O,p'-DDT induction of vitellogenesis and its inhibition by tamoxifen in Nile tilapia (Oreochromis niloticus)

In order to investigate the mechanism by which o,p'-DDT disrupts endocrine functioning of Nile tilapia in vivo, the estrogenicity of o,p'-DDT was investigated in conjunction with 17beta-estradiol (E2) and tamoxifen. Mature, male tilapia were treated intraperitoneally with o,p'-DDT (60 mg/kg, one dose) or E2 (5 mg/kg, four doses) in the presence or absence of tamoxifen (5 mg/kg, six doses) for 12 days and then plasma vitellogenin (Vtg) (measured as alkaline-labile phosphorous), E2, and testosterone (T) were measured. Vtg levels were increased dramatically by E2 (1,744 +/- 171 microg/ml) and moderately by o,p'-DDT (82 +/- 15 microg/ml) compared with controls (23 +/- 3.5 microg/ml). Tamoxifen alone had no effect on Vtg production, but inhibited both E2 and o,p'-DDT stimulated vitellogenesis. T levels were reduced with E2 administration (1,688 +/- 383 pg/ml) and declined further with the combined treatment of E2 and tamoxifen (281 +/- 70 pg/ml), compared with controls (6,558 +/- 1,438 pg/ml). Tamoxifen or o,p'-DDT alone did not affect T levels, but their combined treatment did (2,069 +/- 647 pg/ml). The results of this study suggest that o,p'-DDT is weakly estrogenic in male tilapia, and that this activity may be mediated through the estrogen receptor.     

Spatio-temporal and interspecific variation in otolith trace-elemental fingerprints in a temperate estuarine fish assemblage

We tested whether estuarine fishes have site-specific differences in the concentrations of trace elements in their otoliths that can be used as ‘fingerprints’ to identify them to their estuary of origin. To evaluate the robustness of this approach, we tested whether elemental fingerprints were consistent among individuals of five species that were collected in 1996 from three temperate estuaries in southern California. We also tested whether elemental fingerprints were consistent between spring and autumn 1996 for three species in one of the sites, Carpinteria Marsh. The species evaluated comprised a mid-water-dwelling smelt (Atherinops affinis), two benthic gobies (Clevelandia ios and Ilypnus gilberti), and two flatfish (Paralichthys californicus and Hypsopsetta guttulata). The concentrations of six elements (Mn, Cu, Zn, Sr, Ba, and Pb) were determined in the otoliths using inductively coupled plasma-mass spectrometry (ICP-MS). Within estuaries, the five species exhibited strong variation in elemental concentration, indicating substantial interspecific differences in otolith environmental history. When the five fish species were considered separately, multivariate (MANOVA) and univariate (ANOVA) analyses of variance indicated that the elemental composition of otoliths differed significantly among the estuaries in four of the five species. Based on linear discriminant function analyses (DFA), differences were strong enough that trace element composition could be used to accurately assign fish to their site of origin [mean (range): 93.5% (74–100%)]. However, elemental signatures within Carpinteria Marsh were not consistent between spring and autumn 1996, and this was reflected in a substantial reduction in the accuracy of assigning fish to their true site of origin. When we compared site differences between fish species (site×species interactions), the elemental fingerprints were most similar between closely related species (e.g. the two gobies and the two flatfish) and most dissimilar between distantly related species, both phylogenetically and ecologically. Among the six elements analyzed, Sr and Ba exhibited the most inconsistent pattern among species, with significant differences in 80 and 70% of the pairwise species comparisons, respectively. The remaining four elements showed ≥70% consistency in the pattern of variation among sites for the different species. Thus, while otolith elemental fingerprinting can be a useful tool for inferring estuarine residency, such fingerprints may be temporally variable and species specific.     

Simulation by CMIP5 models of the atlantic multidecadal oscillation and its climate impacts

This study focuses on the climatic impacts of the Atlantic Multidecadal Oscillation (AMO) as a mode of internal variability. Given the difficulties involved in excluding the effects of external forcing from internal variation, i.e., owing to the short record length of instrumental observations and historical simulations, we assess and compare the AMO and its related climatic impacts both in observations and in the “Pre-industrial” experiments of models participating in CMIP5. First, we evaluate the skill of the 25 CMIP5 models’ “Historical” simulations in simulating the observational AMO, and find there is generally a considerable range of skill among them in this regard. Six of the models with higher skill relative to the other models are selected to investigate the AMO-related climate impacts, and it is found that their “Pre-industrial” simulations capture the essential features of the AMO. A positive AMO favors warmer surface temperature around the North Atlantic, and the Atlantic ITCZ shifts northward leading to more rainfall in the Sahel and less rainfall in Brazil. Furthermore, the results confirm the existence of a teleconnection between the AMO and East Asian surface temperature, as well as the late withdrawal of the Indian summer monsoon, during positive AMO phases. These connections could be mainly caused by internal climate variability. Opposite patterns are true for the negative phase of the AMO.     

Timing of the first drainage of the Baltic Ice Lake synchronous with the onset of Greenland Stadial 1

Glacial varves can give significant insights into recession and melting rates of decaying ice sheets. Moreover, varve chronologies can provide an independent means of comparison to other annually resolved climatic archives, which ultimately help to assess the timing and response of an ice sheet to changes across rapid climate transitions. Here we report a composite 1257‐year‐long varve chronology from southeastern Sweden spanning the regional late Allerød–late Younger Dryas pollen zone. The chronology was correlated to the Greenland Ice‐Core Chronology 2005 using the time‐synchronous Vedde Ash volcanic marker, which can be found in both successions. For the first time, this enables secure placement of the Lateglacial Swedish varve chronology in absolute time. Geochemical analysis from new varve successions indicate a marked change in sedimentation regime accompanied by an interruption of ice‐rafted debris deposition synchronous with the onset of Greenland Stadial 1 (GS‐1; 12 846 years before AD 1950). With the support of a simple ice‐flow/calving model, we suggest that slowdown of sediment transfer can be explained by ice‐sheet margin stabilization/advance in response to a significant drop of the Baltic Ice Lake level. A reassessment of chronological evidence from central‐western and southern Sweden further supports the hypothesis of synchronicity between the first (penultimate) catastrophic drainage of the Baltic Ice Lake and the start of GS‐1 in Greenland ice‐cores. Our results may therefore provide the first chronologically robust evidence linking continental meltwater forcing to rapid atmosphere–ocean circulation changes in the North Atlantic.     

European summer temperature response to annually dated volcanic eruptions over the past nine centuries

The drop in temperature following large volcanic eruptions has been identified as an important component of natural climate variability. However, due to the limited number of large eruptions that occurred during the period of instrumental observations, the precise amplitude of post-volcanic cooling is not well constrained. Here we present new evidence on summer temperature cooling over Europe in years following volcanic eruptions. We compile and analyze an updated network of tree-ring maximum latewood density chronologies, spanning the past nine centuries, and compare cooling signatures in this network with exceptionally long instrumental station records and state-of-the-art general circulation models. Results indicate post-volcanic June–August cooling is strongest in Northern Europe 2 years after an eruption (?0.52?±?0.05 °C), whereas in Central Europe the temperature response is smaller and occurs 1 year after an eruption (?0.18?±?0.07 °C). We validate these estimates by comparison with the shorter instrumental network and evaluate the statistical significance of post-volcanic summer temperature cooling in the context of natural climate variability over the past nine centuries. Finding no significant post-volcanic temperature cooling lasting longer than 2 years, our results question the ability of large eruptions to initiate long-term temperature changes through feedback mechanisms in the climate system. We discuss the implications of these findings with respect to the response seen in general circulation models and emphasize the importance of considering well-documented, annually dated eruptions when assessing the significance of volcanic forcing on continental-scale temperature variations.     

Quantification of turbate microstructures through a subglacial till: dimensions and characteristics

Despite extensive study and debate regarding the significance of turbate (also known as ‘rotational’) microstructures in glacially deformed sediments, characteristics regarding the dimensions of these features remain unresolved. This study presents the first explicitly quantitative measurement and analysis of turbate microstructure dimensions, and their relation to till texture through thin section analysis. Samples were taken from coarse‐resolution horizontal and vertical transects of a macroscopically homogenous subglacial till, with subset areas of each thin section (30 mm²) analysed. The frequency and apparent a‐axes and b‐axes of both coreless and cored turbate structures (and their corestones) were measured, and simple univariate statistical methods used to establish the (in‐)variability of these dimensions through the till profile. Summarizing findings, (i) the dimensions of both cored and coreless turbate populations display log‐normal distributions when all measurements are analysed together, although not all individual sample populations possess these same distributions; (ii) turbate dimension populations are inconsistent within a sample block, precluding evaluation of turbate variability through a profile from single thin sections; (iii) analysis of turbate morphology and variability provisionally indicate that the three‐dimensional structure of turbates are likely to be cylindrical or flared, while weak relationships are also observed amongst till texture, turbate dimensions and frequency.     

The formation of iron hydroxide coatings in an Emscher Marl: inverse reactive transport modeling of reactive surface area

The possible effects of iron oxide coatings on the reactive surface area of calcite in column experiments have been studied and then modeled numerically. A column with six compartments separated by teflon filters was packed with Emscher Marl (essentially calcite). The marl was initially mixed with corundum as an internal standard. Hydrochloric acid with pH 3 was percolated through the column for a given period, after which the mineralogical changes were quantified by X-ray diffraction ex-situ. Then, the column compartments were re-filled and again percolated with HCl. This procedure was repeated five times. The losses and gains of calcite in the column compartments provided the data basis for modeling the entire experiment with the reactive transport code TOUGHREACT using a kinetic rate law. The experimental results showed that during the first period, loss of calcite in the first compartment is about 50 % less than that determined from the theoretical analysis. This showed the entrance of acid into the higher compartments through preferential flow paths (wormholes) which was observed at the boundary between sample and cell wall. This pattern could also be verified by the relatively high Peclet and low Damköhler numbers, showing a strongly advection-dominant system. Apart from calcite dissolution, structural Fe²⁺ released from calcite oxidized and formed iron hydroxide (FeOOH) coatings along preferential fluid pathways. Despite specific assumptions such as using pure calcite in the model, a comparison between modeling results and lab observations is instructive. The simulated calcite change patterns in the most compartments are consistent with the experiments. Some discrepancies are noted in the last compartment, which may bring the attention to a need for model improvements.     

Post fire induced soil water repellency—Modeling short and long-term processes

Soil water repellency has direct implications to hydrological as well as geomorphological processes, especially in fire-prone ecosystems. Five predominant mechanisms have been described as generating water repellency in soils: fungal and microbial activity, growth of particular vegetation species, organic matter, heating of the soils by wildfires and soil characteristics. Herein we synthesize among these mechanisms and propose a general model describing the long-term properties of water repellency in soils. Using non-linear regression analysis methods we compare among different variants of the model in order to assess the relative role of vegetation on water-repellency dynamics. We suggest that following a wildfire event hydrophobic peak soil properties are dictated by vegetation properties, but that the rapid decrease is not associated with the vegetation. Following wildfires, the recovery of the ecosystem commences and water-repellency is characterized by increased predominance of the biotic activity. Thus, the general pattern of a rapid decrease and a long-term increase in water repellency can be described by a mathematical model presented herein.     

Automated facies identification by Direct Push-based sensing methods (CPT,HPT) and multivariate linear discriminant analysis to decipher geomorphological changes and storm surge impact on a medieval coastal landscape

In ad 1362, a major storm surge drowned wide areas of cultivated medieval marshland along the north-western coast of Germany and turned them into tidal flats. This study presents a new methodological approach for the reconstruction of changing coastal landscapes developed from a study site in the Wadden Sea of North Frisia. Initially, we deciphered long-term as well as event-related short-term geomorphological changes, using a geoscientific standard approach of vibracoring, analyses of sedimentary, geochemical and microfaunal palaeoenvironmental parameters and radiocarbon dating. In a next step, Direct Push (DP)-based Cone Penetration Testing (CPT) and the Hydraulic Profiling Tool (HPT) were applied at vibracore locations to obtain in situ high-resolution stratigraphic data. In a last step, multivariate linear discriminant analysis (LDA) was successfully applied to efficiently identify different sedimentary facies (e.g., fossil marsh or tidal flat deposits) from the CPT and HPT test dataset, to map the facies' lateral distribution, also in comparison to reflection seismic measurements and test their potential to interpolate the borehole and CPT/HPT data. The training dataset acquired for the key site from coring and DP sensing finally allows an automated facies classification of CPT/HPT data obtained elsewhere within the study area. The new methodological approach allowed a detailed reconstruction of the local coastal landscape development in the interplay of natural marsh formation, medieval land reclamation and storm surge-related land losses.