A probabilistic approach to quantifying hydrologic thresholds regulating migration of adult Atlantic salmon into spawning streams

Acknowledgment Data to support this study are provided by the Marine Scotland Science Freshwater Laboratory (MSS-FL) and are available for free download on line [Glover and Malcolm, 2015a, 2015b].Peer reviewedPublisher PD

Enhancing the significance of gravitational wave bursts through signal classification

The quest to observe gravitational waves challenges our ability to discriminate signals from detector noise. This issue is especially relevant for transient gravitational waves searches with a robust eyes wide open approach, the so called all- sky burst searches. Here we show how signal classification methods inspired by broad astrophysical characteristics can be implemented in all-sky burst searches preserving their generality. In our case study, we apply a multivariate analyses based on artificial neural networks to classify waves emitted in compact binary coalescences. We enhance by orders of magnitude the significance of signals belonging to this broad astrophysical class against the noise background. Alternatively, at a given level of mis-classification of noise events, we can detect about 1/4 more of the total signal population. We also show that a more general strategy of signal classification can actually be performed, by testing the ability of artificial neural networks in discriminating different signal classes. The possible impact on future observations by the LIGO-Virgo network of detectors is discussed by analysing recoloured noise from previous LIGO-Virgo data with coherent WaveBurst, one of the flagship pipelines dedicated to all-sky searches for transient gravitational waves

Water-energy-ecosystem nexus in small run-of-river hydropower : Optimal design and policy

Acknowledgment This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors. Support from the Helmholtz Centre for Environmental Research - UFZ is gratefully acknowledged.Peer reviewedPublisher PD

Les réseaux trophiques lacustres: structure, fonctionnement, interactions et variations spatio-temporelles

L'analyse comparative des réseaux trophiques lacustres est d'un grand intérêt pour le développement de la limnologie contemporaine et l'aménagement des lacs. L'analyse des mécanismes écologiques déterminant la structure et le fonctionnement des réseaux trophiques dans les lacs tempérés a permis l'émergence de plusieurs modèles, souvent contradictoires, et suscité d'intenses débats sur le rôle respectif des ressources et des prédateurs. Par contre, dans les lacs tropicaux, les études sont en majorité descriptives et la recherche de principes généraux et de concepts unificateurs y est rare. Cette synthèse présente l'état des connaissances, les approches méthodologiques, les modèles de régulation concernant la structure et le fonctionnement des réseaux trophiques lacustres. Les réseaux trophiques semblent varier selon un gradient de situations intermédiaires entre deux modèles extrêmes : (a) les milieux à cascades trophiques intenses et à effet atténué des ressources (lacs tempérés oligo-mésotrophes) caractérisés par la présence de poissons piscivores et de zooplancton herbivore de grande taille (tels Daphnia spp.) et (b) les milieux à régulation intermédiaire (lacs tempérés méso-eutrophes et la plupart des lacs tropicaux), caractérisés par la présence de poissons filtreurs microphages omnivores et de zooplancton herbivore de petite taille. Notre synthèse souligne aussi l'importance d'allier les approches expérimentales en enceintes ou par biomanipulation à des suivis à long terme et des modélisations pour avoir une bonne compréhension et des prédictions précises du fonctionnement des écosystèmes lacustres à différentes échelles spatiales et temporelles et pour différentes conditions climatiques, géographiques ou trophiques.Comparative analysis of lake food webs is a focal point of research in contemporary limnology and lake management. The study of ecological processes determining foodweb structure and function lead to the emergence of constrasting hypotheses and intense debates on the relative role of nutrients and food web structure in regulating temperate lake ecosystems. In contrast, studies in tropical lakes are in general descriptive and the search for integrate concepts and models is yet in development. This review paper presents an overview and a critical analysis of actual knowledge, methodological approaches, regulation models and controversies on foodweb structure and function in temperate and tropical lakes. Our synthesis suggests that the apparent diversity in models of lake foodwebs could reflect a gradient (or contiuum) of intermediate foodweb situations, regulated by various environmental factors. The differences among lakes could be related to three main biotic factors, independently of the climatic, geographical and trophic conditions: 1. the important cascading effect of strictly piscivorous fish in temperate lakes compared to the weak cascades induced by opportunistic omnivorous fish in tropical lakes, 2. the primacy of omnivory and opportunistic feeding behaviour of tropical fish, 3. the key role of herbivorous macrozooplankton (cladocerans, mostly Daphnia spp.) in temperate lakes where they are both selective preys of planktivorous fish and efficient grazers of nanophytoplankton, and 4. the synchronous reproduction of fish with seasonal plankton succession in temperate lakes, compared to continuous reproduction of fish and lack of seasonal coupling in tropical lakes. Consequently, food webs regulation ranges along a gradient of situations with two extreme models: 1. a model with intense cascading (top-down) regulation and attenuation of bottom-up effects typical of oligo-mesotrophic temperate lakes, characterized by the dominance of piscivorous fish and large herbivorous zooplankton (Daphnia spp.), and 2. a model with intermediate regulation encountered in eutrophic temperate lakes and most of tropical lakes, characterized par the dominance of filter omnivorous fish and small size zooplankton. Our synthesis also emphasizes the importance of coupling experimental approches in mesocosms or whole-lake biomanipulation with long-term monitoring and modelisation to fully understand and predict the functionning of lake ecosystems over different spatial and temporal scale

Mitigation of 42^{42}Ar/42^{42}K background for the GERDA Phase II experiment

Background coming from the $^{42}$Ar decay chain is considered to be one of the most relevant for the GERDA experiment, which aims to search of the neutrinoless double beta decay of $^{76}$Ge. The sensitivity strongly relies on the absence of background around the Q-value of the decay. Background coming from $^{42}$K, a progeny of $^{42}$Ar, can contribute to that background via electrons from the continuous spectrum with an endpoint of 3.5 MeV. Research and development on the suppression methods targeting this source of background were performed at the low-background test facility LArGe. It was demonstrated that by reducing $^{42}$K ion collection on the surfaces of the broad energy germanium detectors in combination with pulse shape discrimination techniques and an argon scintillation veto, it is possible to suppress the $^{42}$K background by three orders of magnitude. This is sufficient for Phase II of the GERDA experiment

The evolutionary costs of immunological maintenance and deployment

<p>Abstract</p> <p>Background</p> <p>The evolution of disease resistance and immune function may be limited if increased immunocompetence comes at the expense of other fitness-determining traits. Both the maintenance of an immune system and the deployment of an immune response can be costly, and the observed costs may be evaluated as either physiological or evolutionary in origin. Evolutionary costs of immunological maintenance are revealed as negative genetic correlations between immunocompetence and fitness in the absence of infection. Costs of deployment are most often studied as physiological costs associated with immune system induction, however, evolutionary costs of deployment may also be present if genotypes vary in the extent of the physiological cost experienced.</p> <p>Results</p> <p>In this study we analyzed evolutionary and physiological costs of immunity in two environments representing food-limited and food-unlimited conditions. Patterns of genetic variation were estimated in females from 40 'hemiclone families' isolated from a population of <it>D. melanogaster</it>. Phenotypes evaluated included fecundity, weight measures at different time periods and resistance to <it>Providencia rettgeri</it>, a naturally occurring Gram-negative pathogen of <it>D. melanogaster</it>. In the food-limited environment we found a negative genetic correlation between fecundity in the absence of infection and resistance, indicative of an evolutionary cost of maintenance. No such correlation was observed in the food-unlimited environment, and the slopes of these correlations significantly differed, demonstrating a genotype-by-environment interaction for the cost of maintenance. Physiological costs of deployment were also observed, but costs were primarily due to wounding. Deployment costs were slightly exaggerated in the food-limited environment. Evolutionary costs of immunological deployment on fecundity were not observed, and there was only marginally significant genetic variation in the cost expressed by changes in dry weight.</p> <p>Conclusion</p> <p>Our results suggest that the costs of immunity may be an important factor limiting the evolution of resistance in food-limited environments. However, the significant genotype-by-environment interaction for maintenance costs, combined with the observation that deployment costs were partially mitigated in the food-unlimited environment, emphasizes the importance of considering environmental variation when estimating patterns of genetic variance and covariance, and the dubious nature of predicting evolutionary responses to selection from quantitative genetic estimates carried out in a single environment.</p