Hydrological and sedimentological investigation of Radok Lake, Amery Oasis, East Antarctica

Radok Lake in Amery Oasis, East Antarctica, has a water depth of ca. 360 m, making it the deepest non-subglacial lake in Antarctica. Limnological analyses revealed that the lake had, despite a 3 m thick ice cover, a completely mixed water column during austral summer 2001/2002. High oxygen contents, low ion concentrations, and lack of planktonic diatoms throughout the water column indicate that Radok Lake is ultra-oligotrophic today.The late glacial and postglacial lake history is documented in a succession of glacial, glaciolimnic, and limnic sediments at different locations in the lake basin. The sediments record regional differences and past changes in allochthonous sediment supply and lake productivity. However, the lack of age control on these changes, due to extensive sediment redeposition and the lack of applicable dating methods, excluded Radok Lake sediments for advanced paleoenvironmental reconstructions.

Collectanea variae doctrinae : obtulerunt Ludwig Bertalot ... [et al.] /

German or Italian.

Multi-proxy records of Two-Yurts Lake

Within the scope of Russian-German palaeoenvironmental research, Two-Yurts Lake (TYL, Dvuh-Yurtochnoe in Russian) was chosen as the main scientific target area to decipher Holocene climate variability on Kamchatka. The 5x2 km large and 26 m deep lake is of proglacial origin and situated on the eastern flank of Sredinny Ridge at the northwestern end of the Central Kamchatka Valley, outside the direct influence of active volcanism. Here, we present results of a multi-proxy study on sediment cores, spanning about the last 7000 years. The general tenor of the TYL record is an increase in continentality and winter snow cover in conjunction with a decrease in temperature, humidity, and biological productivity after 5000-4500 cal yrs BP, inferred from pollen and diatom data and the isotopic composition of organic carbon. The TYL proxy data also show that the late Holocene was punctuated by two colder spells, roughly between 4500 and 3500 cal yrs BP and between 1000 and 200 cal yrs BP, as local expressions of the Neoglacial and Little Ice Age, respectively. These environmental changes can be regarded as direct and indirect responses to climate change, as also demonstrated by other records in the regional terrestrial and marine realm. Long-term climate deterioration was driven by decreasing insolation, while the short-term climate excursions are best explained by local climatic processes. The latter affect the configuration of atmospheric pressure systems that control the sources as well as the temperature and moisture of air masses reaching Kamchatka.

Sedimentology, biogeochemistry stable isotopes, pollen, plant macrofossils, and diatoms from two sediments cores from the northern Yukon permafrost peatlands (Canada)

Ice-wedge polygon (IWP) mires in the Arctic and Subarctic are extremely vulnerable to climatic and environmental change. We present the results of a multidisciplinary paleoenvironmental study on IWPs in the northern Yukon, Canada. High-resolution laboratory analyses were carried out on a permafrost core and the overlying seasonally thawed (active) layer, from a low-centered IWP located in a drained lake basin on Herschel Island. In relation to 14 Accelerator Mass Spectrometry (AMS) radiocarbon dates spanning the last 5000 years, we report sedimentary data including grain size distribution and biogeochemical parameters (organic carbon, nitrogen, C/N ratio, d13C), stable water isotopes (d18O, dD), as well as fossil pollen, plant macrofossil and diatom assemblages. Three sediment units (SUs) correspond to the main stages of deposition (1) in a thermokarst lake (SU1: 4950 to 3950 cal yrs BP), (2) during transition from lacustrine to palustrine conditions after lake drainage (SU2: 3950 to 3120 cal yrs BP), and (3) in palustrine conditions in the IWP field that developed after drainage (SU3: 3120 cal yrs BP to AD 2012). The lacustrine phase (pre 3950 cal yrs BP) is characterized by planktonic-benthic and pioneer diatoms species indicating circumneutral waters, and very few plant macrofossils. The pollen record has captured a regional signal of relatively stable vegetation composition and climate for the lacustrine stage of the record until 3950 cal yrs BP. Palustrine conditions with benthic and acidophilic species characterize the peaty shallow-water environments of the low-centered IWP. The transition from lacustrine to palustrine conditions was accompanied by acidification and rapid revegetation of the lake bottom within about 100 years. Since the palustrine phase we consider the pollen record as a local vegetation proxy dominated by the plant communities growing in the IWP. Ice-wedge cracking in water-saturated sediments started immediately after lake drainage at about 3950 cal yrs BP and led to the formation of an IWP mire. Permafrost aggradation through downward closed-system freezing of the lake talik is indicated by the stable water isotope record. The originally submerged IWP center underwent gradual drying during the past 2000 years. This study highlights the sensitivity of permafrost landscapes to climate and environmental change throughout the Holocene.

江汉平原晚更新世化石硅藻新种和新记录属种

在对江汉平原钻孔中属晚更新世地层的化石硅藻进行鉴定时,发现1个新种:Geissleria jianghanensis sp.nov.Li,2个中国新记录属:Geissleria和Aneumast us,6个中国新记录:Cymbella neuquina var.fastigata(Krasske)Krammer,Maidana et Villanueva,Cymbella perfossilis Krammer,Cymbella neocistula Krammer,Cym-bella neocistul

Predictores de cambio en la función ventricular izquierda posterior a implante valvular aórtico transcateter comparado con reemplazo valvular aórtico quirúrgico en el hospital universitario fundación Cardioinfantil instituto de cardiología – Bogotá

Objetivos: Identificar predictores de recuperación de la función ventricular izquierda y comparar los hallazgos ecocardiográficos en pacientes con estenosis aórtica crítica sometidos a reemplazo quirúrgico de la válvula aórtica (RVA) o implantación de válvula aórtica transcatéter (TAVI). Métodos: Cuarenta y cuatro pacientes tratados con RVA se compararon con 34 pacientes con TAVI, los datos ecocardiográficos fueron retrospectivamente obtenidos antes de la intervención y previo al alta. Resultados: Se analizaron retrospectivamente pacientes tratados en la FCI - IC desde 2009 - 2015 (n = 78 pacientes, con una media de edad 70,29 ± 11,63, EuroSCORE logístico 3,75 (3-8,55) en RVA y 20,4 (15 , 47-23,32) en TAVI. Ambos grupos mostraron una disminución en los gradientes de la válvula aórtica, más en pacientes de TAVI, con un gradiente transaórtico pico (24,5 vs 18,5, p = 0,001) y medio (14 vs 10, p = 0,002) En comparación con RVA, TAVI presentó un mayor número de pacientes con insuficiencia aórtica paravalvular (47,1% frente a 2,3% p = 0.000). En total, el 61,5% presentó mejoría precoz de la función ventricular, el predictor en severo compromiso de la función del ventrículo izquierdo fue un alto índice de masa ventricular izquierda. Conclusiones: La implantación transcatéter de válvula aórtica es una alternativa al reemplazo quirúrgico de la válvula aórtica en pacientes con estenosis aórtica y alto riesgo quirúrgico. La recuperación postoperatoria precoz de la función ventricular izquierda en pacientes con severo compromiso de la función ventricular estuvo asociada a alto índice de masa ventricular izquierda.

Diatomáceas de lagos rasos do pantanal da nhecolândia, área úmida Brasileira

The diatom flora of the shallow lakes in the Pantanal of Nhecolândia is poorly known. Thus, our aim was to know the diatom biodiversity in three types of shallow lakes called baías, salitradas and salinas, characterized by differences in pH, electrical conductivity, contact with the coalescent system and the presence of macrophytes. The samples were collected in dry and rainy seasons, from 2004 to 2007. For taxonomic identification, the material was cleaned with H2O2 and analyzed using light microscopy. A total of 23 diatom species were identified and each lake presented a unique species richness and composition. The greatest species richness was found in the Baía da Sede Nhumirim (21 species), followed by the Salitrada Campo Dora (8 species) and finally the lowest species richness was observed in the Salina do Meio (3 species). Only Anomoeoneis sphaerophora Pfitzer var. sphaerophora and Craticula cf. buderi (Hustedt) Lange-Bertalot occurred in the three studied systems. Except for Eunotia binularis (Ehrenberg) Souza and Aulacoseira ambigua (Grunow) Simonsen, all the others are new records to the Brazilian Pantanal.

Diatoms (Bacillariophyceae) of Iguacu National Park, Foz do Iguacu, Brazil

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Taxonomy and distribution of taxa in the genus Gomphonema from the Florida Everglades, U.S.A.

Located at a subtropical latitude, the expansive Florida Everglades contains a mixture of tropical and temperate diatom taxa, as well as a unique flora adapted to the calcareous, often excessively hot, seasonally flooded wetland conditions. This flora has been poorly documented taxonomically, although diatoms are recognized as important indicators of environmental change in this threatened ecosystem. Gomphonema is a dominant genus in the freshwater marsh, and is represented by highly variable species complexes, including Gomphonema gracile Ehrenberg, Gomphonema intricatum var. vibrio Ehrenberg sensu Fricke, Gomphonema vibrioides Reichardt & Lange-Bertalot and Gomphonema parvulum (Kützing) Grunow. These taxa have been shown to exhibit wide morphological variation in other regions, resulting in considerable nomenclatural confusion. We collected Gomphonema from 237 sites distributed throughout the freshwater Everglades and used qualitative and quantitative morphological data to identify 20 distinguishable populations. Taxonomie assignments were based on descriptions and/or observations of type material of relevant taxa when possible, but deviations from original morphological range descriptions were common. We then compared morphological variation in Everglades Gomphonema taxa to that reported for the same taxa in other regions and suggest revisions of taxonomie concepts when necessary.