Growth rates, seed size, and physiology: do small-seeded species really grow faster?

Relative growth rate (RGR) is currently the most commonly used method for measuring and comparing species' intrinsic growth potential. Comparative studies have, for example, revealed that small-seeded species have higher RGR, leading to the common belief that small-seeded species possess physiological adaptations for rapid growth that would allow them to outgrow large-seeded species, given sufficient time. We show that, because RGR declines as individual plants grow, it is heavily biased by initial size and does not measure the size-corrected growth potential that determines the outcome of competition in the long-term. We develop a daily growth model that includes a simple mechanistic representation of aboveground and belowground growth and its dependency on plant size and environmental factors. Intrinsic growth potential is encapsulated by the size-independent growth coefficient, G. We parameterized the model using repeated-harvest data from 1724 plants of nine species growing in contrasting nutrient and temperature regimes. Using information-theoretic criteria, we found evidence for interspecific differences in only three of nine model parameters: G, aboveground allocation, and frost damage. With other parameters shared between species, the model accurately reproduced above- and belowground biomass trajectories for all nine species in each set of environmental conditions. In contrast to conventional wisdom, the relationship between G and seed size was positive, despite a strong negative correlation between seed size and average RGR, meaning that large-seeded rather than small-seeded species have higher size-corrected growth potential. Further, we found a significant positive correlation between G and frost damage that, according to simulations, causes rank reversals in final biomass under daily temperature changes of +/- 5 degrees C. We recommend the wider use of this new kind of plant growth analysis as a better way of understanding underlying differences in species' physiology; but we recognize that RGR is still a useful metric if considering the potential rate of population increase in empty habitats.     

Simulation of information propagation in real-life primate networks: longevity, fecundity, fidelity

In many vertebrate species, we find temporally stable traditions of socially learned behaviors. The social structure of animal populations is highly diverse and it has been proposed that differences in the social organization influence the patterns of information propagation. Here, we provide results of a simulation study of information propagation on real-life social networks of 70 primate groups comprising 30 different species. We found that models that include the social structure of a group differ significantly from those that assume random associations of individuals. Information spreads slower in the structured groups than in the well-mixed groups. While we found only a minor effect on the path lengths of the transmission chains, robustness against information extinction was strongly influenced by the group structure. Interestingly, robustness against information loss was not correlated with propagation speed but could be predicted reasonably well by relative strength assortativity—a structural network metric. In those groups where highly pro-social individuals preferentially interact with other pro-social individuals, information was more likely to be lost. Our results show that incorporating group structure in any social propagation model significantly alters predictions for spreading patterns, speed, and robustness of information.     

Ökotoxikologische Untersuchung von Sedimenten und Schwebstoffen

The potential risk of ground-water contamination through the infiltration of contaminants originating from suspended matter and sediments deposited within flood retention areas in the Upper Rhine valley, as well as subsequent problems for drinking water production, were analyzed by means of the bacterial dehydrogenase activity (DHA; sediment contact test) assay with Arthrobacter globiformis and in a prolonged embryo toxicity assay using zebrafish (Danio rerio). Since the direct uptake of contaminants from particle-bound sources has usually been assumed to play only a minor role in bioaccumulation, the availability of organic extracts to biota has generally been regarded as being overestimated. In order to confirm or discard this hypothesis, organic (acetone) extracts of recently suspended, freeze-dried matter, as well as freeze-dried sediments collected from Rhine flood plains (i.e. soil samples) were compared to corresponding native samples in order to screen for the relative availability of particle-bound contaminants. Whereas a significantly higher ecotoxicological burden was observed for some native soil samples, organic extracts of suspended matter proved to be more toxic than corresponding native samples when compared to organic extracts using each test system. With respect to organic extracts, the suspended matter samples were more toxic than soil samples taken from a rarely flooded site. In contrast to the native samples, the rarely flooded soils revealed a higher toxicity than suspended matter. Therefore, organic extracts did not necessarily overestimate the toxicity of soil and suspended matter samples. Moreover, considerable toxicity of particle-bound contaminants to both bacteria and fish embryos, even in native samples, corroborate the hypothesis that particle-bound contaminants may be more readily available than is generally assumed.     

Sorption of Zn(II) in aqueous solutions by scoria

We conducted kinetic and equilibrium sorption experiments on removal of Zn(II) from aqueous solutions by scoria (a vesicular pyroclastic rock with basaltic composition) from Jeju Island, Korea, in order to examine its potential use as an efficient sorbent. The batch-type kinetic sorption tests under variable conditions indicated that the percentage of Zn(II) removal by scoria increases with decreasing initial Zn(II) concentration, particle size, and sorbate/sorbent ratio. However, the sorption capacity decreases with the decrease of the initial Zn(II) concentration and sorbate/sorbent ratio. Equilibrium sorption tests show that Jeju scoria has a larger capacity and affinity for Zn(II) sorption than commercial powdered activated carbon (PAC); at initial Zn(II) concentrations of more than 10mM, the sorption capacity of Jeju scoria is about 1.5 times higher than that of PAC. The acquired sorption data are better fitted to the Langmuir isotherm than the Freundlich isotherm. Careful examination of ionic concentrations in sorption batches suggests that the sorption behavior is mainly controlled by cation exchange and typically displays characteristics of 'cation sorption'. The Zn(II) removal capacity decreases when solution pH decreases because of the competition with hydrogen ions for sorption sites, while the Zn(II) removal capacity increases under higher pH conditions, likely due to hydroxide precipitation. At an initial Zn(II) concentration of 5.0mM, the removal increases from 70% to 96% with the increase of initial pH from 3.0 to 7.0. We recommend Jeju scoria as an economic and efficient sorbent for Zn(II) in contaminated water.     

The sensitivity of current and future forest managers to climate-induced changes in ecological processes

Climate vulnerability of managed forest ecosystems is not only determined by ecological processes but also influenced by the adaptive capacity of forest managers. To better understand adaptive behaviour, we conducted a questionnaire study among current and future forest managers (i.e. active managers and forestry students) in Austria. We found widespread belief in climate change (94.7 % of respondents), and no significant difference between current and future managers. Based on intended responses to climate-induced ecosystem changes, we distinguished four groups: highly sensitive managers (27.7 %), those mainly sensitive to changes in growth and regeneration processes (46.7 %), managers primarily sensitive to regeneration changes (11.2 %), and insensitive managers (14.4 %). Experiences and beliefs with regard to disturbance-related tree mortality were found to particularly influence a manager’s sensitivity to climate change. Our findings underline the importance of the social dimension of climate change adaptation, and suggest potentially strong adaptive feedbacks between ecosystems and their managers.

Electronic supplementary material

The online version of this article (doi:10.1007/s13280-015-0737-6) contains supplementary material, which is available to authorized users.     

Visualizing different uranium oxidation states during the surface alteration of uraninite and uranium tetrachloride

Low-temperature alteration reactions on uranium phases may lead to the mobilization of uranium and thereby poses a potential threat to humans living close to uranium-contaminated sites. In this study, the surface alteration of uraninite (UO₂) and uranium tetrachloride (UCl₄) in air atmosphere was studied by confocal laser scanning microscopy (CLSM) and laser-induced fluorescence spectroscopy using an excitation wavelength of 408 nm. It was found that within minutes the oxidation state on the surface of the uraninite and the uranium tetrachloride changed. During the surface alteration process U(IV) atoms on the uraninite and uranium tetrachloride surface became stepwise oxidized by a one-electron step at first to U(V) and then further to U(VI). These observed changes in the oxidation states of the uraninite surface were microscopically visualized and spectroscopically identified on the basis of their fluorescence emission signal. A fluorescence signal in the wavelength range of 415–475 nm was indicative for metastable uranium(V), and a fluorescence signal in the range of 480–560 nm was identified as uranium(VI). In addition, the oxidation process of tetravalent uranium in aqueous solution at pH 0.3 was visualized by CLSM and U(V) was fluorescence spectroscopically identified. The combination of microscopy and fluorescence spectroscopy provided a very convincing visualization of the brief presence of U(V) as a metastable reaction intermediate and of the simultaneous coexistence of the three states U(IV), U(V), and U(VI). These results have a significant importance for fundamental uranium redox chemistry and should contribute to a better understanding of the geochemical behavior of uranium in nature. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Inhibition of phosphoenolpyruvate carboxykinase activity appears to be the key biochemical lesion in the acute toxicity of 2,3,7,8-tetrachlorodibenzo-p-dioxin in rats

2,3,7,8-Tetrachlorodibenzo-p-dioxin (TCDD) exerts its acute toxicity by inducing a gradually increasing voluntary feed refusal. However, this seems not to be caused by a direct effect on the central nervous system, as far higher concentrations of TCDD were found in the brain after intracerebroventricular (i.c.v.) than after lethal intravenous (i.v.) injections, but were not accompanied by a wasting syndrome. TCDD causes inhibition of several key enzymes of gluconeogenesis, with phosphoenolpyruvate carboxykinase (PEPCK) responding earliest and strongest to the insult. Responses of pyruvate carboxylase (PC) and glucose-6-phosphatase (G-6-Pase) are less pronounced and begin at later time points. Blood and brain levels of tryptophan increase following TCDD treatment with a lag period of about three days, shortly after the decrease of PEPCK activity becomes apparent. Since thi samino acid is the precursor of the appetite suppressant neurotransmitter serotonin, and since it is normally degraded via gluconeogenesis, a series of events can be suggested to explain the TCDD-induced wasting syndrome. By an as yet unrevealed mechanism TCDD decreases the activity of PEPCK to about 40 percent of normal, leading to a back-up of gluconeogenic substrates, among them tryptophan, which in turn can further inhibit PEPCK activity in vivo. This causes an increase in serotonin turnover in brain and possibly in other tissues. Increased serotonergic activity in turn is likely to play an important role in the increasing feed refusal of TCDD-treated rats which eventually leads to death.     

Biomonitoring of persistent organochlorine pesticides, PCDD/PCDFs and dioxin-like PCBs in blood of children from South West Germany (Baden-Wuerttemberg) from 1993 to 2003

In the context of a monitoring program, persistent organic pollutants (POPs) were quantified in the blood of 10 year old children at four different demographic regions in Baden-Wuerttemberg, a highly industrialised federal state in South West Germany. DDE, HCB, PCB 138, PCB 153 and PCB 180 were measured in 1996/1997, 1998/1999, 2000/2001 and 2002/2003 in individual samples of about 400 children per year. PCDD/PCDFs and some relevant coplanar PCBs were determined in pooled samples from children in seven cycles from 1993 to 2003. Blood concentrations of the investigated compounds decreased in that time period by a factor of 2-4 with the exception of most PCDFs. The concentrations of POPs in the blood of the children were distinctly lower than the concentrations reported for adults. Breast feeding was associated with about 30% higher median concentrations of DDE, HCB, PCBs and a 30% increase for mean PCDD/PCDF concentrations. Concerning demographic differences, significant lower concentrations of HCB, PCBs and PCDD/PCDFs could be seen in children from Mannheim compared to the region of Aulendorf. About 10-20% higher concentrations were found in boys compared to girls for HCB, indicator PCBs and PCDD/PCDFs. The pattern of non-ortho and mono-ortho PCBs in the blood of children was similar to the pattern reported for mother's milk, and PCB 126 and PCB 156 contributed about 70% to the toxicity of dioxin-like PCBs and about one-third to total TEQ including PCDD/PCDFs.     

Elektronen-Energieverlust-Spektroskopie (FELS) als Methode zur Lokalisierung von Antigenen und anderen Substanzen in Zellen und Geweben

The localization of antigens and other substances in cells and tissues by electron microscopy is usually performed by immunohistochemical techniques employing labelled conventional or monoclonal antibodies. For the ultrastructural localization of the antibodies, they are coupled to electron-dense labels like gold or ferritin. Here, we demonstrate a novel method to localize antigens in cells, tissues, and on other supports. By electron energy loss spectroscopy (EELS) it is possible to directly analyze the distribution of antigens, metabolites or other substances without the use of labelled antibodies: as an example we demonstrate the distribution of the immunomodulator lipopeptide in B lymphocytes and macrophages. EELS represents a novel, sensitive, and generally applicable method for the detection and localization of antigens and other substances in biology and medicine.