Phenotypic responses of invasive species to removals affect ecosystem functioning and restoration.

Reducing the abundances of invasive species by removals aims to minimize their ecological impacts and enable ecosystem recovery. Removal methods are usually selective, modifying phenotypic traits in the managed populations. However, there is little empirical evidence of how removal-driven changes in multiple phenotypic traits of surviving individuals of invasive species can affect ecosystem functioning and recovery. Overcoming this knowledge gap is highly relevant because individuals are the elemental units of ecological processes and so integrating individual-level responses into the management of biological invasions could improve their efficiency. Here we provide novel demonstration that removals by trapping, angling and biocontrol from lakes of the globally invasive crayfish Procambarus clarkii induced substantial changes in multiple phenotypic traits. A mesocosm experiment then revealed that these changes in phenotypic traits constrain recovery of basic ecosystem functions (decomposition of organic matter, benthic primary production) by acting in the opposite direction than the effects of reduced invader abundance. However, only minor ecological impacts of invader abundance and phenotypic traits variation remained a year after its complete eradication. Our study provides quantitative evidence to an original idea that removal-driven trait changes can dampen recovery of invaded ecosystems even when the abundance of invasive species is substantially reduced. We suggest that the phenotypic responses of invaders to the removal programme have strong effects on ecosystem recovery and should be considered within the management of biological invasions, particularly when complete eradication is not achievable

Laboratory captivity can affect scores of metabolic rates and activity in wild brown trout

Phenotypic scoring of wild animals under standardized laboratory conditions is important as it allows field ecologists and evolutionary biologists to understand the development and maintenance of interindividual differences in plastic traits (e.g. behaviour and physiology). However, captivity is associated with a shift from a natural familiar environment to an unfamiliar and artificial environment, which may affect estimates of plastic phenotypic traits. In this study, we tested how previous experience with laboratory environments and time spent in captivity affects behavioural (i.e. activity) and metabolic (i.e. standard and maximum metabolic rates) scoring of our model species, wild brown trout Salmo trutta. We found that individuals with previous experience of laboratory captivity (10.5 months earlier) showed higher activity in an open field test than individuals with no prior experience of laboratory captivity. Previous experience with captivity had no significant effect on metabolic rates. However, metabolic rates seemed to increase with increasing time spent in captivity prior to the collection of measurements. Although there are benefits of keeping wild animals in captivity prior to scoring, our results suggest that while allowing for sufficient acclimatization researchers should aim at minimizing time in captivity of wild animals to increase accuracy and ecological relevance of the scoring of plastic phenotypic traits

Monitoring mixed neutron-proton field near the primary proton and deuteron beams in spallation targets

282-293At the Joint Institute for Nuclear Research (JINR) we are involved in the Accelerator-Driven-System (ADS) research. We perform experiments with assemblies composed of a spallation target and a subcritical blanket irradiated with high-energy proton or deuteron beams that generate high-energy neutron fields by spallation and fission reactions. In this paper, three uranium assemblies are presented: Energy plus Transmutation (E+T), QUINTA and BURAN. We discuss the results of the E+T and QUINTA irradiations by 1.6 GeV deuterons and 660 MeV protons, respectively. We have focused on the regions close to the primary beam passage through the targets. The field has been measured using activation detectors of 209Bi, 59Co, and natPb. Monte Carlo simulations using MCNPX 2.7.0 have been performed and compared to the experimental results. We discovered that the field intensity near the primary beam is very dependent on the precision of the accelerator beam settings. Therefore, a Monte Carlo-based study of the influence of the uncertainty of primary proton beam parameters on experimental result accuracy of the QUINTA assembly has been carried out. The usage of MCNPX 2.7.0 in the future BURAN irradiations has been assessed.</span

Monitoring mixed neutron-proton field near the primary proton and deuteron beams in spallation targets

At the Joint Institute for Nuclear Research (JINR) we are involved in the Accelerator-Driven-System (ADS) research. We perform experiments with assemblies composed of a spallation target and a subcritical blanket irradiated with high-energy proton or deuteron beams that generate high-energy neutron fields by spallation and fission reactions. In this paper, three uranium assemblies are presented: Energy plus Transmutation (E+T), QUINTA and BURAN. We discuss the results of the E+T and QUINTA irradiations by 1.6 GeV deuterons and 660 MeV protons, respectively. We have focused on the regions close to the primary beam passage through the targets. The field has been measured using activation detectors of 209Bi, 59Co, and natPb. Monte Carlo simulations using MCNPX 2.7.0 have been performed and compared to the experimental results. We discovered that the field intensity near the primary beam is very dependent on the precision of the accelerator beam settings. Therefore, a Monte Carlo-based study of the influence of the uncertainty of primary proton beam parameters on experimental result accuracy of the QUINTA assembly has been carried out. The usage of MCNPX 2.7.0 in the future BURAN irradiations has been assessed

Effect of individuals’ local persistence, and spatial and temporal scale, on density-dependent growth: a study in brown troutSalmo trutta

This study focuses on the mechanism of density-dependent growth in a stream-dwelling landlocked population of brown trout Salmo trutta. Specifically, body growth estimated by scale reading was examined in relation to population density and recapture rate (approximation of persistence of individuals within a location associated with dispersal and mortality) across 7 years and two spatial scales – a reach and a whole stream. In concordance with previous studies, the whole-stream population density had a crucial effect on body growth in juveniles, but not in adult individuals. Furthermore, growth was negatively associated with the whole-stream population density in reaches with a low recapture rate, whereas no such relationship could be detected in reaches with a high recapture rate. Since persistence within a certain locality increases the familiarity of individuals with the habitat and with other conspecifics, we suggest that the negative effect of population density on growth might be relaxed in groups with a high recapture rate by positive influence of the familiarity both within the habitat but also towards other conspecifics, which decreases competition pressure

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The proton and deuteron induced reactions have a great interest for the assessment of induced radioactivity of accelerator components. Such data are needed for estimation of the potential radiation hazard from the accelerating cavities and beam transport elements. Continuing previous irradiation experiments on copper, we provided two short run to obtain cross-section data for 65Cu(d, p)66Cu reaction. We carried out irradiation experiments with the variable-energy cyclotron U-120M of the Nuclear Physics Institute Řež. The stacked-foil technique was utilized. Because of a relatively short half life (T1/2 = 5, 120  min) and a strong annihilation peak, we placed the 1 cm Pb plate between the irradiated sample and the gamma-ray detector to reduce the dead time. The absolute values of cross-sections were calculated from the induced activities measured by the calibrated HPGe detector. The comparison of present results with data of other authors and prediction of different libraries and model calculation is discussed

65Cu(d,p)66Cu excitation function at deuteron energies up to 20 MeV

The proton and deuteron induced reactions have a great interest for the assessment of induced radioactivity of accelerator components. Such data are needed for estimation of the potential radiation hazard from the accelerating cavities and beam transport elements. Continuing previous irradiation experiments on copper, we provided two short run to obtain cross-section data for 65Cu(d, p)66Cu reaction. We carried out irradiation experiments with the variable-energy cyclotron U-120M of the Nuclear Physics Institute Řež. The stacked-foil technique was utilized. Because of a relatively short half life (T1/2 = 5, 120  min) and a strong annihilation peak, we placed the 1 cm Pb plate between the irradiated sample and the gamma-ray detector to reduce the dead time. The absolute values of cross-sections were calculated from the induced activities measured by the calibrated HPGe detector. The comparison of present results with data of other authors and prediction of different libraries and model calculation is discussed

Experimental investigation and Monte Carlo simulations of radionuclide production inside the Uranium spallation target QUINTA irradiated with a 660-MeV proton beam

The accelerator-Driven-System (ADS) is very important to study the neutron field and radionuclide production inside simple-geometry uranium subcritical setups irradiated with high energy particle beams. A subcritical setup QUINTA was irradiated with the 660-MeV proton beam from Phasotron accelerator at the Joint Institute for Nuclear Research (JINR). The radionuclide production in the region along the beam axis was investigated by the activation technique. The aim was to compare (n,x) with (p,x) reactions using activation detectors of 59Co and natPb, and compare experimental results with the calculated results using Monte Carlo simulation code MCNPX 2.7

Cross-section studies of relativistic deuteron reactions obtained by activation method

The cross-sections of relativistic deuteron reactions on natural copper were studied in detail by means of activation method. The copper foils were irradiated during experiments with the big Quinta uranium target at Joint Institute for Nuclear Research (JINR) in Dubna, Russia. The deuteron beams with energies ranging from 1 GeV up to 8 GeV were produced by JINR Nuclotron. Residual nuclides were identified by the gamma spectrometry. Lack of such experimental cross-section values prevents the usage of copper foils from beam integral monitoring