Modeling radiocarbon constraints on the dilution of dissolved organic carbon in the deep ocean

The recalcitrance of dissolved organic carbon (DOC) that leads to its accumulation in the deep ocean is typically considered a function of its reactivity. Yet, recent experimental evidence has shown that DOC from the deep ocean, if concentrated, can support significant microbial growth. This supports an alternative hypothesis that [DOC] may become too dilute to support microbial growth. The radiocarbon signature of DOC is a key constraint on the DOC cycling that allows testing of the plausibility of this hypothesis. Here we use a box model of diluted DOC in the deep ocean and its radiocarbon signature that is constrained on the basis of the new experimental evidence, as well as current knowledge of deep ocean DOC cycling to quantitatively test the dilution hypothesis. We explore the uncertainty in model results across a range of plausible dilution thresholds, additional processes, and fluxes of DOC to the deep ocean. Results show that the model is able to predict the observed radiocarbon signature for a dilution threshold close to the observed deep ocean [DOC] and for fluxes close to published estimates. Sensitivity analysis shows that this result is highly sensitive to variations in the dilution threshold and the assumption that diluted DOC is able to survive ocean overturning. The experimental findings can be alternatively reconciled over a large range of different conditions assuming a small pool of diluted DOC with a modern radiocarbon signature, consistent with recent observations, and offering a parsimonious interpretation of dilution with existing hypotheses on DOC recalcitrance.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Linking biogeochemistry to hydro-geometrical variability in tidal estuaries:a generic modeling approach

This study applies the Carbon-Generic Estuary Model (C-GEM) modeling platform to simulate the estuarine biogeochemical dynamics – in particular the air-water CO₂ exchange – in three idealized end-member systems covering the main features of tidal alluvial estuaries. C-GEM uses a generic biogeochemical reaction network and a unique set of model parameters extracted from a comprehensive literature survey to perform steady-state simulations representing average conditions for temperate estuaries worldwide. Climate and boundary conditions are extracted from published global databases (e.g. World Ocean Atlas, GLORICH) and catchment model outputs (GlobalNEWS2). The whole-system biogeochemical indicators Net Ecosystem Metabolism (NEM), C and N filtering capacities (FC_TC and FC_TN, respectively) and CO₂ gas exchanges (FCO₂) are calculated across the three end-member systems and are related to their main hydrodynamic and transport characteristics. A sensitivity analysis, which propagates the parameter uncertainties, is also carried out, followed by projections of changes in the biogeochemical indicators for the year 2050. <br><br> Results show that the average C filtering capacities for baseline conditions are 40, 30 and 22% for the marine, mixed and riverine estuary, respectively. This translates into a first-order, global CO₂ outgassing flux for tidal estuaries between 0.04 and 0.07 Pg C yr^&minus;1. N filtering capacities, calculated in similar fashion, range from 22% for the marine estuary to 18 and 15% for the mixed and the riverine estuary, respectively. Sensitivity analysis performed by varying the rate constants for aerobic degradation, denitrification and nitrification over the range of values reported in the literature significantly widens these ranges for both C and N. Simulations for the year 2050 indicate that all end-member estuaries will remain net heterotrophic and while the riverine and mixed systems will only marginally be affected by river load changes and increase in atmospheric <i>p</i>CO₂, the marine estuary is likely to become a significant CO₂ sink in its downstream section. In the decades to come, such change of behavior might strengthen the overall CO₂ sink of the estuary-coastal ocean continuum

Bridging the divide:A model-data approach to Polar and Alpine microbiology

Advances in microbial ecology in the cryosphere continue to be driven by empirical approaches including field sampling and laboratory-based analyses. Although mathematical models are commonly used to investigate the physical dynamics of Polar and Alpine regions, they are rarely applied in microbial studies. Yet integrating modelling approaches with ongoing observational and laboratory-based work is ideally suited to Polar and Alpine microbial ecosystems given their harsh environmental and biogeochemical characteristics, simple trophic structures, distinct seasonality, often difficult accessibility, geographical expansiveness and susceptibility to accelerated climate changes. In this opinion paper, we explain how mathematical modelling ideally complements field and laboratory-based analyses. We thus argue that mathematical modelling is a powerful tool for the investigation of these extreme environments and that fully integrated, interdisciplinary model-data approaches could help the Polar and Alpine microbiology community address some of the great research challenges of the 21st century (e.g. assessing global significance and response to climate change). However, a better integration of field and laboratory work with model design and calibration/validation, as well as a stronger focus on quantitative information is required to advance models that can be used to make predictions and upscale processes and fluxes beyond what can be captured by observations alone.info:eu-repo/semantics/publishe

Assessing global-scale organic matter reactivity patterns in marine sediments using a lognormal reactive continuum model

Organic matter (OM) degradation in marine sediments is largely controlled by its reactivity and profoundly affects the global carbon cycle. Yet, there is currently no general framework that can constrain OM reactivity on a global scale. In this study, we propose a reactive continuum model based on a lognormal distribution (l-RCM), where OM reactivity is fully described by parameters μ (the mean reactivity of the initial OM bulk mixture) and σ (the variance of OM components around the mean reactivity). We use the l-RCM to inversely determine μ and σ at 123 sites across the global ocean. The results show that the apparent OM reactivity (〈k〉=μ⋅exp⁡(σ2/2)) decreases with decreasing sedimentation rate (ω) and that OM reactivity is more than 3 orders of magnitude higher in shelf than in abyssal regions. Despite the general global trends, higher than expected OM reactivity is observed in certain ocean regions characterized by great water depth or pronounced oxygen minimum zones, such as the eastern–western coastal equatorial Pacific and the Arabian Sea, emphasizing the complex control of the depositional environment (e.g., OM flux, oxygen content in the water column) on benthic OM reactivity. Notably, the l-RCM can also highlight the variability in OM reactivity in these regions. Based on inverse modeling results in our dataset, we establish the significant statistical relationships between 〈k〉 and ω and further map the global OM reactivity distribution. The novelty of this study lies in its unifying view but also in contributing a new framework that allows predicting OM reactivity in data-poor areas based on readily available (or more easily obtainable) information. Such a framework is currently lacking and limits our abilities to constrain OM reactivity in global biogeochemical or Earth system models

Ernährungsinformation im Internet: Technologien, Geschäftsmodelle und Inhalte

Für die Einschätzung der Auswirkungen der Web-2.0-Technologien, insbesondere von Blogs und von Wikis, sind vor allem die folgenden Überlegungen wichtig: (1) Das Web 2.0 ist ein Bündel von Medien, die, wie andere innovative Internetanwendungen zuvor, etablierte Medien nicht verdrängen werden; sie werden zu einem Teil der immer zahlreicher werdenden Medien-Optionen, aus denen Anbieter und Nachfrager von Ernährungsinformationen sich ein Medien-Mix zusammenstellen können, das ihren speziellen Bedürfnissen entspricht. (2) Web-2.0-Medien sind partizipativ, aggregativ und egalitär; die Informations-dominanz von großen Unternehmen, Organisationen und Behörden gegenüber Einzelpersonen und kleinen Organisationen als Informationsanbieter wird durch Blogs und Wikis geschmälert. (3) Spezielle Informationsbedürfnisse lassen sich wegen des verminderten Aufwands der Informationsbereitstellung durch Blogs und Wikis leichter bedienen als durch konventionelle Web-Medien. (4) Web-Medien begünstigen die Polarisierung von Meinungen und die Ent-stehung von Informationskaskaden, dies gilt auch für Blogs und, vermutlich in geringerem Ausmaß, für Wikis; die Diskurskultur wird dadurch nicht verbessert. (5) Blogs und Wikis eignen sich, wie alle Medien, für Propaganda und Fehlinformation; das Instrumentarium des unlauteren Informationswettbewerbs wird vergrößert und Maßnahmen zur Abwehr unlauterer Informationsangriffe sind erforderlich. Für Unternehmen und Organisationen der Ernährungswirtschaft ist jetzt die Zeit gekommen, sich aufs Web 2.0 einzurichten. --

Comparison of Reference Management Systems

The document offers a comparison of five literature management programmes - Zotero, Citavi, Mendeley, EndNote and JabRef. Versions as of 10/2021 were tested. The following criteria are taken into account: General and installation, import / export variants, data entry and editing, display and search, citation and bibliography, cooperation, knowledge organisation, special features and support. The comparison concludes with an overall assessment of strengths and weaknesses and provides target group-specific selection recommendations

Surviving rapid climate change in the deep sea during the Paleogene hyperthermals

Predicting the impact of ongoing anthropogenic CO2 emissions on calcifying marine organisms is complex, owing to the synergy between direct changes (acidification) and indirect changes through climate change (e.g. warming, changes in ocean circulation, and deoxygenation). Laboratory experiments, particularly on longer-lived organisms, tend to be too short to reveal the potential of organisms to acclimatize, adapt, or evolve and usually do not incorporate multiple stressors. We studied two examples of rapid carbon release in the geological record, Eocene Thermal Maximum 2 (∼53.2 Ma) and the Paleocene Eocene Thermal Maximum (PETM, ∼55.5 Ma), the best analogs over the last 65 Ma for future ocean acidification related to high atmospheric CO2 levels. We use benthic foraminifers, which suffered severe extinction during the PETM, as a model group. Using synchrotron radiation X-ray tomographic microscopy, we reconstruct the calcification response of survivor species and find, contrary to expectations, that calcification significantly increased during the PETM. In contrast, there was no significant response to the smaller Eocene Thermal Maximum 2, which was associated with a minor change in diversity only. These observations suggest that there is a response threshold for extinction and calcification response, while highlighting the utility of the geological record in helping constrain the sensitivity of biotic response to environmental change.info:eu-repo/semantics/publishe

Regulationsmechanismen der Ausprägung von Chemotypen in Thymian (Thymus vulgaris)

Das ätherische Öl von Thymianarten hat aufgrund seiner starken antibakteriellen Wirkung vielfältige Anwendungen in der Pharmazie und der Lebensmittelindustrie. Die wertvollsten antibakteriellen Inhaltstoffe des ätherischen Öls, die Monoterpenalkohole Carvacrol und Thymol, werden nur in einigen Kultivaren des Thymians gebildet und unterliegen einer komplizierten genetischen Kontrolle. Wir wollen die Regulation der Terpenproduktion in Thymian mit molekularen Methoden aufklären und die Züchtung von Thymianarten mit genau definiertem Terpengehalt ermöglichen. Stichwörter: Terpensynthese, Monoterpene, Chemotypen, ThymianMechanisms of chemotype formation in thyme (Thymus vulgaris)The essential oil of thyme has a strong antibacterial effect and is utilized in pharmaceutical applications as well as food production. Especially the phenolic monoterpene alcohols thymol and carvacrol are valuable due to their antibacterial, antiseptic and spasmolytical effects. Production of these compounds is subjected to a complex genetic control and found only in some cultivars of thyme. We study the molecular basis of terpene production to elucidate the mechanisms of chemotype formation. Keywords: Terpene biosynthesis, monoterpenes, chemotypes, thym