1,721,498 research outputs found
Master track of ALKOR cruise AL632 in 1 sec resolution (zipped, 45 MB)
No full textRaw data acquired by position sensors on board RV Alkor during expedition AL632 were processed to receive a validated master track which can be used as reference of further expedition data. During AL632 data from the Seapath 330 system, the Furuno GP-170 and the Furuno GP-150 GPS receivers were used to calculate the mastertrack. Data were downloaded from DAVIS SHIP data base (http://dship.bsh.de) with a resolution of 1 sec. Processing and evaluation of the data is outlined in the data processing report. Processed data are provided as a master track with 1 sec resolution derived from the position sensors' data selected by priority and a generalized track with a reduced set of the most significant positions of the master track
Physical oceanography during ALKOR cruise AL573
No full textConductivity-temperature-depth profiles were measured using a CTD during RV ALKOR cruise AL573. The CTD was equipped with duplicate sensors for temperature, conductivity and oxygen. All sensors are calibrated irregularly. Data were connected to the station book of the specific cruise as available in the DSHIP database
Physical oceanography during ALKOR cruise AL556
No full textConductivity-temperature-depth profiles were measured using a CTD during RV ALKOR cruise AL556. The CTD was equipped with duplicate sensors for temperature, conductivity and oxygen. All sensors are calibrated irregularly. Data were connected to the station book of the specific cruise as available in the DSHIP database
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Do seagrasses feel the heat? Assessing the potential for microevolutionary change in a marine ecosystem engineering plant in response to global warming
Get PDFA central question in ecology is how organisms react to changing environmental conditions induced by global climate change. This is particularly important for ecosystem engineering species, as the fate of whole ecosystems is depending upon their performance and survival. In coastal marine habitats, seagrasses are of outstanding importance as ecosystem builders. Eelgrass, the study species of this thesis, is the most widespread and locally abundant seagrass along soft-sediment coasts of the northern hemisphere. In this thesis I assessed variation among and within eelgrass populations in response to heat stress. I conducted heat stress experiments in a “common stress garden”, simulating a summer heat wave of three weeks followed by a recovery phase. I measured various physiological parameters and assessed the expression profile of selected heat stress associated genes with qPCR as well as the whole transcriptome with next generation sequencing using eelgrass with differing thermal history (a southern population from the Mediterranean Sea and northern populations from the Kattegat and Limfjord, Baltic Sea). To assess variation within populations, I used genotypes originating from a Baltic population. I found that different genotypes showed varying growth rates in control and heat treatment at acute heat stress, but that all populations lost shoots in response to the heat wave, irrespective of their thermal pre-adaptation. While populations diverged in their expression profiles of selected heat stress associated genes already at the onset of heat stress, subsequent global transcription profiling revealed that those effects were of relatively minor importance compared to massive differences in gene expression during the recovery phase between two of the populations. This is in line with findings on the genotype level within one population which showed differences in the expression profiles of selected stress-associated genes between replicated individuals only in the recovery phase. This thesis provides a basis for investigating the potential for microevolution of eelgrass populations in the face of global climate change. Both, cold- as well as warm adapted eelgrass populations responded to heat stress with shoot reduction, a finding that is in line with worldwide records of seagrass decline. On the other hand, there is considerable variation for heat stress-related gene expression within populations, a trait that is likely to be important under global change. As this variation among genotypes is the prerequisite for natural selection and adaptation, populations may succeed to persist
Vergleichende Populationsgenetik, Larvenverdriftung und evolutionäre Aspekte von Antarktisfischen (Notothenioidei)
Get PDFIn this thesis, population genetic structures and evolutionary aspects of speciation in notothenioid fishes from the Southern Ocean have been investigated. Special emphasis was given to the role of pelagic larval dispersal on gene flow between geographically separated populations, since notothenioids are characterized by unusually long pelagic larval durations of up to one year, which is assumed to counteract genetic divergence of populations and ultimately allopatric speciation processes. By elucidating the population genetic structures of selected notothenioid species, inferences were made about the level of gene flow between populations. The major goal of this thesis was to compare the population genetic structures of sympatric species within the Atlantic sector of the Southern Ocean to determine factors responsible for regulating gene flow. Species-specific traits, such as larval durations, were expected to result in differences between the observed patterns, while environmental factors, such as oceanographic currents or frontal systems, were assumed to influence multiple species in a similar way. In addition, it has been tested whether the evolution of notothenioids fulfills the criteria of an adaptive radiation, of which only a few examples are known from the marine realm.In dieser Doktorarbeit wurden die populationsgenetischen Strukturen und weitere evolutionäre Aspekte von Artbildungsprozessen innerhalb von Antarktisfischen (Notothenioidei) aus dem Südpolarmeer untersucht. Ein besonderer Schwerpunkt war es, den Einfluss pelagischer Larvenverdriftung auf den Genfluss zwischen geografisch getrennten Populationen zu ermitteln, da notothenioide Fische durch ungewöhnlich lange, pelagische Larvenphasen von bis zu über einem Jahr charakterisiert sind, wodurch erhöhter Genfluss einer Auseinanderentwicklung von Populationen und damit auch allopatrischer Artbildung entgegen wirken kann. Die Untersuchung der populationsgenetischen Strukturen erlaubt es, Rückschlüsse auf das Ausmaß des genetischen Austauschs zwischen Populationen zu ziehen. Das Hauptziel dieser Arbeit war es, durch einen Vergleich der genetischen Populationsstrukturen sympatrischer Arten, Faktoren zu identifizieren, die maßgeblich den Genfluss beeinflussen. Dabei wurde angenommen, das artspezifische Merkmale, wie z. B. die Dauer der Larvenphase, in Unterschieden zwischen den beobachteten Populationsstrukturen zum Ausdruck kommen, während Umweltfaktoren, wie ozeanografische Strömungen und Fronten, verschiedene Arten gleichermaßen beeinflussen. Des weiteren wurde untersucht, ob die Evolution der Antarktisfische den Kriterien einer Adaptativen Radiation entspricht, für welche es im marinen Lebensraum bisher nur wenige bekannte Beispiele gibt
Assessing marine phytoplankton eco-evolutionary dynamics and physiological responses to environmental change
Get PDFAnthropogenic emissions of carbon dioxide (CO2) resulting from fossil fuel burning and changes in land use are affecting our marine environment; for example leading to ocean acidification or ocean warming. In order to understand how climate change will affect biological communities we need to understand all levels of biological responses. Community change as a response to environmental drivers are composed of three components: the physiological responses within an organism, described by its phenotypic plasticity or reaction norm and the ecological and evolutionary responses which are associated with changes on the species and genotype level, respectively. Moreover, there may be eco-evolutionary coupling, thus either ecological interactions such as competition that modify evolutionary responses to physico-chemical changes, or evolutionary change that feeds back to change ecological interactions. Here I study for the first time over the long-term (up to 220 generations) how among two competing phytoplankton species the different response types play out, and whether or not coupling of ecological and evolutionary processes can be found. Additionally I investigated the short-term inter- and intraspecific responses of three phytoplankton species to increased CO2 and what role competitive interactions play on the short-term in a two-species ´community´
Challenges and solutions in regionalized stock assessment of the European eel (Anguilla anguilla)
Get PDFAn accurate assessment of fish stock status is pivotal in fisheries management, to guide decisions about sustainable exploitation levels or conservation measures. The abundance or biomass of a fish stock, however, is seldom directly observable, whereby population models have become the primary alternative to gauge fish stock status. Comprehensive and accurate assessments for widely distributed or highly migratory species are particularly challenging, involving a devolution of responsibilities for data collection, and sometimes also for the assessment itself, to the regional level among contracting countries. The critically endangered, facultative diadromous European eel (Anguilla anguilla) has a complex life-cycle, forming a single panmictic stock with a wide continental distribution, thereby epitomizing the challenges of regionalized stock assessment and management. This thesis reviews and examines the accuracy of currently used methods for the assessment of local eel stock status in terms of potential spawner (so-called “silver eel”) escapement, which is mandatory across EU countries. Particular focus was placed on the German Eel Model (GEM), which was validated through a comprehensive mark-recapture study on the Ems River as an exemplary system. The study found a substantial overestimation of the silver eel escapement by GEM compared to the monitored biomass, illustrative of the great uncertainties in local eel stock assessments. A comprehensive meta-analysis of similar validation studies for the heterogeneous regional eel assessment models across Europe underscored the tendency towards over-optimistic estimates for specific model types. Misestimations of stock size can have severe consequences for both the ecological and economic sustainability of a fish stock and its fishery, while over-optimistic assessments in particular increase the risk of insufficient conservation measures needed to enable species recovery
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
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