47242 research outputs found
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Fossil diatoms and their significance for paleoenvironment construction on the shelf of Northern South China Sea
No full textThe analysis of fossil diatoms preserved in continental shelf sediments can provide detailed insights into the paleoecological and environmental history of marginal seas. In this study, we consider the development of the northern South China Sea based on a 302-m-long drilling core taken on the outer continental shelf. Diatoms were absent in more than half of the analyzed samples, a relatively low absolute abundance, so that a diatom-based biostratigraphy could not be established. The low absolute abundance suggests that diatom preservation was poor because of highly dynamic oceanographic conditions and significant biosilica dissolution. The dominance of coastal species and the intermittent presence of mostly tropical open-sea diatoms along the core reflects strong land-sea interactions and a current circulation influenced by sea-level fluctuations, following the glacial and interglacial cycles of the Quaternary period. This study provides clues concerning the evaluation of diatom fossils in micropaleontology, as well as their role in biogeochemical cycles within complex sedimentary processes across various marginal sea shelves
Exploiting the Fractionation of Stable Isotopes in Biochemical Processes for Medical Diagnosis: A Narrative Review
No full textAnalysis of isotope distributions plays a crucial role in medical diagnostics. While radioactive and radiogenic isotopes - those that undergo or result from radioactive decay - are widely used, stable isotopes are less commonly applied despite their significant diagnostic potential. For example, calcium isotope ratio analysis is already commercially utilized for calcium loss and the early diagnosis of osteoporosis. Additionally, analyses of iron, copper, and zinc isotope ratios have been explored in various conditions, including hemochromatosis, Wilson's disease, cancer, Alzheimer's disease, and amyotrophic lateral sclerosis. Altered isotope ratios in these diseases are thought to reflect pathophysiologically relevant processes, making them promising biomarkers. This review provides a comprehensive overview of the current and potential applications of stable isotope analysis in medicine
Assessing Marine Snow Dynamics During the Demise of the North Atlantic Spring Bloom Using In Situ Particle Imagery
No full textThe ocean's biological pump, a critical component of the Earth's carbon cycle, transports organic matter from the surface ocean to depth and is dominated by sinking particles, often in the form of marine snow-sized (diameter ≥0.5 mm) aggregates. Controls of sinking particle carbon export are thought to be driven largely using ecological processes that create and transform sinking particles. We diagnose the importance of both biotic and abiotic processes in the dynamics of marine snow and other suspended particles using image-based determination of their size distribution. These observations were made during the demise of the North Atlantic spring bloom in May 2021 as part of the Export Processes in the Ocean from RemoTe Sensing-North Atlantic (EXPORTS-NA) field campaign. We show that intense storm events generated high turbulent mixing rates in the upper ocean that impacted the abundance, size distribution, porosity and sinking of marine snow. Mixed-layer turbulence levels both created and destroyed marine snow and the sequence of entrainment and detrainment of the mixed layer induced by repeated storm forcings enhanced the vertical transport of aggregates to depth. Evidence of biological transformations was also observed at mesopelagic depths, both for the consumption of particulate matter and in the creation of smaller particles from larger ones, likely due to interactions with zooplankton. Collectively, these results illustrate the complex interplay of physical and biological processes regulating the dynamics of marine snow and suggest their inclusion in predictive models of the ocean's biological pump
Impact of horizontal resolution and model time step on European precipitation extremes in the OpenIFS 43r3 atmospheric model
No full textEvents of extreme precipitation pose a hazard to many parts of Europe but are typically not well represented in climate models. Here, we evaluate daily extreme precipitation over Europe during 1982–2019 in observations (GPCC), reanalysis (ERA5), and a set of atmosphere-only simulations at low (100 km), medium (50 km), and high (25 km) horizontal resolution and also at different time steps (i.e., 60, 30, and 15 min) using low resolution (100 km) with identical vertical resolutions using OpenIFS (version 43r3). We find that both OpenIFS simulations and reanalysis underestimate the rates of extreme precipitation compared to observations. The biases are largest for the lowest resolution (100 km) and decrease with higher-horizontal-resolution (50 and 25 km) simulations in all seasons. The sensitivity to horizontal resolution is particularly high in mountain regions (such as the Alps, Scandinavia, Iberian Peninsula), likely linked to the sensitivity of vertical velocity to the representation of topography. The sensitivity of precipitation to model resolution increases dramatically with increasing percentiles, with modest biases in the 70th–80th percentile range and large biases above the 99th percentile range. We also find that precipitation above the 99th percentile mostly consists of large-scale precipitation (∼ 80 %) in winter, while in summer it is mostly large-scale precipitation in northern Europe (∼ 70 %) and convective precipitation in southern Europe (∼ 70 %). Convective precipitation is more sensitive to model time step than to horizontal resolution. Large-scale precipitation increases significantly with both higher horizontal resolution and a shorter model time step
From Individual Observations to Global Assessments: Tracing the Marine Carbon Knowledge Value Chain
No full textMarine carbon observations (MCOs) provide essential data to trace historical and current changes in marine carbon storage and fluxes that ultimately feed into the Global Carbon Budget and the Intergovernmental Panel on Climate Change report. Therefore, MCOs play a key role in informing global climate policy as well as ocean governance. However, they only achieve this potential if multiple sources of observations are combined and analyzed jointly. This implies an immense coordination effort by the international MCO community which developed, e.g., joint standards for the collection of (meta‐)data, quality control processes, data platforms, etc. This article traces the value chain of MCOs, concretely for CO2, from data collection to the Intergovernmental Panel on Climate Change report. Based on an interdisciplinary research project, the study illuminates which structures and practices the marine carbon community has developed to integrate different observations and measurement technologies, starting from German research institutes and agencies and expanding to the European and international networks to which they contribute. Combining a social network analysis with qualitative insights from in‐depth interviews, the article identifies key information providers and brokers and pinpoints systemic vulnerabilities, e.g., where connections between observation networks or data platforms are maintained based on personal relationships or ad‐hoc interactions rather than automated data submissions, or where temporally limited third party funding threatens the continued existence of the observation network
The 1831 CE mystery eruption identified as Zavaritskii caldera, Simushir Island (Kurils)
No full textPolar ice cores and historical records evidence a large-magnitude volcanic eruption in 1831 CE. This event was estimated to have injected ~13 Tg of sulfur (S) into the stratosphere which produced various atmospheric optical phenomena and led to Northern Hemisphere climate cooling of ~1 °C. The source of this volcanic event remains enigmatic, though one hypothesis has linked it to a modest phreatomagmatic eruption of Ferdinandea in the Strait of Sicily, which may have emitted additional S through magma–crust interactions with evaporite rocks. Here, we undertake a high-resolution multiproxy geochemical analysis of ice-core archives spanning the 1831 CE volcanic event. S isotopes confirm a major Northern Hemisphere stratospheric eruption but, importantly, rule out significant contributions from external evaporite S. In multiple ice cores, we identify cryptotephra layers of low K andesite-dacite glass shards occurring in summer 1831 CE and immediately prior to the stratospheric S fallout. This tephra matches the chemistry of the youngest Plinian eruption of Zavaritskii, a remote nested caldera on Simushir Island (Kurils). Radiocarbon ages confirm a recent (<300 y) eruption of Zavaritskii, and erupted volume estimates are consistent with a magnitude 5 to 6 event. The reconstructed radiative forcing of Zavaritskii (−2 ± 1 W m −2 ) is comparable to the 1991 CE Pinatubo eruption and can readily account for the climate cooling in 1831–1833 CE. These data provide compelling evidence that Zavaritskii was the source of the 1831 CE mystery eruption and solve a confounding case of multiple closely spaced observed and unobserved volcanic eruptions
Relating Dimethyl Sulphide and Methanethiol Fluxes to Surface Biota in the South‐West Pacific Using Shipboard Air‐Sea Interface Tanks
No full textDimethyl sulphide (DMS) and methanethiol (MeSH) emissions from South Pacific surface seawater were determined in deck board Air‐Sea Interface Tanks during the Sea2Cloud voyage in March 2020. The measured fluxes from water to headspace (F) varied with water mass type, with lowest fluxes observed with Subtropical and Subantarctic waters and highest fluxes from Frontal waters. Measured DMS fluxes were consistent with fluxes calculated using a two‐layer model and seawater DMS concentrations. The MeSH:DMS flux ratio was 11%–18% across the three water mass types, confirming that MeSH may represent a significant unaccounted contribution to the atmospheric sulfur budget, with potentially important implications for marine aerosol formation and growth in models. Combining data from the ASITs and ambient surface seawater identified significant Spearman rank correlations for both dissolved DMS and MeSH with nanophytoplankton cell abundance ( p value < 0.012), suggesting an important role for this phytoplankton size class in determining regional DMS and MeSH emissions. Applying a nanophytoplankton‐based parameterization to estimate DMS w provided good agreement with a recent DMS climatology. Consequently, the observed relationship between DMS w , MeSH w and nanophytoplankton cell abundances may be applicable for modeling atmospheric fluxes.
Plain Language Summary
In March 2020, researchers conducted experiments during the Sea2Cloud voyage east of New Zealand in which they measured the emissions of the climate relevant gases dimethyl sulphide (DMS) and methanethiol (MeSH). These sulfur gases are produced by marine microorganisms and their emissions were measured in tanks containing different sea water types. Lowest emissions were observed in Subtropical and Subantarctic waters while the highest were in Frontal waters where Subantarctic and Subtropical seawaters meet and support large phytoplankton blooms. While DMS has been extensively studied, there are far fewer measurements of MeSH which this study confirmed be a significant, relatively constantly scaled to DMS and previously underestimated contributor to atmospheric sulfur levels with potential implications for climate. The study established significant correlations between DMS and MeSH fluxes and nanophytoplankton cell abundance, highlighting the importance of this phytoplankton size class in marine emissions to the atmosphere. The results presented here can help constrain emissions of these sulfur gases in climate models.
Key Points
Ratio of methanethiol (MeSH) to dimethyl sulphide (DMS) fluxes of 11%–18% is consistent across different water types in Southern Ocean waters
Significant correlations between DMS w and MeSH w and nanophytoplankton were observed, enabling development of parameterizations for model
Geophysical Student Field Trip Baltic Sea Cruise No. AL619
No full text02.09.2024 – 10.09.2024
Kiel (Germany) – Kiel (Germany)
GÜ Uni Kie
Invertebrate models of nervous system regeneration
No full textThe establishment and maintenance of axonal and dendritic connections are vital for the proper functioning of the central and peripheral nervous systems (CNS and PNS). Neural injury can disrupt these connections, leading to impaired neural communication. In the adult mammalian CNS, axons and dendrites typically fail to regenerate. Although the PNS exhibits some regenerative capacity, the rates of regeneration are slow, reinnervation often fails, and regenerative capacity declines with age. It is imperative to understand the bases of and develop strategies to enhance the extent of neurite regeneration and nervous system recovery. Invertebrate models provide excellent systems for exploring regenerative mechanisms in depth. Furthermore, invertebrate animal models exhibit extensive spontaneous regeneration with facile injury protocols, and some models offer strong genetic toolkits for nervous system visualization and identification of factors involved in nervous system regeneration. Here, we review models of nervous system regeneration in planaria, echinoderms, mollusks, fruit flies, and nematodes