to construct pollen—climate functional relationships. Five modern vegetation types were clearly identifiable through their associated pollen spectra: Pinus forest, Quercus forest, mountain mesophyllous forest, tropical rainforest, and tropical seasonal forest. The last group includes three subcategories (evergreen seasonal, tropical semi-deciduous, and tropical deciduous forests), which were not separable via this analysis. Precipitation and temperature trends were consistent and robust for at least 28 and 30 taxa, respectively, in the LOESS regression. While floristic patterns driven by temperature were clearly reflected by the pollen spectra, those driven by precipitation were less sharply defined. Nevertheless, pollen data from the study area offered good resolution to identify broad biogeographic patterns. Furthermore, individual taxa showed high predictability along precipitation and temperature gradients, allowing the theoretical construction of pollen—climate transfer functions. This study provided valuable tools for the interpretation of fossil pollen sequences from Central America.

This study presents limnological and morphological characteristics, physical and chemical properties of waters, and geochemistry of surface sediments for 63 aquatic ecosystems located on the karst Yucatan Peninsula and surrounding areas of Belize and the Guatemalan highlands and eastern lowlands. Our principal goal was to classify the aquatic systems based on their water variables. A principal component analysis (PCA) of the surface water chemistry data showed that a large fraction of the variance (29%) in water chemistry is explained by conductivity and major ion concentrations. The broad conductivity range, from 168 to 55,300 μS cm−1 reflects saline water intrusion affecting coastal aquatic environments, and the steep NW–S precipitation gradient, from ~450 to >3,200 mm year−1. Coastal waterbodies Celestun and Laguna Rosada displayed the highest conductivities. Minimum surface water temperatures of 21.6°C were measured in highland lakes, and warmest temperatures, up to 31.7°C, were recorded in the lowland waterbodies. Most lakes showed thermal stratification during the sampling period, with the exception of some shallow (

For Lake Nam Co, south-central Tibetan Plateau, geomorphological features and hydrological characteristics have been compiled to provide an overview of the landscape character. Information is based on primary data, collected during field campaigns in the summers of 2005 and 2006, and secondary data as available from satellite images. Nam Co is located at the intersection of the Westerlies, the winter monsoon, the South West Asian monsoon, and the East Asian monsoon. It is situated in a graben structure. Landforms of the drainage basin are highly influenced by tectonics, superimposed by fluvial and periglacial processes, and locally by glacial and aeolian processes. Its drainage basin is endorheic. Thus, lake level is primarily controlled by the balance between input through precipitation or inflow streams and evaporation as the output. The significance of lake water evaporation is evidenced by the salinity and measurable increase of 2H and 18O of the lake water when compared to the inflow streams and precipitation. Maximum conductivities total 431 μS mm−1 for the inflowing river waters and 1920 μS mm−1 for the lake water. Overall, the solute contents are low and characterise Nam Co as a pristine environment. Dominant ions are calcium and bicarbonate in river waters. Sulphate contents are relatively high in Nam Co, and the lake is also characterised by high boron values. A significant decrease in lake water salinity during the past two decades is likely related to increased freshwater input.

Holocene sediments from a 9 m high outcrop at the Gangyasang Qu's entry into Lake Nam Co, on the south-eastern Tibetan Plateau, were studied in a multiproxy approach. The lowermost part of the section is of early Holocene age and consists of varved sediments deposited in a proglacial lake. Geomorphological investigations of fossil beach ridges and fossil cliff lines in the littoral zone of Nam Co indicate a late Pleistocene lake level high of 29 m above the present level. A warming is visible in ostracode-rich silts deposited after 9.6 ka BP. An ostracode-based transfer function estimates a lake level 28 m higher than today from this time until about 5.2 ka BP. A late Pleistocene lake level high was accompanied by an increase in lake size, causing Nam Co to overflow into the lower course of Gangyasang Qu, where a bay with slack-water conditions formed. Between 4.2 and 1.3 ka BP the lake level was approximately 10 m higher than today. The progradation of the Gangyasang Qu delta into Nam Co and the decreasing lake level shifted the study site into a fluvio-lacustrine environment. The sandy character and relatively low numbers of ostracode valves in the topmost sediments indicate increased fluvial activity, possibly due to a temporary increase in flood frequency. This facies lasted at least until 1.3 ka BP, when the lake level of Nam Co dropped again and the river incised more than 10 m into the underlying fluvio-lacustrine and lacustrine sediments.

From a 332-cm long lacustrine core taken at 60 m water depth and 25 surface sediment samples taken at different water depth sites in Nam Co lake (4,718 m a.s.l.) in the middle-south part of the Tibetan Plateau, we identified nine species of ostracods (Crustacea: Ostracoda) belonging to six genera. Using lithological data, auto-ecological information of the recovered taxa and an ostracod-based transfer function for water depth reconstruction, we distinguished three main environmental stages over the past 8,400 years: during Stage I (8,400–6,800 yr BP), the climate changed from warm-humid to cold-humid, and eventually to cold-arid. The water depth of the site was much lower than today and changed from an estimated 50 to 20–30 m. During Stage II (6,800–2,900 yr BP), environmental conditions were again warm-humid, turning into a cold-arid episode. The lake water depth initially stayed much shallower than today, but then gradually deepened to around 50 m. At the earlier period of Stage III (2,900 yr BP–present), the climate became again warm-humid from cold-arid status. There was a cold-dry event between 1,700 and 1,500 yr BP, which intensified afterward while the surface run off weakened. Early in this stage, lake depth decreased slightly, but then it continuously deepened to 60 m. Our results revealed that central Tibet experienced wavily warm toward tendency in early Holocene, a shift from warm-humid to cold-dry conditions in the middle Holocene, and from warm-humid to cold-dry conditions in the late Holocene. They also show that ostracod assemblages are not only indicative of cold-warm conditions, but are also usable to imply the dry–wet status of a lake area by the inferring water depth variations. Finally, this study provides baseline data on (natural) climate change in this mountain region against which to compare global change impacts.

Ostracode species assemblages and stable oxygen and carbon isotopes of shells from two 210 Pb-dated short cores of 78 cm and 47 cm length taken from Lake Nam Co, southern Tibet, provide information about lake level history of the past approximately 600 years at decadal resolution. A transfer function is applied to reconstruct paleo-water depths from modern ostracodes. Ostracode assemblages and isotope data from five species allow a subdivision into phases of lake level evolution. Before ∼1600 AD relatively low oxygen isotope values and high abundances of deep water (>30 m) ostracodes (i.e. ? Leucocythere dorsotuberosa , ? Leucocythere dorsotuberosa f. postilirata ) suggest a lake level ∼10 m higher than today. Between ∼1600 AD and 1800 AD, more positive oxygen isotope values and higher abundances of shallow water ostracodes (i.e. Ilyocypris cf. mongolica , Candona xizangensis ) suggest a lake level approximately 40 m below modern level. Between 1800 AD and ∼1920 AD oxygen isotopes are characterized by a trend to more negative values followed by a trend to more positive ones. These trends are interrupted by several short-term fluctuations but overall, oxygen isotope values suggest a drop in lake level. A clearer lake level picture is provided by species assemblages that suggest a continuously increasing lake level since 1900 AD. Precipitation data from meteorological stations nearby show an increase in precipitation in the last 30 years. The low lake level between 1600 AD and 1800 AD is contemporary to the Little Ice Age. During that cold period, meltwater input into the lake decreased. This underlines the sensitivity of the level of Lake Nam Co to temperature changes on the Tibetan Plateau.

In this paper we present sedimentologic, petrographic, and paleoecologic data from a ~ 810-m-thick section of late Neogene (ca. 9–7 to 1 Ma) fluvio-lacustrine deposits in the high-elevation Zhada Basin of SW-Tibet. The tectonic evolution of the Zhada Basin region, located between the Himalayan Mountains in the S and the Transhimalayan Mountains in the N, is poorly understood, but sediment accumulation was probably initiated in response to the middle/late Miocene uplift of the Gurla Mandhata and Leo Pargil domes in the E and W, respectively. The sedimentary record can be subdivided into five stratigraphic units with distinctly different lithofacies associations (LA); these are, from bottom to top: a bedload-dominated fluvial LA (Unit 1, 0–90 m); a nearshore lacustrine, deltaic LA (Unit 2, 90–220 m); an offshore lacustrine LA (Unit 3, 220–500 m); a nearshore lacustrine, fan-delta LA (Unit 4, 500–600 m); and a fan-delta/alluvial fan LA (Unit 5, 600–810 m). Clast and heavy mineral compositions revealed sediment supply from two different provenance areas, one from the south and one from the north/east, based on catchment geology of the Himalaya and Transhimalaya. Ostracode faunal assemblages are largely comparable to those of modern Tibetan lakes and allow the reconstruction of paleo-lake environments, including lake-level changes and salinity. The sedimentary pattern shows strong cyclicity at various scales (m, 10 s m, and >100 m). Small-scale cycles are interpreted as intrinsically-controlled depositional processes of deltas (lobe switching), whereas medium- and large-scale cycles are most likely forced by climate fluctuations. The overall evolution of the sedimentologic record includes: a strong and rapid increase in fluvial discharge in the uppermost portion of Unit 1, a transition from fluvial to lacustrine deposition during deposition of Unit 2, rhythmic variations in the style of lacustrine sedimentation during deposition of Unit 3, an increase in the supply of coarse clastics starting with deposition of Unit 4, and a transition from lacustrine to alluvial sedimentation during deposition of Unit 5. We speculate that the increase in discharge and, presumably, precipitation leading to the establishment of lacustrine conditions in the lower part of the section (Unit 2) is largely due to regional summer monsoon intensification during the late Miocene, and that the transition from lacustrine to alluvial sedimentation in the uppper part of the section reflects the onset of Northern Hemisphere glaciation and winter monsoon strengthening at ~ 2.6 Ma.

A 332-cm long lacustrine core was drilled in the Nam Co in the central-southern part of the Tibetan Plateau. From the core, 15 species of ostracods (Crustacea: Ostracoda), which belong to 6 genera have been identified. According to the variations of the ostracod assemblages and the ostracods ecological features, which are sensitive to the changing environment, three main stages can be distinguished as follows: Stage I was from 8400 to 6800 a BP, during which the climate was cold-humid, and the lake depth changed from shallow to deep. Stage II was from 6400 to 2500 a BP, during which the climate changed from warm-humid to cold-humid, and then to cold-dry. The lake depth gradually became deep. The shifting of climate, from wet-cold to dry-cold during this period, had constructed the basis of present environment in the Nam Co. Stage III was from 2500 a BP to the present, which showed a trait of lake depth increasing. At the earlier period of this stage, the climate kept as cold-dry as that in the former stage, but the salinity of the lake increased. At the later period of this stage, the degree of cold-dry was enhanced, and the activities of land surface runoff tended to be weakened. Our research also found that the peak values of ostracods with black shell was coherent with the maximum production of the ostracods, and agreed with the increasing sedimentary water dynamics. This indicated that the ostracods with black shell was simultaneous with the high prolificacy of ostracod, and transported from other places. The abundance of Candona juvenile shells reflected the high mortality of that kind of ostracods under an unfavorable condition. This was probably a result of the rapid change of water dynamics of sedimentary environment.

The n-alkanes are extracted from NMLC-1 core that was drilled in the Nam Co, central Tibet. They are measured by using Gas Chromatography and Mass Spectrometry (GC/MS) for componential and quantitative analyses. According to the constructed depth-age model, the component and concentration of n-alkanes, together with total organic carbon (TOC), total nitrogen (TN) and carbonate are used to elucidate palaeoenvironmental changes of Nam Co during the past 8.4 ka. The results indicate that Holocene environment performs three stages in the lake area. In the stage of 8.4–6.7 kaB.P., it was warmer while precipitation slightly increased. This stage was ended by an obvious cold/dry event. During 6.7–5.8 kaB.P., temperature increased rapidly and reached its maximum values at about 6.0 kaB.P. The environments were warm/wet optimum for the blooming of terrestrial plants and submerged aquatic plants. After that, temperature decreased continuously and showed the lowest values at about 3.0 kaB.P. From 2.9 kaB.P. to the present, temperature rose again but alternated with cold and warm. The lake area tended to be dry after 1.4 kaB.P. During 600–400 aB.P., the environmental feature was the reflection of “Little Ice Age”.

Lake Ohrid, at the Macedonian/Albanian border, was likely tectonically formed during the Tertiary and therefore is one of the oldest lakes in Europe. However, only a few studies exist concerning the potential of Lake Ohrid sediments for long-term palaeoenvironmental reconstructions within the scope of future potential deep-drilling campaigns. Therefore, as a first step, a transect of short surface sediment cores was investigated for chronology, physical properties, grain size, and biogeochemistry. The results were compared with information derived from a shallow hydro-acoustic seismic survey. The investigations indicate a rather uniform and bioturbated sedimentation in the central part of the lake basin with mean sedimentation rates of ca. 0.5–1 mm/year. The sediment composition is dominated by authigenetic carbonates. Diatom frustules or fragments form the major part of biogenic matter deposits, as indicated by the relatively high contents of biogenic opal and low contents of total organic carbon and total nitrogen. The shallow hydro-acoustic seismic survey indicates that horizons of sediment redeposition occur sporadically. Towards the shore of the lake, the sedimentation rate increases and sedimentation is increasingly influenced by local inflows or mass-movement processes triggered by tectonic activities. Thus Lake Ohrid has a high potential for palaeoenvironmental reconstructions on a multi-decadal scale and provides additional information concerning tectonic activity in the region.

Eine Detailuntersuchung des Rheineinzugsgebietes erbrachte ein System der fluviatilen Fazies (die "Fluviatile Serie"), der Struktur, der texturellen Anordnung fluviatiler Terrassenkorper und unterschiedliche Terrassenmuster. Der Talgrund erweist sich als durch zehn fluviatile Akkumulationsphasen gestaltet, drei oberwurmzeitliche und sieben holozane. Zeitgleiche Phasen fluviatiler Aktivitat und Ruhe an grosen und kleinen Flussen belegen klimatische Steuerung. Die Ruhephasen werden nicht nur aus still werdender Sedimentation ersichtlich, sondern auch aus fossilen Boden, die die Auensedimentdecken verschiedener fluviatiler Serien trennen. Regionale Pragung durch die individuellen Flusseinzugsgebiete beeinflussen Textur, Terrassenmuster, Innenaufbau und typologische Auenbodenpragung der Terrassenabfolgen. Menschliche Einflussnahme modifiziert seit dem Neolithikum zunehmend die naturlichen talformenden Prozesse, wie Feinsedimenteintrag in die Auen seit dem Atlantikum, deutliche Auenverbreiterung seit Beginn des Subatlantikums, Flussbettverflachung mit Tendenz zur Verzweigung seit dem Fruhmittelalter, Kanalisierung des Flussbetts und Umgestaltung der Aue seit dem Verlauf des 19. Jahrhunderts. Dennoch bleibt neben anthropogener Uberpragung die naturliche Steuerung die Haupttriebfeder fluviatiler Aktivitat und bleibt als solche deutlich sichtbar. Erste Versuche der Budgetierung der Sedimentflussraten von einzelnen Zeitausschnitten der drei Perioden, der glazialen, der waldholozanen und kulturholozanen Perioden, sind dem Text in drei Fallbeispielen angefugt, die nach Zeitauflosung und Raum noch bescheiden sind: das Rheindelta im oberen Bodensee, das zum unteren Neckar gehorige Elsenz-Einzugsgebiet nahe Heidelberg und ein Ausschnitt des Siebengebirgsgehanges gegen den Rhein. /// A detailed investigation of the River Rhine catchment resulted in a system of the fluvial facies (the "fluvial series"), the structure and the texture of fluviatile terrace bodies and different terrace patterns. The valley bottom is formed by ten fluvial accumulation phases, three of upper Wurmian age and seven of Holocene age. Synchronous phases of alternating increased fluvial activity and quiescence on major and smaller rivers give proof of climatic control over the fluvial rhythmicity. The quiescence phases are not only marked by a retreat of the river sedimentation but also by fossil soils that are separating flood loam veneers of the individual fluviatile series. Local forming of the valley ground by the individual river catchment does affect the texture, pattern, structure and floodplain soil types of the terrace sequences. Man's impact since the Neolithic period modifies increasingly the natural valley-forming processes: input of fines into the floodplain since the Atlantic period, essential widening of the floodplain since the beginning of the Subatlantic period, flattening of the channel with a tendency to braiding since the early Middle Ages, canalising of the channel and remodelling of the floodplain since the course of the 19th century. But despite human modification, the natural imprints are dominating and remain visible. A first small onset of budgeting of the sediment flux rates of parts of the three periods, the glacial, the natural Holocene and the human Holocene periods, is shown by three case studies still rather restricted in space and resolution of time: the Rhine delta within the Lake Constance, the Elsenz catchment as a Neckar tributary close to Heidelberg and a versant area in the Siebengebirge directed towards the River Rhine.

The Tibetan Plateau (TP) is primarily influenced by the northern hemispheric middle latitude Westerlies and the Indian summer monsoon (ISM). The extent, long-distance effects and potential long-term changes of these two atmospheric circulations are not yet fully understood. Here, we analyse modern airborne pollen in a transition zone of seasonally alternating dominance of the Westerlies and the ISM to develop a pollen discrimination index (PDI) that allows us to distinguish between the intensities of the two circulation systems. This index is applied to interpret a continuous lacustrine sedimentary record from Lake Nam Co covering the past 24 cal kyr BP to investigate long-term variations in the atmospheric circulation systems. Climatic variations on the central TP widely correspond to those of the North Atlantic (NA) realm, but are controlled through different mechanisms resulting from the changing climatic conditions since the Last Glacial Maximum (LGM). During the LGM, until 16.5 cal kyr BP, the TP was dominated by the Westerlies. After 16.5 cal kyr BP, the climatic conditions were mainly controlled by the ISM. From 11.6 to 9 cal kyr BP, the TP was exposed to enhanced solar radiation at the low latitudes, resulting in greater water availability.

In general, a moderate drying trend is observed in mid-latitude arid Central Asia since the Mid-Holocene, attributed to the progressively weakening influence of the mid-latitude Westerlies on regional climate. However, as the spatio-temporal pattern of this development and the underlying climatic mechanisms are yet not fully understood, new high-resolution paleoclimate records from this region are needed. Within this study, a sediment core from Lake Son Kol (Central Kyrgyzstan) was investigated using sedimentological, (bio)geochemical, isotopic, and palynological analyses, aiming at reconstructing regional climate development during the last 6000 years. Biogeochemical data, mainly reflecting summer moisture conditions, indicate predominantly wet conditions until 4950 cal. yr BP, succeeded by a pronounced dry interval between 4950 and 3900 cal. yr BP. In the following, a return to wet conditions and a subsequent moderate drying trend until present times are observed. This is consistent with other regional paleoclimate records and likely reflects the gradual Late Holocene diminishment of the amount of summer moisture provided by the mid-latitude Westerlies. However, climate impact of the Westerlies was apparently not only restricted to the summer season but also significant during winter as indicated by recurrent episodes of enhanced allochthonous input through snowmelt, occurring before 6000 cal. yr BP and at 5100–4350, 3450–2850, and 1900–1500 cal. yr BP. The distinct ~1500-year periodicity of these episodes of increased winter precipitation in Central Kyrgyzstan resembles similar cyclicities observed in paleoclimate records around the North Atlantic, likely indicating a hemispheric-scale climatic teleconnection and an impact of North Atlantic Oscillation (NAO) variability in Central Asia.

Sedimentological parameters and stable O- and C-isotopic composition of marl and ostracode calcite selected from a 17.7-m-long core from the 8-m-deep center of Pickerel Lake, northeastern South Dakota, provide one of the longest (ca. 12ky) paleoenvironmental records from the northern Great Plains. The late Glacial to early Holocene climate in the northern Great Plains was characterized by changes from cold and wet to cold and dry, and back to cold and wet conditions. These climatic changes were controlled by fluctuations in the positions of the Laurentide ice sheet and the extent of glacial Lake Agassiz. We speculate that the cold and dry phase may correspond to the Younger Dryas event. A salinity maximum was reached between 10.3 and 9.5 ka, after which Pickerel Lake shifted from a system controlled by atmospheric changes to a system controlled by groundwater seepage that might have been initiated by the final withdrawal of Glacial Lake Agassiz. A prairie lake was established at approximately 8.7 ka, and lasted until about 2.2 ka. During this mid-Holocene prairie period, drier conditions than today prevailed, interrupted by periods of increased moisture at about 8, 4, and 2.2 ka. Prairie conditions were more likely dry and cool rather than dry and warm. The last 2.2 ka are characterized by higher climatic variability with 400-yr aridity cycles including the Medieval Warm Period and the Little Ice Age. Although the signal of changing atmospheric circulation is overprinted by fluctuations in the positions of the ice sheet and glacial Lake Agassiz during the late Glacial-Holocene transition, a combination of strong zonal circulation and strong monsoons induced by the presence of the ice sheet and high insolation may have provided mechanisms for increased precipitation. Zonal flow introducing dry Pacific air became more important during the prairie period but seems to have been interrupted by short periods of stronger meridional circulation with intrusions of moist air from the Gulf of Mexico. More frequent switching between periods of zonal and meridional circulation seem to be responsible for increased climatic variability during the last 2.2 ka.

Stable oxygen and carbon isotope geochemistry of ostracode calcite from a core taken at a site 40 m deep in Lake Neuchâtel, Switzerland, shows distinct and rapid shifts since deglaciation. These shifts are interpreted in terms both of climatic changes and of the impact of major changes in the catchment input. The Aar River, draining a high-altitude Alpine catchment, either entered or bypassed the lake during the latest Pleistocene to the mid-Holocene. During the Preboreal and two short intervals between interpolated ages of 7200 and 6950 yr BP and since 4850 yr BP the Aar River has bypassed the lake.

Holocene lake level fluctuations were reconstructed from a 2.7-m sediment core from Nam Co, Central Tibet, China dating to > 7.2 cal ka BP. Results were compared to existing lake records from the Tibetan Plateau to infer variations in the strength of the Asian Monsoon. Geomorphological features in the Nam Co catchment, such as beach ridges and lake terraces, indicate high lake stands during the late Glacial. A major low stand is suggested for the Last Glacial Maximum (LGM). Sands and sandy silts at the base of the core are transgressive facies, with material transported by melt water and deposited under rising lake level conditions that followed the LGM low stand. Variations in grain size, major elements, biomarker stable isotopes and minerals in the core suggest a climate evolution reflected in at least five depositional units and subunits. Sediments in Unit I (similar to 7.2 to similar to 5.4 cal ka BP) were deposited at highest lake levels. Large amounts of allogenic minerals and allochthonous organic matter suggest high precipitation and melt water input, implying positive water balance. Increasing aquatic productivity points to favourable environmental conditions. Unit II (similar to 5.4 to similar to 4.0 cal ka BP) marks a transition between favourable, stable hydrological conditions and lake level decrease. Lower lake levels were a consequence of drier climate with less monsoonal precipitation, higher evaporation rates, and increased moisture recycling in the catchment. Unit III (similar to 4.0 to similar to 1.4 cal ka BP) reflects the driest periods recorded, at similar to 3.7 cal ka BP and 1.6 cal ka BP. Lake shrinkage and salinization was interrupted as suggested by the deposition of Unit IV (similar to 1.4 to similar to 0.8 cal ka BP), when increased precipitation and runoff that might be related to the Medieval Warm Period, led to a stable, but still low lake level. Unit V (800 cal years BP-present) is characterized by progressive lake shrinkage due to intense evaporation. Large fluctuations in geochemical variables indicate humid and arid periods, respectively, at Nam Co between similar to 450 and similar to 200 cal years BP, with the latter assumed to correspond to the Little Ice Age. Modern hydrological data indicate the lake level is rising. Comparison of the Nam Co record with other lake records from the Tibetan Plateau suggests general agreement with the broader picture of Holocene environmental evolution. The timing of dry and wet climate conditions at lake sites across Tibet indicates a gradually decreasing influence of the southern monsoon during the Holocene, from NW to SE. Nevertheless, further research is needed to improve our understanding of Holocene spatio-temporal hydrological variations across the Asian continent.

Ostracod and diatom assemblages, mollusc remains, plus pollen and sediment stratigraphy from three cores taken at sites 40, 80 and 135 m deep in Lake Neuchâtel, Switzerland, show distinct changes since deglaciation. Shifts are interpreted in terms both of climatic change and major changes in the catchment input caused by the Aar River entering or bypassing Lake Neuchâtel. Three palaeoenvironmental phases are recognized: (1) the Late Glacial, with the inflow of the river before 10,000 yr B.P.; (2) the early to mid-Holocene, with temporary bypassing of the river between 10,000 and 4850 yr B.P.; and (3) the mid- to late Holocene, without river input after approx. 4850 yr B.P. During periods with river input, rhythmites were deposited. Ostracods indicate a well oxygenated hypolimnion, suggesting deep ventilation enhanced by the river inflow. The diatom assemblage indicates eutrophic to mesotrophic conditions and is dominated by generally well preserved periphytic species. The high number of unidentifiable pollen suggests oxidation during transport in the river. During periods without river input, a massive calcareous silt with abundant authigenic calcite was deposited, diatoms indicate a change to mesotrophic and oligotrophic conditions, and decreased sedimentation rates and higher alkalinity enhanced the dissolution of diatoms. Terrestrial and littoral molluscs as well as periphytic diatoms indicate erosion of the shore when the lake level rose or fell with onset or offset of the river inflow. Before 12,600 yr B.P., the patchy vegetation cover led to intensive soil erosion and high sedimentation rates. The lake was still frozen during the winter months. After approx. 12,600 yr B.P. the sediment changed from clastic rhythmites to thinly bedded, non-glacial rhythmites, the vegetation cover became denser, the abundance of ostracods increased, and molluscs started to colonize the profundal zone of the lake. The Younger Dryas (approx. 10,700–10,000 yr B.P.) displays maximum abundance of ostracods, indicating deep ventilation. The transition to the Holocene is characterized by a change in the ostracod assemblage and the river bypassed the lake between approximately 10,000 and 8900 yr B.P. When the river reentered the lake after approximately 8900 yr B.P., a new ostracod species appeared. After two short periods of river bypassing between approximately 7200 and 6950 yr B.P., diatoms indicate a higher trophic level about 6000–5000 yr B.P. associated with higher erosion rates and increased nutrient input due to Neolithic agricultural activities. After approximately 4850 yr B.P. the river bypassed the lake again and the trophic level decreased. In contrast to the early to mid-Holocene periods of decreased oxygen supply, the mid- to late Holocene is characterized by deep ventilation. This is attributed to the northward retreat of the polarfront and enhanced westerlies consequent to decreased insolation after 6000 yr B.P. The change of the river flow pattern correlates with glacier oscillations and may suggest a climatic control. The final cessation of the inflow is attributed to diversion of the river consequent to isostatic uplift and late Neolithic clearance activity.

Ostracode taxonomy has been of great interest because of their possible use as indicator species in climate and ecosystem changes. In Central and South America, few studies have been carried out and this study includes a contribution to the group. Eleven ostracode species were collected in Lago Petén Itzá (~100km2), the second largest lowland lake in Guatemala, and from its inflow tributary, Río Ixlú in November 2005 and February 2008. Twenty-seven surface sediment samples were retrieved at water depths from the littoral zone to the lake’s maximum depth (>160m). Hard and soft parts of ostracodes were analyzed, and each ostracode species was described for taxonomy, size, ecology, biology and geographic distribution. Species recorded include: Candonocypris serratomarginata?, Cypretta brevisaepta?, Cypridopsis okeechobei, Cytheridella ilosvayi, Darwinula stevensoni, Heterocypris punctata, Limnocythere opesta, Physocypria globula, Pseudocandona sp., Stenocypris major and Strandesia intrepida. Most of the species have a neotropical distribution, two are distributed world-wide (D. stevensoni and S. major), and C. okeechobei and P. globula display nearctic and neotropical distributions. We present new records of C. brevisaepta?, C. serratomarginata?, S. major, and S. intrepida in Guatemala. Physocypria globula was misidentified previously in Lago Petén Itzá as Cypria petenensis, Pseudocandona sp. was misidentified as Candona sp., and C. okeechobei was identified in the past as C. vidua. Limnocythere opesta is the only endemic species of the Petén Lake District, Guatemala. The most abundant and widely distributed species in the lake are P. globula, C. okeechobei, and Pseudocandona sp. Species restricted to the littoral zones and water depths La taxonomía de los ostrácodos ha sido de gran interés debido a su posible uso como especies indicadoras de cambios del clima y de los ecosistemas. En América Central y del Sur se han llevado a cabo pocos estudios. Once especies de ostrácodos fueron colectadas en el 2005 y 2008 en el Lago Petén Itzá (~100km²), el segundo lago más grande de Guatemala y en su afluente, el Río Ixlú. Veintisiete muestras de sedimentos superficiales fueron extraídas a diferentes profundidades desde la zona litoral hasta la profundidad máxima (160m) del lago. Partes duras y blandas de los ostracódos colectados fueron analizadas. Este estudio describe cada especie de ostrácodo con respecto a su taxonomía, tamaño, ecología, biología y distribución geográfica. Especies reportadas incluyen: Candonocypris serratomarginata?, Cypretta brevisaepta?, Cypridopsis okeechobei, Cytheridella ilosvayi, Darwinula stevensoni, Heterocypris punctata, Limnocythere opesta, Physocypria globula, Pseudocandona sp., Stenocypris major y Strandesia intrepida. La mayoría de las especies poseen una distribución neotropical, dos tienen una distribución mundial (D. stevensoni and S. major) y C. okeechobei y P. globula tienen una distribución neártica y neotropical. Presentamos un nuevo récord de C. brevisaepta?, C. serratomarginata?, S. major y S. intrepida para Guatemala. Physocypria globula fue identificada erróneamente en el Lago Petén Itzá como Cypria petenensis, Pseudocandona sp. había sido identificada como Candona sp. y C. okeechobei como C. vidua. Limnocythere opesta es una especie endémica de la región. Las especies más abundantes y de mayor distribución en el lago son P. globula, C. okeechobei y Pseudocandona sp. Especies restringidas a zonas litorales y aguas con una pronfundidad