The ‘Little Ice Age’ in the Southern Hemisphere in the context of the last 3000 years : Peat-based proxy-climate data from Tierra del Fuego

DM’s research (at Department of Earth Sciences, Uppsala University) was supported through a European Community Marie Curie Fellowship (Contract HPMF-CT-2000-01056).Peer reviewedPostprin

A new peat bog testate amoeba transfer function and quantitative palaeohydrological reconstructions from southern Patagonia

Testate amoebae have been extensively used as proxies for environmental change and palaeoclimate reconstructions in European and North American peatlands. The presence of these micro-organisms near the peat surface is generally significantly linked to the local water table depth (WTD) and therefore preservation of the amoeba shells downcore allows for water table reconstructions over millennia. In the last decades, attention for the palaeoecology of the southern Patagonian peat bogs has increased, partly because of the particular climatological setting under the influence of the southern westerlies. These atypical peat bogs are characterised by a wide range of water tables, from wet hollows to hummocks exceeding 100 cm above the water table, and a dominance of Sphagnum magellanicum on low lawns up to the highest hummocks. Here we present the first transfer function for this region that allows for reliable WTD reconstructions, along with 2k-year palaeorecords from local peat bogs.A modern dataset (155 samples) was sampled along transects from five bogs in 2012 and 2013. Measurements of WTD, pH and conductivity were taken for all samples. Transfer function model was based on the 2012 dataset while the 2013 samples served as an independent test set to validate the model. Besides the standard leave-one- out cross-validation we applied leave-one-site-out and leave-one transect-out cross-validation, which are effective means of verifying the degree of clustering in the dataset. To assure the environmental gradient had been evenly sampled we quantified the root-mean-squared error of prediction (RMSEP) individually for segments of this gradient.Ordinations showed a clear hydrological gradient in amoeba assemblages, with the dominant Assulina muscorum at the dry end and Amphitrema wrightianum and Difflugia globulosa at the wet end. Taxa as Nebela certesi and Nebela cockayni, possibly exclusive to the southern hemisphere, were identified and their optima and tolerances were determined. Canonical correspondence analysis showed that WTD was the most important environmental variable, accounting for 18% of the variance in amoeba assemblages. A weighted averaging-partial least squares model showed best performance in cross-validation and using the 2013 data as an independent test set. Any spatial autocorrelation was minimal although the model still appeared less effective in predicting WTD for sites not included in the training set. The segment-wise RMSEP showed that the WTD gradient was generally evenly sampled with RMSEP below 15 cm for most of the gradient, much lower than the standard deviation of the mean of all WTDs (26 cm).Preliminary results from peat cores sampled from the same peat bogs show surprisingly stable water tables over the last 2k years in Andorra bog but more variation in nearby Tierra Australis bog. Peat accumulation rates in Andorra bog are among the highest recorded in temperate bogs with around 4 m of peat accumulated during the last 2000 year

Reconstructing sea-level change in the Falkland Islands (Islas Malvinas) using salt-marsh foraminifera, diatoms and testate amoebae

Proxy records of past sea-level change provide a means of extending sea-level histories from tide gauges into the pre-industrial period. This is especially valuable in the South Atlantic region where sea-level data are limited to only a few tide-gauge records. Multi-proxy approaches to sea-level reconstruction are relatively rare but have distinct benefits when groups of micro-organisms are sparse or under-represented in modern or fossil sediments. Here, we address this challenge by utilising surface foraminifera, testate amoebae and diatoms from a salt marsh at Swan Inlet, East Falkland. All three micro-organism groups occupied distinct vertical niches in the contemporary salt-marsh. We investigated the relative performance of each group of micro-organisms in providing a sea-level reconstruction using individual (group-specific) regression models and with a multi-proxy regression model that combined all three groups. Foraminifera alone were not a suitable proxy. Surveyed sample elevations were closely matched by estimated elevations using Weighted-Average (WA) and Weighted-Average Partial-Least-Squares (WA- PLS) regressions. Relative sea-level reconstructions were derived by applying each model to microfossil assemblages recovered from a core (SI-2) from the same site. The combined transfer function yielded reconstructive precision (± 0.08 m) comparable to our best single-proxy transfer function (± 0.06 m) but only 18% of palaeo-samples were identified as having “close” or “good” analogues in the combined training data set. We highlight the benefit of a pragmatic approach to sea-level reconstructions whereby additional proxies should be employed if the use of only one proxy performs poorly across the width of the elevation gradient

The Grizzly, April 7, 1997

Airband Sets Its New Fundraising Record • Ursinus Students Participate in Model U.N. • Women\u27s Health Discussed in Merck Lecture • Changes for Summer Classes • Letters: Letter of Thanks; Faculty Member Remembered • Opinion: Seminar on Post-Abortion Trauma • Pfahler Observatory Open House for Hale-Bopp Viewing • Something for Everyone in proTheatre Production of The Two Noble Kinsmen • Another Look at the Ursinus Gymnastics Team • The Dangers of Halogen Lamps • Men\u27s Tennis Wins • Courtney Named an All-American • Trecroce Named Player of the Week • Women\u27s Tennis Action • Women\u27s Lacrosse Falls to Middlebury • Softball Drops 3 in a Row • Dickinson Rallies to Take Two From the Bearshttps://digitalcommons.ursinus.edu/grizzlynews/1401/thumbnail.jp

The Grizzly, November 18, 1996

Bears Beat Dickinson, Make NCAA Playoffs • Security and RLO Work Through Changes • Opinion: Question of Security; An Insider Throwing out a Line; One of Four Seasons; It\u27s All in Your Head • Concert and Jazz Bands to Perform • Jude: Hardy\u27s Novel Arrives in the Flesh • Bears Win Conference Championship To Make NCAA Playoffs!!! • Getz and Finnegan Receive Post-Season Honorshttps://digitalcommons.ursinus.edu/grizzlynews/1392/thumbnail.jp

Reversible vancomycin susceptibility within emerging ST1421 Enterococcus faecium strains is associated with rearranged vanA-gene clusters and increased vanA plasmid copy number

Vancomycin variable enterococci (VVE) are van-positive enterococci with a vancomycin-susceptible phenotype (VVE-S) that can convert to a resistant phenotype (VVE-R) and be selected for during vancomycin exposure. VVE-R outbreaks have been reported in Canada and Scandinavian countries. The aim of this study was to examine the presence of VVE in whole genome sequenced (WGS) Australian bacteremia Enterococcus faecium (Efm) isolates collected through the Australian Group on Antimicrobial resistance (AGAR) network. Eight potential VVEAus isolates, all identified as Efm ST1421, were selected based on the presence of vanA and a vancomycin-susceptible phenotype. During vancomycin selection, two potential VVE-S harboring intact vanHAX genes, but lacking the prototypic vanRS and vanZ genes, reverted to a resistant phenotype (VVEAus-R). Spontaneous VVEAus-R reversion occurred at a frequency of 4-6 × 10−8 resistant colonies per parent cell in vitro after 48 h and led to high-level vancomycin and teicoplanin resistance. The S to R reversion was associated with a 44-bp deletion in the vanHAX promoter region and an increased vanA plasmid copy number. The deletion in the vanHAX promoter region enables an alternative constitutive promoter for the expression of vanHAX. Acquisition of vancomycin resistance was associated with a low fitness cost compared with the corresponding VVEAus-S isolate. The relative proportion of VVEAus-R vs. VVEAus-S decreased over time in serial passages without vancomycin selection. Efm ST1421 is one of the predominant VanA-Efm multilocus sequence types found across most regions of Australia, and has also been associated with a major prolonged VVE outbreak in Danish hospitals

Late-Holocene climate dynamics recorded in the peat bogs of Tierra del Fuego, South America

The ombrotrophic peat bogs of Tierra del Fuego are located within the southern westerly wind belt (SWWB), which dominates climate variability in this region. We have reconstructed late-Holocene water-table depths from three peat bogs and aimed to relate these records to shifts in regional climate. Water-table depths were quantified by the analysis of testate amoeba assemblages, and a regional transfer function was used to infer past water-table depths. During the last 2000 years, testate amoeba assemblages have been relatively stable, with a dominance of Difflugia pulex and Difflugia pristis type, and an increase in Assulina muscorum and other Euglyphida at the top of each section. Multivariate analyses show that water-table depth remained the main environmental variable explaining assemblages along the TiA12 core, but reconstructions were not significant for the two other cores. In line with the low variability in assemblages, water tables were relatively stable during the last 2000 years. Slightly wetter conditions were found between ~1400 and 900 cal. BP and a pronounced recent dry shift was reconstructed in all of the three peat profiles. Considering the regional climatic context, this recent shift may have been forced by a decrease in precipitation and warmer conditions linked to an increase in the importance of the SWWB. Nevertheless, we cannot exclude the influence of higher UV-B radiation resulting from the local degradation of the ozone layer since the late 1970s, which may have had an additional effect on the relative presence of A. muscorum in the southern Patagonian region

The Lantern Vol. 64, No. 1, Fall 1996

• Sleepwalk • Icky • Hauling the Load • Between Days • First Day • Slipping • College Roommates • Full Moon in Scorpio • Summer Madness • Learning French • nEverglades • The Way Around • Rain • Solacehttps://digitalcommons.ursinus.edu/lantern/1149/thumbnail.jp

Holocene variations in the Asian Summer and Winter Monsoons reconstructed from extensive lacustrine sediments in the Mu Us Desert, northern China

The Salawusu River Valley cuts through the Mu Us Desert in north central China, and lies at the interface of the East Asian Summer and Winter Monsoonal regions. Exposed at numerous locations in the valley side are extensive late Quaternary deposits, consisting of interbedded aeolian sands, fluvio-lacustrine units and palaeosols. Due to the importance of the location in potentially elucidating both summer and winter monsoonal regimes, and the quality of the sedimentary record, the region has a rich history of study, and yet even within the Holocene sequence, many conflicting interpretations have arisen based on studies on different sections. This paper aims to synthesize and explore these differences by exploring the lateral continuity of the Holocene sequences along a ~ 45 km reach of the valley, and presenting new, detailed physical and geochemical analyses of three sections, focusing on the lacustrine Holocene Dagouwan Formation. The absence of the lacustrine unit at several locations confirms that rather than representing a single lake, the Dagouwan Formation instead represents a series of palaeolakes, probably at least partially hydrologically isolated from each other by aeolian sands. All begin with sand-dominated deposits during the early−/mid-Holocene, which is interpreted as the result of abundant sand-supply to the north and west, under the influence of an enhanced East Asian Winter Monsoon, and all switch to silt-dominated, more carbonate-rich deposits during the mid−/late-Holocene, which is attributed to an enhanced East Asian Summer Monsoon bringing loessic silts from the Chinese Loess Plateau to the east and south. The timing of this change, perhaps as late as 5.5 ka, supports the idea of a relatively enhancement late mid-Holocene of the summer monsoonal circulation in the region. However, despite the proximity of the sections and consistent analytical approaches, marked differences between the sections occur in all proxies studied. The timing and rate of the switch from sand- to silt-dominated lacustrine deposition varies between the sites by as much as 2000 years within just a few kilometres of each other, and at some sites the switch was gradual, whereas at others it was very rapid. Similar dramatic variations are also seen with organic carbon content, carbonate content, C:N ratio, and especially the δ13C isotopic ratio. These point to the lake basins behaving very differently, and emphasize that consideration must be given to the local geomorphology and palaeolimnological evolution of individual sections

The Grizzly, April 14, 1997

Student Art Collection to be Exhibited at Berman Museum • Author Lee Gutkind Speaks • Ursinus Jazz Ensemble Performs • Opinion: Ursinus Needs a Foreign Revolution; Common Sense; Let\u27s Get Things Nice and Clear • Letter: Thanks to Volunteers • Shakespeare\u27s Two Noble Kinsmen Visit Ursinus • College Choir to Perform Sacred Service • Right On, My Sister! • Women\u27s Lacrosse Deals Rowan a Defeat • Guenther Named New Football Coach • Women\u27s Tennis Team Transformed • Haverford Pounds Bears • Men\u27s Tennis Falls to Widener • Softball Team Drops Eight of Last Ninehttps://digitalcommons.ursinus.edu/grizzlynews/1402/thumbnail.jp