Die Ausnutzung des Zooplanktons durch planktonfressende Fische in Abhängigkeit von abiotischen Faktoren im Oderhaff

Zusammenfassung 1. In den Jahren 1955–1958 wurden im Oderhaff Untersuchungen durchgeführt über die quantitative Dynamik zwischen Artzusammensetzung und Quantität des Zooplanktons einerseits und Wachstum und Nahrungsaufnahme planktonfressender Fische andererseits.2. Die jahreszeitlich bedingten Veränderungen in der Planktonzusammensetzung üben einen starken quantitativen und qualitativen Einfluß aus auf die Nahrungszusammensetzung planktonfressender Fische (Mageninhaltsuntersuchungen).3. Die pro Zeiteinheit aufgenommene Nahrungsmenge ist in starkem Maße von der Quantität des zur Verfügung stehenden Zooplanktons abhängig.4. Die Dynamik der Beziehungen Fischfraß — Zooplankton und Zooplankton — Fischfraß ist eng verbunden mit jahreszeitlichen Fluktuationen der abiotischen Umweltfaktoren.5. Futterreichtum bewirkt eine Erhöhung des Zuwachstempos und des Futterverwertungskoeffizienten der Fische.6. Fischarten, deren Nahrung nicht ausschließlich aus Zooplankton besteht, erschließen sich in Zeiten mit geringer Zooplanktonbiomasse andere Nahrungsquellen und andere Futterplätze.7. Der Einfluß des Fischfraßes auf die Bildung und Vermehrung der Zooplanktongemeinschaften ist schwer zu beurteilen. Er läßt sich aber nachweisen, und zwar vor allem in Perioden mit herabgesetzter Reproduktionskapazität der Planktonorganismen und mit gesteigertem Nahrungskonsum der Fische. Es wurden zwei solche Perioden pro Jahr im Oderhaff festgestellt.

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The utilization of zooplankton by plankton-eating fishes in relation to abiotic factors in the Szczecin Gulf

The investigations were carried out in the middle area of the Szczecin Gulf, Poland, from 1955 to 1958. The seasonal and year-by-year fluctuations in the quality and quantity of zooplankton stocks may cause parallel changes in the food uptake of plankton-eating fishes. In fishes feeding primarily on zooplankton, changes were found in stomach contents, daily food consumption, efficiency of food utilization and growth rate. Fishes feeding only temporarily on zooplankton either increase their consumption of other food organisms as the zooplankton biomass decreases (2-year-oldOsmerus eperlanus andLucioperca lucioperca) or look for new feeding grounds (young ofAcerina cernua andAbramis brama). In order to analyse the effects of fish predation on the zooplankton biomass, the following phenomena were investigated: (a) annual fluctuations of fish predations (mainlyO. eperlanus); (b) annual fluctuations in reproduction patterns of Cladocera species of importance as fish food(Daphnia hyalina, D. cuculata) relative to changes in the abiotic environment; (c) annual fluctuations in total mortality of the twoDaphnia species mentioned. During the reproductive period the rate of reproduction inDaphnia is always higher than the maximum increase in daily food requirements of the growingO. eperlanus. Fish predation may represent a severe stress for theDaphnia populations during two periods per year. In these periods the situation is characterized by (a) decrease of prey reproduction rate and increase in daily food requirements of the growingO. eperlanus; (b) faster decrease of prey reproduction rate relative to a parallel decrease in food requirements of the predator.

     

Fast reactivation of photosynthesis in arctic phytoplankton during the polar night1

Arctic microalgae experience long periods of continuous darkness during the polar night, when they are unable to photosynthesize. Despite numerous studies on overwintering strategies, such as utilization of stored energy products, formation of resting stages, reduction of metabolic rates and heterotrophic lifestyles, there have been few attempts to assess the in situ physiological state and restoration of the photosynthetic apparatus upon re‐illumination. In this study, we found diverse and active marine phytoplankton communities during the polar night at 78°N. Furthermore, we observed rapid changes (≤20 min) in the efficiency of photosynthetic electron transport upon re‐illumination. High photosynthetic capacity and net primary production were established after 24 h of re‐illumination. Our results suggest that some Arctic autotrophs maintain fully functional photosystem II and downstream electron acceptors during the polar night even though the low in situ net primary production levels measured in January prove that light was not sufficient to support any measurable primary production. Due to low temperatures resulting in low respiratory rates as well as the absence of photodamage during the polar night, maintenance of basic photosynthetic machinery may actually pose relatively low metabolic costs for algal cells. This could allow Arctic microalgae to endure the polar night without the formation of dormant stages, enabling them to recover and take advantage of light immediately upon the suns return during the winter–spring transition.     

Autonomic resource management in virtualized data centers using fuzzy logic-based approaches

Data centers, as resource providers, are expected to deliver on performance guarantees while optimizing resource utilization to reduce cost. Virtualization techniques provide the opportunity of consolidating multiple separately managed containers of virtual resources on underutilized physical servers. A key challenge that comes with virtualization is the simultaneous on-demand provisioning of shared physical resources to virtual containers and the management of their capacities to meet service-quality targets at the least cost. This paper proposes a two-level resource management system to dynamically allocate resources to individual virtual containers. It uses local controllers at the virtual-container level and a global controller at the resource-pool level. An important advantage of this two-level control architecture is that it allows independent controller designs for separately optimizing the performance of applications and the use of resources. Autonomic resource allocation is realized through the interaction of the local and global controllers. A novelty of the local controller designs is their use of fuzzy logic-based approaches to efficiently and robustly deal with the complexity and uncertainties of dynamically changing workloads and resource usage. The global controller determines the resource allocation based on a proposed profit model, with the goal of maximizing the total profit of the data center. Experimental results obtained through a prototype implementation demonstrate that, for the scenarios under consideration, the proposed resource management system can significantly reduce resource consumption while still achieving application performance targets.

First record of a pterosaur landing trackway

The terrestrial progression of pterosaurs, the flying reptiles of the Mesozoic Era, has been debated for over two centuries. The recent discovery of quadrupedal pterodactyloid pterosaur tracks from Late Jurassic sediments near Crayssac, France, shows that the hindlimbs moved parasagittally, as in mammals, birds and other dinosaurs, and the hypertrophied forelimbs could make tracks both close to the body wall and far outside it. Their manus tracks are unique in form, position and kinematics, which would be expected because the forelimbs were used for flight. Here, we report the first record of a pterosaur landing track, which differs substantially from typical walking trackways. The individual landed on both hind feet in parallel fashion, dragged its toes slightly as it left the track, landed again almost immediately and placed the hindfeet parallel again, then placed its forelimbs on the ground, took another short step with both hindlimbs and adjusted its forelimbs, and then began to walk off normally. The trackway shows that pterosaurs stalled to land, a reflection of their highly developed capacity for flight control and manoeuverability.     

Tracing Si–N–P ecosystem-pathways: is relative uptake in riparian vegetation influenced by soil waterlogging,mowing management and species diversity?

Despite the growing concern about the importance of silicon (Si) in controlling ecological processes in aquatic ecosystems, little is known about its processing in riparian vegetation, especially compared to nitrogen (N) and phosphorus (P). We present experimental evidence that relative plant uptake of N and P compared to Si in riparian vegetation is dependent on mowing practices, water-logging and species composition. Results are obtained from a controlled and replicated mesocosm experiment, with a full-factorial design of soil water logging and mowing management. In our experiments, the Si excluding species Plantago lanceolata was dominant in the mown and non-waterlogged treatments, while Si accumulating meadow grasses and Phalaris arundinacea dominated the waterlogged treatments. Although species composition, management and soil moisture interacted strongly in their effect on relative Si:N and Si:P uptake ratios, the uptake of N to P remained virtually unchanged over the different treatments. Our study sheds new light on the impact of riparian wetland ecosystems on nutrient transport to rivers. It indicates that it is essential to include Si in future studies of the impact of riparian vegetation on nutrient transport, as these are often implemented as a measure to moderate excessive N and P inputs.     

Integrating Pathways of Parkinson's Disease in a Molecular Interaction Map

Parkinson's disease (PD) is a major neurodegenerative chronic disease, most likely caused by a complex interplay of genetic and environmental factors. Information on various aspects of PD pathogenesis is rapidly increasing and needs to be efficiently organized, so that the resulting data is available for exploration and analysis. Here we introduce a computationally tractable, comprehensive molecular interaction map of PD. This map integrates pathways implicated in PD pathogenesis such as synaptic and mitochondrial dysfunction, impaired protein degradation, alpha-synuclein pathobiology and neuroinflammation. We also present bioinformatics tools for the analysis, enrichment and annotation of the map, allowing the research community to open new avenues in PD research. The PD map is accessible at http://minerva.uni.lu/pd_map.     

C4′/H4′ selective,non-uniformly sampled 4D HC(P)CH experiment for sequential assignments of 13C-labeled RNAs

A through bond, C4′/H4′ selective, “out and stay” type 4D HC(P)CH experiment is introduced which provides sequential connectivity via H4′_(i)–C4′_(i)–C4′_(i?1)–H4′_(i?1) correlations. The ³¹P dimension (used in the conventional 3D HCP experiment) is replaced with evolution of better dispersed C4′ dimension. The experiment fully utilizes ¹³C-labeling of RNA by inclusion of two C4′ evolution periods. An additional evolution of H4′ is included to further enhance peak resolution. Band selective ¹³C inversion pulses are used to achieve selectivity and prevent signal dephasing due to the of C4′–C3′ and C4′–C5′ homonuclear couplings. For reasonable resolution, non-uniform sampling is employed in all indirect dimensions. To reduce sensitivity losses, multiple quantum coherences are preserved during shared-time evolution and coherence transfer delays. In the experiment the intra-nucleotide peaks are suppressed whereas inter-nucleotide peaks are enhanced to reduce the ambiguities. The performance of the experiment is verified on a fully ¹³C, ¹⁵N-labeled 34-nt hairpin RNA comprising typical structure elements.     

Interpretation of Appearance: The Effect of Facial Features on First Impressions and Personality

Appearance is known to influence social interactions, which in turn could potentially influence personality development. In this study we focus on discovering the relationship between self-reported personality traits, first impressions and facial characteristics. The results reveal that several personality traits can be read above chance from a face, and that facial features influence first impressions. Despite the former, our prediction model fails to reliably infer personality traits from either facial features or first impressions. First impressions, however, could be inferred more reliably from facial features. We have generated artificial, extreme faces visualising the characteristics having an effect on first impressions for several traits. Conclusively, we find a relationship between first impressions, some personality traits and facial features and consolidate that people on average assess a given face in a highly similar manner.     

Axon targeting of the alpha 7 nicotinic receptor in developing hippocampal neurons by Gprin1 regulates growth

Cholinergic signaling plays an important role in regulating the growth and regeneration of axons in the nervous system. The α7 nicotinic receptor (α7) can drive synaptic development and plasticity in the hippocampus. Here, we show that activation of α7 significantly reduces axon growth in hippocampal neurons by coupling to G protein‐regulated inducer of neurite outgrowth 1 (Gprin1), which targets it to the growth cone. Knockdown of Gprin1 expression using RNAi is found sufficient to abolish the localization and calcium signaling of α7 at the growth cone. In addition, an α7/Gprin1 interaction appears intimately linked to a Gαo, growth‐associated protein 43, and CDC42 cytoskeletal regulatory pathway within the developing axon. These findings demonstrate that α7 regulates axon growth in hippocampal neurons, thereby likely contributing to synaptic formation in the developing brain.